Continental silicate weathering acts as a crucial negative feedback mechanism for removing atmospheric CO_(2) and maintaining Earth's long-term climate stability.However,quantifying continental silicate weathering...Continental silicate weathering acts as a crucial negative feedback mechanism for removing atmospheric CO_(2) and maintaining Earth's long-term climate stability.However,quantifying continental silicate weathering rates and fluxes continues to pose a fundamental challenge in Earth system science.This study utilizes the GEOCLIM carbon cycle model,which integrates modern high-resolution(0.1°×0.1°)datasets on surface temperature,runoff,topography,and lithology to model the spatial distribution of global silicate weathering fluxes.Results indicate a strong correlation between modeled basin-scale outputs and hydrological observations,with weathering rates falling within consistent error margins.Silicate weathering fluxes exhibit distinct latitudinal patterns,with the highest values concentrated within 30°of the equator,accounting for 76.9%of the global total.Continental contributions differ significantly,with Asian river basins representing 36.9%of global fluxes,primarily from Southeast Asia(17.4%),South Asia(8.2%),and East Asia(6.6%).They are followed by South America(29.2%)and Africa(21.7%).Tectonically active regions contribute 21.9%of global silicate weathering,while stable regions account for 72.6%.Multivariate regression analyses using RF and XGBoost machine learning algorithms identify runoff as the primary controlling factor of weathering on a global scale.Weathering in stable regions is jointly regulated by runoff and erosion rates,whereas temperature is the prevailing factor in tectonically active zones.The GEOCLIM model offers a robust framework for quantifying continental weathering processes.Future studies should incorporate organic carbon oxidation,burial,and sulfide oxidation dynamics to clarify carbon cycle interactions and reveal climate-dependent mechanisms for weathering responses and feedback.展开更多
Silicon(Si)is an important element in aquatic ecosystems.Based on the observed data in the Huanghe(Yellow)River Basin,a forward model was used to evaluate the silicate weathering rate in the Huanghe River Basin.The ef...Silicon(Si)is an important element in aquatic ecosystems.Based on the observed data in the Huanghe(Yellow)River Basin,a forward model was used to evaluate the silicate weathering rate in the Huanghe River Basin.The effects of silicate weathering,damming,and land use change on the Si concentration and flux were analyzed.Results show that the dissolved Si(DSi)concentration decreased first and then increased,and was 0.82–2.96 mg/L.As a silicon source in the Huanghe River Basin,the silicate weathering rate in the upper reaches of Lanzhou was high,and a large amount of DSi was transported to the lower reaches.Agricultural irrigation in the middle reaches caused a large amount of DSi loss,and the interception of large-scale cascade reservoirs caused a large amount of DSi retention.The DSi released by sediment re-suspension due to high runoff scouring in the downstream channel also served as a silicon source to supplement the DSi flux transported to the sea.Suspended particulate matter and biogenic Si(BSi)increased first and then decreased in the ranges of 24.1–1590.7 mg/L and 0.08–2.17 mg/L,respectively,due mainly to severe soil erosion in the eastern Loess Plateau,which caused significant amounts of phytoliths to enter the water.展开更多
1 Introduction Global climate change is one of the greatest challenges facing humankind in the 21st century.Studying,and utilising,the carbon sink caused by the weathering of silicate minerals has been a key research ...1 Introduction Global climate change is one of the greatest challenges facing humankind in the 21st century.Studying,and utilising,the carbon sink caused by the weathering of silicate minerals has been a key research focus for展开更多
The water chemistry of Bhimtal Lake revealed the dominance of Ca￣(2+) and HCO_3￣- ions.The lake water chemistry is controlled by the dominance of Ca-Mg silicate weathering(mainly pumpellyite and epidote-bearing rock...The water chemistry of Bhimtal Lake revealed the dominance of Ca￣(2+) and HCO_3￣- ions.The lake water chemistry is controlled by the dominance of Ca-Mg silicate weathering(mainly pumpellyite and epidote-bearing rocks) supported by anthropogenic activity involving extensive road cutting and house holding activities, increased industrialization in the catchment area of the lake. On the basis of phosphate values. a transitional mesotrophic-eutrophic conditions exist in this lake.The observed chemical data of the Bhimtal Lake was used to predict the mineral assemblages in the carbonate and alumino-silicate system. It demonstrates that the calcite and dolomite are the possible minerals which are in equilibrium with the lake water system and that the lake water is in the range of stability of kaolinite.展开更多
