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Bega JMM, Saltarelli WA, Gücker B, Boëchat IG, Finkler NR, Cunha DGF. Effects of riparian vegetation restoration and environmental context on ecosystem functioning in tropical streams of southeastern Brazil. THE SCIENCE OF THE TOTAL ENVIRONMENT 2024; 948:174906. [PMID: 39034000 DOI: 10.1016/j.scitotenv.2024.174906] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/15/2024] [Revised: 07/15/2024] [Accepted: 07/18/2024] [Indexed: 07/23/2024]
Abstract
Tropical stream ecosystems are under increasing human pressure, making the development of effective restoration approaches and expanding knowledge in this field urgent. This study evaluated the impact of riparian vegetation restoration and environmental context on stream ecosystem functioning by measuring key ecosystem functions - gross primary production (GPP), ecosystem respiration (ER), and nutrient uptake of ammonium and soluble reactive phosphorus - across ten tropical streams in southeastern Brazil. The streams represented a gradient from clearcut areas (impacted reaches) to relatively pristine conditions (reference reaches), including intermediate stages of vegetation recovery (restored reaches). In the short-term (~15-20 years after restoration), restoration led to reduced GPP akin to reference reaches. Yet, ER did not show the anticipated increase, suggesting a longer timeframe is necessary for restored streams to emulate the functional characteristics of reference reaches. Additionally, the restored reaches did not achieve the nutrient uptake efficiencies observed in both impacted and reference reaches, pointing to a partial recovery of ecosystem function. This study suggests that while riparian vegetation restoration contributes positively to certain aspects of stream function, environmental variables less related to this type of restoration, such as discharge and hydromorphology, significantly influence stream ecosystem functioning, highlighting the importance of considering environmental context in restoration efforts. A more holistic approach, possibly encompassing broader hydromorphological and habitat enhancements, is needed to fully restore ecological processes in these vital ecosystems. These insights are critical for informing future tropical stream restoration projects, advocating the use of ecosystem function metrics as comprehensive indicators of ecological recovery and restoration success.
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Affiliation(s)
- João M M Bega
- Department of Hydraulics and Sanitation, São Carlos School of Engineering, University of São Paulo, São Carlos, SP, Brazil.
| | - Wesley A Saltarelli
- Department of Hydraulics and Sanitation, São Carlos School of Engineering, University of São Paulo, São Carlos, SP, Brazil
| | - Björn Gücker
- Department of Geosciences, Federal University of São João del-Rei, MG, Brazil
| | - Iola G Boëchat
- Department of Geosciences, Federal University of São João del-Rei, MG, Brazil
| | - Nicolas R Finkler
- Department of Ecology and Environmental Science, Umeå University, Umeå, Sweden
| | - Davi G F Cunha
- Department of Hydraulics and Sanitation, São Carlos School of Engineering, University of São Paulo, São Carlos, SP, Brazil
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Malin JT, Kaushal SS, Mayer PM, Maas CM, Hohman SP, Rippy MA. Longitudinal stream synoptic (LSS) monitoring to evaluate water quality in restored streams. ENVIRONMENTAL MONITORING AND ASSESSMENT 2024; 196:437. [PMID: 38592553 PMCID: PMC11069387 DOI: 10.1007/s10661-024-12570-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/17/2023] [Accepted: 03/23/2024] [Indexed: 04/10/2024]
Abstract
Impervious surface cover increases peak flows and degrades stream health, contributing to a variety of hydrologic, water quality, and ecological symptoms, collectively known as the urban stream syndrome. Strategies to combat the urban stream syndrome often employ engineering approaches to enhance stream-floodplain reconnection, dissipate erosive forces from urban runoff, and enhance contaminant retention, but it is not always clear how effective such practices are or how to monitor for their effectiveness. In this study, we explore applications of longitudinal stream synoptic (LSS) monitoring (an approach where multiple samples are collected along stream flowpaths across both space and time) to narrow this knowledge gap. Specifically, we investigate (1) whether LSS monitoring can be used to detect changes in water chemistry along longitudinal flowpaths in response to stream-floodplain reconnection and (2) what is the scale over which restoration efforts improve stream quality. We present results for four different classes of water quality constituents (carbon, nutrients, salt ions, and metals) across five watersheds with varying degrees of stream-floodplain reconnection. Our work suggests that LSS monitoring can be used to evaluate stream restoration strategies when implemented at meter to kilometer scales. As streams flow through restoration features, concentrations of nutrients, salts, and metals significantly decline (p < 0.05) or remain unchanged. This same pattern is not evident in unrestored streams, where salt ion concentrations (e.g., Na+, Ca2+, K+) significantly increase with increasing impervious cover. When used in concert with statistical approaches like principal component analysis, we find that LSS monitoring reveals changes in entire chemical mixtures (e.g., salts, metals, and nutrients), not just individual water quality constituents. These chemical mixtures are locally responsive to restoration projects, but can be obscured at the watershed scale and overwhelmed during storm events.
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Affiliation(s)
- Joseph T Malin
- Department of Geology & Earth System Science Interdisciplinary Center, University of Maryland, College Park, MD, 20742, USA.
- Environmental Quality Resources, L.L.C., 2391 Brandermill Blvd., Suite 301, Gambrills, MD, 21054, USA.
