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Laglera LM, Uskaikar H, Klaas C, Naqvi SWA, Wolf-Gladrow DA, Tovar-Sánchez A. Dissolved and particulate iron redox speciation during the LOHAFEX fertilization experiment. MARINE POLLUTION BULLETIN 2022; 184:114161. [PMID: 36179387 DOI: 10.1016/j.marpolbul.2022.114161] [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: 07/14/2022] [Revised: 09/15/2022] [Accepted: 09/17/2022] [Indexed: 06/16/2023]
Abstract
The redox speciation of iron was determined during the iron fertilization LOHAFEX and for the first time, the chemiluminescence assay of filtered and unfiltered samples was systematically compared. We hypothesize that higher chemiluminescence in unfiltered samples was caused by Fe(II) adsorbed onto biological particles. Dissolved and particulate Fe(II) increased in the mixed layer steadily 6-fold during the first two weeks and decreased back to initial levels by the end of LOHAFEX. Both Fe(II) forms did not show diel cycles downplaying the role of photoreduction. The chemiluminescence of unfiltered samples across the patch boundaries showed strong gradients, correlated significantly to biomass and the photosynthetic efficiency and were higher at night, indicative of a biological control. At 150 m deep, a secondary maximum of dissolved Fe(II) was associated with maxima of nitrite and ammonium despite high oxygen concentrations. We hypothesize that during LOHAFEX, iron redox speciation was mostly regulated by trophic interactions.
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Affiliation(s)
- Luis M Laglera
- FI-TRACE, Departamento de Química, Universidad de las Islas Baleares, Palma, Balearic Islands 07122, Spain; Laboratori Interdisciplinari sobre Canvi Climàtic, Universidad de las Islas Baleares, Palma, Balearic Islands 07122, Spain.
| | - Hema Uskaikar
- National Institute of Oceanography, Dona Paula, Goa, India
| | - Christine Klaas
- Alfred Wegener Institute for Polar and Marine Research, Am Handelshafen 12, 27570 Bremerhaven, Germany
| | | | - Dieter A Wolf-Gladrow
- Alfred Wegener Institute for Polar and Marine Research, Am Handelshafen 12, 27570 Bremerhaven, Germany
| | - Antonio Tovar-Sánchez
- Department of Ecology and Coastal Management, Andalusian Institute for Marine Science, ICMAN (CSIC), Campus Universitario Río San Pedro, Puerto Real, Cádiz, Spain
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2
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Santana-Casiano JM, González-Santana D, Devresse Q, Hepach H, Santana-González C, Quack B, Engel A, González-Dávila M. Exploring the Effects of Organic Matter Characteristics on Fe(II) Oxidation Kinetics in Coastal Seawater. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2022; 56:2718-2728. [PMID: 35077144 PMCID: PMC8851691 DOI: 10.1021/acs.est.1c04512] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/06/2021] [Revised: 01/10/2022] [Accepted: 01/11/2022] [Indexed: 06/14/2023]
Abstract
The iron(II) oxidation kinetic process was studied at 25 stations in coastal seawater of the Macaronesia region (9 around Cape Verde, 11 around the Canary Islands, and 5 around Madeira). In a physicochemical context, experiments were carried out to study the pseudo-first-order oxidation rate constant (k', min-1) over a range of pH (7.8, 7.9, 8.0, and 8.1) and temperature (10, 15, 20, and 25 °C). Deviations from the calculated kcal' at the same T, pH, and S were observed for most of the stations. The measured t1/2 (ln 2/k', min) values at the 25 stations ranged from 1.82 to 3.47 min (mean 1.93 ± 0.76 min) and for all but two stations were lower than the calculated t1/2 of 3.21 ± 0.2 min. In a biogeochemical context, nutrients and variables associated with the organic matter spectral properties (CDOM and FDOM) were analyzed to explain the observed deviations. The application of a multilinear regression model indicated that k' can be described (R = 0.921 and SEE = 0.064 for pH = 8 and T = 25 °C) from a linear combination of three organic variables, k'OM = kcal' -0.11* TDN + 29.9*bDOM + 33.4*C1humic, where TDN is the total dissolved nitrogen, bDOM is the spectral peak obtained from colored dissolved organic matter (DOM) analysis when protein-like or tyrosine-like components are present, and C1humic is the component associated with humic-like compounds obtained from the parallel factor analysis of the fluorescent DOM. Results show that compounds with N in their structures mainly explain the observed k' increase for most of the samples, although other components could also play a relevant role. Experimentally, k' provides the net result between the compounds that accelerate the process and those that slow it down.
