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Dai M, Xu Y, Genjebay Y, Lu L, Wang C, Yang H, Huang C, Huang T. Urbanization significantly increases greenhouse gas emissions from a subtropical headwater stream in Southeast China. THE SCIENCE OF THE TOTAL ENVIRONMENT 2024; 945:173508. [PMID: 38851353 DOI: 10.1016/j.scitotenv.2024.173508] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/19/2024] [Revised: 05/09/2024] [Accepted: 05/23/2024] [Indexed: 06/10/2024]
Abstract
Streams are disproportionately significant contributors to increases in greenhouse gas (GHG) effluxes in river networks. In the context of global urbanization, a growing number of streams are affected by urbanization, which has been suggested to stimulate the water-air GHG emissions from fluvial systems. This study investigated the seasonal and longitudinal profiles of GHG (N2O, CH4, and CO2) concentrations of Jiuxianghe Stream, a headwater stream undergoing urbanization, and estimated its GHG diffusive fluxes and global warming potentials (GWPs) using the boundary layer method. The results showed that N2O, CH4, and CO2 concentrations in Jiuxianghe Stream were 0.45-7.19 μg L-1, 0.31-586.85 μg L-1, and 0.16-11.60 mg L-1, respectively. N2O, CH4, and CO2 concentrations in the stream showed 4.55-, 23.70-, and 7.68-fold increases from headwaters to downstream, respectively, corresponding to the forest-urban transition within the watershed. Multiple linear regression indicated that NO3--N, NH4+-N, and DOC:NO3--N accurately predicted N2O and CO2 concentrations, indicating that N nutrients were the driving factors. The Jiuxianghe Stream was a source of atmospheric GHGs with a daily GWP of 7.31 g CO2-eq m-2 d-1 on average and was significantly positively correlated with the ratio of construction land and forest in the sub-watershed. This study highlights the critical role of urbanization in amplifying GHG emissions from streams, thereby augmenting our understanding of GHG emissions from river networks. With global urbanization on the rise, streams experiencing urbanization are expected to make an unprecedentedly significant contribution to riverine GHG budgets in the future.
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Affiliation(s)
- Mutan Dai
- School of Geography, Nanjing Normal University, Nanjing 210023, China; Jiangsu Centre for Collaborative Innovation in Geographical Information Resource Development and Application, Nanjing Normal University, Nanjing 210023, China; Jiangsu Provincial Key Laboratory of Materials Cycling and Pollution Control, Nanjing 210023, China
| | - Yuanhui Xu
- School of Geography, Nanjing Normal University, Nanjing 210023, China; Jiangsu Centre for Collaborative Innovation in Geographical Information Resource Development and Application, Nanjing Normal University, Nanjing 210023, China; Jiangsu Provincial Key Laboratory of Materials Cycling and Pollution Control, Nanjing 210023, China
| | | | - Lingfeng Lu
- School of Geography, Nanjing Normal University, Nanjing 210023, China; Jiangsu Centre for Collaborative Innovation in Geographical Information Resource Development and Application, Nanjing Normal University, Nanjing 210023, China; Jiangsu Provincial Key Laboratory of Materials Cycling and Pollution Control, Nanjing 210023, China
| | - Chuan Wang
- School of Geography, Nanjing Normal University, Nanjing 210023, China; Jiangsu Centre for Collaborative Innovation in Geographical Information Resource Development and Application, Nanjing Normal University, Nanjing 210023, China; Jiangsu Provincial Key Laboratory of Materials Cycling and Pollution Control, Nanjing 210023, China
| | - Hao Yang
- School of Geography, Nanjing Normal University, Nanjing 210023, China; Jiangsu Centre for Collaborative Innovation in Geographical Information Resource Development and Application, Nanjing Normal University, Nanjing 210023, China; Jiangsu Provincial Key Laboratory of Materials Cycling and Pollution Control, Nanjing 210023, China
| | - Changchun Huang
- School of Geography, Nanjing Normal University, Nanjing 210023, China; Jiangsu Centre for Collaborative Innovation in Geographical Information Resource Development and Application, Nanjing Normal University, Nanjing 210023, China; Jiangsu Provincial Key Laboratory of Materials Cycling and Pollution Control, Nanjing 210023, China
| | - Tao Huang
- School of Geography, Nanjing Normal University, Nanjing 210023, China; Jiangsu Centre for Collaborative Innovation in Geographical Information Resource Development and Application, Nanjing Normal University, Nanjing 210023, China; Jiangsu Provincial Key Laboratory of Materials Cycling and Pollution Control, Nanjing 210023, China.
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2
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Sun C, Liu N, Song J, Chen L, Zhang Y, Wang X. High-Resolution Estimates of N 2O Emissions from Inland Waters and Wetlands in China. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2024; 58:8736-8747. [PMID: 38723264 DOI: 10.1021/acs.est.4c02229] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2024]
Abstract
Inland waters (rivers, lakes, and reservoirs) and wetlands (marshes and coastal wetlands) represent large and continuous sources of nitrous oxide (N2O) emissions, in view of adequate biomass and anaerobic conditions. Considerable uncertainties remain in quantifying spatially explicit N2O emissions from aquatic systems, attributable to the limitations of models and a lack of comprehensive data sets. Herein, we conducted a synthesis of 1659 observations of N2O emission rates to determine the major environmental drivers across five aquatic systems. A framework for spatially explicit estimates of N2O emissions in China was established, employing a data-driven approach that upscaled from site-specific N2O fluxes to robust multiple-regression models. Results revealed the effectiveness of models incorporating soil organic carbon and water content for marshes and coastal wetlands, as well as water nitrate concentration and dissolved organic carbon for lakes, rivers, and reservoirs for predicting emissions. Total national N2O emissions from inland waters and wetlands were 1.02 × 105 t N2O yr-1, with contributions from marshes (36.33%), rivers (27.77%), lakes (25.27%), reservoirs (6.47%), and coastal wetlands (4.16%). Spatially, larger emissions occurred in the Songliao River Basin and Continental River Basin, primarily due to their substantial terrestrial biomass. This study offers a vital national inventory of N2O emissions from inland waters and wetlands in China, providing paradigms for the inventorying work in other countries and insights to formulate effective mitigation strategies for climate change.