| | - Sujay S Kaushal
- Department of Geology & Earth System Science Interdisciplinary Center, University of Maryland, College Park, MD, 20742, USA
| | - Paul M Mayer
- Environmental Protection Agency, 805 SW Broadway #500, Portland, OR, 97205, USA
| | - Carly M Maas
- Department of Geology & Earth System Science Interdisciplinary Center, University of Maryland, College Park, MD, 20742, USA
- United States Geological Survey, 1730 E Parham Road, Richmond, VA, 23228, USA
| | - Steven P Hohman
- Environmental Protection Agency, 1650 Arch St, Philadelphia, PA, 19103, USA
| | - Megan A Rippy
- Occoquan Watershed Monitoring Laboratory, The Charles E. Via, Jr. Department of Civil and Environmental Engineering, Virginia Tech, 9408 Prince William Street, Manassas, VA, USA
- Center for Coastal Studies, Virginia Tech, 1068A Derring Hall (0420), Blacksburg, VA, USA
- Disaster Resilience and Risk Management (DRRM), 1068A Derring Hall, 405 Perry Street, Blacksburg, VA, 24061, USA
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Deng Y, Shao Z, Dang C, Huang X, Wu W, Zhuang Q, Ding Q. Assessing urban wetlands dynamics in Wuhan and Nanchang, China. THE SCIENCE OF THE TOTAL ENVIRONMENT 2023; 901:165777. [PMID: 37524189 DOI: 10.1016/j.scitotenv.2023.165777] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/04/2023] [Revised: 07/06/2023] [Accepted: 07/23/2023] [Indexed: 08/02/2023]
Abstract
Urban wetlands play a crucial role in sustainable social development. However, current research mainly focuses on specific wetland types, and fine extraction of urban wetlands remains a challenge. This study proposes a fine extraction framework based on hierarchical decision trees and shape features for urban wetlands, using Sentinel-2 remote sensing data to obtain detailed wetland data of Wuhan and Nanchang from 2016 to 2022. Our framework applies random forests to classify land cover, extracts urban fine wetlands by hierarchical decision trees and shape features, and assesses the dynamics of wetlands in the two cities. We also analyzed and discussed the characteristics of urban wetlands in the two cities. The results show that wetland accuracies of Wuhan and Nanchang are greater than 84.5 % and 82.9 %, respectively. The wetland areas of Wuhan in 2016, 2019, and 2022 are 1969.4 km2, 1713.8 km2, and 1681.1 km2, while those in Nanchang are 1405.9 km2, 1361.6 km2, and 766.9 km2. Inland wetlands are the main wetland types in both regions, with lake wetlands accounting for the highest proportion (over 40 %). The urban wetlands in the two cities exhibit different spatial and temporal evolution patterns, with varying change trends of wetland area and the structural proportions of fine wetlands. Besides, Wuhan's urban wetlands are primarily located in the south, while Nanchang's urban wetlands are concentrated in the east, exhibiting higher spatial and temporal dynamics. Analysis suggests that the reduced urban wetlands from 2016 to 2022 are related to fluctuating decreasing precipitation, growing population, and gross domestic product (GDP). Our study provides support for the conservation of urban wetland resources in Wuhan and Nanchang and highlights the need for targeted management strategies.
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Affiliation(s)
- Ying Deng
- State Key Laboratory of Information Engineering in Surveying, Mapping and Remote Sensing, Wuhan University, Wuhan 430079, China
| | - Zhenfeng Shao
- State Key Laboratory of Information Engineering in Surveying, Mapping and Remote Sensing, Wuhan University, Wuhan 430079, China.
| | - Chaoya Dang
- State Key Laboratory of Information Engineering in Surveying, Mapping and Remote Sensing, Wuhan University, Wuhan 430079, China
| | - Xiao Huang
- Department of Geosciences, University of Arkansas, Fayetteville, AR 72701, USA
| | - Wenfu Wu
- School of Remote Sensing and Information Engineering, Wuhan University, Wuhan 430079, China
| | - Qingwei Zhuang
- State Key Laboratory of Information Engineering in Surveying, Mapping and Remote Sensing, Wuhan University, Wuhan 430079, China
| | - Qing Ding
- State Key Laboratory of Information Engineering in Surveying, Mapping and Remote Sensing, Wuhan University, Wuhan 430079, China
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Kaushal SS, Reimer JE, Mayer PM, Shatkay RR, Maas CM, Nguyen WD, Boger WL, Yaculak AM, Doody TR, Pennino MJ, Bailey NW, Galella JG, Weingrad A, Collison DC, Wood KL, Haq S, Johnson TAN, Duan S, Belt KT. Freshwater Salinization Syndrome Alters Retention and Release of 'Chemical Cocktails' along Flowpaths: from Stormwater Management to Urban Streams. FRESHWATER SCIENCE (PRINT) 2022; 41:420-441. [PMID: 36213200 PMCID: PMC9533665 DOI: 10.1086/721469] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
We investigate impacts of Freshwater Salinization Syndrome (FSS) on mobilization of salts, nutrients, and metals in urban streams and stormwater BMPs by analyzing original data on concentrations and fluxes of salts, nutrients, and metals from 7 urban watersheds in the Mid-Atlantic U.S. and synthesizing literature data. We also explore future critical research needs through a survey of practitioners and scientists. Our original data show: (1) sharp pulses in concentrations of salt ions and metals in urban streams directly following both road salt events and stream restoration construction (e.g., similar to the way concentrations increase during other soil disturbance activities); (2) sharp declines in pH (acidification) in response to road salt applications due to mobilization of H+ from soil exchange sites by Na+; (3) sharp increases in organic matter from microbial and algal sources (based on fluorescence spectroscopy) in response to road salt applications likely due to lysing cells and/or changes in solubility; (4) significant retention (~30-40%) of Na+ in stormwater BMP sediments and floodplains in response to salinization; (5) increased ion exchange and mobilization of diverse salt ions (Na+, Ca2+, K+, Mg2+), nutrients (N, P), and trace metals (Cu, Sr) from stormwater BMPs and restored streams in response to FSS; (6) downstream increasing loads of Cl-, SO4 2-, Br-, F-, and I- along flowpaths through urban streams, and P release from urban stormwater BMPs in response to salinization, and (7) a significant annual reduction (> 50%) in Na+ concentrations in an urban stream when road salt applications were dramatically reduced, which suggests potential for ecosystem recovery. We compared our original results to published metrics of contaminant retention and release across a broad range of stormwater management BMPs from North America and Europe. Overall, urban streams and stormwater management BMPs consistently retain Na+ and Cl- but mobilize multiple contaminants based on salt types and salinity levels. Finally, we present our top 10 research questions regarding FSS impacts on urban streams and stormwater management BMPs. Reducing diverse 'chemical cocktails' of contaminants mobilized by freshwater salinization is now a priority for effectively and holistically restoring urban waters.
