1
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Buckley S, McKay G, Leresche F, Rosario-Ortiz F. Inferring the Molecular Basis for Dissolved Organic Matter Photochemical and Optical Properties. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2024; 58:9040-9050. [PMID: 38743693 DOI: 10.1021/acs.est.3c10881] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/16/2024]
Abstract
Despite the widespread use of photochemical and optical properties to characterize dissolved organic matter (DOM), a significant gap persists in our understanding of the relationship among these properties. This study infers the molecular basis for the optical and photochemical properties of DOM using a comprehensive framework and known structural moieties within DOM. Utilizing Suwannee River Fulvic Acid (SRFA) as a model DOM, carboxylated aromatics, phenols, and quinones were identified as dominant contributors to the absorbance spectra, and phenols, quinones, aldehydes, and ketones were identified as major contributors to radiative energy pathways. It was estimated that chromophores constitute ∼63% w/w of dissolved organic carbon in SRFA and ∼47% w/w of overall SRFA. Notably, estimations indicate the pool of fluorescent compounds and photosensitizing compounds in SRFA are likely distinct from each other at wavelengths below 400 nm. This perspective offers a practical tool to aid in the identification of probable chemical groups when interpreting optical and photochemical data and challenges the current "black box" thinking. Instead, DOM photochemical and optical properties can be closely estimated by assuming the DOM is composed of a mixture of individual compounds.
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Affiliation(s)
- Shelby Buckley
- Environmental Engineering Program, University of Colorado Boulder, Boulder, Colorado 80309, United States
| | - Garrett McKay
- Zachry Department of Civil & Environmental Engineering, Texas A&M University, College Station, Texas 77845, United States
| | - Frank Leresche
- Department of Civil, Environmental, and Architectural Engineering, University of Colorado Boulder, Boulder, Colorado 80309, United States
| | - Fernando Rosario-Ortiz
- Environmental Engineering Program, University of Colorado Boulder, Boulder, Colorado 80309, United States
- Department of Civil, Environmental, and Architectural Engineering, University of Colorado Boulder, Boulder, Colorado 80309, United States
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2
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Li S, Harir M, Bastviken D, Schmitt-Kopplin P, Gonsior M, Enrich-Prast A, Valle J, Hertkorn N. Dearomatization drives complexity generation in freshwater organic matter. Nature 2024; 628:776-781. [PMID: 38658683 PMCID: PMC11043043 DOI: 10.1038/s41586-024-07210-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2022] [Accepted: 02/20/2024] [Indexed: 04/26/2024]
Abstract
Dissolved organic matter (DOM) is one of the most complex, dynamic and abundant sources of organic carbon, but its chemical reactivity remains uncertain1-3. Greater insights into DOM structural features could facilitate understanding its synthesis, turnover and processing in the global carbon cycle4,5. Here we use complementary multiplicity-edited 13C nuclear magnetic resonance (NMR) spectra to quantify key substructures assembling the carbon skeletons of DOM from four main Amazon rivers and two mid-size Swedish boreal lakes. We find that one type of reaction mechanism, oxidative dearomatization (ODA), widely used in organic synthetic chemistry to create natural product scaffolds6-10, is probably a key driver for generating structural diversity during processing of DOM that are rich in suitable polyphenolic precursor molecules. Our data suggest a high abundance of tetrahedral quaternary carbons bound to one oxygen and three carbon atoms (OCqC3 units). These units are rare in common biomolecules but could be readily produced by ODA of lignin-derived and tannin-derived polyphenols. Tautomerization of (poly)phenols by ODA creates non-planar cyclohexadienones, which are subject to immediate and parallel cycloadditions. This combination leads to a proliferation of structural diversity of DOM compounds from early stages of DOM processing, with an increase in oxygenated aliphatic structures. Overall, we propose that ODA is a key reaction mechanism for complexity acceleration in the processing of DOM molecules, creation of new oxygenated aliphatic molecules and that it could be prevalent in nature.
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Affiliation(s)
- Siyu Li
- Research Unit Analytical Biogeochemistry (BGC), Helmholtz Munich, German Research Center for Environmental Health, Neuherberg, Germany
| | - Mourad Harir
- Research Unit Analytical Biogeochemistry (BGC), Helmholtz Munich, German Research Center for Environmental Health, Neuherberg, Germany
- Chair of Analytical Food Chemistry, Technische Universität München, Freising-Weihenstephan, Germany
| | - David Bastviken
- Department of Thematic Studies - Environmental Change, Linköping University, Linköping, Sweden
| | - Philippe Schmitt-Kopplin
- Research Unit Analytical Biogeochemistry (BGC), Helmholtz Munich, German Research Center for Environmental Health, Neuherberg, Germany
- Chair of Analytical Food Chemistry, Technische Universität München, Freising-Weihenstephan, Germany
| | - Michael Gonsior
- Chesapeake Biological Laboratory, University of Maryland Center for Environmental Science, Solomons, MD, USA
| | - Alex Enrich-Prast
- Department of Thematic Studies - Environmental Change, Linköping University, Linköping, Sweden
- Institute of Marine Science, Federal University of São Paulo, Santos, Brazil
| | - Juliana Valle
- Research Unit Analytical Biogeochemistry (BGC), Helmholtz Munich, German Research Center for Environmental Health, Neuherberg, Germany
| | - Norbert Hertkorn
- Research Unit Analytical Biogeochemistry (BGC), Helmholtz Munich, German Research Center for Environmental Health, Neuherberg, Germany.
- Department of Thematic Studies - Environmental Change, Linköping University, Linköping, Sweden.
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3
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Pan Y, Garg S, Fu QL, Peng J, Yang X, Waite TD. Copper Safeguards Dissolved Organic Matter from Sunlight-Driven Photooxidation. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2023; 57:21178-21189. [PMID: 38064756 DOI: 10.1021/acs.est.3c07549] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/20/2023]
Abstract
Sunlight plays a crucial role in the transformation of dissolved organic matter (DOM) and the associated carbon cycle in aquatic environments. This study demonstrates that the presence of nanomolar concentrations of copper (Cu) significantly decreases the rate of photobleaching and the rate of loss of electron-donating moieties of three selected types of DOM (including both terrestrial and microbially derived DOM) under simulated sunlight irradiation. Employing Fourier transform ion cyclotron resonance mass spectrometry, we further confirm that Cu selectively inhibits the photooxidation of lignin- and tannin-like phenolic moieties present within the DOM, in agreement with the reported inhibitory impact of Cu on the photooxidation of phenolic compounds. On the basis of the inhibitory impact of Cu on the DOM photobleaching rate, we calculate the contribution of phenolic moieties to DOM photobleaching to be at least 29-55% in the wavelength range of 220-460 nm. The inhibition of loss of electrons from DOM during irradiation in the presence of Cu is also explained quantitatively by developing a mathematical model describing hydrogen peroxide (a proxy measure of loss of electrons from DOM) formation on DOM irradiation in the absence and presence of Cu. Overall, this study advances our understanding of DOM transformation in natural sunlit waters.
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Affiliation(s)
- Yanheng Pan
- School of Civil and Environmental Engineering, The University of New South Wales, Sydney, New South Wales 2052, Australia
- School of Environmental Science and Engineering, Guangdong Provincial Key Laboratory of Environmental Pollution Control and Remediation Technology, Sun Yat-sen University, Guangzhou 510275, China
| | - Shikha Garg
- School of Civil and Environmental Engineering, The University of New South Wales, Sydney, New South Wales 2052, Australia
| | - Qing-Long Fu
- School of Environmental Studies, China University of Geosciences, Wuhan 430078, China
| | - Jianglin Peng
- School of Environmental Science and Engineering, Guangdong Provincial Key Laboratory of Environmental Pollution Control and Remediation Technology, Sun Yat-sen University, Guangzhou 510275, China
| | - Xin Yang
- School of Environmental Science and Engineering, Guangdong Provincial Key Laboratory of Environmental Pollution Control and Remediation Technology, Sun Yat-sen University, Guangzhou 510275, China
| | - T David Waite
- School of Civil and Environmental Engineering, The University of New South Wales, Sydney, New South Wales 2052, Australia
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4
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Wei Z, Li N, Zhang X, Zheng L, Mo S, Korshin G, Li Q, Yan M. Characterizing photochemical production carboxyl content of dissolved organic matters using absorbance spectroscopy combined with FT-ICR MS. CHEMOSPHERE 2023; 344:140352. [PMID: 37806326 DOI: 10.1016/j.chemosphere.2023.140352] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/16/2023] [Revised: 08/27/2023] [Accepted: 10/02/2023] [Indexed: 10/10/2023]
Abstract
Irradiation can significantly impact the structure, reactivity and environmental behavior of dissolved organic matter (DOM). The extent of these processes remains to be ascertained in more detail but the heterogeneity and site-specificity of DOM, and the lack of methods to characterize DOM at its environmentally-relevant concentrations make it a challenge. In this study, the differences of DOM response to photodegradation in four typical origins (i.e., surface water, sediment and intracellular and extracellular algal DOM) were tracked on the molecular-level using Fourier Transform Ion Cyclotron Resonance Mass Spectrometry (FT-ICR MS). Changes of the carboxyl and phenolic DOM moieties induced by irradiation were quantified by spectroscopic titrations, and the mechanism of functional groups affecting the changes of specific molecular composition was qualitatively proposed. The results demonstrated that intracellular algal organic matter (I-DOM) was most susceptible to photodegradation (ca. 63% DOM loss), then came extracellular algal organic matter (E-DOM) and surface water DOM (W-DOM) (ca. 15% DOM loss). Sediment DOM (S-DOM) was most resistant to irradiation, with a very small level of its mineralization. Lipids, lignin-like compounds and tannin-like compounds in I-DOM and E-DOM were relatively photo-labile. The photodegradation of lipids was related to the decarboxylation of carboxyl functional groups, while the photodegradation of tannin-like compounds was related to the rupture of phenolic functional groups. In comparison, the molecular composition of W-DOM and S-DOM was less affected by irradiation, which was also reflected in the fact that the carboxyl and phenolic functional groups were highly photo-resistant. This study showed that the photoactivity of DOM in surface water was closely related to the abundance of algae, so controlling the excessive reproduction of algae may have a positive effect on stability of quality and quantity of organic matter in surface water.
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Affiliation(s)
- Zizhuo Wei
- College of Resources and Civil Engineering, Northeastern University, Shenyang, 110819, Liaoning, China; Qinhuangdao key Laboratory of Water-saving Pollution Control and Ecological Restoration, College of Resources and Materials, Northeastern University at Qinhuangdao, Qinhuangdao, 066004, Hebei, China
| | - Na Li
- College of Resources and Civil Engineering, Northeastern University, Shenyang, 110819, Liaoning, China; Qinhuangdao key Laboratory of Water-saving Pollution Control and Ecological Restoration, College of Resources and Materials, Northeastern University at Qinhuangdao, Qinhuangdao, 066004, Hebei, China
| | - Xinyi Zhang
- College of Water Resources and Hydropower Engineering, North China Electric Power University, Beijing 102208, China
| | - Lei Zheng
- College of Water Resources and Hydropower Engineering, North China Electric Power University, Beijing 102208, China
| | - Shansheng Mo
- Department of Environmental Engineering, Peking University, The Key Laboratory of Water and Sediment Sciences, Ministry of Education, Beijing 100871, China
| | - Gregory Korshin
- Department of Civil and Environmental Engineering, University of Washington, Box 352700, Seattle, WA 98195-2700, United States
| | - Qingwei Li
- College of Resources and Civil Engineering, Northeastern University, Shenyang, 110819, Liaoning, China; Qinhuangdao key Laboratory of Water-saving Pollution Control and Ecological Restoration, College of Resources and Materials, Northeastern University at Qinhuangdao, Qinhuangdao, 066004, Hebei, China
| | - Mingquan Yan
- Department of Environmental Engineering, Peking University, The Key Laboratory of Water and Sediment Sciences, Ministry of Education, Beijing 100871, China.
