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Qin C, Li SL, Wu Y, Bass AM, Luo W, Ding H, Yue FJ, Zhang P. High sensitivity of dissolved organic carbon transport during hydrological events in a small subtropical karst catchment. THE SCIENCE OF THE TOTAL ENVIRONMENT 2024; 946:174090. [PMID: 38914338 DOI: 10.1016/j.scitotenv.2024.174090] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/04/2024] [Revised: 05/10/2024] [Accepted: 06/16/2024] [Indexed: 06/26/2024]
Abstract
Dissolved organic carbon (DOC) and discharge are often tightly coupled, though these relationships in karst environments remain poorly constrained. In this study, DOC dynamics over 13 hydrological events, alongside monthly monitoring over an entire hydrological year were monitored in a small karst catchment, SW China. The concurrent analyses of power-law model and hysteresis patterns reveal that DOC behavior is generally transport-limited due to flushing effects of increased discharge but highly variable at both intra- and inter-event scales. The initial discharge at event onset and discharge-weighted mean concentration of DOC ([DOC]DW) of individual events can explain 37.7 % and 19.9 % of the variance of DOC behavior among events, respectively. The sustained dry-cold antecedent conditions make DOC hysteresis behavior during the earliest event complex and different from subsequent events. At event scale, the variability in DOC export is primarily controlled by [DOC]DW (explaining 64.3 %) and the yield of total dissolved solutes (YTDS, explaining 30.4 %), reflecting the impacts of variable hydrological connectivity and intense soil-water-rock interactions in this karst catchment. On an annual scale, DOC yield (YDOC, 222.86 kg C km-2) was mostly derived during the wet season (98.19 %) under the hydrological driving force. The difference in annual YDOC between this karst catchment and other regions can be well explained by annual water yield (Ywater, explaining 24.2 %) and [DOC] (explaining 35.4 %), whereas the variance in DOC export efficiency among catchments is almost exclusively controlled by [DOC] alone, independent of drainage area and annual Ywater. This study highlights the necessity of high-frequency sampling for modeling carbon biogeochemical processes and the particularity of the earliest hydrological events occurred after a long cold-dry period in karst catchments. Under the changing climate, whether DOC dynamics in karst catchments will present source-limited patterns during more extreme hydrological events merits further study.
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Affiliation(s)
- Caiqing Qin
- Department of Earth & Environmental Science, School of Human Settlements and Civil Engineering, Xi'an Jiaotong University, Xi'an, 710049, China; Institute of Surface-Earth System Science, School of Earth System Science, Tianjin University, Tianjin 300072, China
| | - Si-Liang Li
- Institute of Surface-Earth System Science, School of Earth System Science, Tianjin University, Tianjin 300072, China.
| | - Yiping Wu
- Department of Earth & Environmental Science, School of Human Settlements and Civil Engineering, Xi'an Jiaotong University, Xi'an, 710049, China.
| | - Adrian M Bass
- School of Geographical and Earth Sciences, University of Glasgow, Glasgow G12 8QQ, United Kingdom
| | - Weijun Luo
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China
| | - Hu Ding
- Institute of Surface-Earth System Science, School of Earth System Science, Tianjin University, Tianjin 300072, China
| | - Fu-Jun Yue
- Institute of Surface-Earth System Science, School of Earth System Science, Tianjin University, Tianjin 300072, China
| | - Pan Zhang
- Department of Earth & Environmental Science, School of Human Settlements and Civil Engineering, Xi'an Jiaotong University, Xi'an, 710049, China
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Yue FJ, Li SL, Waldron S, Oliver DM, Chen X, Li P, Peng T, Liu CQ. Source availability and hydrological connectivity determined nitrate-discharge relationships during rainfall events in karst catchment as revealed by high-frequency nitrate sensing. WATER RESEARCH 2023; 231:119616. [PMID: 36696876 DOI: 10.1016/j.watres.2023.119616] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/21/2022] [Revised: 01/09/2023] [Accepted: 01/14/2023] [Indexed: 06/17/2023]
Abstract
Karst terrain seasonal monsoonal rainfall is often associated with high concentrations of nitrate-N in streams draining agricultural land. Such high concentrations can pose problems for environmental and human health. However, the relationship between rainfall events that mobilize nitrate and resulting nitrate export remains poorly understood in karst terrain. To better understand the processes that drive nitrate dynamics during rainfall events, the characteristics of individual rainfall events were analyzed using sensor technology. Thirty-eight rainfall events were separated from the high-frequency dataset spanning 19 months at a karst spring site. The results revealed that nitrate-discharge (N-Q) hysteresis in 79% of rainfall events showed anticlockwise hysteresis loop patterns, indicating nitrate export from long distances within short event periods. Karstic hydrological connectivity and source availability were considered two major determining factors of N-Q hysteresis. Gradual increase in hydrological connectivity during intensive rainfall period accelerated nitrate transportation by karst aquifer systems. Four principal components (PCs, including antecedent conditions PC1&3 and rainfall characteristics PC2&4 explained 82% of the cumulative variance contribution to the rainfall events. Multiple linear regression of four PCs explained more than 50% of the variation of nitrate loading and amplitude during rainfall events, but poorly described nitrate concentrations and hydro-chemistry parameters, which may be influenced by other factors, e.g., nitrate transformation, fertilization time and water-rock interaction. Although variation of N concentration during event flow is evident, accounting for antecedent conditions and rainfall factors can help to predict rainfall event N loading during rainfall events. Pollution of the karstic catchment occurred by a flush of nitrate input following rainfall events; antecedent and rainfall conditions are therefore important factors to consider for the water quality management. Reducing source availability during the wet season may facilitate to reduction of nitrogen loading in similar karst areas.