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Affiliation(s)
- Sujay S Kaushal
- Department of Geology & Earth System Science Interdisciplinary Center, University of Maryland, College Park, Maryland 20740, USA
| | - Jenna E Reimer
- US Environmental Protection Agency, Office of Research and Development, Center for Public Health and Environmental Assessment, Pacific Ecological Systems Division, Corvallis, Oregon, 97333, USA
| | - Paul M Mayer
- Department of Geology & Earth System Science Interdisciplinary Center, University of Maryland, College Park, Maryland 20740, USA
| | - Ruth R Shatkay
- Department of Geology & Earth System Science Interdisciplinary Center, University of Maryland, College Park, Maryland 20740, USA
| | - Carly M Maas
- Department of Geology & Earth System Science Interdisciplinary Center, University of Maryland, College Park, Maryland 20740, USA
| | - William D Nguyen
- Department of Geology & Earth System Science Interdisciplinary Center, University of Maryland, College Park, Maryland 20740, USA
| | - Walter L Boger
- Department of Geology & Earth System Science Interdisciplinary Center, University of Maryland, College Park, Maryland 20740, USA
| | - Alexis M Yaculak
- Department of Geology & Earth System Science Interdisciplinary Center, University of Maryland, College Park, Maryland 20740, USA
| | - Thomas R Doody
- Department of Geology & Earth System Science Interdisciplinary Center, University of Maryland, College Park, Maryland 20740, USA
| | - Michael J Pennino
- US Environmental Protection Agency, Office of Research and Development, Center for Public Health and Environmental Assessment, Integrate Environmental Assessment Branch, 1200 Pennsylvania Ave, NW, Washington, D.C. 20460, USA
| | - Nathan W Bailey
- Department of Geology & Earth System Science Interdisciplinary Center, University of Maryland, College Park, Maryland 20740, USA
| | - Joseph G Galella
- Department of Geology & Earth System Science Interdisciplinary Center, University of Maryland, College Park, Maryland 20740, USA
| | - Aaron Weingrad
- Department of Geology & Earth System Science Interdisciplinary Center, University of Maryland, College Park, Maryland 20740, USA
| | - Daniel C Collison
- Department of Geology & Earth System Science Interdisciplinary Center, University of Maryland, College Park, Maryland 20740, USA
| | - Kelsey L Wood
- Department of Geology & Earth System Science Interdisciplinary Center, University of Maryland, College Park, Maryland 20740, USA
| | - Shahan Haq
- Department of Geology & Earth System Science Interdisciplinary Center, University of Maryland, College Park, Maryland 20740, USA
| | - Tamara A Newcomer Johnson
- US Environmental Protection Agency, Center for Environmental Measurement and Modeling, Watershed and Ecosystem Characterization Division, 26 W. Martin Luther King Drive, Cincinnati, Ohio 45268, USA
| | - Shuiwang Duan
- Department of Geology & Earth System Science Interdisciplinary Center, University of Maryland, College Park, Maryland 20740, USA
| | - Kenneth T Belt
- Department of Geography and Environmental Systems, University of Maryland Baltimore County, 1000 Hilltop Circle, Baltimore, Maryland 21250, USA
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Lorah MM, Vogler E, Gebhardt FE, Graves D, Grabowski JF. Enhanced bioremediation of RDX and Co-Contaminants perchlorate and nitrate using an anaerobic dehalogenating consortium in a fractured rock aquifer. CHEMOSPHERE 2022; 294:133674. [PMID: 35065174 DOI: 10.1016/j.chemosphere.2022.133674] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/21/2021] [Revised: 01/15/2022] [Accepted: 01/16/2022] [Indexed: 06/14/2023]
Abstract
The potential neurotoxic and carcinogenic effects of the explosives compound RDX (hexahydro-1,3,5-trinitro-1,3,5-triazine) on human health requires groundwater remediation strategies to meet low cleanup goals. Bioremediation of RDX is feasible through biostimulation of native microbes with an organic carbon donor but may be less efficient, or not occur at all, in the presence of the common co-contaminants perchlorate and nitrate. Laboratory tests compared biostimulation with bioaugmentation to achieve anaerobic degradation of RDX, perchlorate, and nitrate; a field pilot test was then conducted in a fractured rock aquifer with the selected bioaugmentation approach. Insignificant reduction of RDX, perchlorate, or nitrate was observed by the native microbes in microcosms, with or without biostimulation by addition of lactate. Tests of the RDX-degrading ability of the microbial consortium WBC-2, originally developed for dehalogenation of chlorinated volatile organic compounds, showed first-order biodegradation rate constants ranging from 0.57 to 0.90 per day (half-lives 1.2 to 0.80 days). WBC-2 sustained degradation without daughter product accumulation when repeatedly amended with RDX and lactate for a year. In microcosms with groundwater containing perchlorate and nitrate, RDX degradation began without delay when bioaugmented with 10% WBC-2. Slower RDX degradation occurred with 3% or 5% WBC-2 amendment, indicating a direct relation with cell density. Transient RDX daughter compounds included methylene dinitramine, MNX, and DNX. With WBC-2 amendment, nitrate concentrations immediately decreased to near or below detection, and perchlorate degradation occurred with half-lives of 25-34 days. Single-well injection tests with WBC-2 and lactate showed that the onset of RDX degradation coincided with the onset of sulfide production, which was affected by the initial perchlorate concentration. Biodegradation rates in the pilot injection tests agreed well with those measured in the microcosms. These results support bioaugmentation with an anaerobic culture as a remedial strategy for sites contaminated with RDX, nitrate, and perchlorate.
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Affiliation(s)
| | - Eric Vogler
- U.S. Geological Survey, Albuquerque, NM, USA.
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6
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Sahavacharin A, Sompongchaiyakul P, Thaitakoo D. The effects of land-based change on coastal ecosystems. LANDSCAPE AND ECOLOGICAL ENGINEERING 2022. [DOI: 10.1007/s11355-022-00505-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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Handler AM, Suchy AK, Grimm NB. Denitrification and DNRA in Urban Accidental Wetlands in Phoenix, Arizona. JOURNAL OF GEOPHYSICAL RESEARCH. BIOGEOSCIENCES 2022; 127:1-15. [PMID: 35251875 PMCID: PMC8896236 DOI: 10.1029/2021jg006552] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/22/2021] [Accepted: 01/14/2022] [Indexed: 06/14/2023]
Abstract
Denitrification and dissimilatory nitrate reduction to ammonium (DNRA) both require low oxygen and high organic carbon conditions common in wetland ecosystems. Denitrification permanently removes nitrogen from the ecosystem as a gas while DNRA recycles nitrogen within the ecosystem via production of ammonium. The relative prevalence of denitrification versus DNRA has implications for the fate of nitrate in ecosystems. Unplanned and unmanaged urban accidental wetlands in the Salt River channel near downtown Phoenix, Arizona, USA receive high nitrate relative to non-urban wetlands and have a high capacity for denitrification, but unknown capacity for DNRA. We conducted in-situ push-pull tests with isotopically labelled nitrate to measure denitrification and DNRA rates in three of the dominant vegetative patch types in these urban accidental wetlands. DNRA accounted for between 2 and 40% of nitrate reduction (DNRA plus denitrification) with the highest rates measured in patches of Ludwigia peploides compared to Typha spp. and non-vegetated patches. The wetland patches were similar with respect to dissolved organic carbon concentration but may have differed in carbon lability or strength of reducing conditions due to a combination of litter decomposition and oxygen supply via diffusion and aerenchyma. The ratio of DNRA to denitrification was negatively correlated with nitrate concentration, indicating that DNRA may become a more important pathway for nitrate attenuation at low nitrate concentration. Although DNRA was generally lower than denitrification, this pathway was an important component of nitrate attenuation within certain patches in these unmanaged urban accidental wetlands.