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Affiliation(s)
- Cheng Sun
- Key Laboratory of Groundwater Resources and Environment Ministry of Education, Jilin University, Changchun, Jilin 130021, China
- Jilin Provincial Key Laboratory of Water Resources and Environment, Jilin University, Changchun ,Jilin 130021, China
- College of New Energy and Environment, Jilin University, Changchun, Jilin 130021, China
| | - Nuo Liu
- Key Laboratory of Groundwater Resources and Environment Ministry of Education, Jilin University, Changchun, Jilin 130021, China
- Jilin Provincial Key Laboratory of Water Resources and Environment, Jilin University, Changchun ,Jilin 130021, China
- College of New Energy and Environment, Jilin University, Changchun, Jilin 130021, China
| | - Junnian Song
- Key Laboratory of Groundwater Resources and Environment Ministry of Education, Jilin University, Changchun, Jilin 130021, China
- Jilin Provincial Key Laboratory of Water Resources and Environment, Jilin University, Changchun ,Jilin 130021, China
- College of New Energy and Environment, Jilin University, Changchun, Jilin 130021, China
- The Bartlett School of Sustainable Construction, University College London, London WC1E 7HB, U.K
| | - Lei Chen
- State Key Laboratory of Water Environment Simulation, School of Environment, Beijing Normal University, Beijing 100875, China
| | - Ying Zhang
- Key Laboratory of Groundwater Resources and Environment Ministry of Education, Jilin University, Changchun, Jilin 130021, China
- Jilin Provincial Key Laboratory of Water Resources and Environment, Jilin University, Changchun ,Jilin 130021, China
- College of New Energy and Environment, Jilin University, Changchun, Jilin 130021, China
| | - Xian'en Wang
- Key Laboratory of Groundwater Resources and Environment Ministry of Education, Jilin University, Changchun, Jilin 130021, China
- Jilin Provincial Key Laboratory of Water Resources and Environment, Jilin University, Changchun ,Jilin 130021, China
- College of New Energy and Environment, Jilin University, Changchun, Jilin 130021, China
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3
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Shu W, Zhang Q, Audet J, Li Z, Leng P, Qiao Y, Tian C, Chen G, Zhao J, Cheng H, Li F. Non-negligible N 2O emission hotspots: Rivers impacted by ion-adsorption rare earth mining. WATER RESEARCH 2024; 251:121124. [PMID: 38237464 DOI: 10.1016/j.watres.2024.121124] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/19/2023] [Revised: 12/06/2023] [Accepted: 01/08/2024] [Indexed: 02/12/2024]
Abstract
Rare earth mining causes severe riverine nitrogen pollution, but its effect on nitrous oxide (N2O) emissions and the associated nitrogen transformation processes remain unclear. Here, we characterized N2O fluxes from China's largest ion-adsorption rare earth mining watershed and elucidated the mechanisms that drove N2O production and consumption using advanced isotope mapping and molecular biology techniques. Compared to the undisturbed river, the mining-affected river exhibited higher N2O fluxes (7.96 ± 10.18 mmol m-2d-1 vs. 2.88 ± 8.27 mmol m-2d-1, P = 0.002), confirming that mining-affected rivers are N2O emission hotspots. Flux variations scaled with high nitrogen supply (resulting from mining activities), and were mainly attributed to changes in water chemistry (i.e., pH, and metal concentrations), sediment property (i.e., particle size), and hydrogeomorphic factors (e.g., river order and slope). Coupled nitrification-denitrification and N2O reduction were the dominant processes controlling the N2O dynamics. Of these, the contribution of incomplete denitrification to N2O production was greater than that of nitrification, especially in the heavily mining-affected reaches. Co-occurrence network analysis identified Thiomonas and Rhodanobacter as the key genus closely associated with N2O production, suggesting their potential roles for denitrification. This is the first study to elucidate N2O emission and influential mechanisms in mining-affected rivers using combined isotopic and molecular techniques. The discovery of this study enhances our understanding of the distinctive processes driving N2O production and consumption in highly anthropogenically disturbed aquatic systems, and also provides the foundation for accurate assessment of N2O emissions from mining-affected rivers on regional and global scales.
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Affiliation(s)
- Wang Shu
- Shandong Yucheng Agro-Ecosystem National Observation and Research Station, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China; Sino-Danish College of University of Chinese Academy of Sciences, Beijing 101408, China; Sino-Danish Centre for Education and Research, Beijing 101408, China
| | - Qiuying Zhang
- State Key Laboratory of Environmental Criteria and Risk Assessment, Chinese Research Academy of Environmental Sciences, Beijing 100012, China.
| | - Joachim Audet
- Department of Ecoscience, Aarhus University, C.F. Møllers Allé, Aarhus 8000, Denmark
| | - Zhao Li
- Shandong Yucheng Agro-Ecosystem National Observation and Research Station, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China
| | - Peifang Leng
- Shandong Yucheng Agro-Ecosystem National Observation and Research Station, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China
| | - Yunfeng Qiao
- Shandong Yucheng Agro-Ecosystem National Observation and Research Station, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China
| | - Chao Tian
- Shandong Yucheng Agro-Ecosystem National Observation and Research Station, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China
| | - Gang Chen
- Department of Civil and Environmental Engineering, Florida A&M University (FAMU)-Florida State University (FSU) Joint College of Engineering, 32310, United States
| | - Jun Zhao
- School of Geography and Ocean Science, Nanjing University, Nanjing 210023, China
| | - Hefa Cheng
- MOE Laboratory for Earth Surface Processes, College of Urban and Environmental Sciences, Peking University, Beijing 100871, China
| | - Fadong Li
- Shandong Yucheng Agro-Ecosystem National Observation and Research Station, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China; Sino-Danish College of University of Chinese Academy of Sciences, Beijing 101408, China.
