scholarly journals Chemical Weathering and Riverine Carbonate System Driven by Human Activities in a Subtropical Karst Basin, South China

Water ◽  
2018 ◽  
Vol 10 (11) ◽  
pp. 1524 ◽  
Author(s):  
Xiaoxi Lyu ◽  
Zhen Tao ◽  
Quanzhou Gao ◽  
Haixia Peng ◽  
Mei Zhou
Keyword(s):  
Sulfuric Acid ◽  
Nitric Acid ◽  
South China ◽  
Human Activities ◽  
Chemical Weathering ◽  
Carbonic Acid ◽  
Total Alkalinity ◽  
Karst Water ◽  
Carbonate System ◽  
Co2 Consumption

In the context of climate change, the input of acid substances into rivers, caused by human activities in the process of industrial and agricultural development, has significantly disrupted river systems and has had a profound impact on the carbon cycle. The hydrochemical composition and which main sources of the Lianjiang River (LR), a subtropical karst river in northern Guangdong Province, South China, were analyzed in January 2018. The objective was to explicate the influence on the deficit proportion of CO2 consumption, resulting from carbonate chemical weathering (CCW), driven by nitric acid (HNO3) and sulfuric acid (H2SO4), which is affected by exogenous acids from the industrial regions in north of the Nanling Mountains and the Pearl River Delta. The response of the riverine carbonate system to exogenous acid-related weathering was also discussed. HCO3− and Ca2+, respectively, accounted for 84.97% of the total anions and 78.71% of the total cations in the surface runoff of the LR, which was characterized as typical karst water. CCW was the most important material source of river dissolved loads in the LR, followed by human activities and silicate chemical weathering (SCW). Dissolved inorganic carbon (DIC), derived from CCW induced by carbonic acid (H2CO3), had the largest contribution to the total amount of DIC in the LR (76.79%), and those from CCW induced by anthropogenic acids (HNO3 and H2SO4) and SCW contributed 13.56% and 9.64% to the total DIC, respectively. The deficit proportion of CO2 consumption associated with CCW resulting from sulfuric acid and nitric acid (13.56%), was slightly lower than that of the Guizhou Plateau in rainy and pre-rainy seasons (15.67% and 14.17%, respectively). The deficit percentage of CO2 uptake associated with CCW induced by sulfuric acid and nitric acid, accounted for 38.44% of the total CO2 consumption related to natural CCW and 18.84% of the anthropogenic acids from external areas. DIC derived from CCW induced by human activities, had a significant positive correlation with the total alkalinity, SIc and pCO2 in river water, indicating that the carbonate system of the LR was also driven by exogenous acids, with the exception of carbonic acid. More attention should be paid to the effects of human activities on the chemical weathering and riverine carbonate system in the karst drainage basin.

scholarly journals Silicate weathering and CO<sub>2</sub> consumption within agricultural landscapes, the Ohio-Tennessee River Basin, USA

2011 ◽  
Vol 8 (5) ◽  
pp. 9431-9469 ◽  
Author(s):  
S. K. Fortner ◽  
W. B. Lyons ◽  
A. E. Carey ◽  
M. J. Shipitalo ◽  
S. A. Welch ◽  
...  
Keyword(s):  
River Basin ◽  
Chemical Weathering ◽  
Carbonic Acid ◽  
Global Climate ◽  
Agricultural Landscapes ◽  
Total Alkalinity ◽  
Molar Ratio ◽  
Silicate Weathering ◽  
Tennessee River ◽  
Co2 Consumption