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5
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Leyva D, Usman Tariq M, Jaffé R, Saeed F, Fernandez-Lima F. Description of Dissolved Organic Matter Transformational Networks at the Molecular Level. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2023; 57:2672-2681. [PMID: 36724500 DOI: 10.1021/acs.est.2c04715] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/18/2023]
Abstract
Dissolved Organic Matter (DOM) is an important component of the global carbon cycle. Unscrambling the structural footprint of DOM is key to understand its biogeochemical transformations at the mechanistic level. Although numerous studies have improved our knowledge of DOM chemical makeup, its three-dimensional picture remains largely unrevealed. In this work, we compare four solid phase extracted (SPE) DOM samples from three different freshwater ecosystems using high resolution mobility and ultrahigh-resolution Fourier transform ion cyclotron resonance tandem mass spectrometry (FT-ICR MS/MS). Structural families were identified based on neutral losses at the level of nominal mass using continuous accumulation of selected ions-collision induced dissociation (CASI-CID)FT-ICR MS/MS. Comparison of the structural families indicated dissimilarities in the structural footprint of this sample set. The structural family representation using Cytoscape software revealed characteristic clustering patterns among the DOM samples, thus confirming clear differences at the structural level (Only 10% is common across the four samples.). The analysis at the level of neutral loss-based functionalities suggests that hydration and carboxylation are ubiquitous transformational processes across the three ecosystems. In contrast, transformation mechanisms involving methoxy moieties may be constrained in estuarine systems due to extensive upstream lignin biodegradation. The inclusion of the isomeric content (mobility measurements at the level of chemical formula) in the structural family description suggests that additional transformation pathways and/or source variations are possible and account for the dissimilarities observed. While the structural character of more and diverse types of DOM samples needs to be assessed and added to this database, the results presented here demonstrate that Graph-DOM is a powerful tool capable of providing novel information on the DOM chemical footprint, based on structural interconnections of precursor molecules generated by fragmentation pathways and collisional cross sections.
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Affiliation(s)
- Dennys Leyva
- Department of Chemistry and Biochemistry, Florida International University, Miami, Florida33199, United States
| | - Muhammad Usman Tariq
- School of Computing and Information Science, Florida International University, Miami, Florida33199, United States
| | - Rudolf Jaffé
- Institute of Environment and Department of Chemistry and Biochemistry, Florida International University, Miami, Florida33199, United States
| | - Fahad Saeed
- School of Computing and Information Science, Florida International University, Miami, Florida33199, United States
| | - Francisco Fernandez-Lima
- Department of Chemistry and Biochemistry, Florida International University, Miami, Florida33199, United States
- Biomolecular Sciences Institute, Florida International University, Miami, Florida33199, United States
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6
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Sutherland KM, Johnston DT, Hemingway JD, Wankel SD, Ward CP. Revised microbial and photochemical triple-oxygen isotope effects improve marine gross oxygen production estimates. PNAS NEXUS 2022; 1:pgac233. [PMID: 36712381 PMCID: PMC9802178 DOI: 10.1093/pnasnexus/pgac233] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/06/2022] [Accepted: 10/08/2022] [Indexed: 11/05/2022]
Abstract
The biogeochemical fluxes that cycle oxygen (O2) play a critical role in regulating Earth's climate and habitability. Triple-oxygen isotope (TOI) compositions of marine dissolved O2 are considered a robust tool for tracing oxygen cycling and quantifying gross photosynthetic O2 production. This method assumes that photosynthesis, microbial respiration, and gas exchange with the atmosphere are the primary influences on dissolved O2 content, and that they have predictable, fixed isotope effects. Despite its widespread use, there are major elements of this approach that remain uncharacterized, including the TOI dynamics of respiration by marine heterotrophic bacteria and abiotic O2 sinks such as the photochemical oxidation of dissolved organic carbon (DOC). Here, we report the TOI fractionation for O2 utilization by two model marine heterotrophs and by abiotic photo-oxidation of representative terrestrial and coastal marine DOC. We demonstrate that TOI slopes associated with these processes span a significant range of the mass-dependent domain (λ = 0.499 to 0.521). A sensitivity analysis reveals that even under moderate productivity and photo-oxidation scenarios, true gross oxygen production may deviate from previous estimates by more than 20% in either direction. By considering a broader suite of oxygen cycle reactions, our findings challenge current gross oxygen production estimates and highlight several paths forward to better understanding the marine oxygen and carbon cycles.
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Affiliation(s)
| | - David T Johnston
- Department of Earth and Planetary Sciences, Harvard University, Cambridge, MA 02138, USA
| | - Jordon D Hemingway
- ETH Zürich, Geological Institute, Department of Earth Sciences, Zürich 8092, Switzerland
| | - Scott D Wankel
- Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA
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7
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Walsh AN, Mazzotta MG, Nelson TF, Reddy CM, Ward CP. Synergy between Sunlight, Titanium Dioxide, and Microbes Enhances Cellulose Diacetate Degradation in the Ocean. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2022; 56:13810-13819. [PMID: 36103552 PMCID: PMC9535896 DOI: 10.1021/acs.est.2c04348] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/17/2022] [Revised: 08/26/2022] [Accepted: 08/29/2022] [Indexed: 05/28/2023]
Abstract
Sunlight chemically transforms marine plastics into a suite of products, with formulation─the specific mixture of polymers and additives─driving rates and products. However, the effect of light-driven transformations on subsequent microbial lability is poorly understood. Here, we examined the interplay between photochemical and biological degradation of fabrics made from cellulose diacetate (CDA), a biobased polymer used commonly in consumer products. We also examined the influence of ∼1% titanium dioxide (TiO2), a common pigment and photocatalyst. We sequentially exposed CDA to simulated sunlight and native marine microbes to understand how photodegradation influences metabolic rates and pathways. Nuclear magnetic resonance spectroscopy revealed that sunlight initiated chain scission reactions, reducing CDA's average molecular weight. Natural abundance carbon isotope measurements demonstrated that chain scission ultimately yields CO2, a newly identified abiotic loss term of CDA in the environment. Measurements of fabric mass loss and enzymatic activities in seawater implied that photodegradation enhanced biodegradation by performing steps typically facilitated by cellulase. TiO2 accelerated CDA photodegradation, expediting biodegradation. Collectively, these findings (i) underline the importance of formulation in plastic's environmental fate and (ii) suggest that overlooking synergy between photochemical and biological degradation may lead to overestimates of marine plastic persistence.
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Affiliation(s)
- Anna N. Walsh
- Department
of Marine Chemistry and Geochemistry, Woods
Hole Oceanographic Institution, Woods Hole, Massachusetts 02543, United States
- Department
of Civil and Environmental Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Michael G. Mazzotta
- Department
of Marine Chemistry and Geochemistry, Woods
Hole Oceanographic Institution, Woods Hole, Massachusetts 02543, United States
- Eastman
Chemical Company, Kingsport, Tennessee 37660, United States
| | - Taylor F. Nelson
- Department
of Marine Chemistry and Geochemistry, Woods
Hole Oceanographic Institution, Woods Hole, Massachusetts 02543, United States
| | - Christopher M. Reddy
- Department
of Marine Chemistry and Geochemistry, Woods
Hole Oceanographic Institution, Woods Hole, Massachusetts 02543, United States
| | - Collin P. Ward
- Department
of Marine Chemistry and Geochemistry, Woods
Hole Oceanographic Institution, Woods Hole, Massachusetts 02543, United States
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8
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Liu Y, Wang M, Yin S, Xie L, Qu X, Fu H, Shi Q, Zhou F, Xu F, Tao S, Zhu D. Comparing Photoactivities of Dissolved Organic Matter Released from Rice Straw-Pyrolyzed Biochar and Composted Rice Straw. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2022; 56:2803-2815. [PMID: 35089700 DOI: 10.1021/acs.est.1c08061] [Citation(s) in RCA: 31] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Here, we systematically compared the photoactivity and photobleaching behavior between dissolved black carbon (DBC) from rice straw biochar and leached dissolved organic carbon (LDOC) from rice straw compost using complementary techniques. The Fourier transform-ion cyclotron resonance mass spectrometry (FT-ICR MS) analysis showed that DBC was dominated by polycyclic aromatic (55.1%) and tannin-like molecules (24.1%), while LDOC was dominated by lignin-like (58.9%) and tannin-like molecules (19.7%). Under simulated sunlight conditions, DBC had much higher apparent quantum yields for 3DOM* and 1O2 but much lower apparent quantum yields for •OH than LDOC. After a 168 h irradiation, the total number of LDOC formulas identified by FT-ICR MS decreased by 40.1% with concurrent increases in O/C and H/C ratios and also decreases in double bond equivalence minus oxygen (DBE - O) and average molecular weight identified by gel permeation chromatography. However, despite the large decreases in UVA254 and DOC, the total number of DBC formulas decreased only by 12.0% with nearly unchanged O/C ratio, DBE - O values, molecular weight distribution, and benzenepolycarboxylic aromatic condensation (BACon) index regardless of the decreased percentage of condensed aromatic carbon (ConAC %). Compared with LDOC, the photolysis of DBC was much less oxidative and destructive mainly via breakup of a small portion of the highly condensed aromatic rings, probably accompanied by photodecarboxylation.
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Affiliation(s)
- Yafang Liu
- School of Urban and Environmental Sciences, Key Laboratory of the Ministry of Education for Earth Surface Processes, Peking University, Beijing 100871, China
| | - Minli Wang
- School of the Environment, State Key Laboratory of Pollution Control and Resource Reuse, Nanjing University, Nanjing, Jiangsu 210046, China
| | - Shujun Yin
- School of Urban and Environmental Sciences, Key Laboratory of the Ministry of Education for Earth Surface Processes, Peking University, Beijing 100871, China
| | - Lekai Xie
- School of Urban and Environmental Sciences, Key Laboratory of the Ministry of Education for Earth Surface Processes, Peking University, Beijing 100871, China
| | - Xiaolei Qu
- School of the Environment, State Key Laboratory of Pollution Control and Resource Reuse, Nanjing University, Nanjing, Jiangsu 210046, China
| | - Heyun Fu
- School of the Environment, State Key Laboratory of Pollution Control and Resource Reuse, Nanjing University, Nanjing, Jiangsu 210046, China
| | - Quan Shi
- School of Chemical Engineering and Environment, State Key Laboratory of Heavy Oil Processing, China University of Petroleum, Beijing 102249, China
| | - Feng Zhou
- School of Urban and Environmental Sciences, Key Laboratory of the Ministry of Education for Earth Surface Processes, Peking University, Beijing 100871, China
| | - Fuliu Xu
- School of Urban and Environmental Sciences, Key Laboratory of the Ministry of Education for Earth Surface Processes, Peking University, Beijing 100871, China
| | - Shu Tao
- School of Urban and Environmental Sciences, Key Laboratory of the Ministry of Education for Earth Surface Processes, Peking University, Beijing 100871, China
| | - Dongqiang Zhu
- School of Urban and Environmental Sciences, Key Laboratory of the Ministry of Education for Earth Surface Processes, Peking University, Beijing 100871, China
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9
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Johannsson OE, Ferreira MS, Smith DS, Wood CM, Val AL. Interplay of oxygen and light in the photo-oxidation of dissolved organic carbon. WATER RESEARCH 2021; 201:117332. [PMID: 34182350 DOI: 10.1016/j.watres.2021.117332] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/03/2021] [Revised: 05/14/2021] [Accepted: 06/01/2021] [Indexed: 06/13/2023]
Abstract
Light energy and oxygen drive photo-oxidation of dissolved organic carbon (DOC). The longer the wavelength the greater its depth of penetration into water, changing the spectral environment with depth. We asked how oxygen concentration and light spectral composition might affect photo-oxidation processes in DOC. Outdoor experiments compared responses of fluorescence and absorbance indices to photo-oxidation of filtered (0.45 µm) Rio Negro water (Amazon Basin) under near-anoxia, normoxia and hyperoxia exposed to natural sunlight or reduced sunlight (≥340, reduced-UVR). Near-anoxia decreased all absorbance and fluorescence indices. Absorbance changed across the spectrum (≥250 nm) even under reduced-UVR provided that oxygen was present. This phenomenon maintains broader photo-oxidation and the release of CO2 at depth. Slope350-400 was responsive to changes in the irradiance field but not to oxygen concentration, while Slope275-295 responded to both. Thus, larger molecules are broken down near the water's surface and medium to smaller molecules continue to be processed at depth. The production of fulvic acid-like fluorescence required both UVB and oxygen, restricting its production to surface waters. The relatively small increase in R254/365 compared with the loss of SUVA254 under near-anoxia indicated a slower breakdown of larger DOC molecules as oxygen becomes limiting. Breakdown of larger molecules which absorb in the 350-400 nm range, appears to involve two steps - one by radiant energy and another involving oxygen. The study results reflect the dynamic gradients in photo-oxidation with depth.