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Affiliation(s)
- Amalia M Handler
- School of Life Sciences, Arizona State University, PO Box 874501, Tempe, AZ 85287
| | - Amanda K Suchy
- School of Life Sciences, Arizona State University, PO Box 874501, Tempe, AZ 85287
| | - Nancy B Grimm
- School of Life Sciences, Arizona State University, PO Box 874501, Tempe, AZ 85287
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8
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Tree trade-offs in stream restoration: impacts on riparian groundwater quality. Urban Ecosyst 2022; 25:773-795. [DOI: 10.1007/s11252-021-01182-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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9
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Long-term assessment of floodplain reconnection as a stream restoration approach for managing nitrogen in ground and surface waters. Urban Ecosyst 2022; 25:879-907. [DOI: 10.1007/s11252-021-01199-z] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Abstract
AbstractStream restoration is a popular approach for managing nitrogen (N) in degraded, flashy urban streams. Here, we investigated the long-term effects of stream restoration involving floodplain reconnection on riparian and in-stream N transport and transformation in an urban stream in the Chesapeake Bay watershed. We examined relationships between hydrology, chemistry, and biology using a Before/After-Control/Impact (BACI) study design to determine how hydrologic flashiness, nitrate (NO3−) concentrations (mg/L), and N flux, both NO3− and total N (kg/yr), changed after the restoration and floodplain hydrologic reconnection to its stream channel. We examined two independent surface water and groundwater data sets (EPA and USGS) collected from 2002–2012 at our study sites in the Minebank Run watershed. Restoration was completed during 2004 and 2005. Afterward, the monthly hydrologic flashiness index, based on mean monthly discharge, decreased over time from 2002 and 2008. However, from 2008–2012 hydrologic flashiness returned to pre-restoration levels. Based on the EPA data set, NO3− concentration in groundwater and surface water was significantly less after restoration while the control site showed no change. DOC and NO3− were negatively related before and after restoration suggesting C limitation of N transformations. Long-term trends in surface water NO3− concentrations based on USGS surface water data showed downward trends after restoration at both the restored and control sites, whereas specific conductance showed no trend. Comparisons of NO3− concentrations with Cl− concentrations and specific conductance in both ground and surface waters suggested that NO3− reduction after restoration was not due to dilution or load reductions from the watershed. Modeled NO3− flux decreased post restoration over time but the rate of decrease was reduced likely due to failure of restoration features that facilitated N transformations. Groundwater NO3− concentrations varied among stream features suggesting that some engineered features may be functionally better at creating optimal conditions for N retention. However, some engineered features eroded and failed post restoration thereby reducing efficacy of the stream restoration to reduce flashiness and NO3− flux. N management via stream restoration will be most effective where flashiness can be reduced and DOC made available for denitrifiers. Stream restoration may be an important component of holistic watershed management including stormwater management and nutrient source control if stream restoration and floodplain reconnection can be done in a manner to resist the erosive effects of large storm events that can degrade streams to pre-restoration conditions. Long-term evolution of water quality functions in response to degradation of restored stream channels and floodplains from urban stressors and storms over time warrants further study, however.
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Wang S, Reid MC. Kinetics of nitrous oxide mass transfer from porewater into root aerenchyma of wetland plants. JOURNAL OF ENVIRONMENTAL QUALITY 2020; 49:1717-1729. [PMID: 33169413 DOI: 10.1002/jeq2.20162] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/08/2020] [Accepted: 09/21/2020] [Indexed: 06/11/2023]
Abstract
The creation and/or restoration of wetlands is an important strategy for controlling the release of reactive nitrogen (N) via denitrification, but there can be tradeoffs between enhanced denitrification and the production of nitrous oxide (N2 O), a potent greenhouse gas. A knowledge gap in current understanding of belowground wetland N dynamics is the role of gas transfer through the root aerenchyma system of wetland plants as a shortcut emission pathway for N2 O in denitrifying wetland soils. This investigation evaluates the significance of mass transfer into gas-filled root aerenchyma for the N2 O budget in wetland mesocosms planted with Sagittaria latifolia Willd. and Schoenoplectus acutus (Muhl. ex Bigelow) Á. Löve & D. Löve. Dissolved gas tracer push-pull tests with N2 O and the nonreactive gas tracers helium, sulfur hexafluoride, and ethane were used to estimate first-order rate constants for gas transfer into roots and microbial N2 O reduction and thereby disentangle the effects of root-mediated gas transport from microbial metabolism on N2 O balances in saturated soils. Root-mediated gas transport was estimated to account for up to 37% of overall N2 O removal from the wetland soils. Rates of microbial N2 O reduction varied widely based on the organic matter content of the soil media and served as a key control on the fraction of N2 O that transferred into roots. This research identifies transport through root aerenchyma as a potential shortcut pathway for N2 O emission from wetland soils and sediments and indicates that this process should be considered in both measurements and mechanistic modeling of belowground wetland N dynamics.
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Affiliation(s)
- Simiao Wang
- School of Civil and Environmental Engineering, Cornell Univ., Ithaca, NY, 14853, USA
| | - Matthew C Reid
- School of Civil and Environmental Engineering, Cornell Univ., Ithaca, NY, 14853, USA
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11
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Tremblay CC, Botrel M, Lapierre JF, Franssen J, Maranger R. Relative influence of watershed and geomorphic features on nutrient and carbon fluxes in a pristine and moderately urbanized stream. THE SCIENCE OF THE TOTAL ENVIRONMENT 2020; 715:136411. [PMID: 32040988 DOI: 10.1016/j.scitotenv.2019.136411] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/31/2019] [Revised: 12/26/2019] [Accepted: 12/27/2019] [Indexed: 06/10/2023]
Abstract
Streams are important sites of elemental transformations due to the relatively high contact rates between flowing water and biogeochemically reactive sediments. Increased urbanization typically results in higher nutrient and carbon (C) inputs to streams from their watersheds and increased flow rates due to modification in channel form, reducing within stream net retention and increasing downstream exports. However, less is known on how moderate urbanization might influence the joint processing of C, nitrogen (N), and phosphorus (P) in streams or the relative influence of changes in watershed and stream features on their fluxes. In this study, we performed mass-balances of different C, N, and P species in multiple reaches with contrasting land use land cover and geomorphic features (pools, riffles, runs) to determine the effects of geomorphology versus human influence on elemental fluxes in a pristine and a semi-urban stream. N was the most responsive of all elements, where nitrate concentrations were 3.5-fold higher in the peri-urban stream. Dissolved organic carbon was only slightly higher in the peri-urban site whereas total P not significantly different between streams. In terms of fluxes, nitrate behaved differently between the streams with net retention occurring in the majority of the reaches of the pristine site, whereas net export was observed in all of the reaches of the semi-urban one. We found a decrease in nitrate concentrations with an increase in excess deuterium of the water (d-excess), an indicator of how overall water retention capacity of the watershed favored N loss. Within the stream, the presence of pools, and reduced channel slope, which also increase water retention time, again favored N loss. Overall, nitrate was the most sensitive nutrient to slight urbanization, where higher export to stream was influenced by land use, but where geomorphic features were more important in driving retention capacity.