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Cheng G, Zhang X, Zhu M, Zhang Z, Jing L, Wang L, Li Q, Zhang X, Wang H, Wang W. Tree diversity, growth status, and spatial distribution affected soil N availability and N 2O efflux: Interaction with soil physiochemical properties. JOURNAL OF ENVIRONMENTAL MANAGEMENT 2023; 344:118375. [PMID: 37356331 DOI: 10.1016/j.jenvman.2023.118375] [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: 12/01/2022] [Revised: 06/04/2023] [Accepted: 06/10/2023] [Indexed: 06/27/2023]
Abstract
Soil nitrogen (N) is an essential nutrient for tree growth, and excessive N is a source of pollution. This paper aims to define the effects of plant diversity and forest structure on various aspects of soil N cycling. Herein, we collected soils from 720 plots to measure total N content (TN), alkali-hydrolyzed N (AN), nitrate N (NO3--N), ammonium N (NH4+-N) in a 7.2 ha experimental forest in northeast China. Four plant diversity indices, seven structural metrics, four soil properties, and in situ N2O efflux were also measured. We found that: 1) high tree diversity had 1.3-1.4-fold NO3--N, 1.1-fold NH4+-N, and 1.5-1.8-fold N2O efflux (p < 0.05). 2) Tree growth decreased soil TN, AN, and NO3--N by more than 13%, and tree mixing and un-uniform distribution increased TN, AN, and NH4+-N by 11-22%. 3) Soil organic carbon (SOC) explained 34.3% of the N variations, followed by soil water content (1.5%), tree diameter (1.5%) and pH (1%), and soil bulk density (0.5%). SOC had the most robust linear relations to TN (R2 = 0.59) and AN (R2 = 0.5). 4) The partial least squares path model revealed that the tree diversity directly increased NO3--N, NH4+-N, and N2O efflux, and they were strengthened indirectly from soil properties by 1%-4%. The effects of tree size-density (-0.24) and spatial structure (0.16) were mainly achieved via their soil interaction and thus indirectly decreased NH4+-N, AN, and TN. Overall, high tree diversity forests improved soil N availability and N2O efflux, and un-uniform spatial tree assemblages could partially balance the soil N consumed by tree growth. Our data support soil N management in high northern hemisphere temperate forests from tree diversity and forest structural regulations.
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Affiliation(s)
- Guanchao Cheng
- Key Laboratory of Forest Plant Ecology, Ministry of Education, Heilongjiang Provincial Key Laboratory of Ecological Utilization of Forestry-based Active Substances, College of Chemistry, Chemical Engineering and Resource Utilization, Northeast Forestry University, Harbin, 150040, China
| | - Xu Zhang
- Key Laboratory of Forest Plant Ecology, Ministry of Education, Heilongjiang Provincial Key Laboratory of Ecological Utilization of Forestry-based Active Substances, College of Chemistry, Chemical Engineering and Resource Utilization, Northeast Forestry University, Harbin, 150040, China
| | - Meina Zhu
- Key Laboratory of Forest Plant Ecology, Ministry of Education, Heilongjiang Provincial Key Laboratory of Ecological Utilization of Forestry-based Active Substances, College of Chemistry, Chemical Engineering and Resource Utilization, Northeast Forestry University, Harbin, 150040, China
| | - Zhonghua Zhang
- Key Laboratory of Forest Plant Ecology, Ministry of Education, Heilongjiang Provincial Key Laboratory of Ecological Utilization of Forestry-based Active Substances, College of Chemistry, Chemical Engineering and Resource Utilization, Northeast Forestry University, Harbin, 150040, China
| | - Lixin Jing
- Key Laboratory of Forest Plant Ecology, Ministry of Education, Heilongjiang Provincial Key Laboratory of Ecological Utilization of Forestry-based Active Substances, College of Chemistry, Chemical Engineering and Resource Utilization, Northeast Forestry University, Harbin, 150040, China
| | - Lei Wang
- Key Laboratory of Forest Plant Ecology, Ministry of Education, Heilongjiang Provincial Key Laboratory of Ecological Utilization of Forestry-based Active Substances, College of Chemistry, Chemical Engineering and Resource Utilization, Northeast Forestry University, Harbin, 150040, China
| | - Qi Li
- Key Laboratory of Forest Plant Ecology, Ministry of Education, Heilongjiang Provincial Key Laboratory of Ecological Utilization of Forestry-based Active Substances, College of Chemistry, Chemical Engineering and Resource Utilization, Northeast Forestry University, Harbin, 150040, China
| | - Xiting Zhang
- Key Laboratory of Forest Plant Ecology, Ministry of Education, Heilongjiang Provincial Key Laboratory of Ecological Utilization of Forestry-based Active Substances, College of Chemistry, Chemical Engineering and Resource Utilization, Northeast Forestry University, Harbin, 150040, China
| | - Huimei Wang
- State Key Laboratory of Subtropical Silviculture, College of Forestry and Biotechnology, Zhejiang A&F University, Hangzhou, 311300, Zhejiang, China.
| | - Wenjie Wang
- State Key Laboratory of Subtropical Silviculture, College of Forestry and Biotechnology, Zhejiang A&F University, Hangzhou, 311300, Zhejiang, China; Key Laboratory of Wetland Ecology and Environment, Northeast Institute of Geography and Agroecology, CAS, Changchun, 130102, China.
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5
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Åhlén D, Peacock M, Brodin Y, Hambäck PA. Wetland productivity determines trade-off between biodiversity support and greenhouse gas production. Ecol Evol 2023; 13:e10619. [PMID: 37869431 PMCID: PMC10587742 DOI: 10.1002/ece3.10619] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2023] [Revised: 09/13/2023] [Accepted: 10/04/2023] [Indexed: 10/24/2023] Open
Abstract
Establishing wetlands for nutrient capture and biodiversity support may introduce trade-offs between environmentally beneficial functions and detrimental greenhouse gas emissions. Investigating the interaction of nutrient capture, primary production, greenhouse gas production and biodiversity support is imperative to understanding the overall function of wetlands and determining possible beneficial synergistic effects and trade-offs. Here, we present temporally replicated data from 17 wetlands in hemi-boreal Sweden. We explored the relationship between nutrient load, primary producing algae, production of methane and nitrous oxide, and emergence rates of chironomids to determine what factors affected each and how they related to each other. Chironomid emergence rates correlated positively with methane production and negatively with nitrous oxide production, where water temperature was the main driving factor. Increasing nutrient loads reduced methanogenesis through elevated nitrogen concentrations, while simultaneously enhancing nitrous oxide production. Nutrient loads only indirectly increased chironomid emergence rates through increased chlorophyll-a concentration, via increased phosphorus concentrations, with certain taxa and food preference functional groups benefitting from increased chlorophyll-a concentrations. However, water temperature seemed to be the main driving factor for chironomid emergence rates, community composition and diversity, as well as for greenhouse gas production. These findings increase our understanding of the governing relationships between biodiversity support and greenhouse gas production, and should inform future management when constructing wetlands.