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Affiliation(s)
- J. Magdalena Santana-Casiano
- Instituto
de Oceanografía y Cambio Global, Universidad de Las Palmas de Gran Canaria, Campus de Tafira, 35017 Las Palmas, Spain
| | - David González-Santana
- Instituto
de Oceanografía y Cambio Global, Universidad de Las Palmas de Gran Canaria, Campus de Tafira, 35017 Las Palmas, Spain
- Université
de Brest, CNRS, IRD, Ifremer, LEMAR, F-29280 Plouzane, France
| | - Quentin Devresse
- GEOMAR—Helmholtz
Centre for Ocean Research Kiel, Düsternbrooker Weg 20, 24105 Kiel, Germany
| | - Helmke Hepach
- GEOMAR—Helmholtz
Centre for Ocean Research Kiel, Düsternbrooker Weg 20, 24105 Kiel, Germany
| | - Carolina Santana-González
- Instituto
de Oceanografía y Cambio Global, Universidad de Las Palmas de Gran Canaria, Campus de Tafira, 35017 Las Palmas, Spain
| | - Birgit Quack
- GEOMAR—Helmholtz
Centre for Ocean Research Kiel, Düsternbrooker Weg 20, 24105 Kiel, Germany
| | - Anja Engel
- GEOMAR—Helmholtz
Centre for Ocean Research Kiel, Düsternbrooker Weg 20, 24105 Kiel, Germany
| | - Melchor González-Dávila
- Instituto
de Oceanografía y Cambio Global, Universidad de Las Palmas de Gran Canaria, Campus de Tafira, 35017 Las Palmas, Spain
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3
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Nakaya Y, Nakashima S, Otsuka T. Gas Cell Infrared and Attenuated Total Reflection Infrared Spectroscopic Studies for Organic-Inorganic Interactions in Adsorption of Fulvic Acid on the Goethite Surface Generating Carbon Dioxide. APPLIED SPECTROSCOPY 2021; 75:1114-1123. [PMID: 33464151 DOI: 10.1177/0003702821991219] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
The generation of carbon dioxide (CO2) from Nordic fulvic acid (FA) solution in the presence of goethite (α-FeOOH) was observed in FA-goethite interaction experiments at 25-80 ℃. CO2 generation processes observed by gas cell infrared (IR) spectroscopy indicated two steps: the zeroth order slower CO2 generation from FA solution commonly occurring in the heating experiments of the FA in the presence and absence of goethite (activation energy: 16-19 kJ mol-1), and the first order faster CO2 generation from FA solution with goethite (activation energy: 14 kJ mol-1). This CO2 generation from FA is possibly related to redox reactions between FA and goethite. In situ attenuated total reflection infrared (ATR-IR) spectroscopic measurements indicated rapid increases with time in IR bands due to COOH and COO- of FA on the goethite surface. These are considered to be due to adsorption of FA on the goethite surface possibly driven by electrostatic attraction between the positively charged goethite surface and negatively charged deprotonated carboxylates (COO-) in FA. Changes in concentration of the FA adsorbed on the goethite surface were well reproduced by the second order reaction model giving an activation energy around 13 kJ mol-1. This process was faster than the CO2 generation and was not its rate-determining step. The CO2 generation from FA solution with goethite is faster than the experimental thermal decoloration of stable structures of Nordic FA in our previous report possibly due to partial degradations of redox-sensitive labile structures in FA.