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Affiliation(s)
- Fu-Jun Yue
- Institute of Surface-Earth System Science, School of Earth System Science, Tianjin University, Tianjin 300072, China; School of Geographical and Earth Sciences, University of Glasgow, Glasgow G12 8QQ, United Kingdom
| | - Si-Liang Li
- Institute of Surface-Earth System Science, School of Earth System Science, Tianjin University, Tianjin 300072, China.
| | - Susan Waldron
- School of Geographical and Earth Sciences, University of Glasgow, Glasgow G12 8QQ, United Kingdom
| | - David M Oliver
- Biological & Environmental Sciences, Faculty of Natural Sciences, University of Stirling, Stirling FK9 4LA, United Kingdom
| | - Xi Chen
- Institute of Surface-Earth System Science, School of Earth System Science, Tianjin University, Tianjin 300072, China
| | - Pan Li
- Institute of Surface-Earth System Science, School of Earth System Science, Tianjin University, Tianjin 300072, China
| | - Tao Peng
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China
| | - Cong-Qiang Liu
- Institute of Surface-Earth System Science, School of Earth System Science, Tianjin University, Tianjin 300072, China
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Li X, Wang J, Lin J, Yin W, Shi YY, Wang L, Xiao HB, Zhong ZM, Jiang H, Shi ZH. Hysteresis analysis reveals dissolved carbon concentration - discharge relationships during and between storm events. WATER RESEARCH 2022; 226:119220. [PMID: 36242935 DOI: 10.1016/j.watres.2022.119220] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/21/2022] [Revised: 09/30/2022] [Accepted: 10/05/2022] [Indexed: 06/16/2023]
Abstract
The dissolved carbon concentration, which is responsible for aquatic ecosystem productivity and water quality, is tightly coupled with hydrological processes. Excess dissolved carbon may exacerbate eutrophication and hypoxia in aquatic ecosystems and lead to deterioration of water quality. Storm events dominate the dynamics of dissolved carbon concentrations, and this nonlinear behavior exhibits significant time scale dependence. Here, we identified inter- and intra-event variability in the dissolved carbon concentration-discharge (C-Q) relationship in an agriculture-intensive catchment. The driving factors of C-Q hysteresis patterns for dissolved inorganic carbon (DIC) and organic carbon (DOC) were quantified by redundancy analysis combined with hierarchical partitioning. At the inter-event scale, DIC exhibited mainly clockwise hysteresis, indicating an exhaustible, proximal source (e.g., groundwater). However, DOC hysteresis was generally counter-clockwise, indicating distal and plentiful sources (e.g., soil water) in the agricultural catchment. Hierarchical partitioning showed that total rainfall, peak discharge and flood intensity explained 28.38% of the total variation in C-Q hysteresis for DIC and 39.87% for DOC at the inter-event scale. At the intra-event scale, time series analysis of dissolved carbon concentration and discharge indicated the interconversion of supply limitation to transport limitation, which depends on the activation of the specific DIC or DOC source zones. These findings provide significant insights into understanding the dynamics of dissolved carbon during storm periods and are important for targeted watershed management practices aimed at reducing carbon loading to surface waters.
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Affiliation(s)
- X Li
- State Environmental Protection Key Laboratory of Soil Health and Green Remediation, College of Resources and Environment, Huazhong Agricultural University, Wuhan 430070, China
| | - J Wang
- State Environmental Protection Key Laboratory of Soil Health and Green Remediation, College of Resources and Environment, Huazhong Agricultural University, Wuhan 430070, China.
| | - J Lin
- Nanjing Forestry University, Nanjing 210037, China
| | - W Yin
- Changjiang Water Resources Protection Institute, Wuhan 430051, China
| | - Y Y Shi
- State Environmental Protection Key Laboratory of Soil Health and Green Remediation, College of Resources and Environment, Huazhong Agricultural University, Wuhan 430070, China
| | - L Wang
- State Environmental Protection Key Laboratory of Soil Health and Green Remediation, College of Resources and Environment, Huazhong Agricultural University, Wuhan 430070, China
| | - H B Xiao
- State Environmental Protection Key Laboratory of Soil Health and Green Remediation, College of Resources and Environment, Huazhong Agricultural University, Wuhan 430070, China
| | - Z M Zhong
- State Environmental Protection Key Laboratory of Soil Health and Green Remediation, College of Resources and Environment, Huazhong Agricultural University, Wuhan 430070, China
| | - H Jiang
- Soil and Water Conservation Monitoring Centre, Danjiangkou 442700, China
| | - Z H Shi
- State Environmental Protection Key Laboratory of Soil Health and Green Remediation, College of Resources and Environment, Huazhong Agricultural University, Wuhan 430070, China.