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Affiliation(s)
- David Åhlén
- Department of Ecology, Environment and Plant SciencesStockholm UniversityStockholmSweden
| | - Mike Peacock
- Department of Aquatic Sciences and AssessmentSwedish University of Agricultural SciencesUppsalaSweden
- Department of Geography and Planning, School of Environmental SciencesUniversity of LiverpoolLiverpoolUK
| | - Yngve Brodin
- Department of ZoologyThe Swedish Museum of Natural HistoryStockholmSweden
| | - Peter A. Hambäck
- Department of Ecology, Environment and Plant SciencesStockholm UniversityStockholmSweden
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Kwakwa PA, Aboagye S, Alhassan H, Gyamfi BA. Reducing agricultural nitrous oxide emissions in China: the role of food production, forest cover, income, trade openness, and rural population. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2023; 30:95773-95788. [PMID: 37556053 DOI: 10.1007/s11356-023-28990-z] [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: 01/05/2023] [Accepted: 07/22/2023] [Indexed: 08/10/2023]
Abstract
In the light of China's carbon-neutral goal, this study examines how food production, forest cover, trade openness, and rural population contribute to the quest of addressing China's agricultural nitrous oxide emissions. Time series data ranging from 1971 to 2018 was used for analysis in this study. The autoregressive distributed lag (ARDL) technique was employed to evaluate potential cointegration as well as to ascertain the long and short-run effects of food production, forest cover, income, trade openness, and rural population on agricultural nitrous oxide emission. The Toda-Yamomoto causality analysis was also used to identify the causal relations between covariates (food production, forest cover, income, trade openness, and rural population) and the outcome variable (agricultural nitrous oxide emission). The long-run evidence is that rural population in itself tends to increase agricultural nitrous oxide emissions likewise food production. There is also validation of the existence of environmental Kuznets curve for agricultural nitrous oxide emissions. Moreover, income interacts with rural population to reduce agricultural nitrous oxide emissions in the long-run. Causality analysis indicated rural population affects the level of forest cover; forest cover is found to cause agricultural nitrous oxide emissions but the converse is not established, and income as well as the interaction between income and rural population determines agricultural nitrous oxide emissions. The short-run dynamics results establish an oscillatory equilibrium convergence for agricultural nitrous oxide emissions in event of structural disturbances. From the findings, the EKC hypothesis is relevant by offering avenue to reduce emission. Thus, income growth remains helpful in addressing nitrous oxide emission from the agricultural sector. However, research is needed to unravel why nitrous oxide tends to increase in many forest areas. Since food production cannot be halted, policy makers need to enhance the uptake of efficient food production technologies including developing and using more renewable energy for food production. It is important for authorities to attend to rural development in order to mitigate agricultural nitrous oxide emissions in China.
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Affiliation(s)
- Paul Adjei Kwakwa
- School of Arts and Social Sciences, University of Energy and Natural Resources, Sunyani, Ghana.
| | - Solomon Aboagye
- Department of Economics, University of Cape Town, Cape Town, South Africa
| | - Hamdiyah Alhassan
- Department of Economics, University for Development Studies, Tamale, Ghana
| | - Bright Akwasi Gyamfi
- School of Management, Sir Padampat Singhania University, Bhatewar, Udaipur, Rajasthan, India
- Department of Business Administration Faculty of Economics and Administrative Sciences, Istanbul Gelisin University, Istanbul, Turkey
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7
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Mukhtar H, Ansari A, Ngoc-Dan Cao T, Wunderlich RF, Lin YP. Thermodynamic sensitivity of ammonia oxidizers-driven N 2O fluxes under oxic-suboxic realms. CHEMOSPHERE 2023:138872. [PMID: 37182716 DOI: 10.1016/j.chemosphere.2023.138872] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/26/2023] [Revised: 04/26/2023] [Accepted: 05/06/2023] [Indexed: 05/16/2023]
Abstract
In terrestrial ecosystems, the nitrogen dynamics, including N2O production, are majorly regulated by a complex consortium of microbes favored by different substrates and environmental conditions. To better predict the daily, seasonal and annual variation in N2O fluxes, it is critical to estimate the temperature sensitivity of different ammonia-oxidizing groups under oxic and suboxic conditions prevalent in soils and wetlands. Here, we studied the thermodynamics of N2O fluxes, via nitrification and nitrifier-denitrification, for two ammonia-oxidizers, archaea (AOA) and bacteria (AOB), across a wide temperature gradient (10-55 °C). Using square root theory (SQRT) and macromolecular rate theory (MMRT) models, we estimated thermodynamic parameters, cardinal temperatures, and maximum temperature sensitivity (TSmax). The distinction between N2O pathways was facilitated by microbial-specific inhibitors (PTIO and C2H2) and controlled oxygen supply (oxic: ambient; suboxic: ∼4%) environments. We found that nitrification supported by AOA (NtA) and AOB (NtB) dominated N2O production in an oxic climate, while only AOB-supported nitrifier-denitrification (NDB) majorly contributed (>90%) to suboxic N2O budget. The models predicted significantly higher temperature optima (Topt) and TSmax for NtA and NDB compared to NtB. Intriguingly, both NtB and NDB exhibited significantly wider temperature ranges than NtA. Altogether, our results suggest that temperature and oxygen supply control the dominance of specific AOA- and AOB-supported N2O pathways in soil and sediments. This emergent understanding can potentially contribute toward novel targeted N2O inhibitors for GHG mitigation under global warming.
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Affiliation(s)
- Hussnain Mukhtar
- Department of Bioenvironmental Systems Engineering, National Taiwan University, Taiwan
| | - Andrianto Ansari
- Department of Bioenvironmental Systems Engineering, National Taiwan University, Taiwan
| | - Thanh Ngoc-Dan Cao
- Department of Bioenvironmental Systems Engineering, National Taiwan University, Taiwan
| | | | - Yu-Pin Lin
- Department of Bioenvironmental Systems Engineering, National Taiwan University, Taiwan.