Quantifying the functional relationships relating river discharge and weathering products places key constraints on the negative feedback between the silicate weathering and climate. In this study we analyze the conce...Quantifying the functional relationships relating river discharge and weathering products places key constraints on the negative feedback between the silicate weathering and climate. In this study we analyze the concentration–discharge relationships of weathering products from global rivers using previously compiled time-series datasets for concentrations and discharge from global rivers. To analyze the nature of the covariation between specific discharge and concentrations, we use both a power law equation and a recently developed solute production equation. The solute production equation allows us to quantify weathering efficiency, or the resistance to dilution at high runoff, via the Damkohler coefficient. These results are also compared to those derived using average concentration–discharge pairs.Both the power law exponent and the Damkohler coefficient increase and asymptote as catchments exhibit increasingly chemostatic behavior, resulting in an inverse relationship between the two parameters. We also show that using thedistribution of average concentration–discharge pairs from global rivers, rather than fitting concentration–discharge relationships for each individual river, underestimates global median weathering efficiency by up to a factor of ～10. This study demonstrates the utility of long time-series sampling of global rivers to elucidate controlling processes needed to quantify patterns in global silicate weathering rates.展开更多
The aim of this study was to evaluate groundwater fitness for domestic and irrigational use in Unnao district of Uttar Pradesh,India.For this study,block wise(n=16)groundwater samples were collected,and measured param...The aim of this study was to evaluate groundwater fitness for domestic and irrigational use in Unnao district of Uttar Pradesh,India.For this study,block wise(n=16)groundwater samples were collected,and measured parameters were analyzed using the pollution index of groundwater(PIG),various irrigational indices,and graphical techniques.The results of this study suggested that most of the parameters were within the prescribed limits of WHO and BIS,excluding F-(0.4 to 2.6 mg L^(-1))and Fe^(2+)(0.1 to 1.7 mg L^(-1)).Concentrations of total dissolved solids(TDS)were exceeded the desirable limit(>500 mg L^(-1))in 43.75%of samples at some sites.The Gibbs plot revealed that groundwater chemistry was governed by rock-water interaction in the region,especially silicate weathering.The Piper plot suggested that Ca^(2+)-HCO3-is dominant hydrochemical facies in the area followed by mixed Ca^(2+)-Na^(+)-HCO_(3)^(-)type,Na^(+)-Cl^(-)type,and Na^(+)-HCO_(3)^(-)type.PIG evaluation revealed that the contribution of F-and Fe2+in groundwater degradation is high in comparison to other elements in the region,about 18.75%samples showed low pollution,while about 6.25%samples shows moderate pollution,and 6.25%samples reflected high pollution.The human health risk(HHR)assessment finding suggested that children(mean:1.36)are more vulnerable than adults(mean:1.01).Sodium absorption ration(SAR),Residual sodium carbonate(RSC),and Permeability index(PI)indicated that most of the groundwater was suitable for irrigation,whereas,Magnesium hazard ration(MHR)and Potential salinity(PS)indices suggested that only 37.5%and 56.25%of the samples were suitable for irrigational use,respectively.This regional study would help in decision making for stakeholders and relevant authorities in the execution of groundwater management and remediation plans in the area.展开更多
This study aimed to identify the role of natural and anthropogenic influence on geochemical processes controlling groundwater salinization in the middle portion of the Mono River basin, Togo. Multivariate statistical ...This study aimed to identify the role of natural and anthropogenic influence on geochemical processes controlling groundwater salinization in the middle portion of the Mono River basin, Togo. Multivariate statistical analysis, geochemical masse balance modeling, and conventional graphical methods were applied to the chemical dataset obtained from 110 groundwater samples collected during two campaigns (March-May 2011 and April 2014). The results showed that groundwater is predominantly fresh, acidic to circumneutral and mixed