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Binet S, Charlier JB, Jozja N, Défarge C, Moquet JS. Evidence of long term biogeochemical interactions in carbonate weathering: The role of planktonic microorganisms and riverine bivalves in a large fluviokarst system. THE SCIENCE OF THE TOTAL ENVIRONMENT 2022; 842:156823. [PMID: 35738376 DOI: 10.1016/j.scitotenv.2022.156823] [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: 04/22/2022] [Revised: 06/15/2022] [Accepted: 06/15/2022] [Indexed: 06/15/2023]
Abstract
The infiltration of organic-rich surface waters towards groundwaters, is known to play a significant role in carbonate weathering and in contributing to the atmospheric continental carbon sink. This paper investigated biogeochemical interactions in karst critical zones, with strong surface water /groundwater interactions, and in particular the role of planktonic microorganisms and riverine bivalves through the analysis of particulate organic matter (OM) oxidation on carbonate weathering. In the large Val d'Orléans fluviokarst aquifer (France), a 20-year monthly dataset of Nitrates, Dissolved Oxygen (DO), dissolved inorganic and organic Carbon (DIC and DOC) fluxes was gathered. The surface water-groundwater comparison of geochemical trends showed that planktonic microorganisms had drastically decreased in surface waters, related to the proliferation of Corbicula bivalves spreading and a decrease in nutrients. This decrease in planktonic microorganisms was followed by a DO increase and an DIC decrease at the karst resurgence. The degradation of planktonic microorganisms consumes DO and produces NO3, dissolved inorganic carbon (DIC) and a proton that in turn, dissolves calcite and produces DIC. Without the input from planktonic microorganisms, the fluviokarst has lost 29 % of this nitrification and 12 % of the carbonate dissolution capacities. Thus, the oxidation of particulate organic matter of planktonic microorganisms, which is part of heterotrophic respiration, appears to be a significant source of the inorganic carbon flux in riverine ecosystems. This shows how weathering can remain active under waters saturated versus calcite and suggests that the oxidation of organic matter can be a more appropriate mechanism than autotrophic respiration to explain the relationship between global warming and DIC flux change in rivers. Through the consumption of plankton, the animal life in rivers thus influences the inorganic carbon in groundwaters, creating a negative feedback in the carbon cycle.
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Affiliation(s)
- Stéphane Binet
- University of Orléans - INSU/CNRS - BRGM, UMR 7327, Institut des Sciences de la Terre d'Orléans (ISTO), 1A rue de la Férollerie, F-45071 Orléans Cedex 2, France.
| | - Jean-Baptiste Charlier
- BRGM, Univ. Montpellier, Montpellier, France; G-eau, INRAE, CIRAD, IRD, AgroParisTech, Supagro, BRGM, Montpellier, France
| | - Nevila Jozja
- University of Orléans, CETRAHE, 8 rue Léonard de Vinci, F-45072 Orléans cédex 2, France
| | - Christian Défarge
- University of Orléans - INSU/CNRS - BRGM, UMR 7327, Institut des Sciences de la Terre d'Orléans (ISTO), 1A rue de la Férollerie, F-45071 Orléans Cedex 2, France; University of Orléans, CETRAHE, 8 rue Léonard de Vinci, F-45072 Orléans cédex 2, France
| | - Jean-Sébastien Moquet
- University of Orléans - INSU/CNRS - BRGM, UMR 7327, Institut des Sciences de la Terre d'Orléans (ISTO), 1A rue de la Férollerie, F-45071 Orléans Cedex 2, France
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Zhang S, Han G, Zeng J, Liu M, Li X, Liu J. Multi-isotopes revealing the coastal river anthropogenic pollutants and natural material flux to ocean: Sr, C, N, S, and O isotope study. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2022; 29:61397-61411. [PMID: 35441999 DOI: 10.1007/s11356-022-20223-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: 06/30/2021] [Accepted: 04/08/2022] [Indexed: 06/14/2023]
Abstract