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8
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Li X, Xu YJ, Ni M, Wang C, Li S. Riverine nitrate source and transformation as affected by land use and land cover. ENVIRONMENTAL RESEARCH 2023; 222:115380. [PMID: 36716803 DOI: 10.1016/j.envres.2023.115380] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/27/2022] [Revised: 01/24/2023] [Accepted: 01/26/2023] [Indexed: 06/18/2023]
Abstract
A mixed land use/land cover (LULC) catchment increases the complexity of sources and transformations of nitrate in rivers. Spatial paucity of sampling particularly low-resolution sampling in tributaries can result in a bias for identifying nitrate sources and transformations. In this study, high spatial resolution sampling campaigns covering mainstream and tributaries in combination with hydro-chemical parameters and dual isotopes of nitrate were performed to reveal spatio-temporal variations of nitrate sources and transformations in a river draining a mixed LULC catchment. This study suggested that point sources dominated the nitrate in the summer and winter, while non-point sources dominated the nitrate in the spring and autumn. A positive correlation was observed between proportions from sewage and land use index (LUI). However, negative correlations between soil nitrogen/nitrogen fertilizer and LUI were observed. With an increase of urban areas, the increased contribution from domestic sewage resulted in an increase of NO3- concentrations in rivers. Both urban and agricultural inputs should be considered in nitrate pollution management in a mixed LULC catchment. We concluded that the seasonal variations of nitrate sources were mainly affected by flow velocity conditions and agricultural activities, while spatial variations were mainly affected by LULC. In addition, we found a novel underestimation of dominated sources from Bayesian model because of mixing effect of isotope values from the tributaries to mainstream, however, high spatial resolution sampling can make up for this shortcoming. δ15N and δ18O values of nitrate indicated that nitrate originated from nitrification in soils. The nitrate concentrations and correlation between δ15N and 1/[NO3-] suggested little contribution of nitrate removal by denitrification. Thus, the nitrate reduction in the Yuehe River basin needs to be strengthened. The study provides new implications for estimation of nitrate sources and transformations and basis for nitrate reduction in the river with mixed LULC catchment.
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Affiliation(s)
- Xing Li
- Institute of Changjiang Water Environment and Ecological Security, School of Environmental Ecology and Biological Engineering, Key Laboratory for Green Chemical Process of Ministry of Education, Hubei Key Laboratory of Novel Reactor and Green Chemical Technology, Wuhan Institute of Technology, Wuhan, 430205, China
| | - Y Jun Xu
- School of Renewable Natural Resources, Louisiana State University Agricultural Center, Baton Rouge, LA, 70803, USA; Coastal Studies Institute, Louisiana State University, Baton Rouge, LA, 70803, USA
| | - Maofei Ni
- College of Eco-environmental Engineering, Guizhou Minzu University, Guiyang, China
| | - Chunlin Wang
- Institute of Changjiang Water Environment and Ecological Security, School of Environmental Ecology and Biological Engineering, Key Laboratory for Green Chemical Process of Ministry of Education, Hubei Key Laboratory of Novel Reactor and Green Chemical Technology, Wuhan Institute of Technology, Wuhan, 430205, China
| | - Siyue Li
- Institute of Changjiang Water Environment and Ecological Security, School of Environmental Ecology and Biological Engineering, Key Laboratory for Green Chemical Process of Ministry of Education, Hubei Key Laboratory of Novel Reactor and Green Chemical Technology, Wuhan Institute of Technology, Wuhan, 430205, China.
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9
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Li S, Jiang H, Xu Z, Zhang Q. Backgrounds as a potentially important component of riverine nitrate loads. THE SCIENCE OF THE TOTAL ENVIRONMENT 2022; 838:155999. [PMID: 35597340 DOI: 10.1016/j.scitotenv.2022.155999] [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: 02/01/2022] [Revised: 04/25/2022] [Accepted: 05/12/2022] [Indexed: 06/15/2023]
Abstract
Nitrate (NO3-) is a major trigger for river eutrophication. While efforts have been made to understand the anthropogenic NO3- pollution in rivers, the role of background NO3- in determining NO3- loads remains to be studied. In this study, we used dual-isotopes (δ15N/δ18O-NO3-) and an isotope-mixing model to reveal the natural and anthropogenic processes regulating the NO3- loads in a forest river that acts as a headwater source for the China's South to North Water Transfer Project. Even though the basin is sparsely populated, the mean NO3--N concentration (0.6 ± 0.2 mg/L) was much higher than the median concentration of global rivers (0.3 ± 0.2 mg/L). Meanwhile, the δ15N-NO3- was extremely depleted (as low as -14.4‰). The correlations between the NO3- concentrations and isotopes indicate that the nitrification of different sources (i.e., soil organic nitrogen, chemical fertilizer, manure, and sewage) dominates the NO3- loads. Soil organic nitrogen accounted for c.a. 60% of the riverine NO3- in the high-flow season, which alone exceeds China's national standard. This finding clearly shows that high NO3- loads in rivers could not all be ascribed to direct anthropogenic inputs, and background NO3- could be critical triggers. Therefore, when evaluating the NO3- pollution of rivers, the background NO3- concentrations must be considered along with the actual NO3- loads. In the low-flow season, the contribution from manure and sewage (c.a. 34%) increases. This study highlights the potentially important role of background NO3- in regulating riverine NO3- loads, providing important implications for understanding high riverine NO3- loads worldwide.
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Affiliation(s)
- Siyue Li
- Institute of Changjiang Water Environment and Ecological Security, School of Environmental Ecology and Biological Engineering, Key Laboratory for Green Chemical Process of Ministry of Education, Engineering Research Center of Phosphorus Resources Development and Utilization of Ministry of Education, Hubei Key Laboratory of Novel Reactor and Green Chemical Technology, Wuhan Institute of Technology, Wuhan 430205, China
| | - Hao Jiang
- Key Laboratory of Aquatic Botany and Watershed Ecology, Wuhan Botanical Garden, Chinese Academy of Sciences, Wuhan 430074, China; Center of Plant Ecology, Core Botanical Gardens, Chinese Academy of Sciences, Wuhan 430074, China.
| | - Zhifang Xu
- Key Laboratory of Cenozoic Geology and Environment, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China
| | - Quanfa Zhang
- Key Laboratory of Aquatic Botany and Watershed Ecology, Wuhan Botanical Garden, Chinese Academy of Sciences, Wuhan 430074, China; Center of Plant Ecology, Core Botanical Gardens, Chinese Academy of Sciences, Wuhan 430074, China.