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Affiliation(s)
- Charles Charrier Tremblay
- Département de Sciences Biologiques, Université de Montréal, Groupe de Recherche Interuniversitaire en Limnologie (GRIL), Montréal, QC, Canada.
| | - Morgan Botrel
- Département de Sciences Biologiques, Université de Montréal, Groupe de Recherche Interuniversitaire en Limnologie (GRIL), Montréal, QC, Canada
| | - Jean-François Lapierre
- Département de Sciences Biologiques, Université de Montréal, Groupe de Recherche Interuniversitaire en Limnologie (GRIL), Montréal, QC, Canada
| | - Jan Franssen
- Département de Géographie, Université de Montréal, Groupe de Recherche Interuniversitaire en Limnologie (GRIL), Montréal, QC, Canada
| | - Roxane Maranger
- Département de Sciences Biologiques, Université de Montréal, Groupe de Recherche Interuniversitaire en Limnologie (GRIL), Montréal, QC, Canada
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12
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Hester ET, Lin AYC, Tsai CW. Effect of Floodplain Restoration on Photolytic Removal of Pharmaceuticals. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2020; 54:3278-3287. [PMID: 32062974 DOI: 10.1021/acs.est.9b06850] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Floodplain restoration is popular to address excess nutrients, but its ability to enhance photolysis of emerging contaminants has not been evaluated. We used the numerical model MIKE-21 to simulate photolysis reactions within the inundated surface water of restored floodplains along a mid-size river. We examined both "high" and "low" floodplain scenarios where inundation occurs 5% (storms) and 50% (baseflow) of the year, respectively. We simulated photolysis of the pharmaceuticals morphine, codeine, and methamphetamine and, for context, compared it with nitrate removal (denitrification and plant uptake). Pollutant removal due to floodplain restoration was greater for the low floodplain (e.g., 18.8% for morphine) than for the high floodplain (5.6% for morphine) due to greater water exchange relative to channel flow. The fastest- and slowest-reacting pollutants (morphine and methamphetamine, respectively) were always transport- and reaction/kinetics-limited within floodplain surface water, respectively. Yet, those with intermediate decay-rate constants switched from reaction limitation to transport limitation as the floodplain length increased, and removal leveled off at an optimum length of ∼1000 m. However, as the floodplain width increased, the required floodplain length for 30% removal decreased. Optimal restored floodplain conditions for photolysis would maximize light exposure, which may differ from those for nutrients.
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Affiliation(s)
- Erich T Hester
- Civil and Environmental Engineering, Virginia Tech, 200 Patton Hall, 0105, 750 Drillfield Drive, Blacksburg, Virginia 24061-0105, United States
| | - Angela Y-C Lin
- Graduate Institute of Environmental Engineering, National Taiwan University, Taipei 10617, Taiwan
| | - Christina W Tsai
- Civil Engineering, National Taiwan University, Taipei 10617, Taiwan
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Hinshaw SE, Zhang T, Harrison JA, Dahlgren RA. Excess N 2 and denitrification in hyporheic porewaters and groundwaters of the San Joaquin River, California. WATER RESEARCH 2020; 168:115161. [PMID: 31654960 DOI: 10.1016/j.watres.2019.115161] [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: 05/24/2019] [Revised: 09/10/2019] [Accepted: 10/04/2019] [Indexed: 06/10/2023]
Abstract
The San Joaquin River (SJR) in California is purported to receive high nitrate loadings from surrounding agricultural lands through both surface and groundwater inputs. To investigate the potential removal of nitrate (NO3-) from surface and ground water sources, the spatial variations in dinitrogen (N2) gas concentrations and direct measurements of sediment denitrification potential (DNP), with amended NO3- and carbon (C) treatments, were investigated in the summer along a 95-km reach of the San Joaquin River. Excess N2 in hyporheic porewaters ranged from <0.1 to 8.65 mg L-1 and was significantly higher in porewaters from the 1.3 m (ground water source) versus 0.3 m (mixed surface and ground water) depths. In deep groundwater wells (3-7 m), median excess N2 concentration was 5.39 mg L-1 (range = <0.1-14.6 mg L-1). Excess N2 concentrations were inversely correlated with dissolved oxygen and NO3- concentrations suggesting denitrification as an important process in the dominantly anaerobic sediments. Hyporheic porewater NO3- concentrations exceeded the detection limit of 0.01 mg L-1 in only 20% of the hyporheic porewaters, in spite of high NO3- concentrations measured in both surface waters (mean = 2.25 mg N L-1) and surrounding groundwaters. Sediment DNP rates averaged 253 and 297 μg N kg-1 hr-1 for NO3- amended, and NO3- + C amended sediments, respectively, supporting the prevalence of denitrification in hyporheic sediments. Our results indicate that the hyporheic/riparian zones act as an anoxic barrier to nitrate transport from regional groundwater and as a location to remove NO3- from surface waters exchanging with the hyporheic zone.
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Affiliation(s)
- Sarra E Hinshaw
- University of California, Davis, Land, Air and Water Resources, One Shield Rd, Davis, CA, 95616, USA.
| | - Taiping Zhang
- School of Environment and Energy, South China University of Technology, Guangzhou, 510006, China.
| | - John A Harrison
- Washington State University Vancouver, School of the Environment, Vancouver, WA, 98686, USA.
| | - Randy A Dahlgren
- University of California, Davis, Land, Air and Water Resources, One Shield Rd, Davis, CA, 95616, USA.
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Reisinger AJ, Doody TR, Groffman PM, Kaushal SS, Rosi EJ. Seeing the light: urban stream restoration affects stream metabolism and nitrate uptake via changes in canopy cover. ECOLOGICAL APPLICATIONS : A PUBLICATION OF THE ECOLOGICAL SOCIETY OF AMERICA 2019; 29:e01941. [PMID: 31155778 DOI: 10.1002/eap.1941] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/24/2018] [Revised: 04/05/2019] [Accepted: 04/17/2019] [Indexed: 06/09/2023]
Abstract
The continually increasing global population residing in urban landscapes impacts numerous ecosystem functions and services provided by urban streams. Urban stream restoration is often employed to offset these impacts and conserve or enhance the various functions and services these streams provide. Despite the assumption that "if you build it, [the function] will come," current understanding of the effects of urban stream restoration on stream ecosystem functions are based on short term studies that may not capture variation in restoration effectiveness over time. We quantified the impact of stream restoration on nutrient and energy dynamics of urban streams by studying 10 urban stream reaches (five restored, five unrestored) in the Baltimore, Maryland, USA, region over a two-year period. We measured gross primary production (GPP) and ecosystem respiration (ER) at the whole-stream scale continuously throughout the study and nitrate (NO3- -N) spiraling rates seasonally (spring, summer, autumn) across all reaches. There was no significant restoration effect on NO3- -N spiraling across reaches. However, there was a significant canopy cover effect on NO3- -N spiraling, and directly comparing paired sets of unrestored-restored reaches showed that restoration does affect NO3- -N spiraling after accounting for other environmental variation. Furthermore, there was a change in GPP : ER seasonality, with restored and open-canopied reaches exhibiting higher GPP : ER during summer. The restoration effect, though, appears contingent upon altered canopy cover, which is likely to be a temporary effect of restoration and is a driver of multiple ecosystem services, e.g., habitat, riparian nutrient processing. Our results suggest that decision-making about stream restoration, including evaluations of nutrient benefits, clearly needs to consider spatial and temporal dynamics of canopy cover and trade-offs among multiple ecosystem services.