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Affiliation(s)
- Yuki Nakaya
- Learning Support Center, 47731Setsunan University, Neyagawa-shi, Japan
- Department of Earth and Space Science, Graduate School of Science, 13013Osaka University, Toyonaka-shi, Japan
| | - Satoru Nakashima
- Department of Earth and Space Science, Graduate School of Science, 13013Osaka University, Toyonaka-shi, Japan
- Research Institute for Natural Environment, Science and Technology (RINEST), Suita-shi, Japan
- Faculty of Environmental and Urban Engineering, 12860Kansai University, Suita-shi, Japan
| | - Takahiro Otsuka
- Department of Earth and Space Science, Graduate School of Science, 13013Osaka University, Toyonaka-shi, Japan
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4
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Yang F, Tang C, Antonietti M. Natural and artificial humic substances to manage minerals, ions, water, and soil microorganisms. Chem Soc Rev 2021; 50:6221-6239. [PMID: 34027951 DOI: 10.1039/d0cs01363c] [Citation(s) in RCA: 66] [Impact Index Per Article: 22.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The chemistry of humic substances (HSs) occurs hidden from our sight, but is of key importance to agriculture and the environment, and nowadays even to medicine and technology. HSs are nowadays not only natural, but extracted and engineered, and in the past 20 years such products have been widely used in soil improvement and environment governance. In this review, we collate and summarize the applications and working principles of such HSs in agriculture and environmental ecology, mainly to elaborate the multiple roles of this functional polymer along with physical chemical quantification. Then several of the latest synthesis technologies, including hydrothermal humification technology (HTH), hydrothermal carbonization technology (HTC) and hydrogen peroxide oxidation technology (HOT) are presented, which were introduced to prepare artificial humic substances (A-HSs). The availability of reproducible and tunable synthetic A-HSs is a new chemical tool, and effects such as solubilization of insoluble phosphorus minerals, recovery of phosphorus, improvement of soil fertility for crop growth and reduction of toxicity of typical pollutants, can now be analyzed in detail and quantified. As a result, we can provide an effective chemical technology for utilizing biomass side products ("biowaste") to generate A-HSs of different types, thus realizing improvement in agricultural production and control of environmental pollution by the macro-synthesis of A-HSs-.
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Affiliation(s)
- Fan Yang
- Joint Laboratory of Northeast Agricultural University and Max Planck Institute of Colloids and Interfaces (NEAU-MPICI), Harbin 150030, China. and School of Water Conservancy and Civil Engineering, Northeast Agricultural University, Harbin 150030, China
| | - Chunyu Tang
- Joint Laboratory of Northeast Agricultural University and Max Planck Institute of Colloids and Interfaces (NEAU-MPICI), Harbin 150030, China. and School of Water Conservancy and Civil Engineering, Northeast Agricultural University, Harbin 150030, China
| | - Markus Antonietti
- Max Planck Institute of Colloids and Interfaces, Department of Colloid Chemistry, 14476 Potsdam, Germany.
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5
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Krachler R, Krachler RF. Northern High-Latitude Organic Soils As a Vital Source of River-Borne Dissolved Iron to the Ocean. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2021; 55:9672-9690. [PMID: 34251212 DOI: 10.1021/acs.est.1c01439] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Organic soils in the Arctic-boreal region produce small aquatic humic ligands (SAHLs), a category of naturally occurring complexing agents for iron. Every year, large amounts of SAHLs-loaded with iron mobilized in river basins-reach the oceans via river runoff. Recent studies have shown that a fraction of SAHLs belong to the group of strong iron-binding ligands in the ocean. That means, their Fe(III) complexes withstand dissociation even under the conditions of extremely high dilution in the open ocean. Fe(III)-loaded SAHLs are prone to UV-photoinduced ligand-to-metal charge-transfer which leads to disintegration of the complex and, as a consequence, to enhanced concentrations of bioavailable dissolved Fe(II) in sunlit upper water layers. On the other hand, in water depths below the penetration depth of UV, the Fe(III)-loaded SAHLs are fairly resistant to degradation which makes them ideally suited as long-lived molecular transport vehicles for river-derived iron in ocean currents. At locations where SAHLs are present in excess, they can bind to iron originating from various sources. For example, SAHLs were proposed to contribute substantially to the stabilization of hydrothermal iron in deep North Atlantic waters. Recent discoveries have shown that SAHLs, supplied by the Arctic Great Rivers, greatly improve dissolved iron concentrations in the Arctic Ocean and the North Atlantic Ocean. In these regions, SAHLs play a critical role in relieving iron limitation of phytoplankton, thereby supporting the oceanic sink for anthropogenic CO2. The present Critical Review describes the most recent findings and highlights future research directions.