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Kasak K, Kill K, Uuemaa E, Maddison M, Aunap R, Riibak K, Okiti I, Teemusk A, Mander Ü. Low water level drives high nitrous oxide emissions from treatment wetland. JOURNAL OF ENVIRONMENTAL MANAGEMENT 2022; 312:114914. [PMID: 35339792 DOI: 10.1016/j.jenvman.2022.114914] [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: 12/03/2021] [Revised: 02/21/2022] [Accepted: 03/14/2022] [Indexed: 06/14/2023]
Abstract
Wetlands that are restored for carbon sequestration or created for water treatment are an important sources of greenhouse gases, especially methane. The emission of nitrous oxide (N2O) from these systems is often considered negligible due to the inundation and anerobic conditions that support complete denitrification. We used closed chamber method to analyze N2O fluxes over a long-term period across heterogeneous wetland ecosystem constructed for treating nitrate-rich agricultural runoff. Our results showed that the water depth and temperature were most important factors affecting high N2O emissions. The shallow areas where water depth was less than 9 cm created N2O hot spots that emitted 48.8% of the total wetlands annual emission while only covering 6% of the total area. The annual emission from shallow-water hot spots with dense helophytic vegetation was 4.85 ± 0.5 g N2O-N m-2 y-1 while it was only 0.37 ± 0.01 g N2O-N m-2 y-1 in deeper zones. While the water depth was the main factor for high N2O emissions, the temperatures increased the magnitude of the flux and therefore summer droughts and water drawdown created even larger hot spots. These results also suggest that IPCC benchmarks could underestimate N2O emission from shallow waterbodies. Thus, it is important that the shallow zones and water level drawdown in the created or restored wetlands is avoided to minimize the N2O flux.
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Affiliation(s)
- Kuno Kasak
- Department of Geography, Institute of Ecology and Earth Sciences, University of Tartu, Vanemuise 46, Tartu, 51014, Estonia.
| | - Keit Kill
- Department of Geography, Institute of Ecology and Earth Sciences, University of Tartu, Vanemuise 46, Tartu, 51014, Estonia
| | - Evelyn Uuemaa
- Department of Geography, Institute of Ecology and Earth Sciences, University of Tartu, Vanemuise 46, Tartu, 51014, Estonia
| | - Martin Maddison
- Department of Geography, Institute of Ecology and Earth Sciences, University of Tartu, Vanemuise 46, Tartu, 51014, Estonia
| | - Raivo Aunap
- Department of Geography, Institute of Ecology and Earth Sciences, University of Tartu, Vanemuise 46, Tartu, 51014, Estonia
| | - Kersti Riibak
- Department of Botany, Institute of Ecology and Earth Sciences, University of Tartu, Lai 40, Tartu, 51005, Estonia
| | - Isaac Okiti
- Department of Geography, Institute of Ecology and Earth Sciences, University of Tartu, Vanemuise 46, Tartu, 51014, Estonia
| | - Alar Teemusk
- Department of Geography, Institute of Ecology and Earth Sciences, University of Tartu, Vanemuise 46, Tartu, 51014, Estonia
| | - Ülo Mander
- Department of Geography, Institute of Ecology and Earth Sciences, University of Tartu, Vanemuise 46, Tartu, 51014, Estonia
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11
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Mander Ü, Tournebize J, Espenberg M, Chaumont C, Torga R, Garnier J, Muhel M, Maddison M, Lebrun JD, Uher E, Remm K, Pärn J, Soosaar K. High denitrification potential but low nitrous oxide emission in a constructed wetland treating nitrate-polluted agricultural run-off. THE SCIENCE OF THE TOTAL ENVIRONMENT 2021; 779:146614. [PMID: 34030255 DOI: 10.1016/j.scitotenv.2021.146614] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/13/2021] [Revised: 03/12/2021] [Accepted: 03/16/2021] [Indexed: 06/12/2023]
Abstract
Constructed wetlands (CW) can efficiently remove nitrogen from polluted agricultural run-off, however, a potential caveat is nitrous oxide (N2O), a harmful greenhouse gas and stratospheric ozone depleter. During five sampling campaigns, we measured N2O fluxes from a 0.53 ha off-stream CW treating nitrate-rich water from the intensively fertilized watershed in Rampillon, France, using automated chambers with a quantum cascade laser system, and manual chambers. Sediment samples were analysed for potential N2 flux using the HeO2 incubation method. Both inlet nitrate (NO3-) concentrations and N2O emission varied significantly between the seasons. In the Autumn and Winter inlet concentrations were about 11 mg NO3--N L-1, and < 6.5 mg NO3--N L-1 in the Spring and Summer. N2O emission was highest in the Autumn (mean ± standard error: 9.7 ± 0.2 μg N m-2 h-1) and lowest in the Summer (wet period: 0.2 ± 0.3 μg N m-2 h-1). The CW was a very weak source of N2O emitting 0.32 kg N2O-N ha-1 yr-1 and removing around 938 kg NO3--N ha-1 yr-1, the ratio of N2O-N emitted to NO3--N removed was 0.033%. The automated and manual chambers gave similar results. From the potential N2O formation in the sediment, only 9% was emitted to the atmosphere, the average N2 N 2O ratio was high: 89:1 for N2-Npotential: N2O-Npotential and 1353:1 for N2-Npotential: N2O-Nemitted. These results indicate complete denitrification. The focused principal component analysis showed strong positive correlation between the gaseous N2O fluxes and the following environmental factors: NO3--N concentrations in inlet water, streamflow, and nitrate reduction rate. Water temperature, TOC and DOC in the water and hydraulic residence time showed negative correlations with N2O emissions. Shallow off-stream CWs such as Rampillon may have good nitrate removal capacity with low N2O emissions.