cations-<span style="white-space:nowrap;">HCO<sup>-</sup><sub style="margin-left:-7px;">3</sub> </span>water types. The proportion of ions (Na<sup>+</sup>, K<sup>+</sup>, Cl<sup>-</sup> and <span style="white-space:nowrap;">SO<sup>2-</sup><sub style="margin-left:-7px;">4</sub></span>) occurring ubiquitously in a saline environment increases substantially with TDS. Two factors, defined as natural and anthropogenic, account for 76.5% of the hydrochemical dataset variance. Based on the hierarchical cluster analysis, groundwater samples are classified into four clusters that corroborate the factor analysis results and illustrate different hydrochemical evolution stages along a topographically-driven groundwater flow path. The primary natural process contributing to cations and bicarbonate ions is the weathering of silicate minerals and possibly secondary carbonates by infiltrating water enriched with soil CO<sub>2</sub> gas. Groundwater salinization indicators including Cl<sup>-</sup>, <span style="white-space:nowrap;">SO<sup>2-</sup><sub style="margin-left:-7px;">4</sub> and <span style="white-space:nowrap;">NO<sup>-</sup><sub style="margin-left:-7px;">3</sub></span></span>, originate from potential sources such as human and animal wastes, agrochemicals, and deforestation. Thermodynamic equilibrium conditions ranged from saturation to oversaturation with respect to quartz, chalcedony, amorphous silica, calcite, dolomite, sepiolite, and talc. In conjunction with the lowering of CO<sub>2</sub> partial pressure and evaporation, these conditions restrict acidic hydrolysis of primary silicates but magnify the groundwater salinization process in the lower elevation areas where soil crusts’ formation is favorable. This study showed the effective use of multivariate statistical analysis and complementary techniques in identifying the significant factors and processes controlling groundwater chemistry.展开更多
The Oligocene-Miocene boundary Asian climatic reorganization linked to the northward migration of the East Asian monsoon into subtropical China is a potentially important but poorly constrained atmospheric CO_(2)consu...The Oligocene-Miocene boundary Asian climatic reorganization linked to the northward migration of the East Asian monsoon into subtropical China is a potentially important but poorly constrained atmospheric CO_(2)consumption process.Here,we performed a first-order estimate of the CO_(2)consumption induced by silicate chemical weathering and organic carbon burial in subtropical China related to this climatic reorganization.Our results show that an increase in long-term CO_(2)consumption by silicate weathering varies from 0.06×10^(12)to 0.87×10^(12)mol yr^(-1)depending on erosion flux reconstructions,with an~50%contribution of Mg-silicate weathering since the late Oligocene.The organic carbon burial flux is approximately 25%of the contemporary CO_(2)consumption by silicate weathering.The results highlight the significant role of weathering of the Mg-rich upper continental crust in East China,which would contribute to the rapid decline in atmospheric CO_(2)during the late Oligocene and the Neogene rise in the seawater Mg content.If this climatic reorganization was mainly induced by the Tibetan Plateau uplift,our study suggests that the growth of the Himalayan-Tibetan Plateau can lead to indirect modification of the global carbon and magnesium cycles by changing the regional hydrological cycle in areas of East Asia that are tectonically less active.展开更多
Riverine boron(B) and its isotopic compositions(δ^(11)B) are commonly used to trace silicate weathering within watersheds, but its sources and isotopic fractionation mechanisms remain contentious. In this study, we c...Riverine boron(B) and its isotopic compositions(δ^(11)B) are commonly used to trace silicate weathering within watersheds, but its sources and isotopic fractionation mechanisms remain contentious. In this study, we collected the seasonal river waters of the Buha River, the largest inlet river of Qinghai Lake, which is sensitive to climate change, and analyzed its seasonal variations of the major ions, B concentrations, and δ^(11)B, to explore its sources and controlling factors. The results indicate that B in the Buha River predominantly originates from weathering of silicate rocks, with significantly seasonal variations in the geochemical behaviour of B isotopes. In the rainy seasons, the riverine B isotopic fractionation is primarily controlled by weathering of silicate rocks under the influence of hydrological conditions, where clay minerals preferentially absorb10B, leading to the enrichment of heavier B isotopes in river waters. In contrast, in the dry seasons, the B of river waters may mainly come from the recharge of groundwater(whose δ^(11)B with a notable p H dependence);owing to prolonged retention of fluids, the steady state of δ^(11)B is reached by the isotopic equilibrium through adsorption of clay minerals. This study highlights that the seasonal variations in riverine δ^(11)B in semi-arid regions are jointly governed by silicate weathering, hydrological conditions, and water-rock interactions, with water p H and rainfall as key regulators. Consequently, riverine δ^(11)B in the rainy seasons under semi-arid climatic conditions can effectively trace hydrologically-controlled silicate weathering processes within the watershed.展开更多