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Affiliation(s)
- Ora E Johannsson
- Zoology Department, University of British Columbia, Vancouver, BC, V6T 1Z4 Canada.
| | - Marcio S Ferreira
- Laboratory of Ecophysiology and Molecular Evolution, Brazilian National Institute for Research of the Amazon, INPA, Manaus, AM, Brazil.
| | - D Scott Smith
- Department of Chemistry and Biochemistry, Wilfrid Laurier University, Waterloo, ON, N2L 3C5 Canada.
| | - Chris M Wood
- Zoology Department, University of British Columbia, Vancouver, BC, V6T 1Z4 Canada; Laboratory of Ecophysiology and Molecular Evolution, Brazilian National Institute for Research of the Amazon, INPA, Manaus, AM, Brazil.
| | - Adalberto L Val
- Laboratory of Ecophysiology and Molecular Evolution, Brazilian National Institute for Research of the Amazon, INPA, Manaus, AM, Brazil
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10
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Retelletti Brogi S, Balestra C, Casotti R, Cossarini G, Galletti Y, Gonnelli M, Vestri S, Santinelli C. Time resolved data unveils the complex DOM dynamics in a Mediterranean river. THE SCIENCE OF THE TOTAL ENVIRONMENT 2020; 733:139212. [PMID: 32446062 DOI: 10.1016/j.scitotenv.2020.139212] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/17/2020] [Revised: 05/02/2020] [Accepted: 05/02/2020] [Indexed: 06/11/2023]
Abstract
In this study, dissolved organic carbon (DOC) data and optical properties (absorbance and fluorescence) of DOM, weekly collected in the Arno River for 2 years, are used to investigate the main processes determining DOM temporal dynamics in a small Mediterranean river, with torrential hydrology and medium-high human impact, and to quantify the contribution of this river to Med Sea carbon budget. A clear seasonal cycle of DOM, with DOC values ranging between 170 and 490 μM, was observed. Optical properties indicates that DOM quality in the river is different depending on the season; terrestrial humic-like substances prevail in winter, when discharge and floods are the main drivers of DOM concentration and quality, whereas autochthonous protein-like substances prevail in spring and summer, when biological processes dominate. Our results provide a robust estimate of the DOC flux to the Med Sea (9.6 · 109 g DOC yr-1) and of its range of variability (12.95 · 109-5.12 · 109 g DOC yr-1). The 80% of this flux was generally delivered during autumn/winter with significant amounts ascribed to single flood events (up to 26% in 2014). This study, by providing a rich dataset on water quantity and quality and by quantifying the importance of the hydrological regime on DOC transport, represents an important step toward a quantitative modeling of the Arno River.
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Affiliation(s)
| | - Cecilia Balestra
- Stazione Zoologica Anton Dohrn, Villa Comunale, Naples 80121, Italy
| | | | - Gianpiero Cossarini
- Istituto Nazionale di Oceanografia e Geofisica Sperimentale (OGS), Borgo Grotta Gigante 42/C, 34010 Sgonico, (TS), Italy
| | - Yuri Galletti
- Istituto di Biofisica, CNR, Via G. Moruzzi, Pisa 56124, Italy
| | | | - Stefano Vestri
- Istituto di Biofisica, CNR, Via G. Moruzzi, Pisa 56124, Italy
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11
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Nalven SG, Ward CP, Payet JP, Cory RM, Kling GW, Sharpton TJ, Sullivan CM, Crump BC. Experimental metatranscriptomics reveals the costs and benefits of dissolved organic matter photo‐alteration for freshwater microbes. Environ Microbiol 2020; 22:3505-3521. [DOI: 10.1111/1462-2920.15121] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2019] [Accepted: 06/03/2020] [Indexed: 12/25/2022]
Affiliation(s)
- Sarah G. Nalven
- Oregon State University Corvallis OR USA
- College of Earth, Ocean, and Atmospheric Sciences Oregon State University Corvallis OR USA
| | | | - Jérôme P. Payet
- Oregon State University Corvallis OR USA
- College of Earth, Ocean, and Atmospheric Sciences Oregon State University Corvallis OR USA
| | - Rose M. Cory
- College of Literature, Science, and the Arts Earth and Environmental Sciences University of Michigan Ann Arbor MI USA
- University of Michigan Ann Arbor MI USA
| | - George W. Kling
- University of Michigan Ann Arbor MI USA
- College of Literature, Science, and the Arts Ecology and Evolutionary Biology University of Michigan Ann Arbor MI USA
| | - Thomas J. Sharpton
- Oregon State University Corvallis OR USA
- Department of Microbiology Oregon State University Corvallis OR USA
| | - Christopher M. Sullivan
- Oregon State University Corvallis OR USA
- Center for Genome Research and Biocomputing Oregon State University Corvallis OR USA
| | - Byron C. Crump
- Oregon State University Corvallis OR USA
- College of Earth, Ocean, and Atmospheric Sciences Oregon State University Corvallis OR USA
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12
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Ward CP, Cory RM. Assessing the prevalence, products, and pathways of dissolved organic matter partial photo-oxidation in arctic surface waters. ENVIRONMENTAL SCIENCE. PROCESSES & IMPACTS 2020; 22:1214-1223. [PMID: 32073091 DOI: 10.1039/c9em00504h] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
In sunlit waters, photodegradation of dissolved organic matter (DOM) yields completely oxidized carbon (i.e., CO2) as well as a suite of partially oxidized compounds formed from oxygen incorporation (i.e., partial photo-oxidation). Of these two groups of DOM photo-products, more studies focus on CO2 (a greenhouse gas) than on partially oxidized DOM, which is likely a diverse group of compounds with poorly constrained roles in aquatic carbon cycling or biogeochemistry. The objective of this study is to address knowledge gaps on the prevalence, products, and pathways of DOM partial photo-oxidation. Here we traced the photochemical incorporation of isotopically labelled 18O2 into DOM isolated from Alaskan Arctic surface waters using high-resolution mass spectrometry. Complete and partial photo-oxidation of DOM was also quantified as CO2 production and O2 consumption. The majority of 18O-containing partial oxidation photo-products were classified as carboxylic rich alicyclic molecules (CRAM) and overlapped in composition with previously reported photo-products known to result from the oxidation of DOM by singlet oxygen. These results support a previously proposed hypothesis that photo-oxidation by singlet oxygen may contribute to the formation of CRAM, a compound class of DOM ubiquitously observed in surface waters. The novel application of an isotopic tracer for oxygen incorporation with a mass balance approach to quantify complete and partial photo-oxidation of DOM revealed that less than one mol of O2 is required to produce one mol of CO2. A sensitivity analysis based on this new knowledge demonstrated that the magnitude of DOM partial photo-oxidation may be underestimated by up to four-fold. Consequently, partial photo-oxidation likely plays a more prominent role in shaping DOM composition in sunlit waters of the Arctic than previously understood. Therefore, partial photo-oxidation should be increasingly incorporated into the experimental framework of studies focused on DOM composition in surface waters.
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Affiliation(s)
- Collin P Ward
- Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts 02543, USA.
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13
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Zhou Q, Li Y, Yang H, Gao Y. A collaborative strategy for enhanced reduction of Cr(VI) by Fe(0) in the presence of oxalate under sunlight: Performance and mechanism. J Environ Sci (China) 2020; 90:385-394. [PMID: 32081334 DOI: 10.1016/j.jes.2019.12.003] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2019] [Revised: 12/03/2019] [Accepted: 12/03/2019] [Indexed: 06/10/2023]
Abstract
Nanometer-size zero-valent iron (NZVI) is an efficient reducing agent, but its surface is easily passivated with an oxide layer, leading to reaction inefficiency. In our study, oxalate (OA) was introduced into this heterogeneous system of NZVI, which could form ferrioxalate complexes with the NZVI surface-bound Fe3+ and dissolved Fe3+ in the solution. Photolysis of ferrioxalate complexes can facilitate the generation of Fe2+ from Fe3+ and CO2•- radical, both species have strong reduction capacity. Hence, a "photo-oxalate-Fe(0)" system through sunlight induction was established, which not only prohibited the formation of a surface passivation layer, but also displayed a synergetic mechanism of ferrioxalate photolysis to enhance reduction, exhibiting remarkably higher degradation activity (several times faster) toward the model pollutant Cr(VI) than the mechanism with NZVI alone. Factor tests suggested that both NZVI dosage and OA content markedly affected the reduction rate. Low pH was beneficial to the reduction efficiency. Moreover, recyclability experiment showed that the reduction rate decreased from 0.21706 to 0.03977 min-1 after three cycles of reuse due to the NZVI losing reaction activity generally, but the system still maintained considerable reduction capacity. Finally, a mechanism was revealed whereby NZVI would transform to Fe oxides after the exhaustion of its reductive power, and the photolysis of ferrioxalate to promote the cycling of iron species played the predominant role in providing extra reduction ability. These features confirm that introduction of OA into Cr(VI) reduction by NZVI through sunlight induction is advantageous and promising.
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Affiliation(s)
- Qi Zhou
- College of Chemistry and Chemical Engineering, Anhui University, Hefei 230601, China.
| | - Yang Li
- Guangzhou Key Laboratory of Environmental Catalysis and Pollution Control, School of Environmental Science and Engineering, Institute of Environmental Health and Pollution Control, Guangdong University of Technology, Guangzhou 510006, China
| | - Heng Yang
- Chengdu Integrated Testing Center of Rocks and Ores, Sichuan Geology and Mineral Exploration and Development Bureau, Chengdu 610081, China
| | - Yun Gao
- Anhui Electric Power Construction Second Engineering Co. Ltd., China Energy Construction Group, Hefei 230000, China
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14
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Lian L, Yan S, Zhou H, Song W. Overview of the Phototransformation of Wastewater Effluents by High-Resolution Mass Spectrometry. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2020; 54:1816-1826. [PMID: 31893633 DOI: 10.1021/acs.est.9b04669] [Citation(s) in RCA: 29] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Photochemical transformation driven by sunlight is one of the most important natural processes for organic contaminant attenuation. In the current study, statistical analysis-assisted high-resolution mass spectrometry was employed to investigate the phototransformation of nontarget features in wastewater effluents under various radical quenching/enhancing conditions. A total of 9694 nontarget features were extracted from the effluents, including photoresistant features, photolabile features, and transformation products. 65% of the wastewater effluent features were photoresistant, and the photolabile features could be classified into five groups: direct photolysis group (group I), HO•-originated species-dominated group (group II), 3OM*-dominated group (group III), photochemically produced reactive intermediates combination-dominated group (group IV), and non-first-order degradation group (group V). The direct photolyzed features were observed to degrade significantly faster than the indirect photolyzed features. Moreover, group II dominated by HO•-originated species contributed 34% to the photolabile features. The reaction types that occurred in the phototransformation process were analyzed by linkage analysis. The results suggested that oxygen addition and dealkyl group reactions were the most common reaction types identified in the phototransformation process. Overall, high-resolution mass spectrometry coupled with statistical analysis was applied here to understand the photochemical behavior of the unknown features in wastewater effluents.