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Affiliation(s)
- Ülo Mander
- Department of Geography, Institute of Ecology and Earth Sciences, University of Tartu, Tartu, Estonia; UR 1462 HYCAR, University Paris Saclay, French National Institute for Agriculture, Food, and Environment (INRAE), Antony, France.
| | - Julien Tournebize
- UR 1462 HYCAR, University Paris Saclay, French National Institute for Agriculture, Food, and Environment (INRAE), Antony, France
| | - Mikk Espenberg
- Department of Geography, Institute of Ecology and Earth Sciences, University of Tartu, Tartu, Estonia
| | - Cedric Chaumont
- UR 1462 HYCAR, University Paris Saclay, French National Institute for Agriculture, Food, and Environment (INRAE), Antony, France
| | - Raili Torga
- Department of Geography, Institute of Ecology and Earth Sciences, University of Tartu, Tartu, Estonia
| | | | - Mart Muhel
- Department of Geography, Institute of Ecology and Earth Sciences, University of Tartu, Tartu, Estonia
| | - Martin Maddison
- Department of Geography, Institute of Ecology and Earth Sciences, University of Tartu, Tartu, Estonia
| | - Jérémie D Lebrun
- UR 1462 HYCAR, University Paris Saclay, French National Institute for Agriculture, Food, and Environment (INRAE), Antony, France
| | - Emmanuelle Uher
- UR 1462 HYCAR, University Paris Saclay, French National Institute for Agriculture, Food, and Environment (INRAE), Antony, France
| | - Kalle Remm
- Department of Geography, Institute of Ecology and Earth Sciences, University of Tartu, Tartu, Estonia
| | - Jaan Pärn
- Department of Geography, Institute of Ecology and Earth Sciences, University of Tartu, Tartu, Estonia
| | - Kaido Soosaar
- Department of Geography, Institute of Ecology and Earth Sciences, University of Tartu, Tartu, Estonia
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12
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Grossel A, Bourennane H, Ayzac A, Pasquier C, Hénault C. Indirect emissions of nitrous oxide in a cropland watershed with contrasting hydrology in central France. THE SCIENCE OF THE TOTAL ENVIRONMENT 2021; 766:142664. [PMID: 33601668 DOI: 10.1016/j.scitotenv.2020.142664] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/26/2020] [Revised: 09/25/2020] [Accepted: 09/25/2020] [Indexed: 06/12/2023]
Abstract
Nitrous oxide (N2O) is an important greenhouse gas. Its atmospheric concentration have increased with the industrialisation and the use of N fertilizer. The contribution of freshwater systems to N2O emissions is still very uncertain, while regional transfer of nitrogen depends on soil and hydrology. Riverine and spring N2O dissolved in water was therefore measured over two years in the 3453 km2 Haut-Loir watershed (France). This temperate cropland watershed is characterized by two different hydrological systems east and west of the Loir River. The eastern rivers, fed by the emergence of the deep Beauce aquifer, exhibited significantly higher dissolved N2O concentrations (Beauce region, mean: 2.93 μg-N L-1) than the western rivers (Perche region, mean: 0.87 μg-N L-1), which were largely influenced by runoff during winter flooding. The eastern rivers had large nitrate concentrations all over the year; in the Perche, nitrate underwent a seasonal cycle with large loads during winter floods, but there were no consistent seasonal patterns in N2O. The ratios of N2O in excess of equilibrium on nitrate, often used as a proxy of emission factor (EF), were much smaller than the default IPCC values, both for rivers (0.014% versus 0.25% for IPCC EF5r) and the Loir spring (0.085% versus 0.6% for the IPCC EF5g for groundwater and springs). EF5r were significantly different between the two parts of the watershed only in winter, because of the seasonal variability of NO3-. Moreover dissolved N2O is controlled not only by NO3-, as it is considered in the calculation of the EF5, but also by water pH and dissolved organic carbon. A good prediction of dissolved N2O was obtained using these physicochemical variables and hydrological regions. Thus, these results suggest that the spatial variability of riverine N2O depends on local hydrology, while further research is needed to understand the seasonal variability.
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Affiliation(s)
| | | | | | | | - Catherine Hénault
- INRAE, URSOLS, F-45074 Orléans, France; INRAE, UMR Agroécologie, Dijon, France
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13
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Marginal Trade-Offs for Improved Agro-Ecological Efficiency Using Data Envelopment Analysis. AGRONOMY-BASEL 2021. [DOI: 10.3390/agronomy11020365] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Today’s agricultural management decisions impact food security and sustainable ecosystems, even when operating with back-to-basic operations. In such endeavors, policymakers usually need a quantitative tool, such as trade-offs margins, to effectively adjust resource consumption or production. This paper applies the weighted slack-based measurement (SBM-DEA) program to 136 developing countries’ agricultural performance. First, it finds the current agricultural efficiency and then makes marginal trade-offs on desirable-output variables (such as crop yield and forest area) to see the effective changes in undesirable-output (such as methane and nitrous oxide emissions). The results show that choosing effective marginal trade-offs does not deteriorate the relative efficiency of the decision-making units (DMUs) below the efficient frontier line. Thus, such a method enables the decision-makers to determine the best marginal trade-off points to reach the optimal efficiencies and decide which output factor needs special brainstorming to design effective policy.
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14
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Li M, Peng C, Zhang K, Xu L, Wang J, Yang Y, Li P, Liu Z, He N. Headwater stream ecosystem: an important source of greenhouse gases to the atmosphere. WATER RESEARCH 2021; 190:116738. [PMID: 33321453 DOI: 10.1016/j.watres.2020.116738] [Citation(s) in RCA: 23] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/07/2020] [Revised: 11/15/2020] [Accepted: 12/07/2020] [Indexed: 06/12/2023]
Abstract
Although an increasing number of reports have revealed that rivers are important sources of greenhouse gases (GHGs), the magnitude and underlying mechanism of riverine GHG emissions are still poorly understood. The global extent of the headwater stream ecosystem may represent one of the important GHG emitters. A global database of GHG measurements from 595 rivers, indicated that the concentrations of riverine GHGs continually decrease as the stream order increases. Further analysis suggested that high GHG emissions from headwater streams (Strahler stream orders of 1 to 3) could be related to the low levels of dissolved oxygen, massive terrestrially derived carbon/nitrogen inputs and large gas exchange velocity. Through a combination of the predicted river surface areas and gas transfer velocities, we estimated that globally, the rivers emit approximately 6.6 (5.5-7.8) Pg CO2, 29.5 (19.6-37.3) Tg CH4, and 0.6 (0.2-0.9) Tg N2O per year, and totally emit 7.6 (6.1-9.1) CO2 equivalent into atmosphere per year. The headwater streams contribute 72.3%, 75.5%, and 77.2% of the global riverine CO2, CH4, and N2O emissions, respectively. This study presents a systematic estimation of GHG emissions from river ecosystems worldwide and highlights the dominant role played by headwater streams in GHG evasions from global rivers.