The Platte River watershed,the largest river basin in Nebraska(1.06×105 km^(2)),crosses the entire state along its W-E course in the approximate N-S center of Nebraska.A plethora of historical(1968-1975)hydrochem...The Platte River watershed,the largest river basin in Nebraska(1.06×105 km^(2)),crosses the entire state along its W-E course in the approximate N-S center of Nebraska.A plethora of historical(1968-1975)hydrochemistry data[major cations and anions,primarily]resulting from collection and analysis by the Nebraska Department of Environment and Energy(NDEE)were statistically and graphically analyzed and subjected to geochemical modeling.Interpretation of this large legacy dataset(31 Platte River systems sampling stations and 34 sampling sites on 22 tributaries)revealed several hydrochemical facies(Ca-HCO_(3)and three additional ones,encompassing Ca-SO_(4)and Na-SO_(4)facies solely in South Platte River discharge),and slight calcite and dolomite supersaturation comprising a line of evidence for the near thermodynamic equilibrium of the studied surface waters.Scatter plots of selected cations versus anions reveal the impact of silicate minerals(e.g.,feldspars)weathering on the aqueous hydrochemistry throughout the watershed.Relatively high concentrations of sulfate(up to 1100 mg/L)in numerous samples from the South Platte River are probably sourced by agricultural fertilizer,irrigation water,and dissolution of gypsum/anhydrite.NETPATH geochemical modeling identified 10 plausible models to simulate the significant decrease in SO_(4)levels downstream along the South Platte River.展开更多
Lithium(L_(i))and its isotopes are potential tracers of silicate weathering in river basins.However,the relationship between the Li isotopic composition(δ^(7)Li)in rivers and silicate weathering intensity remains unc...Lithium(L_(i))and its isotopes are potential tracers of silicate weathering in river basins.However,the relationship between the Li isotopic composition(δ^(7)Li)in rivers and silicate weathering intensity remains unclear.This study analyzed the Li concentration and isotopic composition in river waters from the Niyang River,southern Tibetan Plateau.The results show that these samples have significantly variable Li concentrations(0.31–7.4μg/L)andδ^(7)Li values(+7.0–+20.7‰,n=28),and highδ^(7)Li values are found in several tributaries.Calculations indicate that dissolved Li in river water is predominantly derived from silicate weathering and geothermal water.With the exception of certain tributaries,geothermal water contributes 68%to 85%of the dissolved Li.Geothermal waters have lowδ^(7)Li values(-0.9–+2.9‰)in the Tibetan Plateau.Differences in the proportional contribution of dissolved Li in river samples from silicate weathering and geothermal water may be the main reason for the spatiotemporal variation in riverineδ^(7)Li values.The samples have higherδ^(7)Li values when the dissolved Li in the water samples is mainly derived from silicate weathering contributions,and lower values when the contribution from geothermal waters is high.Furthermore,the interaction of dissolved Li from geothermal water with secondary minerals results in Li isotopic fractionation,which may contribute to variations in river waterδ^(7)Li.It is accepted that the lower weathering intensity in orogenic(or mountainous)belts compared to floodplains is the main controlling factor for lowerδ^(7)Li values in the rivers.This study indicates that geothermal water input may cover the Li isotope signal of silicate weathering in river water,which in turn,affects the accurate understanding of the relationship between riverineδ^(7)Li values and the silicate weathering intensity.Therefore,whether the lowerδ^(7)Li values of river waters in hydrothermal-rich orogenic belts are mainly controlled by the regional weathering intensity or the input of hot springs(or both)requires in-depth study,and this is the key to accurately establishing the relationship between the Li isotopic composition and silicate weathering intensity in the river basin.展开更多