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Affiliation(s)
- Lushi Lian
- Department of Environmental Science and Engineering , Fudan University , Shanghai 200438 , P. R. China
| | - Shuwen Yan
- Department of Environmental Science and Engineering , Fudan University , Shanghai 200438 , P. R. China
- Shanghai Institute of Pollution Control and Ecological Security , Shanghai 200092 , P. R. China
| | - Huaxi Zhou
- Department of Environmental Science and Engineering , Fudan University , Shanghai 200438 , P. R. China
| | - Weihua Song
- Department of Environmental Science and Engineering , Fudan University , Shanghai 200438 , P. R. China
- Shanghai Institute of Pollution Control and Ecological Security , Shanghai 200092 , P. R. China
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15
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Niu XZ, Harir M, Schmitt-Kopplin P, Croué JP. Sunlight-induced phototransformation of transphilic and hydrophobic fractions of Suwannee River dissolved organic matter. THE SCIENCE OF THE TOTAL ENVIRONMENT 2019; 694:133737. [PMID: 31401506 DOI: 10.1016/j.scitotenv.2019.133737] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/04/2019] [Revised: 08/01/2019] [Accepted: 08/01/2019] [Indexed: 06/10/2023]
Abstract
Sunlight-induced chemical changes of both transphilic (SWR-TPH) and hydrophobic (SWR-HPO) fractions of Suwannee River dissolved organic matter (DOM) were followed by ultrahigh resolution Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS). Irradiated SWR-TPH exhibited increase of chemodiversity, loss of some aromatic compounds, and almost no change in terms of average values of m/z, O/C and double bond equivalents (DBE). Irradiated SWR-HPO showed decrease of chemodiversity, average values of m/z, O/C and DBE. Irradiation of SWR-HPO produced oxygenated (O/C > 0.7) and aliphatic new compounds and removed some aromatics and carboxyl-rich alicyclic molecules (CRAM). Comparatively, CHO-compounds of SWR-TPH were relatively stable with a minor class of aromatic compounds disappeared under sunlight irradiation. Photochemical processing of SWR-HPO generated highly oxygenated new compounds that were readily present in SWR-TPH, implying that sunlight changes the hydrophobicity of DOM and that SWR-HPO is a photochemical precursor for SWR-TPH. This study contributed to the developing knowledge on organic matter phototransformation, particularly the transformation pattern of SWR-TPH that was never described previously; it also demonstrated the role of sunlight in producing SWR-TPH compounds from SWR-HPO and consequently driving the transformation of organic matter.
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Affiliation(s)
- Xi-Zhi Niu
- Curtin Water Quality Research Centre, School of Molecular and Life Sciences, Curtin University, GPO Box U1987, Perth, Western Australia 6845, Australia.
| | - Mourad Harir
- Analytical BioGeoChemistry, German Research Centre for Environmental Health, Helmholtz Zentrum München, Ingolstädter landstrasse. 1, 85764 Neuherberg, Germany; Chair of Analytical Food Chemistry, Technische Universität München, Freising-Weihenstephan, Germany
| | - Philippe Schmitt-Kopplin
- Analytical BioGeoChemistry, German Research Centre for Environmental Health, Helmholtz Zentrum München, Ingolstädter landstrasse. 1, 85764 Neuherberg, Germany; Chair of Analytical Food Chemistry, Technische Universität München, Freising-Weihenstephan, Germany
| | - Jean-Philippe Croué
- Curtin Water Quality Research Centre, School of Molecular and Life Sciences, Curtin University, GPO Box U1987, Perth, Western Australia 6845, Australia; Institut de Chimie des Milieux et des Materiaux IC2MP UMR 7285 CNRS, Universite de Poitiers, France.
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16
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Yuan C, Sleighter RL, Weavers LK, Hatcher PG, Chin YP. Fast Photomineralization of Dissolved Organic Matter in Acid Mine Drainage Impacted Waters. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2019; 53:6273-6281. [PMID: 31038308 DOI: 10.1021/acs.est.9b00202] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
Acid mine drainage (AMD) formed from pyrite (iron disulfide) weathering contributes to ecosystem degradation in impacted waters. Solar irradiation has been shown to be an important factor in the biogeochemical cycling of iron in AMD-impacted waters, but its impact on dissolved organic matter (DOM) is unknown. With a typical AMD-impacted water (pH 2.7-3) collected from the Perry State Forest watershed in Ohio, we observed highly efficient (>80%) photochemical mineralization of DOM within hours in a solar simulator resembling twice summer sunlight at 40°N. We confirmed that the mineralization was initially induced by •OH formed from FeOH2+ photodissociation and was inhibited 2-fold by dissolved oxygen removal, suggesting the importance of both the photochemical reaction and oxygen involvement. Size exclusion chromatography and Fourier transform ion cyclotron resonance mass spectrometry elucidated that any remaining organic matter was comprised of smaller and highly aliphatic compounds. The quantitative and qualitative changes in DOM are likely to constitute an important component in regional carbon cycling and nutrient release and to influence downstream aquatic ecosystems in AMD-affected watersheds.
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Affiliation(s)
- Chenyi Yuan
- Environmental Science Graduate Program , The Ohio State University , Columbus , Ohio 43210 , United States
| | - Rachel L Sleighter
- Department of Chemistry and Biochemistry , Old Dominion University , Norfolk , Virginia 23529 , United States
| | - Linda K Weavers
- Department of Civil, Environmental, and Geodetic Engineering , The Ohio State University , Columbus , Ohio 43210 , United States
| | - Patrick G Hatcher
- Department of Chemistry and Biochemistry , Old Dominion University , Norfolk , Virginia 23529 , United States
| | - Yu-Ping Chin
- School of Earth Sciences , The Ohio State University , Columbus , Ohio 43210 , United States
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17
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Zeng J, Chen M, Guo L, Lin H, Mu X, Fan L, Zheng M, Qiu Y. Role of organic components in regulating denitrification in the coastal water of Daya Bay, southern China. ENVIRONMENTAL SCIENCE. PROCESSES & IMPACTS 2019; 21:831-844. [PMID: 31016305 DOI: 10.1039/c8em00558c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Both dissolved and particulate organic materials have been proposed to be important factors in regulating heterotrophic denitrification in various aquatic environments. However, the specific pathways and mechanisms remain elusive. In this study, water column samples were collected from Daya Bay, southern China, to examine the relationships between potential denitrification and different organic components in the water column. Bulk dissolved organic carbon (DOC) was categorized into three major components including terrigenous fluorescent (tFDOC), autochthonous fluorescent (bFDOC) and non-fluorescent (nFDOC) fractions, while the bulk particulate organic carbon (POC) was divided into terrigenous (tPOC) and autochthonous (bPOC) fractions based on an isotope mixing model. Potential denitrification derived from in situ incubation experiments under anoxic conditions was evident (ranging from 6 to 107 nmol N2 per L per h) and varied markedly among stations. When normalized to nitrate concentration, the denitrification rate (NDR) followed a positive trend with either the concentration or proportion of tFDOC, and a negative trend with the proportion of nFDOC, suggesting tFDOC was potentially favorable while nFDOC was unfavorable for denitrifying degradation. In comparison, the NDR showed a significant positive correlation with the proportion of bPOC in the bulk POC (p = 0.01), with a predictive power of >70%, indicating that the composition of POC has a substantial impact on potential denitrification. Furthermore, if both bPOC and suspended particulate matter (SPM) were considered as variables concurrently, the variability of NDR can be better predicted with a predictive power as high as 80%. Therefore, denitrifiers may preferentially utilize fresher and labile autochthonous POC instead of DOC especially in coastal waters where particles/colloids are abundant. Our results thus provide new insights for a better understanding of denitrification mechanisms in water columns and the importance of both suspended particles and POC components in regulating denitrification, especially in turbid and productive coastal environments.
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Affiliation(s)
- Jian Zeng
- College of Ocean and Earth Sciences, Xiamen University, Xiamen 361102, China.
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18
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Brezonik PL, Finlay JC, Griffin CG, Arnold WA, Boardman EH, Germolus N, Hozalski RM, Olmanson LG. Iron influence on dissolved color in lakes of the Upper Great Lakes States. PLoS One 2019; 14:e0211979. [PMID: 30759145 PMCID: PMC6373958 DOI: 10.1371/journal.pone.0211979] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2018] [Accepted: 01/24/2019] [Indexed: 11/18/2022] Open
Abstract
Colored dissolved organic matter (CDOM), a major component of the dissolved organic carbon (DOC) pool in many lakes, is an important controlling factor in lake ecosystem functioning. Absorption coefficients at 440 nm (a440, m-1), a common measure of CDOM, exhibited strong associations with dissolved iron (Fediss) and DOC in 280 lakes of the Upper Great Lakes States (UGLS: Minnesota, Wisconsin, and Michigan), as has been found in Scandinavia and elsewhere. Linear regressions between the three variables on UGLS lake data typically yielded R2 values of 0.6-0.9, suggesting that some underlying common processes influence organic matter and Fediss. Statistical and experimental evidence, however, supports only a minor role for iron contributions to a440 in UGLS lakes. Although both DOC and Fediss were significant variables in linear and log-log regressions on a440, DOC was the stronger predictor; adding Fediss to the linear a440-DOC model improved the R2 only from 0.90 to 0.93. Furthermore, experimental additions of FeIII to colored lake waters had only small effects on a440 (average increase of 0.242 m-1 per 100 μg/L of added FeIII). For 136 visibly stained waters (with a440 > 3.0 m-1), where allochthonous DOM predominates, DOM accounted for 92.3 ± 5.0% of the measured a440 values, and Fediss accounted for the remainder. In 75% of the lakes, Fediss accounted for < 10% of a440, but contributions of 15-30% were observed for 7 river-influenced lakes. Contributions of Fediss in UGLS lakes to specific UV absorbance at 254 nm (SUVA254) generally were also low. Although Fediss accounted for 5-10% of measured SUVA254 in a few samples, on average, 98.1% of the SUVA254 signal was attributable to DOM and only 1.9% to Fediss. DOC predictions from measured a440 were nearly identical to those from a440 corrected to remove Fediss contributions. Overall, variations in Fediss in most UGLS lakes have very small effects on CDOM optical properties, such as a440 and SUVA254, and negligible effects on the accuracy of DOC estimated from a440, data for which can be obtained at broad regional scales by remote sensing methods.