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Affiliation(s)
- Mingxu Li
- Key Laboratory of Ecosystem Network Observation and Modeling, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing, 100101, China
| | - Changhui Peng
- College of Resources and Environmental Science, Hunan Normal University, Changsha, 410081 China; Department of Biology Sciences, Institute of Environment Sciences, University of Quebec at Montreal, C.P. 8888, Succ. Center-Ville, Montreal H3C 3P8, Canada.
| | - Kerou Zhang
- Institute of Wetland Research, Chinese Academy of Forestry, Beijing, 100091, China
| | - Li Xu
- Key Laboratory of Ecosystem Network Observation and Modeling, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing, 100101, China
| | - Jianming Wang
- Key Laboratory of Ecosystem Network Observation and Modeling, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing, 100101, China
| | - Yan Yang
- Key Laboratory of Ecosystem Network Observation and Modeling, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing, 100101, China
| | - Peng Li
- College of Resources and Environmental Science, Hunan Normal University, Changsha, 410081 China
| | - Zelin Liu
- College of Resources and Environmental Science, Hunan Normal University, Changsha, 410081 China
| | - Nianpeng He
- Key Laboratory of Ecosystem Network Observation and Modeling, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing, 100101, China..
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15
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Zhang W, Li H, Xiao Q, Li X. Urban rivers are hotspots of riverine greenhouse gas (N 2O, CH 4, CO 2) emissions in the mixed-landscape chaohu lake basin. WATER RESEARCH 2021; 189:116624. [PMID: 33242788 DOI: 10.1016/j.watres.2020.116624] [Citation(s) in RCA: 49] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/12/2020] [Revised: 10/20/2020] [Accepted: 11/07/2020] [Indexed: 06/11/2023]
Abstract
Growing evidence shows that riverine networks surrounding urban landscapes may be hotspots of riverine greenhouse gas (GHG) emissions. This study strengthens the evidence by investigating the spatial variability of diffusive GHG (N2O, CH4, CO2) emissions from river reaches that drain from different types of landscapes (i.e., urban, agricultural, mixed, and forest landscapes), in the Chaohu Lake basin of eastern China. Our results showed that almost all the rivers were oversaturated with dissolved GHGs. Urban rivers were identified as emission hotspots, with mean fluxes of 470 μmol m-2d-1 for N2O, 7 mmol m-2d-1 for CH4, and 900 mmol m-2d-1 for CO2, corresponding to ~14, seven, and two times of those from the non-urban rivers in the Chaohu Lake basin, respectively. Factors related to the high N2O and CH4 emissions in urban rivers included large nutrient supply and hypoxic environments. The factors affecting CO2 were similar in all the rivers, which were temperature-dependent with suitable environments that allowed rapid decomposition of organic matter. Overall, this study highlights that better recognition of the influence that river networks have on global warming is required-particularly when it comes to urban rivers, as urban land cover and populations will continue to expand in the future. Management measures should incorporate regional hotspots to more efficiently mitigate GHG emissions.
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Affiliation(s)
- Wangshou Zhang
- Key Laboratory of Watershed Geographic Sciences, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing 210008, China.
| | - Hengpeng Li
- Key Laboratory of Watershed Geographic Sciences, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing 210008, China.
| | - Qitao Xiao
- Key Laboratory of Watershed Geographic Sciences, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing 210008, China
| | - Xinyan Li
- Key Laboratory of Watershed Geographic Sciences, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing 210008, China
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16
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Headwater Stream Microbial Diversity and Function across Agricultural and Urban Land Use Gradients. Appl Environ Microbiol 2020; 86:AEM.00018-20. [PMID: 32245755 DOI: 10.1128/aem.00018-20] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2020] [Accepted: 03/26/2020] [Indexed: 12/26/2022] Open
Abstract
Anthropogenic activity impacts stream ecosystems, resulting in a loss of diversity and ecosystem function; however, little is known about the response of aquatic microbial communities to changes in land use. Here, microbial communities were characterized in 82 headwater streams across a gradient of urban and agricultural land uses using 16S rRNA gene amplicon sequencing and compared to a rich data set of physicochemical variables and traditional benthic invertebrate indicators. Microbial diversity and community structures differed among watersheds with high agricultural, urban, and forested land uses, and community structure differed in streams classified as being in good, fair, poor, and very poor condition using benthic invertebrate indicators. Microbial community similarity decayed with geodesic distance across the study region but not with environmental distance. Stream community respiration rates ranged from 21.7 to 1,570 mg O2 m-2 day-1 and 31.9 to 3,670 mg O2 m-2 day-1 for water column and sediments, respectively, and correlated with nutrients associated with anthropogenic influence and microbial community structure. Nitrous oxide (N2O) concentrations ranged from 0.22 to 4.41 μg N2O liter-1; N2O concentration was negatively correlated with forested land use and was positively correlated with dissolved inorganic nitrogen concentrations. Our findings suggest that stream microbial communities are impacted by watershed land use and can potentially be used to assess ecosystem health.IMPORTANCE Stream ecosystems are frequently impacted by changes in watershed land use, resulting in altered hydrology, increased pollutant and nutrient loads, and habitat degradation. Macroinvertebrates and fish are strongly affected by changes in stream conditions and are commonly used in biotic indices to assess ecosystem health. Similarly, microbes respond to environmental stressors, and changes in community composition alter key ecosystem processes. The response of microbes to habitat degradation and their role in global biogeochemical cycles provide an opportunity to use microbes as a monitoring tool. Here, we identify stream microbes that respond to watershed urbanization and agricultural development and demonstrate that microbial diversity and community structure can be used to assess stream conditions and ecosystem functioning.
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