基金supported by the National Key Research and Development Program of China(Grant No.2022YFF0800504)the Major Program of the National Natural Science Foundation of China(Grant No.41991324)the Major Research Plan of the National Natural Science Foundation of China(Grant No.92479106)。
文摘Continental silicate weathering acts as a crucial negative feedback mechanism for removing atmospheric CO_(2) and maintaining Earth's long-term climate stability.However,quantifying continental silicate weathering rates and fluxes continues to pose a fundamental challenge in Earth system science.This study utilizes the GEOCLIM carbon cycle model,which integrates modern high-resolution(0.1°×0.1°)datasets on surface temperature,runoff,topography,and lithology to model the spatial distribution of global silicate weathering fluxes.Results indicate a strong correlation between modeled basin-scale outputs and hydrological observations,with weathering rates falling within consistent error margins.Silicate weathering fluxes exhibit distinct latitudinal patterns,with the highest values concentrated within 30°of the equator,accounting for 76.9%of the global total.Continental contributions differ significantly,with Asian river basins representing 36.9%of global fluxes,primarily from Southeast Asia(17.4%),South Asia(8.2%),and East Asia(6.6%).They are followed by South America(29.2%)and Africa(21.7%).Tectonically active regions contribute 21.9%of global silicate weathering,while stable regions account for 72.6%.Multivariate regression analyses using RF and XGBoost machine learning algorithms identify runoff as the primary controlling factor of weathering on a global scale.Weathering in stable regions is jointly regulated by runoff and erosion rates,whereas temperature is the prevailing factor in tectonically active zones.The GEOCLIM model offers a robust framework for quantifying continental weathering processes.Future studies should incorporate organic carbon oxidation,burial,and sulfide oxidation dynamics to clarify carbon cycle interactions and reveal climate-dependent mechanisms for weathering responses and feedback.
基金Supported by the Joint Fund of National Natural Science Foundation of China(NSFC)and Shandong Province(Nos.U22A20580,U1906210)the Laoshan Laboratory(No.LSKJ202203904)the National Natural Science Foundation of China(No.41876116)。
文摘Silicon(Si)is an important element in aquatic ecosystems.Based on the observed data in the Huanghe(Yellow)River Basin,a forward model was used to evaluate the silicate weathering rate in the Huanghe River Basin.The effects of silicate weathering,damming,and land use change on the Si concentration and flux were analyzed.Results show that the dissolved Si(DSi)concentration decreased first and then increased,and was 0.82–2.96 mg/L.As a silicon source in the Huanghe River Basin,the silicate weathering rate in the upper reaches of Lanzhou was high,and a large amount of DSi was transported to the lower reaches.Agricultural irrigation in the middle reaches caused a large amount of DSi loss,and the interception of large-scale cascade reservoirs caused a large amount of DSi retention.The DSi released by sediment re-suspension due to high runoff scouring in the downstream channel also served as a silicon source to supplement the DSi flux transported to the sea.Suspended particulate matter and biogenic Si(BSi)increased first and then decreased in the ranges of 24.1–1590.7 mg/L and 0.08–2.17 mg/L,respectively,due mainly to severe soil erosion in the eastern Loess Plateau,which caused significant amounts of phytoliths to enter the water.
基金supported by the National Natural Science Foundation of China (Grant Nos. 41373078 41173091)the National Key Basic Research Programme of China (Grant No. 2013CB956702)
文摘1 Introduction Global climate change is one of the greatest challenges facing humankind in the 21st century.Studying,and utilising,the carbon sink caused by the weathering of silicate minerals has been a key research focus for
文摘The water chemistry of Bhimtal Lake revealed the dominance of Ca￣(2+) and HCO_3￣- ions.The lake water chemistry is controlled by the dominance of Ca-Mg silicate weathering(mainly pumpellyite and epidote-bearing rocks) supported by anthropogenic activity involving extensive road cutting and house holding activities, increased industrialization in the catchment area of the lake. On the basis of phosphate values. a transitional mesotrophic-eutrophic conditions exist in this lake.The observed chemical data of the Bhimtal Lake was used to predict the mineral assemblages in the carbonate and alumino-silicate system. It demonstrates that the calcite and dolomite are the possible minerals which are in equilibrium with the lake water system and that the lake water is in the range of stability of kaolinite.