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Affiliation(s)
- Alexander J Reisinger
- Cary Institute of Ecosystem Studies, Millbrook, New York, 12545, USA
- Soil and Water Sciences Department, University of Florida, Gainesville, Florida, 32611, USA
| | - Thomas R Doody
- Department of Geology, Earth System Science Interdisciplinary Center, University of Maryland, College Park, Maryland, 20742, USA
| | - Peter M Groffman
- Cary Institute of Ecosystem Studies, Millbrook, New York, 12545, USA
- Brooklyn College Department of Earth and Environmental Sciences, City University of New York Advanced Science Research Center at the Graduate Center, New York, New York, 10031, USA
| | - Sujay S Kaushal
- Department of Geology, Earth System Science Interdisciplinary Center, University of Maryland, College Park, Maryland, 20742, USA
| | - Emma J Rosi
- Cary Institute of Ecosystem Studies, Millbrook, New York, 12545, USA
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Hassanzadeh YT, Vidon PG, Gold AJ, Pradhanang SM, Addy K. A new approach to generalizing riparian water and air quality function across regions. ENVIRONMENTAL MONITORING AND ASSESSMENT 2019; 191:282. [PMID: 30993469 DOI: 10.1007/s10661-019-7443-y] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/25/2018] [Accepted: 04/01/2019] [Indexed: 06/09/2023]
Abstract
There is growing interest in generalizing the impact of hydrogeomorphology and weather variables on riparian functions. Here, we used RZ-TRADEOFF to estimate nitrogen, phosphorus, water table (WT) depth, and greenhouse gas (GHG: N2O, CO2, CH4) functions for 80 riparian zones typical of the North American Midwest, Northeast (including Southern Ontario, Canada), and Mid-Atlantic. Sensitivity to weather perturbations was calculated for temperature and precipitation-dependent functions (CO2, phosphate concentration, and water table), and multivariate statistical analysis on model outputs was conducted to determine trade-offs between riparian functions. Mean model estimates were 93.10 cm for WT depth, 8.45 mg N L-1 for field edge nitrate concentration, 51.57% for nitrate removal, 0.45 mg PO43- L-1 for field edge phosphate concentration, 1.5% for subsurface phosphate removal, 91.24% for total overland phosphorus removal, 0.51 mg N m-2 day-1 for N2O flux, 5.5 g C m-2 day-1 for CO2 fluxes, and - 0.41 mg C m-2 day-1 and 621.51 mg C m-2 day-1 for CH4 fluxes in non-peat sites and peat sites, respectively. Sites in colder climates were most sensitive to weather perturbations for CO2, sites with deep water tables estimates had the highest sensitivity for WT, and sites in warm climates and/or with deep confining layers had the lowest sensitivity for phosphate concentration. Slope, confining layer depth, and temperature were the primary characteristics influencing similarities and trade-offs between sites. This research contributes to understanding how to optimize riparian restoration and protection in watersheds based on both water (nitrogen, phosphorus) and air quality (GHG) goals.
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Affiliation(s)
- Yasaman T Hassanzadeh
- Department of Forest and Natural Resources Management, The State University of New York College of Environmental Science and Forestry (SUNY ESF), 1 Forestry Drive, Syracuse, NY, 13201, USA
| | - Philippe G Vidon
- Department of Forest and Natural Resources Management, The State University of New York College of Environmental Science and Forestry (SUNY ESF), 1 Forestry Drive, Syracuse, NY, 13201, USA.
| | - Arthur J Gold
- Department of Natural Resources, University of Rhode Island, Kingston, RI, 02881, USA
| | - Soni M Pradhanang
- Department of Geosciences, University of Rhode Island, Kingston, RI, 02881, USA
| | - Kelly Addy
- Department of Natural Resources, University of Rhode Island, Kingston, RI, 02881, USA
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Influence of urban river restoration on nitrogen dynamics at the sediment-water interface. PLoS One 2019; 14:e0212690. [PMID: 30865649 PMCID: PMC6415882 DOI: 10.1371/journal.pone.0212690] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2018] [Accepted: 02/07/2019] [Indexed: 11/19/2022] Open
Abstract
River restoration projects focused on altering flow regimes through use of in-channel structures can facilitate ecosystem services, such as promoting nitrogen (N) storage to reduce eutrophication. In this study we use small flux chambers to examine ammonium (NH4+) and nitrate (NO3-) cycling across the sediment-water interface. Paired restored and unrestored study sites in 5 urban tributaries of the River Thames in Greater London were used to examine N dynamics following physical disturbances (0–3 min exposures) and subsequent biogeochemical activity (3–10 min exposures). Average ambient NH4+ concentrations were significantly different amongst all sites and ranged from 28.0 to 731.7 μg L-1, with the highest concentrations measured at restored sites. Average NO3- concentrations ranged from 9.6 to 26.4 mg L-1, but did not significantly differ between restored and unrestored sites. Average NH4+ fluxes at restored sites ranged from -8.9 to 5.0 μg N m-2 sec-1, however restoration did not significantly influence NH4+ uptake or regeneration (i.e., a measure of release to surface water) between 0–3 minutes and 3–10 minutes. Further, average NO3- fluxes amongst sites responded significantly between 0–3 minutes ranging from -33.6 to 97.7 μg N m-2 sec-1. Neither NH4+ nor NO3- fluxes correlated to sediment chlorophyll-a, total organic matter, or grain size. We attributed variations in overall N fluxes to N-specific sediment storage capacity, biogeochemical transformations, potential legacy effects associated with urban pollution, and variations in river-specific restoration actions.