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Affiliation(s)
- Regina Krachler
- Institute of Inorganic Chemistry, University of Vienna, Althanstrasse 14, 1090 Vienna, Austria; http://anorg-chemie.univie.ac.at
| | - Rudolf F Krachler
- Institute of Inorganic Chemistry, University of Vienna, Althanstrasse 14, 1090 Vienna, Austria; http://anorg-chemie.univie.ac.at
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6
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Gonzalez DH, Diaz DA, Baumann JP, Ghio AJ, Paulson SE. Effects of albumin, transferrin and humic-like substances on iron-mediated OH radical formation in human lung fluids. Free Radic Biol Med 2021; 165:79-87. [PMID: 33486087 DOI: 10.1016/j.freeradbiomed.2021.01.021] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/02/2020] [Revised: 01/01/2021] [Accepted: 01/10/2021] [Indexed: 11/21/2022]
Abstract
Inhalation of particulate matter is hypothesized to contribute to health effects by overproducing reactive oxygen species (ROS) and inducing oxidative stress. Fe(II) has been shown to contribute to ROS generation in acellular simulated lung fluids. Atmospheric humic-like substances (HULIS) have been shown to chelate Fe(II) and significantly enhance this ROS generation. Here, we investigate Fe(II)-mediated .OH generation from the iron active proteins in lung fluid, albumin and transferrin, and fulvic acid, a surrogate for HULIS, in human bronchoalveolar lavage fluid (BALF). We find that albumin enhances .OH generation from inorganic Fe(II) and that transferrin attenuates this enhancement. We estimate the rate constants for albumin-Fe(II) and fulvic acid-Fe(II) mediated O2.- reduction (1.9 ± 0.3) M-1 s-1 and (2.7 ± 0.3) M-1s-1 (pH = 5.5, T = 37 °C), 17-25 times the rate for free iron, which we measured to be (110 ± 20) × 10-3 M-1s-1, in agreement with the literature. .OH generation measured from fulvic acid-Fe(II) in BALF from 8 individuals with added fulvic acid is successfully predicted rates of .OH generation by mixtures of Fe(II), albumin, transferrin, fulvic acid, and ascorbate in saline solution. This indicates that fulvic acid enhances .OH formation in BALF, and that albumin and transferrin in BALF moderate the effect. We propose that fulvic acid, and thereby HULIS, is capable of mobilizing Fe(II) away from albumin and transferrin and this increases the formation rate of O2.- and ultimately of .OH. Furthermore, we find that albumin and transferrin have significantly different impacts on Fe(II)-mediated .OH than citrate, a common component of simulated lung fluids, a factor that should be considered carefully in the interpretation of results obtained from solutions containing citrate.