Coastal river exports massive terrestrial materials to the adjacent marine environment with information about chemical weathering, providing critical insights on riverine flux and the potential impact on marine ecosystem. In this study, the preliminary data of dissolved strontium (Sr) and 87Sr/86Sr in a typical coastal river in southeastern China were collected along with hydrochemistry and C, N, S, and O isotopes to discriminate the source of terrestrial weathering and the riverine flux. Sr concentrations exhibited a range of 0.084 ~ 1.307 μmol L-1, and 87Sr/86Sr values ranged 0.7089 ~ 0.7164. The total cationic charge (TZ+) ranged 0.2 ~ 11.7 meq L-1 with the predominant Ca2+ which accounted for > 50% of TZ+, while the anions were dominated by HCO3-. The extremely high Na+ and Cl- near the estuary indicated seawater mixing in such a coastal river. δ13C-DIC, δ15N-NO3-, δ18O-NO3-, and δ34S-SO42- of river water ranged - 24.1‰ ~ - 9.2‰, 0.3‰ ~ 22.7‰, - 2.1‰ ~ 21.4‰, and - 9.3‰ ~ 18.0‰, respectively. δ13C enhanced correspondingly to decreased δ34S, confirming the attendance of H2SO4 in carbonate weathering. Most δ18O values exhibited within ± 10‰, indicating the dominant nitrification process. δ15N presented slightly negative relationship with δ13C and no obvious correlation with δ34S, indicating relatively limited impact of denitrification. The depleted δ13C and δ15N may be attributed to carbonate dissolution with nitric acids and the oxidation of organic matters into C and N pools. Quantitative analysis revealed that silicate weathering accounts for 79% of total dissolved Sr, indicating the dominant weathering process. The estimated monthly flux of dissolved Sr to the East China Sea was 138.1 tons, demonstrating an potential impact on seawater Sr isotope evolution. Overall, the investigations of multi-isotopes revealed the enhancement of weathering rates and the consequently depleted CO2 consumption, which further proved the involvement of strong acids (H2SO4 and HNO3). This study provides scientific insight in terrestrial weathering and anthropogenic impact of a typical coastal watershed and may orient the management of environmental issues related to coastal ecosystems.
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Affiliation(s)
- Shitong Zhang
- Institute of Earth Sciences, China University of Geosciences (Beijing), Beijing, 100083, China
| | - Guilin Han
- Institute of Earth Sciences, China University of Geosciences (Beijing), Beijing, 100083, China.
| | - Jie Zeng
- Institute of Earth Sciences, China University of Geosciences (Beijing), Beijing, 100083, China
| | - Man Liu
- Institute of Earth Sciences, China University of Geosciences (Beijing), Beijing, 100083, China
| | - Xiaoqiang Li
- Institute of Earth Sciences, China University of Geosciences (Beijing), Beijing, 100083, China
| | - Jinke Liu
- Institute of Earth Sciences, China University of Geosciences (Beijing), Beijing, 100083, China
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Seasonal and Spatial Variations of δ13CDIC Values in the Mun River, Northeast Thailand. WATER 2022. [DOI: 10.3390/w14091340] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
As an important part of the global carbon cycle, dissolved inorganic carbon (DIC) concentration and its stable carbon isotopic composition (δ13CDIC) have been used to constrain the sources of DIC in rivers. In this study, we systematically investigated the water chemistry, DIC contents, and δ13CDIC values in a tropical agricultural river in northeast Thailand. The water temperature ranged from 20.3 to 31.3 °C, and water pH values ranged from 6.4 to 8.4, with seasonal variations. Based on the major ion compositions, the hydro-chemical type of the Mun River water was a unique Na–Ca–Cl–HCO3 type, controlled by evaporite and silicate weathering. Seasonal variation of DIC concentrations and its carbon isotopic composition was obvious; DIC and δ13CDIC were significantly lower in the wet season (135 to 3146 μmol/L and −31.0‰ to −7.0‰) compared to the dry season (185 to 5897 μmol/L and −19.6‰ to −2.7‰). A high level of 12C-enriched DIC/CO2 from soil respiration and organic matter oxidation may cause the low pH values, δ13CDIC values, and high partial pressure of CO2 (pCO2) in the middle and lower reaches during the wet/rainy season compared to the dry season. This may be responsible for the seasonal and spatial variations of DIC concentrations and δ13CDIC values in the Mun River. According to the relationship between pCO2 and δ13CDIC values, CO2 outgassing may be more significant in the dry season, due to the greater influx of groundwater with higher pCO2 levels; and the rapid CO2 diffusion into the atmosphere will continuously increase the δ13CDIC values and decrease pCO2 levels. These results show that riverine biologic effects and CO2 outgassing play important roles in the DIC and δ13CDIC evolution of this typical agriculturally-dominated watershed.