基金supported by a Stanford EDGE-STEM Fellowshipinitiated under NSF EAR-1254156 to Kate Maher and was also supported by the California Alliance Research Exchange NSF HRD-1306595 to C.Page Chamberlain
文摘Quantifying the functional relationships relating river discharge and weathering products places key constraints on the negative feedback between the silicate weathering and climate. In this study we analyze the concentration–discharge relationships of weathering products from global rivers using previously compiled time-series datasets for concentrations and discharge from global rivers. To analyze the nature of the covariation between specific discharge and concentrations, we use both a power law equation and a recently developed solute production equation. The solute production equation allows us to quantify weathering efficiency, or the resistance to dilution at high runoff, via the Damkohler coefficient. These results are also compared to those derived using average concentration–discharge pairs.Both the power law exponent and the Damkohler coefficient increase and asymptote as catchments exhibit increasingly chemostatic behavior, resulting in an inverse relationship between the two parameters. We also show that using thedistribution of average concentration–discharge pairs from global rivers, rather than fitting concentration–discharge relationships for each individual river, underestimates global median weathering efficiency by up to a factor of ～10. This study demonstrates the utility of long time-series sampling of global rivers to elucidate controlling processes needed to quantify patterns in global silicate weathering rates.
文摘The aim of this study was to evaluate groundwater fitness for domestic and irrigational use in Unnao district of Uttar Pradesh,India.For this study,block wise(n=16)groundwater samples were collected,and measured parameters were analyzed using the pollution index of groundwater(PIG),various irrigational indices,and graphical techniques.The results of this study suggested that most of the parameters were within the prescribed limits of WHO and BIS,excluding F-(0.4 to 2.6 mg L^(-1))and Fe^(2+)(0.1 to 1.7 mg L^(-1)).Concentrations of total dissolved solids(TDS)were exceeded the desirable limit(>500 mg L^(-1))in 43.75%of samples at some sites.The Gibbs plot revealed that groundwater chemistry was governed by rock-water interaction in the region,especially silicate weathering.The Piper plot suggested that Ca^(2+)-HCO3-is dominant hydrochemical facies in the area followed by mixed Ca^(2+)-Na^(+)-HCO_(3)^(-)type,Na^(+)-Cl^(-)type,and Na^(+)-HCO_(3)^(-)type.PIG evaluation revealed that the contribution of F-and Fe2+in groundwater degradation is high in comparison to other elements in the region,about 18.75%samples showed low pollution,while about 6.25%samples shows moderate pollution,and 6.25%samples reflected high pollution.The human health risk(HHR)assessment finding suggested that children(mean:1.36)are more vulnerable than adults(mean:1.01).Sodium absorption ration(SAR),Residual sodium carbonate(RSC),and Permeability index(PI)indicated that most of the groundwater was suitable for irrigation,whereas,Magnesium hazard ration(MHR)and Potential salinity(PS)indices suggested that only 37.5%and 56.25%of the samples were suitable for irrigational use,respectively.This regional study would help in decision making for stakeholders and relevant authorities in the execution of groundwater management and remediation plans in the area.