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Affiliation(s)
- David H Gonzalez
- University of California at Los Angeles, Department of Atmospheric and Oceanic Sciences, 405 Hilgard Ave., Los Angeles, CA, 90405, USA
| | - David A Diaz
- California State University, Northridge Department of Environmental & Occupational Health, 18111 Nordhoff St, Northridge, CA, 91330, USA
| | - J Puna Baumann
- California State University, Northridge Department of Environmental & Occupational Health, 18111 Nordhoff St, Northridge, CA, 91330, USA
| | - Andrew J Ghio
- US Environmental Protection Agency, Chapel Hill, NC, 27599, USA
| | - Suzanne E Paulson
- University of California at Los Angeles, Department of Atmospheric and Oceanic Sciences, 405 Hilgard Ave., Los Angeles, CA, 90405, USA.
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7
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Zhang P, Van Cappellen P, Pi K, Yuan S. Oxidation of Fe(II) by Flavins under Anoxic Conditions. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2020; 54:11622-11630. [PMID: 32812763 DOI: 10.1021/acs.est.0c02916] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Flavin-mediated electron transfer is an important pathway for Fe(III) reduction by dissimilatory iron-reducing bacteria. Although the mechanisms and kinetics of Fe(III) reduction by reduced flavins have been widely studied, the reaction between Fe(II) and oxidized flavins is rarely investigated. Results of this study show that under anoxic conditions, Fe(II) can be oxidized by the oxidized forms of riboflavin (RBF) and flavin mononucleotide (FMN) at pH 7-9. For instance, at pH 9, 73% of 17.8 μM Fe(II) was oxidized by 10 μM RBF within 20 min. Both the rate and extent of oxidation increased with increasing concentrations of oxidized flavins and increasing solution pH. Thermodynamic calculations and kinetic analyses implied that the oxidation of Fe(II) proceeded predominantly via the autodecomposition of Fe2+-RBF- and Fe2+-FMN- complexes, along with minor contributions from direct oxidation of Fe(II) by flavins and flavin radicals. Our findings suggest that the reoxidation of Fe(II) by oxidized flavins may be a rate-controlling factor in microbial Fe(III) reduction via flavin-mediated electron transfer.
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Affiliation(s)
- Peng Zhang
- State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, 68 Jincheng Street, East Lake High-Tech Development Zone, Wuhan, Hubei 430078, P. R. China
| | - Philippe Van Cappellen
- Ecohydrology Research Group, Water Institute and Department of Earth and Environmental Sciences, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada
| | - Kunfu Pi
- Ecohydrology Research Group, Water Institute and Department of Earth and Environmental Sciences, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada
| | - Songhu Yuan
- State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, 68 Jincheng Street, East Lake High-Tech Development Zone, Wuhan, Hubei 430078, P. R. China
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8
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Drozdova OY, Aleshina AR, Tikhonov VV, Lapitskiy SA, Pokrovsky OS. Coagulation of organo-mineral colloids and formation of low molecular weight organic and metal complexes in boreal humic river water under UV-irradiation. CHEMOSPHERE 2020; 250:126216. [PMID: 32087384 DOI: 10.1016/j.chemosphere.2020.126216] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/03/2019] [Revised: 02/11/2020] [Accepted: 02/13/2020] [Indexed: 06/10/2023]
Abstract
Photodegradation of dissolved organic matter (DOM) is highly important in humic waters of peatland regions, yet the coupling between organic and organo-mineral colloids, trace metals and bioavailability of photodegraded products is poorly known. Here we studied photo-destruction of organo-mineral colloids induced by UV-irradiation of sterile-filtered mire water. We revealed two simultaneously occurring processes of transformation of DOM and trace elements speciation: (i) disintegration of high molecular weight organo-mineral colloids into lower molecular weight (<1 kDa) DOM and metal complexes and (ii) formation of particulate (>0.22 μm) aggregates of metals and organic matter. Over 26 days of UV-irradiation, up to 20% of dissolved organic carbon from peat waters was transformed into CO2. In addition to transformation of organic compounds, sizeable change in speciation and size fractionation of many trace metals such as Fe, Pb, Cd, Co, Zn, Cu, V, La, Ni and Cr occurred. Although short-term (1 day) UV-irradiation of mire water stimulated growth of cultivable Pseudomonas sp. bacterium, the long-term exposure (26 days) of organic substrate had a negative effect on bacterial development. Therefore, while sizeable transformation of the organic and metal colloidal load of peat water may occur over first 10 days of UV-irradiation, the enhanced bioavailability of UV-treated substrate is achieved after first day of exposure. The present study demonstrates the importance of even short-term UV-irradiation on colloidal transformation and potential bioavailability of humic waters from temperate mires and highlights the need for more detailed study of coupled metal-organic matter transformation induced by sunlight exposure of mire waters.