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Gold AC, Thompson SP, Piehler MF. Nitrogen cycling processes within stormwater control measures: A review and call for research. WATER RESEARCH 2019; 149:578-587. [PMID: 30513447 DOI: 10.1016/j.watres.2018.10.036] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/20/2018] [Revised: 10/11/2018] [Accepted: 10/12/2018] [Indexed: 06/09/2023]
Abstract
Stormwater control measures (SCMs) have the potential to mitigate negative effects of watershed development on hydrology and water quality. Stormwater regulations and scientific literature have assumed that SCMs are important sites for denitrification, the permanent removal of nitrogen, but this assumption has been informed mainly by short-term loading studies and measurements of potential rates of nitrogen cycling. Recent research concluded that SCM nitrogen removal can be dominated by plant and soil assimilation rather than by denitrification, and rates of nitrogen fixation can exceed rates of denitrification in SCM sediments, resulting in a net addition of nitrogen. Nitrogen cycling measurements from other human-impacted aquatic habitats have presented similar results, additionally suggesting that dissimilatory nitrate reduction to ammonium (DNRA) and algal uptake could be important processes for recycling nitrogen in SCMs. Future research should directly measure a suite of nitrogen cycling processes in SCMs and reveal controlling mechanisms of individual rate processes. There is ample opportunity for research on SCM nitrogen cycling, including investigations of seasonal variation, differences between climatic regions, and trade-offs between nitrogen removal and phosphorus removal. Understanding nitrogen dynamics within SCMs will inform more efficient SCM design and management that promotes denitrification to help mitigate negative effects of urban stormwater on downstream ecosystems.
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Affiliation(s)
- Adam C Gold
- UNC Institute of Marine Sciences, 3431 Arendell St., Morehead City, NC, 28557, United States; UNC Environment, Ecology, and Energy Program, 3202 Murray/Venable Hall, CB#3275, Chapel Hill, NC, 27599, United States.
| | - Suzanne P Thompson
- UNC Institute of Marine Sciences, 3431 Arendell St., Morehead City, NC, 28557, United States
| | - Michael F Piehler
- UNC Institute of Marine Sciences, 3431 Arendell St., Morehead City, NC, 28557, United States; UNC Environment, Ecology, and Energy Program, 3202 Murray/Venable Hall, CB#3275, Chapel Hill, NC, 27599, United States; UNC Institute for the Environment, 100 Europa Dr., Suite 490, Chapel Hill, NC, 27517, United States
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Jahangir MMR, Fenton O, Müller C, Harrington R, Johnston P, Richards KG. In situ denitrification and DNRA rates in groundwater beneath an integrated constructed wetland. WATER RESEARCH 2017; 111:254-264. [PMID: 28088722 DOI: 10.1016/j.watres.2017.01.015] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/30/2016] [Revised: 12/26/2016] [Accepted: 01/06/2017] [Indexed: 06/06/2023]
Abstract
Evaluation of the environmental benefits of constructed wetlands (CWs) requires an understanding of their impacts on the groundwater quality under the wetlands. Empirical mass-balance (nitrogen in/nitrogen out) approaches for estimating nitrogen (N) removal in CWs do not characterise the final fate of N; where nitrate (NO3--N) could be reduced to either ammonium (NH4+-N) or N2 with the potential for significant production of N2O. Herein, in situ denitrification and DNRA (dissimilatory nitrate reduction to ammonium) rates were measured in groundwater beneath cells of an earthen lined integrated constructed wetland (ICW, used to remove the nutrients from municipal wastewater) using the 15N-enriched NO3--N push-pull method. Experiments were conducted utilising replicated (n = 3) shallow (1 m depth) and deep (4 m depth) piezometers installed along two control planes. These control planes allowed for the assessment of groundwater underlying high (Cell 2, septic tank waste) and low (Cell 3) load cells of the ICW. Background piezometers were also installed off-site. Results showed that denitrification (N2O-N + N2-N) and DNRA were major NO3--N consumption processes accounting together for 54-79% of the total biochemical consumption of the applied NO3--N. Of which 14-16% and 40-63% were consumed by denitrification and DNRA, respectively. Both processes differed significantly across ICW cells indicating that N transformation depends on nutrient loading rates and were significantly higher in shallow compared to the deep groundwater. In such a reduced environment (low dissolved oxygen and low redox potential), higher DNRA over the denitrification rate can be attributed to the high C concentration and high TC/NO3--N ratio. Low pH (6.5-7.1) in this system might have limited denitrification to some extent to an incomplete state, evidenced by a high N2O-N/(N2O-N+N2-N) ratio (0.35 ± 0.17, SE). A relatively higher N2O-N/(N2O-N+N2-N) ratio and higher DNRA rate over denitrification, suggest that the end products of N transformations are reactive. This N2O can be consumed to N2 and/or emitted to the atmosphere. The DNRA rate and accumulation of NH4+-N indicated that the ICW created a suitable groundwater biogeochemical environment that enhanced NO3--N reduction to NH4+-N. This study showed that CWs significantly influence NO3--N attenuation to reactive forms of N in the groundwater beneath them and that solely focusing on within wetland NO3--N attenuation can underestimate the environmental benefits of wetlands.
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Affiliation(s)
- M M R Jahangir
- Department of Civil, Structural & Environmental Engineering, Trinity College Dublin, Ireland; Teagasc Environment Research Centre, Johnstown Castle, Co. Wexford, Ireland; Department of Soil Science, Bangladesh Agricultural University, Mymenisngh, 2202, Bangladesh.
| | - O Fenton
- Teagasc Environment Research Centre, Johnstown Castle, Co. Wexford, Ireland
| | - C Müller
- School of Biology and Environmental Science, University College Dublin, Belfield, Ireland; Department of Plant Ecology (IFZ), Justus-Liebig University Giessen, Germany
| | | | - P Johnston
- Department of Civil, Structural & Environmental Engineering, Trinity College Dublin, Ireland
| | - K G Richards
- Teagasc Environment Research Centre, Johnstown Castle, Co. Wexford, Ireland
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20
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Urban microbiomes and urban ecology: how do microbes in the built environment affect human sustainability in cities? J Microbiol 2014; 52:721-8. [PMID: 25224504 DOI: 10.1007/s12275-014-4364-x] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2014] [Revised: 08/06/2014] [Accepted: 08/06/2014] [Indexed: 12/30/2022]
Abstract
Humans increasingly occupy cities. Globally, about 50% of the total human population lives in urban environments, and in spite of some trends for deurbanization, the transition from rural to urban life is expected to accelerate in the future, especially in developing nations and regions. The Republic of Korea, for example, has witnessed a dramatic rise in its urban population, which now accounts for nearly 90% of all residents; the increase from about 29% in 1955 has been attributed to multiple factors, but has clearly been driven by extraordinary growth in the gross domestic product accompanying industrialization. While industrialization and urbanization have unarguably led to major improvements in quality of life indices in Korea and elsewhere, numerous serious problems have also been acknowledged, including concerns about resource availability, water quality, amplification of global warming and new threats to health. Questions about sustainability have therefore led Koreans and others to consider deurbanization as a management policy. Whether this offers any realistic prospects for a sustainable future remains to be seen. In the interim, it has become increasingly clear that built environments are no less complex than natural environments, and that they depend on a variety of internal and external connections involving microbes and the processes for which microbes are responsible. I provide here a definition of the urban microbiome, and through examples indicate its centrality to human function and wellbeing in urban systems. I also identify important knowledge gaps and unanswered questions about urban microbiomes that must be addressed to develop a robust, predictive and general understanding of urban biology and ecology that can be used to inform policy-making for sustainable systems.