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A Strontium and Hydro-Geochemical Perspective on Human Impacted Tributary of the Mekong River Basin: Sources Identification, Fluxes, and CO2 Consumption. WATER 2021. [DOI: 10.3390/w13213137] [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
As the largest and most representative tributary of the Mekong River, the Mun River Basin (MRB) provides critical understanding of regional hydro-geochemical features and rock weathering processes on a basin scale. The present study measured strontium (Sr) isotopes with hydro-geochemistry data of 56 water samples in detail in the MRB in northeast Thailand. The dissolved Sr contents and 87Sr/86Sr isotopic ratios were reported to be 8.7–344.6 μg/L (average 126.9 μg/L) and 0.7085–0.7281 (average 0.7156), respectively. The concentrations of dissolved Sr in the mainstream slightly decreased from upstream to downstream, while the variation trend of 87Sr/86Sr was on the contrary. Correlation analysis showed that Na+ strongly correlated with Cl− (0.995, p < 0.01), while Ca2+ exhibited weak relationships with SO42− (0.356, p < 0.01). Samples of the MRB exhibited lower Mg2+/Na+, Ca2+/Na+, HCO3−/Na+ and 1000Sr/Na ratios, and gathered around the end-member of evaporite dissolution, with slight shift to silicate weathering end-member, demonstrating the dominant contribution of evaporite dissolution and silicate weathering on dissolved loads. Comparing with data of major world rivers from previous research, our results remained consistency with rivers draining through similar geological conditions. The dissolved Sr flux to the adjacent Mekong River was estimated to be 20.7 tons/year. In accordance with the forward model, silicate weathering rate and CO2 consumption rate during dry season were calculated to be 0.73 tons/km2/year and 1.94 × 104 mol/km2/year, and may get underestimated due to intense water consumption by extensive agricultural activities. The superimposed effect of anthropogenic impacts on the water environment could enhance chemical weathering, and thus should be taken into account in regional ion cycles and carbon budgets. These findings highlight the coupling analysis of Sr isotopes and hydro-geochemistry in Earth surface processes and provide basic investigation for sustainable regional water treatment mechanisms in the pan basin of the Mekong River.
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Stream Hydrochemical Response to Flood Events in a Multi-Lithological Karstic Catchment from the Pyrenees Mountains (SW France). WATER 2021. [DOI: 10.3390/w13131818] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Hydrological variations hold a significant influence over the water chemistry in the karstic critical zone. In this context, the karstic Baget Catchment (BC) has been monitored at a high resolution over two years at the outlet in order to set up a typology of the flood events. The objective was to assess the multiple streamwater physico-chemical patterns in response to hydrological variations, streamflow component (quick-response, subsurface, and baseflow) and lithological contributions, and biogeochemical processes. The karstic catchment exhibited an impulsive response to flood events in relation to the typical structural and morphological characteristics of the karst. In addition, this response was constrained by the magnitude of the rainfall and the preceding hydroclimatic conditions. The variability of the dissolved load in streamflow was closely associated with the characteristics of the weathered rocks and the hydrological conditions throughout the year. Two simple indicators allow to characterize the concentration–discharge relationships with different hysteresis patterns on a set of floods with various intensities and shapes of the hydrograph and under different hydrological conditions before the flood. Almost all elements exhibited either clockwise loops or more complex behaviors, suggesting a higher overall concentration when the major water contribution comes from the quick-response flow (karst and surface runoff fraction). Besides, the epikarst flushing under dry conditions led counterclockwise hysteresis patterns for calcium (Ca2+) and bicarbonate (HCO3−) which revealed an overall chemostatic behavior as a result of carbonate dissolution in the karst. On the contrary, sulfate (SO42−) exhibited the widest relative variation during flooding and showed a significant sensitivity to the dilution process with increasing discharge. For medium flood episodes (Qmax < 4.4 m3·s−1), an overall concentration increase or chemostatic behavior could be observed during the rising limb of the hydrograph. On the opposite, under extreme flood episodes (Qmax > 8.3 m3·s−1) occurring after several rain events, a dilution pattern was noted for all elements originating from rock weathering. Finally, high-frequency sampling during storm events improved the understanding of the factors controlling the hydrochemical dynamic in karstic catchments.
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Zeng J, Han G. Rainwater chemistry observation in a karst city: variations, influence factors, sources and potential environmental effects. PeerJ 2021; 9:e11167. [PMID: 33976970 PMCID: PMC8065247 DOI: 10.7717/peerj.11167] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2020] [Accepted: 03/05/2021] [Indexed: 12/03/2022] Open
Abstract
The rainwater chemistry and related air contaminants are used to investigate the rainwater ions sources, variations, and influence factors from 2012 to 2014 in Guiyang city (the typical karst urban area of Southwest China). According to temporal rainwater ion concentrations, the obvious variations were presented in the study period, such as Ca2+ (125∼6,652 μeq L−1) and SO42− (11∼4,127 μeq L−1). Consequently, Ca2+, Mg2+, SO42− and Cl− are considered as the leading ions. Three critical influencing factors of rainwater ions concentrations, including sources variations, rainfall amount and long-distance migration (rainfall amount > 100 mm) are identified. Based on the typical ionic ratios, source identification suggested that anthropogenic inputs mainly contributed to F−, NO3− and SO42−, while the dusts (crustal sources) are the primary sources of Mg2+, Ca2+ and K+. Cl− Enrichment in long-distance transport is the main contributor of Cl−. According to the observation of high level of total wet acid deposition, the more detailed spatio-temporal monitoring of rainfall-related acid deposition (particularly sulfur deposition) is required to understand its potential environmental effects in the aquatic ecosystem of the earth surface.