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Affiliation(s)
- Patrick L. Brezonik
- Department of Civil, Environmental, and Geo- Engineering, University of Minnesota, Minneapolis, MN, United States of America
- * E-mail:
| | - Jacques C. Finlay
- Department of Ecology, Evolution, and Behavior, University of Minnesota, St. Paul, MN, United States of America
| | - Claire G. Griffin
- Department of Ecology, Evolution, and Behavior, University of Minnesota, St. Paul, MN, United States of America
| | - William A. Arnold
- Department of Civil, Environmental, and Geo- Engineering, University of Minnesota, Minneapolis, MN, United States of America
| | - Evelyn H. Boardman
- Department of Ecology, Evolution, and Behavior, University of Minnesota, St. Paul, MN, United States of America
| | - Noah Germolus
- Department of Civil, Environmental, and Geo- Engineering, University of Minnesota, Minneapolis, MN, United States of America
| | - Raymond M. Hozalski
- Department of Civil, Environmental, and Geo- Engineering, University of Minnesota, Minneapolis, MN, United States of America
| | - Leif G. Olmanson
- Remote Sensing Laboratory, Department of Forest Resources, University of Minnesota, St. Paul, MN, United States of America
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19
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Dutta Majumdar R, Bliumkin L, Lane D, Soong R, Simpson M, Simpson AJ. Analysis of DOM phototransformation using a looped NMR system integrated with a sunlight simulator. WATER RESEARCH 2017; 120:64-76. [PMID: 28478296 DOI: 10.1016/j.watres.2017.04.067] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/15/2017] [Revised: 04/26/2017] [Accepted: 04/28/2017] [Indexed: 06/07/2023]
Abstract
Photochemical transformation plays an important role in functionalizing and degrading dissolved organic matter (DOM), producing one of the most complex mixtures known. In this study, using a flow-based design, nuclear magnetic resonance (NMR) spectroscopy is directly interfaced with a sunlight simulator enabling the study of DOM photodegradation in situ with high temporal resolution over 5 days. Samples from Suwannee River (Florida), Nordic Reservoir (Norway), and Pony Lake (Antarctic) are studied. Phototransformation of DOM is dominated by the degradation of aromatics and unsaturated structures (many arising from lignin) into carboxylated and hydroxylated products. To assess longer term changes, the samples were continuously irradiated for 17.5 days, followed by the identification a wide range of compounds and assessment of their fate using off-line 2D-NMR. This study demonstrates the applicability of the looped system to follow degradation in a non-targeted fashion (the mixture as a whole) and target analysis (tracing specific metabolites), which holds great potential to study the fate and transformation of contaminants and nutrients in the presence of DOM. It also demonstrates that components that remain unresolved in 1D NMR can be identified using 2D methods.
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Affiliation(s)
- Rudraksha Dutta Majumdar
- Environmental NMR Centre, Department of Physical and Environmental Sciences, University of Toronto Scarborough, Toronto, Ontario, M1C 1A4, Canada
| | - Liora Bliumkin
- Environmental NMR Centre, Department of Physical and Environmental Sciences, University of Toronto Scarborough, Toronto, Ontario, M1C 1A4, Canada
| | - Daniel Lane
- Environmental NMR Centre, Department of Physical and Environmental Sciences, University of Toronto Scarborough, Toronto, Ontario, M1C 1A4, Canada
| | - Ronald Soong
- Environmental NMR Centre, Department of Physical and Environmental Sciences, University of Toronto Scarborough, Toronto, Ontario, M1C 1A4, Canada
| | - Myrna Simpson
- Environmental NMR Centre, Department of Physical and Environmental Sciences, University of Toronto Scarborough, Toronto, Ontario, M1C 1A4, Canada
| | - André J Simpson
- Environmental NMR Centre, Department of Physical and Environmental Sciences, University of Toronto Scarborough, Toronto, Ontario, M1C 1A4, Canada.
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20
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Lin VS, Grandbois M, McNeill K. Fluorescent Molecular Probes for Detection of One-Electron Oxidants Photochemically Generated by Dissolved Organic Matter. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2017; 51:9033-9041. [PMID: 28723081 DOI: 10.1021/acs.est.7b02138] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
We report a dual probe system based on 4'-substituted biphenyl-2-carboxylic acids (BPAs) for analysis of photooxidants generated by dissolved organic matter. The BPA probes are converted to the corresponding benzocoumarins (BZCs) at different rates depending on the mechanism of oxidation; thus, two probes used simultaneously can differentiate strong triplet excited state sensitizers from hydroxylating species such as hydroxyl radical (•OH) present in dissolved organic matter (DOM). Comparison of the ratios of BZC-CH3 and BZC-CF3 product formation using model photooxidants such as NaNO2, a •OH precursor, and model triplet sensitizer lumichrome gave a range of 2 to 250. Application of these probes to DOM isolates and whole natural waters afforded intermediate ratios. Although the oxidation potential of BPAs (>ca. 1.80 V SHE) is significantly higher than the estimated average reduction potential of typical 3CDOM* samples, these results have demonstrated the presence of a small pool of oxidants in the selected DOM isolates and whole water samples that is capable of oxidizing aromatic carboxylates. As an analytical tool, this probe pair can be used between pH 4-6 without affecting the product formation ratio and may find applications in various systems involving complex mixtures of photochemically produced oxidants of differing natures.
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Affiliation(s)
- Vivian S Lin
- Institute of Biogeochemistry and Pollutant Dynamics, ETH Zurich , CH-8092, Zurich, Switzerland
| | - Matthew Grandbois
- The Dow Chemical Company , 455 Forest Street, Marlborough, Massachusetts 01568, United States
| | - Kristopher McNeill
- Institute of Biogeochemistry and Pollutant Dynamics, ETH Zurich , CH-8092, Zurich, Switzerland
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21
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Sun L, Xu C, Zhang S, Lin P, Schwehr KA, Quigg A, Chiu MH, Chin WC, Santschi PH. Light-induced aggregation of microbial exopolymeric substances. CHEMOSPHERE 2017; 181:675-681. [PMID: 28476007 DOI: 10.1016/j.chemosphere.2017.04.099] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/17/2016] [Revised: 04/10/2017] [Accepted: 04/21/2017] [Indexed: 06/07/2023]
Abstract
Sunlight can inhibit or disrupt the aggregation process of marine colloids via cleavage of high molecular weight compounds into smaller, less stable fragments. In contrast, some biomolecules, such as proteins excreted from bacteria can form aggregates via cross-linking due to photo-oxidation. To examine whether light-induced aggregation can occur in the marine environment, we conducted irradiation experiments on a well-characterized protein-containing exopolymeric substance (EPS) from the marine bacterium Sagitulla stellata. Our results show that after 1 h sunlight irradiation, the turbidity level of soluble EPS was 60% higher than in the dark control. Flow cytometry also confirmed that more particles of larger sized were formed by sunlight. In addition, we determined a higher mass of aggregates collected on filter in the irradiated samples. This suggests light can induce aggregation of this bacterial EPS. Reactive oxygen species hydroxyl radical and peroxide played critical roles in the photo-oxidation process, and salts assisted the aggregation process. The observation that Sagitulla stellata EPS with relatively high protein content promoted aggregation, was in contrast to the case where no significant differences were found in the aggregation of a non-protein containing phytoplankton EPS between the dark and light conditions. This, together with the evidence that protein-to-carbohydrate ratio of aggregates formed under light condition is significantly higher than that formed under dark condition suggest that proteins are likely the important component for aggregate formation. Light-induced aggregation provides new insights into polymer assembly, marine snow formation, and the fate/transport of organic carbon and nitrogen in the ocean.
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Affiliation(s)
- Luni Sun
- Department of Marine Science, Texas A&M University Galveston campus, Galveston, TX 77553, USA.
| | - Chen Xu
- Department of Marine Science, Texas A&M University Galveston campus, Galveston, TX 77553, USA
| | - Saijin Zhang
- Department of Marine Science, Texas A&M University Galveston campus, Galveston, TX 77553, USA
| | - Peng Lin
- Department of Marine Science, Texas A&M University Galveston campus, Galveston, TX 77553, USA
| | - Kathleen A Schwehr
- Department of Marine Science, Texas A&M University Galveston campus, Galveston, TX 77553, USA
| | - Antonietta Quigg
- Department of Marine Biology, Texas A&M University Galveston campus, Galveston, TX 77553, USA
| | - Meng-Hsuen Chiu
- Bioengineering Program, School of Engineering, University of California at Merced, Merced, CA 95343, USA
| | - Wei-Chun Chin
- Bioengineering Program, School of Engineering, University of California at Merced, Merced, CA 95343, USA
| | - Peter H Santschi
- Department of Marine Science, Texas A&M University Galveston campus, Galveston, TX 77553, USA
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22
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Lee YP, Fujii M, Kikuchi T, Terao K, Yoshimura C. Variation of iron redox kinetics and its relation with molecular composition of standard humic substances at circumneutral pH. PLoS One 2017; 12:e0176484. [PMID: 28453538 PMCID: PMC5409151 DOI: 10.1371/journal.pone.0176484] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2017] [Accepted: 04/11/2017] [Indexed: 11/18/2022] Open
Abstract
Oxidation and reduction kinetics of iron (Fe) and proportion of steady-state Fe(II) concentration relative to total dissolved Fe (steady-state Fe(II) fraction) were investigated in the presence of various types of standard humic substances (HS) with particular emphasis on the photochemical and thermal reduction of Fe(III) and oxidation of Fe(II) by dissolved oxygen (O2) and hydrogen peroxide (H2O2) at circumneutral pH (pH 7–8). Rates of Fe(III) reduction were spectrophotometrically determined by a ferrozine method under the simulated sunlight and dark conditions, whereas rates of Fe(II) oxidation were examined in air-saturated solution using luminol chemiluminescence technique. The reduction and oxidation rate constants were determined to substantially vary depending on the type of HS. For example, the first-order rate constants varied by up to 10-fold for photochemical reduction and 7-fold for thermal reduction. The degree of variation in Fe(II) oxidation was larger for the H2O2-mediated reaction compared to the O2-mediated reaction (e.g., 15- and 3-fold changes for the former and latter reactions, respectively, at pH 8). The steady-state Fe(II) fraction under the simulated sunlight indicated that the Fe(II) fraction varies by up to 12-fold. The correlation analysis indicated that variation of Fe(II) oxidation is significantly associated with aliphatic content of HS, suggesting that Fe(II) complexation by aliphatic components accelerates Fe(II) oxidation. The reduction rate constant and steady-state Fe(II) fractions in the presence of sunlight had relatively strong positive relations with free radical content of HS, possibly due to the reductive property of radical semiquinone in HS. Overall, the findings in this study indicated that the Fe reduction and oxidation kinetics and resultant Fe(II) formation are substantially influenced by chemical properties of HS.
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Affiliation(s)
- Ying Ping Lee
- Department of Civil and Environmental Engineering, School of Environment and Society, Tokyo Institute of Technology, Ookayama, Meguro-ku, Tokyo, Japan
| | - Manabu Fujii
- Department of Civil and Environmental Engineering, School of Environment and Society, Tokyo Institute of Technology, Ookayama, Meguro-ku, Tokyo, Japan
- * E-mail:
| | - Tetsuro Kikuchi
- Department of Civil and Environmental Engineering, School of Environment and Society, Tokyo Institute of Technology, Ookayama, Meguro-ku, Tokyo, Japan
- Ibaraki Kasumigaura Environmental Science Center, Okijyuku-machi, Tsuchiura, Ibaraki, Japan
| | - Koumei Terao
- Department of Civil and Environmental Engineering, School of Environment and Society, Tokyo Institute of Technology, Ookayama, Meguro-ku, Tokyo, Japan
| | - Chihiro Yoshimura
- Department of Civil and Environmental Engineering, School of Environment and Society, Tokyo Institute of Technology, Ookayama, Meguro-ku, Tokyo, Japan
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Liu R, Zhu X, Chen B. A New Insight of Graphene oxide-Fe(III) Complex Photochemical Behaviors under Visible Light Irradiation. Sci Rep 2017; 7:40711. [PMID: 28084446 PMCID: PMC5234028 DOI: 10.1038/srep40711] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2016] [Accepted: 12/09/2016] [Indexed: 11/09/2022] Open
Abstract
Graphene oxide (GO) contains not only aromatic carbon lattice but also carboxyl groups which enhanced the aqueous solubility of GO. To study the transformation of GO nanosheets in natural environments, GO aqueous dispersion was mixed with Fe3+ ions to form photoactive complex. Under visible light irradiation, Fe(III) of the complex would be reduced to Fe(II) which could subsequently reduce highly toxic Cr(VI) to Cr3+. The electron of the reduction was contributed by the decarboxylation of carboxyl groups on GO and iron was acting as a catalyst during the photoreduction. On the other hand, the consumption of carboxyl groups may convert GO to rGO which are tend to aggregate since the decreased electrostatic repulsion and the increased π-π attraction. The formed Cr3+ may be electrostatically adsorbed by the rGO sheets and simultaneously precipitated with the aggregated rGO sheets, resulting the effective removal of chromium and GO nanosheets from the aqueous environment. This study may shed a light on understanding the environmental transformation of GO and guide the treatment of Cr(VI).