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Jahangir MMR, Minet EP, Johnston P, Premrov A, Coxon CE, Hackett R, Richards KG. Mustard catch crop enhances denitrification in shallow groundwater beneath a spring barley field. CHEMOSPHERE 2014; 103:234-239. [PMID: 24374183 DOI: 10.1016/j.chemosphere.2013.11.072] [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: 06/08/2013] [Revised: 11/22/2013] [Accepted: 11/29/2013] [Indexed: 06/03/2023]
Abstract
Over-winter green cover crops have been reported to increase dissolved organic carbon (DOC) concentrations in groundwater, which can be used as an energy source for denitrifiers. This study investigates the impact of a mustard catch crop on in situ denitrification and nitrous oxide (N2O) emissions from an aquifer overlain by arable land. Denitrification rates and N2O-N/(N2O-N+N2-N) mole fractions were measured in situ with a push-pull method in shallow groundwater under a spring barley system in experimental plots with and without a mustard cover crop. The results suggest that a mustard cover crop could substantially enhance reduction of groundwater nitrate NO3--N via denitrification without significantly increasing N2O emissions. Mean total denitrification (TDN) rates below mustard cover crop and no cover crop were 7.61 and 0.002 μg kg(-1) d(-1), respectively. Estimated N2O-N/(N2O-N+N2-N) ratios, being 0.001 and 1.0 below mustard cover crop and no cover crop respectively, indicate that denitrification below mustard cover crop reduces N2O to N2, unlike the plot with no cover crop. The observed enhanced denitrification under the mustard cover crop may result from the higher groundwater DOC under mustard cover crop (1.53 mg L(-1)) than no cover crop (0.90 mg L(-1)) being added by the root exudates and root masses of mustard. This study gives insights into the missing piece in agricultural nitrogen (N) balance and groundwater derived N2O emissions under arable land and thus helps minimise the uncertainty in agricultural N and N2O-N balances.
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Affiliation(s)
- M M R Jahangir
- Teagasc Environment Research Center, Johnstown Castle, Wexford, Ireland; Dept. of Civil, Structural & Environmental Engineering, Trinity College Dublin, Ireland; Dept. of Soil Science, Bangladesh Agricultural University, Mymensingh, Bangladesh.
| | - E P Minet
- Teagasc Environment Research Center, Johnstown Castle, Wexford, Ireland
| | - P Johnston
- Dept. of Civil, Structural & Environmental Engineering, Trinity College Dublin, Ireland
| | - A Premrov
- Geology Dept., School of Natural Sciences, Trinity College Dublin, Ireland
| | - C E Coxon
- Geology Dept., School of Natural Sciences, Trinity College Dublin, Ireland
| | - R Hackett
- Teagasc, Oak Park Research Centre, Carlow, Ireland
| | - K G Richards
- Teagasc Environment Research Center, Johnstown Castle, Wexford, Ireland
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Anderson TR, Groffman PM, Kaushal SS, Walter MT. Shallow groundwater denitrification in riparian zones of a headwater agricultural landscape. JOURNAL OF ENVIRONMENTAL QUALITY 2014; 43:732-744. [PMID: 25602674 DOI: 10.2134/jeq2013.07.0303] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Riparian zones adjacent to cropped lands are effective at reducing nitrate (NO) loads to receiving water bodies primarily through plant assimilation and denitrification. Denitrification represents a permanent removal pathway and a greenhouse gas source, converting NO to inert N gas or nitrous oxide (NO), and has been the subject of many studies in agricultural landscapes. Despite the prevailing notion that riparian zones can be areas of enhanced denitrification, there is a lack of in situ denitrification measurements from these areas that buffer streams and rivers from NO originating in upland cropped soils, especially over time scales that capture seasonal dynamics. We measured in situ groundwater denitrification rates in two riparian zones of an intensive dairy farm located in the headwaters of the Susquehanna River. Denitrification rates determined monthly over a 1-yr period with the N-NO push-pull method ranged from 0 to 4177 μg N kg soil d (mean, 830 ± 193 μg N kg soil d). Denitrification showed a distinct seasonal pattern, with highest rates observed in the spring and summer, concomitant with warmer temperatures and decreasing dissolved oxygen. We estimate an annual N loss of 470 ± 116 kg yr ha of riparian zone via denitrification in the shallow saturated zone, with the potential for >20% of this amount occurring as NO. Total denitrification from shallow groundwater in the riparian zone was equivalent to 32% of manure N spread on the adjacent upland field, confirming the importance of riparian zones in agricultural landscapes at controlling N loads entering downstream waters.
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Dripps W, Lewis GP, Baxter R, Andersen CB. Hydrogeochemical Characterization of Headwater Seepages Inhabited by the Endangered Bunched Arrowhead (Sagittaria fasciculata) in the Upper Piedmont of South Carolina. SOUTHEAST NAT 2013. [DOI: 10.1656/058.012.0315] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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Reid MC, Jaffé PR. A push-pull test to measure root uptake of volatile chemicals from wetland soils. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2013; 47:3190-3198. [PMID: 23461357 DOI: 10.1021/es304748r] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
This paper introduces a novel modification of the single-well "push-pull" test that uses nonvolatile and multiple volatile tracers to investigate the transport and root uptake kinetics of volatile chemicals in saturated soils. This technique provides an estimate of potential volatilization fluxes without relying on enclosure-based measurements. The new push-pull methodology was validated with mesocosm experiments, and bench-scale hydroponic measurements were performed to develop an empirical relationship for scaling root uptake rates between chemicals. A new modeling approach to interpret data using sulfur hexafluoride and helium as dual volatile tracers was developed and shown to decrease errors relative to existing analytical techniques that utilize bromide as a conservative tracer. Root uptake of the volatile tracers was diffusion-limited, and uptake rate constants (kv) in vegetated experimental mesocosms ranged from 0.021 ± 9.0 × 10(-4) h(-1) for CFC-12 to 2.41 ± 0.98 h(-1) for helium. Hydroponic and mesocosm experiments demonstrate that the molecular diameter is a robust empirical predictor of kv.
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Affiliation(s)
- Matthew C Reid
- Department of Civil and Environmental Engineering, Princeton University, Princeton, New Jersey 08544, United States.
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Newcomer TA, Kaushal SS, Mayer PM, Shields AR, Canuel EA, Groffman PM, Gold AJ. Influence of natural and novel organic carbon sources on denitrification in forest, degraded urban, and restored streams. ECOL MONOGR 2012. [DOI: 10.1890/12-0458.1] [Citation(s) in RCA: 95] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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Addy K, Gold A, Stolt M, Donohue S. Groundwater denitrification capacity and nitrous oxide flux of former fringing salt marshes filled with human-transported materials. Urban Ecosyst 2012. [DOI: 10.1007/s11252-012-0266-z] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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