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Affiliation(s)
- Jie Zeng
- Institute of Earth Sciences, China University of Geosciences (Beijing), Beijing, China
| | - Guilin Han
- Institute of Earth Sciences, China University of Geosciences (Beijing), Beijing, China
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Sun P, He S, Yu S, Pu J, Yuan Y, Zhang C. Dynamics in riverine inorganic and organic carbon based on carbonate weathering coupled with aquatic photosynthesis in a karst catchment, Southwest China. WATER RESEARCH 2021; 189:116658. [PMID: 33249310 DOI: 10.1016/j.watres.2020.116658] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/22/2020] [Revised: 11/17/2020] [Accepted: 11/18/2020] [Indexed: 06/12/2023]
Abstract
Carbonate mineral weathering coupled with aquatic photosynthesis, herein termed 'coupled carbonate weathering' (CCW), represents a significant carbon sink which is determined by riverine hydrochemical variations. The magnitudes, variations and mechanisms responsible for the carbon sink produced by CCW are still unclear. In this study, major ions, TOC and discharge data at the Darongjiang, Lingqu, Guilin and Yangshuo hydrologic stations in Li River basin, a karst catchment typical of this geographic region, were analysed from January 2012 to December 2015 to elucidate the temporal variations in riverine inorganic and organic carbon and their controlling mechanisms. The results show that (1) HCO3- was sourced from carbonate weathering and silicate weathering, carbonate weathering by carbonic acid being predominant; (2) TOC was created chiefly by the transformation of bicarbonate to organic carbon by aquatic phototrophs during the non-flood period; (3) The carbon sink produced by coupled carbonate weathering in the Li River basin was calculated to be 14.41 tC·km-2·yr-1, comprised of the sink attributable to carbonate weathering (12.17 tC·km-2·yr-1) and sink due to the "biological carbon pump" (SBCP) (2.24 tC·km-2·yr-1). The SBCP thus accounted for approximately 15.54% of the total carbon sink, indicating that the proportion of riverine TOC sourced by the transformation from bicarbonate to organic carbon by aquatic phototrophs may be high and must be considered in the estimation of carbonate weathering-related carbon sinks elsewhere.
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Affiliation(s)
- Ping'an Sun
- State Key Laboratory of Biogeology and Environmental Geology, School of Environmental Studies, China University of Geosciences, Wuhan 430074, China; Key Laboratory of Karst Dynamics, Ministry of Natural Resources & Guangxi, Institute of Karst Geology, Chinese Academy of Geological Sciences, Guilin 541004, China
| | - Shiyi He
- Key Laboratory of Karst Dynamics, Ministry of Natural Resources & Guangxi, Institute of Karst Geology, Chinese Academy of Geological Sciences, Guilin 541004, China
| | - Shi Yu
- Key Laboratory of Karst Dynamics, Ministry of Natural Resources & Guangxi, Institute of Karst Geology, Chinese Academy of Geological Sciences, Guilin 541004, China
| | - Junbing Pu
- Key Laboratory of Karst Dynamics, Ministry of Natural Resources & Guangxi, Institute of Karst Geology, Chinese Academy of Geological Sciences, Guilin 541004, China.