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Affiliation(s)
- Renlan Liu
- Department of Environmental Science, Zhejiang University, Hangzhou, Zhejiang 310058, China
- Zhejiang Provincial Key Laboratory of Organic Pollutant Process and Control, Zhejiang University, China
| | - Xiaoying Zhu
- Department of Environmental Science, Zhejiang University, Hangzhou, Zhejiang 310058, China
- Zhejiang Provincial Key Laboratory of Organic Pollutant Process and Control, Zhejiang University, China
| | - Baoliang Chen
- Department of Environmental Science, Zhejiang University, Hangzhou, Zhejiang 310058, China
- Zhejiang Provincial Key Laboratory of Organic Pollutant Process and Control, Zhejiang University, China
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Perkola N, Vaalgamaa S, Jernberg J, Vähätalo AV. Degradation of artificial sweeteners via direct and indirect photochemical reactions. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2016; 23:13288-13297. [PMID: 27023816 DOI: 10.1007/s11356-016-6489-4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/23/2015] [Accepted: 03/16/2016] [Indexed: 06/05/2023]
Abstract
We studied the direct and indirect photochemical reactivity of artificial sweeteners acesulfame, saccharin, cyclamic acid and sucralose in environm entally relevant dilute aqueous solutions. Aqueous solutions of sweeteners were irradiated with simulated solar radiation (>290 nm; 96 and 168 h) or ultraviolet radiation (UVR; up to 24 h) for assessing photochemical reactions in surface waters or in water treatment, respectively. The sweeteners were dissolved in deionised water for examination of direct photochemical reactions. Direct photochemical reactions degraded all sweeteners under UVR but only acesulfame under simulated solar radiation. Acesulfame was degraded over three orders of magnitude faster than the other sweeteners. For examining indirect photochemical reactions, the sweeteners were dissolved in surface waters with indigenous dissolved organic matter or irradiated with aqueous solutions of nitrate (1 mg N/L) and ferric iron (2.8 mg Fe/L) introduced as sensitizers. Iron enhanced the photodegradation rates but nitrate and dissolved organic matter did not. UVR transformed acesulfame into at least three products: iso-acesulfame, hydroxylated acesulfame and hydroxypropanyl sulfate. Photolytic half-life was one year for acesulfame and more than several years for the other sweeteners in surface waters under solar radiation. Our study shows that the photochemical reactivity of commonly used artificial sweeteners is variable: acesulfame may be sensitive to photodegradation in surface waters, while saccharin, cyclamic acid and sucralose degrade very slowly even under the energetic UVR commonly used in water treatment.
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Affiliation(s)
- Noora Perkola
- Finnish Environment Institute (SYKE), Laboratory Centre, Hakuninmaantie 6, FI-00430, Helsinki, Finland.
| | - Sanna Vaalgamaa
- Department of Environmental Sciences, University of Helsinki, P.O. Box 65 (Viikinkaari 1), FI-00014, Helsinki, Finland
- Sito Oy, Tuulikuja 2, FI-02100, Espoo, Finland
| | - Joonas Jernberg
- Department of Environmental Sciences, University of Helsinki, Niemenkatu 73, FI-15140, Lahti, Finland
- Ordior Oy, Konalantie 47 A, FI-00390, Helsinki, Finland
| | - Anssi V Vähätalo
- Department of Environmental Sciences, University of Helsinki, P.O. Box 65 (Viikinkaari 1), FI-00014, Helsinki, Finland
- Department of Biological and Environmental Science, University of Jyväskylä, P.O. Box 35 (Survontie 9), FI-40014, Jyväskylä, Finland
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Ward CP, Cory RM. Complete and Partial Photo-oxidation of Dissolved Organic Matter Draining Permafrost Soils. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2016; 50:3545-53. [PMID: 26910810 DOI: 10.1021/acs.est.5b05354] [Citation(s) in RCA: 73] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Photochemical degradation of dissolved organic matter (DOM) to carbon dioxide (CO2) and partially oxidized compounds is an important component of the carbon cycle in the Arctic. Thawing permafrost soils will change the chemical composition of DOM exported to arctic surface waters, but the molecular controls on DOM photodegradation remain poorly understood, making it difficult to predict how inputs of thawing permafrost DOM may alter its photodegradation. To address this knowledge gap, we quantified the susceptibility of DOM draining the shallow organic mat and the deeper permafrost layer of arctic soils to complete and partial photo-oxidation and investigated changes in the chemical composition of each DOM source following sunlight exposure. Permafrost and organic mat DOM had similar lability to photomineralization despite substantial differences in initial chemical composition. Concurrent losses of carboxyl moieties and shifts in chemical composition during photodegradation indicated that photodecarboxylation could account for 40-90% of DOM photomineralized to CO2. Permafrost DOM had a higher susceptibility to partial photo-oxidation compared to organic mat DOM, potentially due to a lower abundance of phenolic moieties with antioxidant properties. These results suggest that photodegradation will likely continue to be an important control on DOM fate in arctic freshwaters as the climate warms and permafrost soils thaw.
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Affiliation(s)
- Collin P Ward
- Department of Earth and Environmental Sciences, 2534 C.C. Little Building, 1100 North University Avenue, University of Michigan , Ann Arbor, Michigan 48109, United States
| | - Rose M Cory
- Department of Earth and Environmental Sciences, 2534 C.C. Little Building, 1100 North University Avenue, University of Michigan , Ann Arbor, Michigan 48109, United States
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Timko SA, Gonsior M, Cooper WJ. Influence of pH on fluorescent dissolved organic matter photo-degradation. WATER RESEARCH 2015; 85:266-74. [PMID: 26342180 DOI: 10.1016/j.watres.2015.08.047] [Citation(s) in RCA: 48] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/30/2015] [Revised: 08/03/2015] [Accepted: 08/25/2015] [Indexed: 05/26/2023]
Abstract
A novel semi-continuous excitation emission matrix (EEM) fluorescence and absorbance monitoring system has been developed. Full EEMs were collected simultaneously with absorbance spectra every 20 min during 24 h solar-simulated irradiation experiments, and the kinetic change of fluorescence of Suwannee River natural organic matter IHSS standard material (SRNOM) at various pH values was investigated. Parallel factor analysis (PARAFAC) was then used to isolate the photo-labile and pH-influenced fluorescent components of SRNOM. Kinetic analysis showed increasing rates of fluorescence loss with increasing pH. This has significant implications for the photo-degradation of dissolved natural organic matter during estuarine mixing, when large increases of pH are common. The influence of pH on fluorescence and photo-degradation kinetics emphasizes the need for pH to be monitored and accurately controlled during laboratory experiments. It is also highly recommended that when constructing PARAFAC models or monitoring changes in fluorescence data between samples of different origins, that the pH be held constant to remove any potential artifacts or misinterpretation of data.
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Affiliation(s)
- Stephen A Timko
- Department of Civil and Environmental Engineering, University of California, Irvine, Irvine, CA 92697-2175, USA.
| | - Michael Gonsior
- University of Maryland Center for Environmental Science, Chesapeake Biological Laboratory, 146 Williams Street, Solomons, MD 20688, USA.
| | - William J Cooper
- Department of Civil and Environmental Engineering, University of California, Irvine, Irvine, CA 92697-2175, USA.
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Fu L, Zhao Z, Ma J, Hu X. Cavity-confined acceleration of iron cycle for the Fenton-like reaction by β-CD-benzoquinone host–guest complex under visible irradiation. CATAL COMMUN 2015. [DOI: 10.1016/j.catcom.2015.02.012] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022] Open
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Ng TW, Chow AT, Wong PK. Dual roles of dissolved organic matter in photo-irradiated Fe(III)-contained waters. J Photochem Photobiol A Chem 2014. [DOI: 10.1016/j.jphotochem.2014.06.011] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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Cory RM, Ward CP, Crump BC, Kling GW. Sunlight controls water column processing of carbon in arctic fresh waters. Science 2014; 345:925-8. [DOI: 10.1126/science.1253119] [Citation(s) in RCA: 340] [Impact Index Per Article: 34.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
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Chow AT, Díaz FJ, Wong KH, O'Geen AT, Dahlgren RA, Wong PK. Photochemical and bacterial transformations of disinfection by-product precursors in water. JOURNAL OF ENVIRONMENTAL QUALITY 2013; 42:1589-1595. [PMID: 24216437 DOI: 10.2134/jeq2013.01.0022] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
In situ grab sampling from source waters and water extraction from source materials are common methods for determining disinfection by-product (DBP) formation potential (FP) of water samples or reactivity of dissolved organic matter (DOM) in forming DBPs during chlorination. However, DOM, as the main DBP precursor, collected using these techniques may not represent the DOM reacting with disinfectants due to biogeochemical alterations during water conveyance to drinking water treatment facilities. In this study, we exposed leachates from fresh litter and associated decomposed duff to natural sunlight or K-12 for 14 d and evaluated the changes, if any, on the propensity to form trihalomethane (THM), haloacetonitrile (HAN), and chloral hydrate (CHD) during chlorination. Sunlight treatment did not significantly change dissolved organic carbon (DOC) concentration but caused a 24 to 43% decrease in the specific ultraviolet absorbance (SUVA) at 254 nm, indicating that UV-active chromophores were transformed or degraded. There were significant increases ( < 0.05) in specific HAN formation potential (HAN-FP) and specific CHD formation potential (CHD-FP) (i.e., HAN and CHD formation potentials per unit carbon), but no change in specific THM formation potential (THM-FP) after sunlight exposure. In contrast, bacterial treatment did not show any significant effect on SUVA, specific chlorine demand, or any specific DBP-FPs, although bacterial colony counts suggested DOM in leachates was utilized for bacterial growth. Results of this study confirmed that the reactivity of DOM in forming DBPs could be different after biogeochemical processes compared with its source materials. For this study, photochemical reactions had a greater effect on DBP-FPs than did microbial degradation.
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Hou WC, Stuart B, Howes R, Zepp RG. Sunlight-driven reduction of silver ions by natural organic matter: formation and transformation of silver nanoparticles. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2013; 47:7713-7721. [PMID: 23731169 DOI: 10.1021/es400802w] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Photobiogeochemical reactions involving metal species can be a source of naturally occurring nanoscale materials in the aquatic environment. This study demonstrates that, under simulated sunlight exposure, ionic Ag is photoreduced in river water or synthetic natural water samples that contain natural organic matter (NOM), forming Ag nanoparticles (AgNPs) that transform in size and shape and precipitate out upon extended irradiation. We show that the dissolved oxygen concentration does not appear to affect AgNP formation rates, indicating that reactive transients such as superoxide, hydrated electron, and triplet NOM do not play a large role. By varying pH and NOM concentrations and adding competing cations on the AgNP formation, we present three lines of evidence to show that Ag ion photoreduction likely involves ionic Ag binding to NOM. Our work suggests that photochemical reactions involving ionic Ag and NOM can be a source of nanosized Ag in the environment.