文摘This study aimed to identify the role of natural and anthropogenic influence on geochemical processes controlling groundwater salinization in the middle portion of the Mono River basin, Togo. Multivariate statistical analysis, geochemical masse balance modeling, and conventional graphical methods were applied to the chemical dataset obtained from 110 groundwater samples collected during two campaigns (March-May 2011 and April 2014). The results showed that groundwater is predominantly fresh, acidic to circumneutral and mixed cations-<span style="white-space:nowrap;">HCO<sup>-</sup><sub style="margin-left:-7px;">3</sub> </span>water types. The proportion of ions (Na<sup>+</sup>, K<sup>+</sup>, Cl<sup>-</sup> and <span style="white-space:nowrap;">SO<sup>2-</sup><sub style="margin-left:-7px;">4</sub></span>) occurring ubiquitously in a saline environment increases substantially with TDS. Two factors, defined as natural and anthropogenic, account for 76.5% of the hydrochemical dataset variance. Based on the hierarchical cluster analysis, groundwater samples are classified into four clusters that corroborate the factor analysis results and illustrate different hydrochemical evolution stages along a topographically-driven groundwater flow path. The primary natural process contributing to cations and bicarbonate ions is the weathering of silicate minerals and possibly secondary carbonates by infiltrating water enriched with soil CO<sub>2</sub> gas. Groundwater salinization indicators including Cl<sup>-</sup>, <span style="white-space:nowrap;">SO<sup>2-</sup><sub style="margin-left:-7px;">4</sub> and <span style="white-space:nowrap;">NO<sup>-</sup><sub style="margin-left:-7px;">3</sub></span></span>, originate from potential sources such as human and animal wastes, agrochemicals, and deforestation. Thermodynamic equilibrium conditions ranged from saturation to oversaturation with respect to quartz, chalcedony, amorphous silica, calcite, dolomite, sepiolite, and talc. In conjunction with the lowering of CO<sub>2</sub> partial pressure and evaporation, these conditions restrict acidic hydrolysis of primary silicates but magnify the groundwater salinization process in the lower elevation areas where soil crusts’ formation is favorable. This study showed the effective use of multivariate statistical analysis and complementary techniques in identifying the significant factors and processes controlling groundwater chemistry.
基金co-supported by the Second Tibetan Plateau Scientific Expedition and Research(STEP)program(Grant No.2019QZKK0707)the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDA20070201)+2 种基金the National Natural Science Foundation of China(Grant Nos.41771236,41972195,41872098&41620104002)he Basic Science Center for Tibetan Plateau Earth System(CTPES,41988101-01)supported by the Youth Innovation Promotion Association(2018095)of the Chinese Academy of Sciences。
文摘The Oligocene-Miocene boundary Asian climatic reorganization linked to the northward migration of the East Asian monsoon into subtropical China is a potentially important but poorly constrained atmospheric CO_(2)consumption process.Here,we performed a first-order estimate of the CO_(2)consumption induced by silicate chemical weathering and organic carbon burial in subtropical China related to this climatic reorganization.Our results show that an increase in long-term CO_(2)consumption by silicate weathering varies from 0.06×10^(12)to 0.87×10^(12)mol yr^(-1)depending on erosion flux reconstructions,with an~50%contribution of Mg-silicate weathering since the late Oligocene.The organic carbon burial flux is approximately 25%of the contemporary CO_(2)consumption by silicate weathering.The results highlight the significant role of weathering of the Mg-rich upper continental crust in East China,which would contribute to the rapid decline in atmospheric CO_(2)during the late Oligocene and the Neogene rise in the seawater Mg content.If this climatic reorganization was mainly induced by the Tibetan Plateau uplift,our study suggests that the growth of the Himalayan-Tibetan Plateau can lead to indirect modification of the global carbon and magnesium cycles by changing the regional hydrological cycle in areas of East Asia that are tectonically less active.
基金supported by the National Natural Science Foundation of China (Grant Nos. 42221003 & 42103055)the Natural Science Basic Research Program of Shaanxi (Grant No. 2023JC-QN-0276)the Basic Research Fund Project of Central Universities (Grant No. 300102353202)。
文摘Riverine boron(B) and its isotopic compositions(δ^(11)B) are commonly used to trace silicate weathering within watersheds, but its sources and isotopic fractionation mechanisms remain contentious. In this study, we collected the seasonal river waters of the Buha River, the largest inlet river of Qinghai Lake, which is sensitive to climate change, and analyzed its seasonal variations of the major ions, B concentrations, and δ^(11)B, to explore its sources and controlling factors. The results indicate that B in the Buha River predominantly originates from weathering of silicate rocks, with significantly seasonal variations in the geochemical behaviour of B isotopes. In the rainy seasons, the riverine B isotopic fractionation is primarily controlled by weathering of silicate rocks under the influence of hydrological conditions, where clay minerals preferentially absorb10B, leading to the enrichment of heavier B isotopes in river waters. In contrast, in the dry seasons, the B of river waters may mainly come from the recharge of groundwater(whose δ^(11)B with a notable p H dependence);owing to prolonged retention of fluids, the steady state of δ^(11)B is reached by the isotopic equilibrium through adsorption of clay minerals. This study highlights that the seasonal variations in riverine δ^(11)B in semi-arid regions are jointly governed by silicate weathering, hydrological conditions, and water-rock interactions, with water p H and rainfall as key regulators. Consequently, riverine δ^(11)B in the rainy seasons under semi-arid climatic conditions can effectively trace hydrologically-controlled silicate weathering processes within the watershed.