| | - Yaqiong Yuan
- Key Laboratory of Karst Dynamics, Ministry of Natural Resources & Guangxi, Institute of Karst Geology, Chinese Academy of Geological Sciences, Guilin 541004, China
| | - Cheng Zhang
- Key Laboratory of Karst Dynamics, Ministry of Natural Resources & Guangxi, Institute of Karst Geology, Chinese Academy of Geological Sciences, Guilin 541004, China
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Wang Z, Yin JJ, Pu J, Wang P, Liang X, Yang P, He Q, Gou P, Yuan D. Integrated understanding of the Critical Zone processes in a subtropical karst watershed (Qingmuguan, Southwestern China): Hydrochemical and isotopic constraints. THE SCIENCE OF THE TOTAL ENVIRONMENT 2020; 749:141257. [PMID: 32810707 DOI: 10.1016/j.scitotenv.2020.141257] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/31/2020] [Revised: 07/03/2020] [Accepted: 07/24/2020] [Indexed: 06/11/2023]
Abstract
Improving the management and protection of karst groundwater resources and addressing karst-related environmental and ecological problems still face challenges raised from the limited knowledge on the entire karstic Critical Zone (K-CZ), including soil, epikarst, the vadose and saturated zones. Particularly, there is still a lack of integrated understanding of K-CZ properties and major CZ processes across space and time. In this study, we measured and analyzed the hydrochemical and multiple stable isotopic compositions of soil water, surface- and groundwaters from various compartments of the K-CZ in a typical subtropical karst watershed - Qingmuguan (QKW), Southwestern China, in order to explore the source and spatiotemporal variations of water and solutes (C, N, S) within the K-CZ; thereby elucidating the hydrological and biogeochemical processes and their affecting factors. The results show that (i) the K-CZ of QKW is characterized by high heterogeneity and permeability, with fast and strong hydrologic variations in response to rainfall variability; (ii) water-CO2‑carbonate interactions (i.e. carbonate weathering) are remarkably active in different zones and are significantly modulated by hydrologic dynamics and seasonal change in biological activities; (iii) efficient migration of nitrate and sulfate occurs across the surface toward the saturated aquifer zone, which is affected by the source availability, elemental transformation and flow transport processes; (iv) human activities have clearly influenced groundwater quality and the natural K-CZ processes, for example, exogenic acids of anthropogenic origin (e.g. acid precipitation and nitrogenous fertilizers from crop lands) have been proven to be involved in the carbonate weathering, with a contribution of ~20%-30%. Our study highlights the strong coupling of hydrological and various biogeochemical processes and the interactive connection among various layers of K-CZ. Thus, systematical monitoring along the CZ profile and a process-based dynamic approach to elucidating climatic and anthropogenic forcing are necessary to better understand the K-CZ properties and functions.
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Affiliation(s)
- Zhijun Wang
- Key Laboratory of Karst Dynamics, Ministry of Natural Resources & Guangxi, Institute of Karst Geology, Chinese Academy of Geological Sciences, Guilin 541004, China
| | - Jian-Jun Yin
- Key Laboratory of Karst Dynamics, Ministry of Natural Resources & Guangxi, Institute of Karst Geology, Chinese Academy of Geological Sciences, Guilin 541004, China.
| | - Junbing Pu
- Key Laboratory of Karst Dynamics, Ministry of Natural Resources & Guangxi, Institute of Karst Geology, Chinese Academy of Geological Sciences, Guilin 541004, China.
| | - Peng Wang
- Chongqing Key Laboratory of Karst Environment, School of Geographical Sciences, Southwest University, Chongqing 400715, China; School of Environmental Science and Engineering, Guangdong University of Technology, Guangzhou 510006, China
| | - Xuan Liang
- Chongqing Key Laboratory of Karst Environment, School of Geographical Sciences, Southwest University, Chongqing 400715, China
| | - Pingheng Yang
- Chongqing Key Laboratory of Karst Environment, School of Geographical Sciences, Southwest University, Chongqing 400715, China
| | - Qiufang He
- Chongqing Key Laboratory of Karst Environment, School of Geographical Sciences, Southwest University, Chongqing 400715, China
| | - Pengfei Gou
- Chongqing Key Laboratory of Karst Environment, School of Geographical Sciences, Southwest University, Chongqing 400715, China
| | - Daoxian Yuan
- Key Laboratory of Karst Dynamics, Ministry of Natural Resources & Guangxi, Institute of Karst Geology, Chinese Academy of Geological Sciences, Guilin 541004, China; Chongqing Key Laboratory of Karst Environment, School of Geographical Sciences, Southwest University, Chongqing 400715, China
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Rainwater Chemistry Reveals Air Pollution in a Karst Forest: Temporal Variations, Source Apportionment, and Implications for the Forest. ATMOSPHERE 2020. [DOI: 10.3390/atmos11121315] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Temporal rainwater chemistry was used to reveal air pollution in the Maolan National Karst Forest Park (MNKFP), which is representative of the typical karst forest region of southwest China (SW China). The rainwater ions’ sources, variations, trends, and potential environmental effects were investigated from 2007 to 2010 and from 2013 to 2014. Based on the analysis of the temporal ionic concentrations of rainwater in the MNKFP, significant variations of ions were observed, including in NH4+ (9.7~266.6 μeq L−1) and SO42− (14.5~1396.4 μeq L−1), which were mainly controlled by variations in the source and rainfall amount; a decreased trend of rainwater pH was also observed. Accordingly, NH4+, Ca2+, SO42−, and Cl− were regarded as the most dominant ions. Typical ionic ratios and positive matrix factorization (PMF) model-based source apportionment suggested that anthropogenic inputs (coal combustion, industrial, traffic, and agricultural emissions) contributed 51% of F−, 93% of NO3−, 62% of SO42−, and 87% of NH4+, while the natural sources (crustal dust and sea salt) were the main sources of Cl− (74%), Na+ (82%), K+ (79%), Mg2+ (94%), and Ca2+ (93%). In combination with the reducing neutralization trend of temporal rainwater observed in the MNKFP and the potential effect of rainwater ion deposition on karst forests, more detailed monitoring of the rainfall-related deposition process is required for a better understanding of its potential environmental effects on the Earth’s surface.