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Affiliation(s)
- O Yu Drozdova
- Geological Faculty, Moscow State University, Leninskie Gory 1, 119234, Moscow, Russia.
| | - A R Aleshina
- Geological Faculty, Moscow State University, Leninskie Gory 1, 119234, Moscow, Russia; Scientific Geoinformation Center of Russian Academy of Sciences, New Arbat 11/1, 119019, Moscow, Russia
| | - V V Tikhonov
- Faculty of Soil Science, Moscow State University, Leninskie Gory 1/12, 119234, Moscow, Russia
| | - S A Lapitskiy
- Geological Faculty, Moscow State University, Leninskie Gory 1, 119234, Moscow, Russia
| | - O S Pokrovsky
- Geoscience and Environment Toulouse, UMR 5563 CNRS, University of Toulouse, 14 Avenue Edouard Belin, 31400, Toulouse, France; Institute of Ecological Problems of the North, N. Laverov Federal Center for Integrated Arctic Research, Nab. Severnoi Dviny 23, 163000, Arkhangelsk, Russia; BIO-GEO-CLIM Laboratory, Tomsk State University, Lenina Pr. 35, 634050, Tomsk, Russia
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9
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Lueder U, Jørgensen BB, Kappler A, Schmidt C. Fe(III) Photoreduction Producing Fe aq2+ in Oxic Freshwater Sediment. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2020; 54:862-869. [PMID: 31886652 DOI: 10.1021/acs.est.9b05682] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Iron(III) (Fe(III)) photoreduction plays an important role in Fe cycling and Fe(II) bioavailability in the upper ocean. Although well described for water columns, it is currently unknown to what extent light impacts the production of dissolved Fe(II) (Fe2+) in aquatic sediments. We performed high-resolution voltammetric microsensor measurements and demonstrated light-induced Fe2+ release in freshwater sediments from Lake Constance. Fe2+ concentrations increased up to 40 μM in the top 3 mm of the sediment during illumination in the visible range of light (400-700 nm), even in the presence of oxygen (100-280 μM). The Fe2+ release was strongly dependent on the organic matter content of the sediment. A lack of photoreduced Fe2+ was measured in sediments with concentrations of organic carbon <6 mg L-1. The simultaneous presence of sedimentary Fe(III) photoreduction besides microbial and abiotic Fe2+ oxidation by oxygen suggests an active Fe redox cycling in the oxic and photic zone of aquatic sediments. Here, we provide evidence for a relevant contribution of Fe(III) photoreduction to the bio-geochemical Fe redox cycle in aquatic freshwater sediments.