Abstract. Myriad studies have shown the extent of human alteration to global biogeochemical cycles. Yet, there is only a limited understanding of the influence that humans have over silicate weathering fluxes; fluxes that have regulated atmospheric carbon dioxide concentrations and global climate over geologic timescales. Natural landscapes have been reshaped into agricultural ones to meet food needs for growing world populations. These processes modify soil properties, alter hydrology, affect erosion, and consequently impact water-soil-rock interactions such as chemical weathering. Dissolved silica (DSi), Ca2+, Mg2+, NO3−, and total alkalinity were measured in water samples collected from five small (0.65 to 38.3 ha) gauged watersheds at the North Appalachian Experimental Watershed (NAEW) near Coshocton, Ohio, USA. The sampled watersheds in this unglaciated region include: a forested site (70+ yr stand), mixed agricultural use (corn, forest, pasture), an unimproved pasture, tilled corn, and a recently (<3 yr) converted no-till corn field. The first three watersheds had perennial streams, but the two corn watersheds only produced runoff during storms and snowmelt. For the perennial streams, total discharge was an important control of dissolved silicate transport. Median DSi yields (22.1–30.8 kg ha−1 a−1) were similar to the median of annual averages between 1979–2009 for the much larger Ohio-Tennessee River Basin (25.6 kg ha−1 a−1). Corn watersheds, which only had surface runoff, had substantially lower DSi yields (<5.3 kg ha−1 a−1) than the perennial-flow watersheds. The lack of contributions from Si-enriched groundwater largely explained their much lower DSi yields with respect to sites having baseflow. A significant positive correlation between the molar ratio of (Ca2+ + Mg2)/alkalinity to DSi in the tilled corn and the forested site suggested, however, that silicate minerals weathered as alkalinity was lost via enhanced nitrification resulting from fertilizer additions to the corn watershed and from leaf litter decomposition in the forest. This same relation was observed in the Ohio-Tennessee River Basin where dominant landuse types include both agricultural lands receiving nitrogenous fertilizers and forests. Greater gains in DSi with respect to alkalinity losses in the Ohio-Tennessee River Basin than in the NAEW sites suggested that soils derived from younger Pleistocene glacial-till may yield more DSi relative to nitrogenous fertilizer applications than the older NAEW soils. Because silicate weathering occurs via acids released from nitrification, CO2 consumption estimates based on the assumption that silicate weathers via carbonic-acid alone may be especially over-estimated in fertilized agricultural watersheds with little baseflow (i.e. 67% overestimated in the corn till watershed). CO2 consumption estimates based on silicate weathering may be as much as an average of 8% lower than estimates derived from carbonic acid weathering alone for the Ohio-Tennessee River Basin between 1979–2009.

scholarly journals Silicate weathering and CO<sub>2</sub> consumption within agricultural landscapes, the Ohio-Tennessee River Basin, USA

2012 ◽  
Vol 9 (3) ◽  
pp. 941-955 ◽  
Author(s):  
S. K. Fortner ◽  
W. B. Lyons ◽  
A. E. Carey ◽  
M. J. Shipitalo ◽  
S. A. Welch ◽  
...  
Keyword(s):  
River Basin ◽  
Management Practices ◽  
Agricultural Land ◽  
Carbonic Acid ◽  
Agricultural Landscapes ◽  
Total Alkalinity ◽  
Molar Ratio ◽  
Silicate Weathering ◽  
Tennessee River ◽  
Co2 Consumption

Abstract. Myriad studies have shown the extent of human alteration to global biogeochemical cycles. Yet, there is only a limited understanding of the influence that humans have over silicate weathering fluxes; fluxes that have regulated atmospheric carbon dioxide concentrations and global climate over geologic timescales. Natural landscapes have been reshaped into agricultural ones to meet food needs for growing world populations. These processes modify soil properties, alter hydrology, affect erosion, and consequently impact water-soil-rock interactions such as chemical weathering. Dissolved silica (DSi), Ca2+, Mg2+, NO3–, and total alkalinity were measured in water samples collected from five small (0.0065 to 0.383 km2) gauged watersheds at the North Appalachian Experimental Watershed (NAEW) near Coshocton, Ohio, USA. The sampled watersheds in this unglaciated region include: a forested site (70+ year stand), mixed agricultural use (corn, forest, pasture), an unimproved pasture, tilled corn, and a recently (<3 yr) converted no-till corn field. The first three watersheds had perennial streams, but the two corn watersheds only produced runoff during storms and snowmelt. For the perennial streams, total discharge was an important control of dissolved silicate transport. Median DSi yields (2210–3080 kg km−2 yr–1) were similar to the median of annual averages between 1979–2009 for the much larger Ohio-Tennessee River Basin (2560 kg km−2 yr–1). Corn watersheds, which only had surface runoff, had substantially lower DSi yields (<530 kg km−2 yr–1) than the perennial-flow watersheds. The lack of contributions from Si-enriched groundwater largely explained their much lower DSi yields with respect to sites having baseflow. A significant positive correlation between the molar ratio of (Ca2++Mg2+)/alkalinity to DSi in the tilled corn and the forested site suggested, however, that silicate minerals weathered as alkalinity was lost via enhanced nitrification resulting from fertilizer additions to the corn watershed and from leaf litter decomposition in the forest. This same relation was observed in the Ohio-Tennessee River Basin where dominant landuse types include both agricultural lands receiving nitrogenous fertilizers and forests. Greater gains in DSi with respect to alkalinity losses in the Ohio-Tennessee River Basin than in the NAEW sites suggested that soils derived from younger Pleistocene glacial-till may yield more DSi relative to nitrogenous fertilizer applications than the older NAEW soils. Because silicate weathering occurs via acids released from nitrification, CO2 consumption estimates based on the assumption that silicate weathers via carbonic acid alone may be especially over-estimated in fertilized agricultural watersheds with little baseflow (i.e. 67 % overestimated in the corn till watershed). CO2 consumption estimates based on silicate weathering may be as much as 20 % lower than estimates derived from carbonic acid weathering alone for the Ohio-Tennessee River Basin between 1979–2009. Globally, this may mean that younger landscapes with soils favorable for agriculture are susceptible to fertilizer-enhanced silicate weathering. Increases in silicate weathering, however, may be offset by shifts in hydrology resulting from agricultural land management practices or even from soil silica losses in response to repeated acidification.