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Zeng J, Yue FJ, Li SL, Wang ZJ, Wu Q, Qin CQ, Yan ZL. Determining rainwater chemistry to reveal alkaline rain trend in Southwest China: Evidence from a frequent-rainy karst area with extensive agricultural production. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2020; 266:115166. [PMID: 32682186 DOI: 10.1016/j.envpol.2020.115166] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/06/2020] [Revised: 07/01/2020] [Accepted: 07/01/2020] [Indexed: 06/11/2023]
Abstract
Rainwater chemistry plays an important role in the earth-surficial ecosystem, but studies on rainwater chemical composition of karst agro-ecosystem are rare. To explore the rainwater alkalization and the provenance of components responsible for neutralization, two-years chemical monitoring of rainwater was carried out in a karst agricultural catchment in Southwest China. The main findings suggest that SO42-, NO3-, Ca2+, and NH4+ are the principal ions. All the ionic contents show distinctly seasonal variation (highest in winter) in response to variations in seasonal precipitation because the rain-scour process can efficiently remove atmospheric materials. Source identification indicates that Cl- and Na+ are mainly derived from marine input whereas SO42- and NO3- are controlled by anthropogenic emission, in particular, fixed emission sources. The source of NH4+ is attributed to intense agricultural production, while Ca2+ and Mg2+ are mainly derived from calcite dissolution. The rainwater alkalization caused by the seasonal acid neutralization (via basic components, Ca2+ and NH4+) is beneficial to crop growth but also reflect agricultural overfertilization. Sulfur controlled the total wet acid deposition (68%-94%) and could be a potential agent of weathering.
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Affiliation(s)
- Jie Zeng
- Institute of Earth Sciences, China University of Geosciences (Beijing), Beijing, 100083, China
| | - Fu-Jun Yue
- Institute of Surface-Earth System Science, School of Earth System Science, Tianjin University, Tianjin, 300072, China; Tianjin Key Laboratory of Earth Critical Zone Science and Sustainable Development in Bohai Rim, Tianjin University, Tianjin, 300072, China; Puding Karst Ecosystem Research Station, Institute of Geochemistry, Chinese Academy of Sciences, Anshun, 562100, China.
| | - Si-Liang Li
- Institute of Surface-Earth System Science, School of Earth System Science, Tianjin University, Tianjin, 300072, China; Tianjin Key Laboratory of Earth Critical Zone Science and Sustainable Development in Bohai Rim, Tianjin University, Tianjin, 300072, China; Puding Karst Ecosystem Research Station, Institute of Geochemistry, Chinese Academy of Sciences, Anshun, 562100, China
| | - Zhong-Jun Wang
- Puding Karst Ecosystem Research Station, Institute of Geochemistry, Chinese Academy of Sciences, Anshun, 562100, China
| | - Qixin Wu
- Key Laboratory of Karst Environment and Geohazard, Ministry of Land and Resources, Guizhou University, Guiyang, 550025, China
| | - Cai-Qing Qin
- Institute of Surface-Earth System Science, School of Earth System Science, Tianjin University, Tianjin, 300072, China
| | - Ze-Long Yan
- Institute of Surface-Earth System Science, School of Earth System Science, Tianjin University, Tianjin, 300072, China
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A Forty-Year Karstic Critical Zone Survey (Baget Catchment, Pyrenees-France): Lithologic and Hydroclimatic Controls on Seasonal and Inter-Annual Variations of Stream Water Chemical Composition, pCO2, and Carbonate Equilibrium. WATER 2020. [DOI: 10.3390/w12051227] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The long-term trends and seasonal patterns of stream water chemical composition in a small remote forested karst catchment, were investigated from 1978 to 2018. Calcium, magnesium, and bicarbonates, the dominant ions, increased over the period together with temperature, while sulfates decreased. Carbonate and sulfate mineral dissolution was the main source of these elements. These trends and the seasonal opposite patterns of discharge vs. temperature, calcite saturation index vs. pCO2 and bicarbonate vs. sulfates, suggested the influence of discharge, of reduced long-range atmospheric pollution, and of increasing air temperature on biological activity and carbonate dissolution. Furthermore, the hydrological regime controlled the seasonal stream water chemical composition and fluxes by: (i) a dilution during the high discharge period, (ii) a change in the contribution rate of the waters draining different lithological areas in the catchment, e.g., the increased sulfates to bicarbonates ratio during summer low flows, with a maximum alkalinity decrease of 24%, and (iii) a “piston” and a “flushing” effects of dissolved elements stored in soils and epikarst with the first autumn heavy rains. Long-term stream water hydrochemical surveys of karst system have proved to be powerful indicators of biogeochemical processes, water sources and pathways under variable natural and anthropogenic environmental pressure conditions.
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