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Affiliation(s)
- Ulf Lueder
- Geomicrobiology Group, Center for Applied Geoscience (ZAG) , University of Tuebingen , Sigwartstrasse 10 , D-72076 Tuebingen , Germany
| | - Bo Barker Jørgensen
- Center for Geomicrobiology, Department of Bioscience , Aarhus University , Ny Munkegade 114, Building 1540 , 8000 Aarhus , Denmark
| | - Andreas Kappler
- Geomicrobiology Group, Center for Applied Geoscience (ZAG) , University of Tuebingen , Sigwartstrasse 10 , D-72076 Tuebingen , Germany
- Center for Geomicrobiology, Department of Bioscience , Aarhus University , Ny Munkegade 114, Building 1540 , 8000 Aarhus , Denmark
| | - Caroline Schmidt
- Geomicrobiology Group, Center for Applied Geoscience (ZAG) , University of Tuebingen , Sigwartstrasse 10 , D-72076 Tuebingen , Germany
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10
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Lueder U, Jørgensen BB, Kappler A, Schmidt C. Photochemistry of iron in aquatic environments. ENVIRONMENTAL SCIENCE. PROCESSES & IMPACTS 2020; 22:12-24. [PMID: 31904051 DOI: 10.1039/c9em00415g] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Light energy is a driver for many biogeochemical element cycles in aquatic systems. The sunlight-induced photochemical reduction of ferric iron (Fe(iii) photoreduction) to ferrous iron (Fe(ii)) by either direct ligand-to-metal charge transfer or by photochemically produced radicals can be an important source of dissolved Feaq2+ in aqueous and sedimentary environments. Reactive oxygen species (ROS) are formed by a variety of light-dependent reactions. Those ROS can oxidize Fe(ii) or reduce Fe(iii), and due to their high reactivity they are key oxidants in aquatic systems where they influence many other biogeochemical cycles. In oxic waters with circumneutral pH, the produced Fe(ii) reaches nanomolar concentrations and serves as a nutrient, whereas in acidic waters, freshwater and marine sediments, which are rich in Fe(ii), the photochemically formed Fe(ii) can reach concentrations of up to 100 micromolar and be used as additional electron donor for acidophilic aerobic, microaerophilic, phototrophic and, if nitrate is present, for nitrate-reducing Fe(ii)-oxidizing bacteria. Therefore, Fe(iii) photoreduction may not only control the primary productivity in the oceans but has a tremendous impact on Fe cycling in the littoral zone of freshwater and marine environments. In this review, we summarize photochemical reactions involving Fe, discuss the role of ROS in Fe cycling, and highlight the importance of photoreductive processes in the environment.
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Affiliation(s)
- Ulf Lueder
- Geomicrobiology Group, Center for Applied Geoscience (ZAG), University of Tuebingen, Sigwartstrasse 10, D-72076 Tuebingen, Germany.
| | - Bo Barker Jørgensen
- Center for Geomicrobiology, Department of Bioscience, Aarhus University, Ny Munkegade 114, Building 1540, 8000 Aarhus, Denmark
| | - Andreas Kappler
- Geomicrobiology Group, Center for Applied Geoscience (ZAG), University of Tuebingen, Sigwartstrasse 10, D-72076 Tuebingen, Germany. and Center for Geomicrobiology, Department of Bioscience, Aarhus University, Ny Munkegade 114, Building 1540, 8000 Aarhus, Denmark
| | - Caroline Schmidt
- Geomicrobiology Group, Center for Applied Geoscience (ZAG), University of Tuebingen, Sigwartstrasse 10, D-72076 Tuebingen, Germany.
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11
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Xing G, Garg S, Waite TD. Is Superoxide-Mediated Fe(III) Reduction Important in Sunlit Surface Waters? ENVIRONMENTAL SCIENCE & TECHNOLOGY 2019; 53:13179-13190. [PMID: 31638396 DOI: 10.1021/acs.est.9b04718] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Two major pathways are reported to account for photochemical reduction of Fe(III) in sunlit surface waters, namely, ligand-to-metal charge transfer (LMCT) and superoxide-mediated iron reduction (SMIR). In this study, we investigate the impact of Fe(III) speciation (organically complexed (Fe(III)L versus iron oxyhydroxide (AFO)) on Fe(III) reducibility by photogenerated superoxide (O2•-) and LMCT. To simulate conditions typical of fresh, estuarine, and coastal waters, we have used Suwannee River Fulvic Acid (SRFA) as a representative of the natural organic matter likely to associate with Fe(III). Our results show that the photolabile Fe(III)SRFA complex is reduced rapidly by LMCT, while O2•- does not play a role in reduction of these entities. In contrast, the relatively less photolabile AFO is reduced by both O2•- and LMCT. The reduction of AFO by O2•- occurs following the dissolution of AFO, and hence, the contribution of O2•- to reductive dissolution of AFO is dependent on conditions such as the age of the AFO and initial AFO concentration affecting the rate of dissolution of AFO. Our results further show that while colloidal Fe(III) (in this work, particles >0.025 μm) is reduced by O2•-, there is no involvement of O2•- in dissolved Fe(III) reduction. Overall, our results show that superoxide-mediated iron reduction will be important only in natural waters containing limited concentrations of Fe binding ligands.