文摘The Platte River watershed,the largest river basin in Nebraska(1.06×105 km^(2)),crosses the entire state along its W-E course in the approximate N-S center of Nebraska.A plethora of historical(1968-1975)hydrochemistry data[major cations and anions,primarily]resulting from collection and analysis by the Nebraska Department of Environment and Energy(NDEE)were statistically and graphically analyzed and subjected to geochemical modeling.Interpretation of this large legacy dataset(31 Platte River systems sampling stations and 34 sampling sites on 22 tributaries)revealed several hydrochemical facies(Ca-HCO_(3)and three additional ones,encompassing Ca-SO_(4)and Na-SO_(4)facies solely in South Platte River discharge),and slight calcite and dolomite supersaturation comprising a line of evidence for the near thermodynamic equilibrium of the studied surface waters.Scatter plots of selected cations versus anions reveal the impact of silicate minerals(e.g.,feldspars)weathering on the aqueous hydrochemistry throughout the watershed.Relatively high concentrations of sulfate(up to 1100 mg/L)in numerous samples from the South Platte River are probably sourced by agricultural fertilizer,irrigation water,and dissolution of gypsum/anhydrite.NETPATH geochemical modeling identified 10 plausible models to simulate the significant decrease in SO_(4)levels downstream along the South Platte River.
基金supported by the National Natural Science Foundation of China(Grant No.42003007)the Natural Science Foundation of Shaanxi Province(Grant Nos.2022JZ-19 and 2022JQ-229)the Special Fund for Basic Scientific Research of Central Colleges,Chang’an University(Grant No.300102272808)。
文摘Lithium(L_(i))and its isotopes are potential tracers of silicate weathering in river basins.However,the relationship between the Li isotopic composition(δ^(7)Li)in rivers and silicate weathering intensity remains unclear.This study analyzed the Li concentration and isotopic composition in river waters from the Niyang River,southern Tibetan Plateau.The results show that these samples have significantly variable Li concentrations(0.31–7.4μg/L)andδ^(7)Li values(+7.0–+20.7‰,n=28),and highδ^(7)Li values are found in several tributaries.Calculations indicate that dissolved Li in river water is predominantly derived from silicate weathering and geothermal water.With the exception of certain tributaries,geothermal water contributes 68%to 85%of the dissolved Li.Geothermal waters have lowδ^(7)Li values(-0.9–+2.9‰)in the Tibetan Plateau.Differences in the proportional contribution of dissolved Li in river samples from silicate weathering and geothermal water may be the main reason for the spatiotemporal variation in riverineδ^(7)Li values.The samples have higherδ^(7)Li values when the dissolved Li in the water samples is mainly derived from silicate weathering contributions,and lower values when the contribution from geothermal waters is high.Furthermore,the interaction of dissolved Li from geothermal water with secondary minerals results in Li isotopic fractionation,which may contribute to variations in river waterδ^(7)Li.It is accepted that the lower weathering intensity in orogenic(or mountainous)belts compared to floodplains is the main controlling factor for lowerδ^(7)Li values in the rivers.This study indicates that geothermal water input may cover the Li isotope signal of silicate weathering in river water,which in turn,affects the accurate understanding of the relationship between riverineδ^(7)Li values and the silicate weathering intensity.Therefore,whether the lowerδ^(7)Li values of river waters in hydrothermal-rich orogenic belts are mainly controlled by the regional weathering intensity or the input of hot springs(or both)requires in-depth study,and this is the key to accurately establishing the relationship between the Li isotopic composition and silicate weathering intensity in the river basin.