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Affiliation(s)
- Wen-Che Hou
- National Research Council Associate, National Exposure Research Laboratory, Ecosystems Research Division, United States Environmental Protection Agency, Athens, Georgia 30605, USA.
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Mostofa KMG, Liu CQ, Minakata D, Wu F, Vione D, Mottaleb MA, Yoshioka T, Sakugawa H. Photoinduced and Microbial Degradation of Dissolved Organic Matter in Natural Waters. PHOTOBIOGEOCHEMISTRY OF ORGANIC MATTER 2013. [DOI: 10.1007/978-3-642-32223-5_4] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/10/2023]
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Mostofa KMG, Liu CQ, Yoshioka T, Vione D, Zhang Y, Sakugawa H. Fluorescent Dissolved Organic Matter in Natural Waters. PHOTOBIOGEOCHEMISTRY OF ORGANIC MATTER 2013. [DOI: 10.1007/978-3-642-32223-5_6] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
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Mostofa KMG, Liu CQ, Feng X, Yoshioka T, Vione D, Pan X, Wu F. Complexation of Dissolved Organic Matter with Trace Metal Ions in Natural Waters. PHOTOBIOGEOCHEMISTRY OF ORGANIC MATTER 2013. [DOI: 10.1007/978-3-642-32223-5_9] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
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Haverstock S, Sizmur T, Murimboh J, O'Driscoll NJ. Modeling the photo-oxidation of dissolved organic matter by ultraviolet radiation in freshwater lakes: implications for mercury bioavailability. CHEMOSPHERE 2012; 88:1220-1226. [PMID: 22521995 DOI: 10.1016/j.chemosphere.2012.03.073] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/05/2012] [Revised: 03/25/2012] [Accepted: 03/27/2012] [Indexed: 05/31/2023]
Abstract
Uncertainties in projected ultraviolet (UV) radiation may lead to future increases in UV irradiation of freshwater lakes. Because dissolved organic carbon (DOC) is the main binding phase for mercury (Hg) in freshwater lakes, an increase in DOC photo-oxidation may affect Hg speciation and bioavailability. We quantified the effect of DOC concentration on the rate of abiotic DOC photo-oxidation for five lakes (DOC=3.27-12.3 mg L(-1)) in Kejimkujik National Park, Canada. Samples were irradiated with UV-A or UV-B radiation over a 72-h period. UV-B radiation was found to be 2.36 times more efficient at photo-oxidizing DOC than UV-A, with energy-normalized rates of dissolved inorganic carbon (DIC) production ranging from 3.8×10(-5) to 1.1×10(-4) mg L(-1)J(-1) for UV-A, and from 6.0×10(-5) to 3.1×10(-4) mg L(-1)J(-1) for UV-B. Energy normalized rates of DIC production were positively correlated with DOC concentrations. Diffuse integrated attenuation coefficients were quantified in situ (UV-A K(d)=0.056-0.180 J cm(-1); UV-B K(d)=0.015-0.165 J cm(-1)) and a quantitative depth-integrated model for yearly DIC photo-production in each lake was developed. The model predicts that, UV-A produces between 3.2 and 100 times more DIC (1521-2851 mg m(-2) year(-1)) than UV-B radiation (29.17-746.7 mg m(-2) year(-1)). Future increases in UV radiation may increase DIC production and increase Hg bioavailability in low DOC lakes to a greater extent than in high DOC lakes.
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Affiliation(s)
- Sarah Haverstock
- Department of Earth & Environmental Science, Acadia University, Wolfville, NS, Canada
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37
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Meng F, Huang G, Li Z, Li S. Microbial Transformation of Structural and Functional Makeup of Human-Impacted Riverine Dissolved Organic Matter. Ind Eng Chem Res 2012. [DOI: 10.1021/ie300504d] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Fangang Meng
- School of Environmental
Science and Engineering, Sun Yat-sen University, and Guangdong Provincial Key Laboratory of Environmental Pollution Control and Remediation Technology, Guangzhou 510275, P.R. China
| | - Guocheng Huang
- School of Environmental
Science and Engineering, Sun Yat-sen University, and Guangdong Provincial Key Laboratory of Environmental Pollution Control and Remediation Technology, Guangzhou 510275, P.R. China
| | - Zengquan Li
- School of Environmental
Science and Engineering, Sun Yat-sen University, and Guangdong Provincial Key Laboratory of Environmental Pollution Control and Remediation Technology, Guangzhou 510275, P.R. China
| | - Shiyu Li
- School of Environmental
Science and Engineering, Sun Yat-sen University, and Guangdong Provincial Key Laboratory of Environmental Pollution Control and Remediation Technology, Guangzhou 510275, P.R. China
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38
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Aarnos H, Ylöstalo P, Vähätalo AV. Seasonal phototransformation of dissolved organic matter to ammonium, dissolved inorganic carbon, and labile substrates supporting bacterial biomass across the Baltic Sea. ACTA ACUST UNITED AC 2012. [DOI: 10.1029/2010jg001633] [Citation(s) in RCA: 68] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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39
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de Bruyn WJ, Clark CD, Pagel L, Takehara C. Photochemical production of formaldehyde, acetaldehyde and acetone from chromophoric dissolved organic matter in coastal waters. J Photochem Photobiol A Chem 2011. [DOI: 10.1016/j.jphotochem.2011.10.002] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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Hur J, Jung KY, Schlautman MA. Altering the characteristics of a leaf litter-derived humic substance by adsorptive fractionation versus simulated solar irradiation. WATER RESEARCH 2011; 45:6217-6226. [PMID: 21962456 DOI: 10.1016/j.watres.2011.09.023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/15/2011] [Revised: 09/05/2011] [Accepted: 09/10/2011] [Indexed: 05/31/2023]
Abstract
Changes in the characteristics of a leaf litter-derived humic substance (LLHS) that resulted from its adsorption onto kaolinite or exposure to simulated solar irradiation were tracked using selected spectroscopic descriptors, apparent weight-average molecular weight (MW(w)) and pyrene binding. Heterogeneity within the original bulk LLHS was confirmed by a range of different characteristics obtained from ultrafiltration-based size fractions. In general, trends of some changing LLHS characteristics were similar for the adsorption and irradiation processes when tracked against percent carbon removal. For example, the overall values of specific ultraviolet absorbance (SUVA), MW(w), and humification index (HIX) all decreased with increasing irradiation time and with increasing concentration of mineral adsorbent in the respective experiments, indicating that both processes resulted in less aromatic and smaller-sized LLHS components remaining in solution. In addition, both the adsorption and irradiation experiments resulted in enrichment of the relative distribution of protein-like fluorescence (PLF), implying the PLF-related components had low affinities for phototransformation and mineral surface adsorption. Despite these apparently similar overall trends in LLHS characteristics caused by the adsorption and irradiation processes, closer examination revealed considerable differences in how the two processes altered the original material. Net production of intermediate-sized constituents was observed only with the irradiation experiments. In addition, residual LLHS resulting from the adsorptive fractionation experiments exhibited consistently higher pyrene binding versus the irradiated LLHS despite having comparable MW(w) values. Changes in LLHS characteristics due to adsorption by kaolinite were likely caused by physical mechanisms (primarily hydrophobic interactions between LLHS components and the kaolinite surface) whereas the irradiation-induced changes appear to have been governed by the combined effects of several alteration mechanisms, including the transformation of more condensed aromatic structures to less aromatic constituents, conformational changes resulting from selective photooxidation, and the photochemical disruption of intramolecular charge-transfer interactions.
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Affiliation(s)
- Jin Hur
- Department of Environment and Energy, Sejong University, Seoul 143-747, South Korea.
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41
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Song G, Xie H, Aubry C, Zhang Y, Gosselin M, Mundy CJ, Philippe B, Papakyriakou TN. Spatiotemporal variations of dissolved organic carbon and carbon monoxide in first-year sea ice in the western Canadian Arctic. ACTA ACUST UNITED AC 2011. [DOI: 10.1029/2010jc006867] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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42
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Zhang Y, Yin Y, Feng L, Zhu G, Shi Z, Liu X, Zhang Y. Characterizing chromophoric dissolved organic matter in Lake Tianmuhu and its catchment basin using excitation-emission matrix fluorescence and parallel factor analysis. WATER RESEARCH 2011; 45:5110-5122. [PMID: 21840562 DOI: 10.1016/j.watres.2011.07.014] [Citation(s) in RCA: 120] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/22/2011] [Revised: 07/06/2011] [Accepted: 07/11/2011] [Indexed: 05/31/2023]
Abstract
Chromophoric dissolved organic matter (CDOM) is an important optically active substance that transports nutrients, heavy metals, and other pollutants from terrestrial to aquatic systems and is used as a measure of water quality. To investigate how the source and composition of CDOM changes in both space and time, we used chemical, spectroscopic, and fluorescence analyses to characterize CDOM in Lake Tianmuhu (a drinking water source) and its catchment in China. Parallel factor analysis (PARAFAC) identified three individual fluorophore moieties that were attributed to humic-like and protein-like materials in 224 water samples collected between December 2008 and September 2009. The upstream rivers contained significantly higher concentrations of CDOM than did the lake water (a(350) of 4.27±2.51 and 2.32±0.59 m(-1), respectively), indicating that the rivers carried a substantial load of organic matter to the lake. Of the three main rivers that flow into Lake Tianmuhu, the Pingqiao River brought in the most CDOM from the catchment to the lake. CDOM absorption and the microbial and terrestrial humic-like components, but not the protein-like component, were significantly higher in the wet season than in other seasons, indicating that the frequency of rainfall and runoff could significantly impact the quantity and quality of CDOM collected from the catchment. The different relationships between the maximum fluorescence intensities of the three PARAFAC components, CDOM absorption, and chemical oxygen demand (COD) concentration in riverine and lake water indicated the difference in the composition of CDOM between Lake Tianmuhu and the rivers that feed it. This study demonstrates the utility of combining excitation-emission matrix fluorescence and PARAFAC to study CDOM dynamics in inland waters.
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Affiliation(s)
- Yunlin Zhang
- Taihu Lake Laboratory Ecosystem Research Station, State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing 210008, China.
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Porcal P, Amirbahman A, Kopáček J, Norton SA. Experimental photochemical release of organically bound aluminum and iron in three streams in Maine, USA. ENVIRONMENTAL MONITORING AND ASSESSMENT 2010; 171:71-81. [PMID: 20535548 DOI: 10.1007/s10661-010-1529-x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/12/2009] [Accepted: 04/01/2010] [Indexed: 05/29/2023]
Abstract
Laboratory photochemical experiments with stream water were done to characterize the photodegradation of dissolved organic carbon (DOC) and photochemical release of organically bound metals. The samples were collected from Bear Brook Watershed, Hadlock Brook, and Mud Pond Stream in Maine, USA, during January and April 2006. Filtered samples were irradiated in a reactor equipped with 350 nm irradiation lamps. Aliquots of irradiated samples were analyzed for DOC, dissolved aluminum (Al(d)) and iron (Fe(d)), pH, and UV-Vis spectra. Organically bound metals (Fe(o) and Al(o)) were measured after passing the sample through a column filled with a strong cation exchange resin (Dowex HCR-W2). UV radiation resulted in a decrease in DOC concentration and structural changes in DOC composition. UV-Vis spectra showed a decrease in aromaticity and molecular weight of DOC during irradiation. The DOC ranged from 0.1 to 0.35 mmol L(-1) at the beginning of experiments and decreased 5% to 37% after irradiation. Oxidation and structural changes in DOC resulted in the release of organically bound metals. Initial Fe(o) concentrations ranged from 0.16 to 0.79 μmol L(-1) and decreased 56% to 81% during the irradiation. The concentration of Al(o) ranged from 1.0 to 3.85 μmol L(-1) and declined steadily throughout the irradiation, resulting in 8% to 76% decline. Degradation of a small percentage of organically bound Al and Fe occurs rapidly enough so as to be an important process in first- and second-order streams. Irradiation energy absorbed by samples during hours of laboratory experiments equates to days in stream environment. Degradation of more refractory complexes occurs on a time scale that requires longer residence times, such as in lakes. This study demonstrated a strong impact of photochemical degradation of DOC on its metal-complexing ability and capacity. The results also suggest different binding properties of Fe and Al in their organic complexes.