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Affiliation(s)
- Guowei Xing
- School of Civil and Environmental Engineering , The University of New South Wales , Sydney , NSW 2052 , Australia
| | - Shikha Garg
- School of Civil and Environmental Engineering , The University of New South Wales , Sydney , NSW 2052 , Australia
| | - T David Waite
- School of Civil and Environmental Engineering , The University of New South Wales , Sydney , NSW 2052 , Australia
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Peng C, Sundman A, Bryce C, Catrouillet C, Borch T, Kappler A. Oxidation of Fe(II)-Organic Matter Complexes in the Presence of the Mixotrophic Nitrate-Reducing Fe(II)-Oxidizing Bacterium Acidovorax sp. BoFeN1. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2018; 52:5753-5763. [PMID: 29671587 DOI: 10.1021/acs.est.8b00953] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Fe(II)-organic matter (Fe(II)-OM) complexes are abundant in the environment and may play a key role for the behavior of Fe and pollutants. Mixotrophic nitrate-reducing Fe(II)-oxidizing bacteria (NRFeOx) reduce nitrate coupled to the oxidation of organic compounds and Fe(II). Fe(II) oxidation may occur enzymatically or abiotically by reaction with nitrite that forms during heterotrophic denitrification. However, it is unknown whether Fe(II)-OM complexes can be oxidized by NRFeOx. We used cell-suspension experiments with the mixotrophic nitrate-reducing Fe(II)-oxidizing bacterium Acidovorax sp. strain BoFeN1 to reveal the role of nonorganically bound Fe(II) (aqueous Fe(II)) and nitrite for the rates and extent of oxidation of Fe(II)-OM complexes (Fe(II)-citrate, Fe(II)-EDTA, Fe(II)-humic acid, and Fe(II)-fulvic acid). We found that Fe(II)-OM complexation inhibited microbial nitrate-reducing Fe(II) oxidation; large colloidal and negatively charged complexes showed lower oxidation rates than aqueous Fe(II). Accumulation of nitrite and fast abiotic oxidation of Fe(II)-OM complexes only happened in the presence of aqueous Fe(II) that probably interacted with (nitrite-reducing) enzymes in the periplasm causing nitrite accumulation in the periplasm and outside of the cells, whereas Fe(II)-OM complexes probably could not enter the periplasm and cause nitrite accumulation. These results suggest that Fe(II) oxidation by mixotrophic nitrate reducers in the environment depends on Fe(II) speciation, and that aqueous Fe(II) potentially plays a critical role in regulating microbial denitrification processes.
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Affiliation(s)
- Chao Peng
- Geomicrobiology, Center for Applied Geoscience , University of Tuebingen , Sigwartstrasse 10 , 72076 Tuebingen , Germany
| | - Anneli Sundman
- Geomicrobiology, Center for Applied Geoscience , University of Tuebingen , Sigwartstrasse 10 , 72076 Tuebingen , Germany
| | - Casey Bryce
- Geomicrobiology, Center for Applied Geoscience , University of Tuebingen , Sigwartstrasse 10 , 72076 Tuebingen , Germany
| | | | - Thomas Borch
- Department of Soil and Crop Sciences , Colorado State University , Fort Collins , Colorado 80523 , United States
- Department of Chemistry , Colorado State University , Fort Collins , Colorado 80523 , United States
| | - Andreas Kappler
- Geomicrobiology, Center for Applied Geoscience , University of Tuebingen , Sigwartstrasse 10 , 72076 Tuebingen , Germany
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