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Affiliation(s)
- Petr Porcal
- Institute of Hydrobiology, Biology Centre of the AS CR, v.v.i., Na Sádkách 7, České Budějovice, 37005, Czech Republic.
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Yu C, Zhang Y, Quan X, Chen S, Han J, Ou X, Zhao J. Photochemical effect of humic acid components separated using molecular imprinting method applying porphyrin-like substances as templates in aqueous solution. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2010; 44:5812-5817. [PMID: 20608640 DOI: 10.1021/es100806d] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
To elucidate the relationship between photochemical functions with the structure of humic acids (HA), we developed a molecular imprinting method to separate the substances with given structure and investigated their photochemical behavior in aqueous solution. The substances with porphyrin-like core structure, such as chlorophyll or heme, were employed as template substances for preparing molecular imprinting polymers (MIP). The polymers were used to separate the substances with porphyrin-like structure from HA. Photochemical experiments were conducted to evaluate effects of the separated HA fractions on the photodegradation of coexisting organic pollutant. The results showed that all fractions bound by MIP accelerated photochemical degradation of coexisting 2,4-dichlorophenoxyacetic acid (2,4-D) under simulated sunlight (lambda>290 nm) irradiation, indicating that HA with porphyrin-like structure possesses better photoactivity than ones without the structure. The photochemical degradation of 2,4-D was enhanced when Fe(III), the ubiquitous element in natural aquatic systems, was added owing to the formation of Fe(III) complex with the HA. Electron paramagnetic resonance (EPR) spectra indicated that OH* and 1O2 radicals were generated in the solutions of HA fractions bound by MIP under simulated sunlight irradiation, implying that 2,4-D degradation could be related to oxidation reactions caused by reactive oxygen species (ROS).
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Affiliation(s)
- Chunyan Yu
- Key Laboratory of Industrial Ecology and Environmental Engineering (Ministry of Education), School of Environmental Science and Technology, Dalian University of Technology, Linggong Road 2, Dalian 116024, P. R. China
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Thorn KA, Younger SJ, Cox LG. Order of functionality loss during photodegradation of aquatic humic substances. JOURNAL OF ENVIRONMENTAL QUALITY 2010; 39:1416-28. [PMID: 20830929 DOI: 10.2134/jeq2009.0408] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
The time course photodegradation of the Nordic aquatic fulvic and humic acids and Suwannee River XAD-4 acids subjected to UV irradiation with an unfiltered medium pressure mercury lamp was studied by liquid-state 13C nuclear magnetic resonance. Photodecarboxylation was a significant pathway in all cases. Decreases in ketone, aromatic, and O-alkyl carbons were observed throughout the course of the irradiations, whereas C-alkyl carbons resisted photodegradation. Peaks attributable to the low-molecular-weight photodegradation products bicarbonate, formate, acetate, and succinate grew in intensity with irradiation time. The final products of the irradiations were decarboxylated, hydrophobic, predominantly C-alkyl and O-alkyl materials that were resistant to further photodegradation. The total amount of carbon susceptible to loss appeared to be related mainly to the total concentration of carbonyl and aromatic carbons and partly to the concentration of O-alkyl carbons in the fulvic, humic, and XAD-4 acids. The carbon losses for Nordic fulvic, Nordic Humic, Suwannee fulvic, and Suwannee XAD-4 acids were estimated to be 75, 63, 56, and 17%, respectively. More detailed analyses of the effects of irradiation on the carbonyl functionality in Nordic humic acid and Laurentian soil fulvic acid through reaction with hydroxylamine in conjunction with 15N nuclear magnetic resonance analysis confirmed preferential photodegradation of the quinone/hydroquinone functionality over ketone groups and the loss of ester groups in Laurentian fulvic acid.
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Affiliation(s)
- Kevin A Thorn
- U.S. Geological Survey, Denver Federal Center, MS 408, Denver, CO 80225-0046, USA.
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Zhang Y, Xie H, Fichot CG, Chen G. Dark production of carbon monoxide (CO) from dissolved organic matter in the St. Lawrence estuarine system: Implication for the global coastal and blue water CO budgets. ACTA ACUST UNITED AC 2008. [DOI: 10.1029/2008jc004811] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Yong Zhang
- Institut des Sciences de la Mer de Rimouski; Université du Québec à Rimouski; Rimouski, Québec Canada
- Yantai Institute of Coastal Zone Research for Sustainable Development; Chinese Academy of Sciences; Yantai China
| | - Huixiang Xie
- Institut des Sciences de la Mer de Rimouski; Université du Québec à Rimouski; Rimouski, Québec Canada
| | - Cédric G. Fichot
- Department of Marine Sciences; University of Georgia; Athens Georgia USA
| | - Guohua Chen
- College of Chemistry and Chemical Engineering; Ocean University of China; Qingdao China
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Wang Z, Ma W, Chen C, Zhao J. Photochemical coupling reactions between Fe(III)/Fe(II), Cr(VI)/Cr(III), and polycarboxylates: inhibitory effect of Cr species. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2008; 42:7260-7266. [PMID: 18939556 DOI: 10.1021/es801379j] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
The roles of chromium species on photochemical cycling of iron and mineralization of polycarboxylates are examined in the presence of Cr(VI) or Cr(III) at pH 2.2-4.0. Under UV irradiation, Cr(III) altered the redox equilibrium of iron species, leading to the shift of the photosteady state toward Fe(II). After a longer time of illumination, total organic carbon (TOC) approached a steady state in the presence of Cr(III) or Cr(VI), whereas oxalate was thoroughly mineralized in the absence of Cr species. The TOC of steady state was closely related to the kind of polycarboxylates, Cr species dosages, pH and O2 atmosphere, but hardly affected by more addition of Fe(III). ESI-MS data indicates that several Cr-oxalate complexes formed in the photochemical reactions, which are responsible for protecting oxalate against further oxidation. A mechanism is proposed for the inhibitory effect of Cr species on oxidation of oxalate and Fe(II). The present study may provide a new insight into the dual environmental effects induced by Cr contaminants especially at heavily chromium-contaminated and dissolved organic matter (DOM)-rich sites.
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Affiliation(s)
- Zhaohui Wang
- Beijing National Laboratory for Molecular Sciences, Key Laboratory of Photochemistry, Institute of Chemistry, The Chinese Academy of Sciences, Beijing 100190, China
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Ou X, Chen S, Quan X, Zhao H. Photoinductive activity of humic acid fractions with the presence of Fe(III): the role of aromaticity and oxygen groups involved in fractions. CHEMOSPHERE 2008; 72:925-931. [PMID: 18462778 DOI: 10.1016/j.chemosphere.2008.03.031] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/22/2008] [Revised: 03/16/2008] [Accepted: 03/17/2008] [Indexed: 05/26/2023]
Abstract
Relationship between the photoinductive activity and the properties of humic acids (HA) fractions were investigated with and without Fe(III). Three fractions were separated based on the molecular weight (M(w)) and were obtained following the order of M(w): F(A)>F(B)>F(C). Compared to F(A) and F(B), photodegradation of atrazine under simulated sunlight was much faster in solution containing F(C), whose structure was dominated by greater aromaticity, more oxygen groups and fluorophores. The interaction of HA fractions and Fe(III) was studied using fluorescence spectrometry and F(C) had the largest quenching constant. The capacity of electron transfer, estimated from the amount of photoformed Fe(II), was also highest for F(C). Thus, the Fe(III)-F(C) complex was efficient in phototransformation of atrazine in nearly neutral aqueous solutions. These results suggest that the aromaticity and oxygen groups content of HA exert great influence on the binding ability of metals and on the fate of pollutants in natural waters.
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Affiliation(s)
- Xiaoxia Ou
- Key Laboratory of Industrial Ecology and Environmental Engineering (Ministry of Education), School of Environmental and Biological Science and Technology, Dalian University of Technology, Dalian 116024, China
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Carvalho SIM, Otero M, Duarte AC, Santos EBH. Effects of solar radiation on the fluorescence properties and molecular weight of fulvic acids from pulp mill effluents. CHEMOSPHERE 2008; 71:1539-1546. [PMID: 18177918 DOI: 10.1016/j.chemosphere.2007.11.046] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/26/2007] [Revised: 11/17/2007] [Accepted: 11/19/2007] [Indexed: 05/25/2023]
Abstract
The pulp and paper industry generates large volume of wastewater that adversely affects water resources. Lignin derived macromolecular compounds, similar to natural humic substances, are the main waste products in the pulp mill effluents. The UV-Vis and fluorescence spectroscopies were used to assess the effect of solar exposition on fulvic acids from a kraft pulp mill effluent. Solar irradiation of the solutions of these fulvic acids caused solution acidification and decay both in the UV-Vis absorbance and in the fluorescence. This decay was not the same for the whole spectra but pointed to the selective photodegradation of lignin typical structures. Furthermore, by sequential ultrafiltration it was found that during irradiation, the high-molecular weight fractions were destroyed and low-molecular-weight constituents, potentially more able to penetrate the cell membranes of living organisms were formed. Photodegradation of macromolecular organic matter from a kraft pulp mill effluent may be a key process occurring in natural waters that modifies the physicochemical properties of such effluents.
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Affiliation(s)
- Sandra I M Carvalho
- CESAM and Department of Chemistry, University of Aveiro, 3810-193 Aveiro, Portugal
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Rodríguez-Zúñiga UF, Milori DMBP, da Silva WTL, Martin-Neto L, Oliveira LC, Rocha JC. Changes in optical properties caused by UV-irradiation of aquatic humic substances from the amazon river basin: seasonal variability evaluation. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2008; 42:1948-1953. [PMID: 18409619 DOI: 10.1021/es702156n] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
Aquatic humic substances (AHS) isolated from two characteristic seasons of the Negro river, winter and summer corresponding to floody and dry periods, were structurally characterized by 13C nuclear magnetic ressonance. Subsequently, AHS aqueous solutions were irradiated with a polychromatic lamp (290-475 nm) and monitored by its total organic carbon (TOC) content, ultraviolet-visible (UV-vis) absorbance, fluorescence, and Fourier transformed infrared spectroscopy (FTIR). As a result, a photobleaching up to 80% after irradiation of 48 h was observed. Conformational rearrangements and formation of low molecular complexity structures were formed during the irradiation, as deduced from the pH decrement and the fluorescence shifting to lower wavelengths. Additionally a significant mineralization with the formation of CO2, CO, and inorganic carbon compounds was registered, as assumed by TOC losses of up to 70%. The differences in photodegradation between samples expressed by photobleaching efficiency were enhanced in the summer sample and related to its elevated aromatic content. Aromatic structures are assumed to have high autosensitization capacity effects mediated by the free radical generation from quinone and phenolic moieties.
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