scholarly journals Current estimates of K<sub>1</sub>* and K<sub>2</sub>* appear inconsistent with measured CO<sub>2</sub> system parameters in cold oceanic regions

Ocean Science ◽  
2020 ◽  
Vol 16 (4) ◽  
pp. 847-862 ◽  
Author(s):  
Olivier Sulpis ◽  
Siv K. Lauvset ◽  
Mathilde Hagens
Keyword(s):  
Surface Water ◽  
Ocean Acidification ◽  
Carbonic Acid ◽  
Dissolved Inorganic Carbon ◽  
Dissociation Constants ◽  
Total Alkalinity ◽  
Global Ocean ◽  
Polar Regions ◽  
Carbonate System ◽  
System Variables

Abstract. Seawater absorption of anthropogenic atmospheric carbon dioxide (CO2) has led to a range of changes in carbonate chemistry, collectively referred to as ocean acidification. Stoichiometric dissociation constants used to convert measured carbonate system variables (pH, pCO2, dissolved inorganic carbon, total alkalinity) into globally comparable parameters are crucial for accurately quantifying these changes. The temperature and salinity coefficients of these constants have generally been experimentally derived under controlled laboratory conditions. Here, we use field measurements of carbonate system variables taken from the Global Ocean Data Analysis Project version 2 and the Surface Ocean CO2 Atlas data products to evaluate the temperature dependence of the carbonic acid stoichiometric dissociation constants. By applying a novel iterative procedure to a large dataset of 948 surface-water, quality-controlled samples where four carbonate system variables were independently measured, we show that the set of equations published by Lueker et al. (2000), currently preferred by the ocean acidification community, overestimates the stoichiometric dissociation constants at temperatures below about 8 ∘C. We apply these newly derived temperature coefficients to high-latitude Argo float and cruise data to quantify the effects on surface-water pCO2 and calcite saturation states. These findings highlight the critical implications of uncertainty in stoichiometric dissociation constants for future projections of ocean acidification in polar regions and the need to improve knowledge of what causes the CO2 system inconsistencies in cold waters.

scholarly journals A Method for Quantifying the Role of Carbonate Acid, Sulfuric Acid and Nitric Acid in Carbonate Weathering After Modifying the Effect of Evaporite in Qingjiang Karst Catchment

2021 ◽  
Author(s):  
Xinhui He ◽  
Hong Zhou ◽  
Junwei Wan ◽  
Heng Zhao ◽  
Shiyi He
Keyword(s):  
Sulfuric Acid ◽  
Nitric Acid ◽  
Carbonate Rock ◽  
Carbonic Acid ◽  
Hydrodynamic Condition ◽  
Hydrochemical Modeling ◽  
Carbonate Weathering ◽  
Karst Catchment ◽  
The Impact

Abstract Qingjiang river is the second largest tributary of the Yangtze River in Hubei province, it’s also a typical karst catchment. Eighty-two important groundwater samples were collected during high and low water period of 2019. The results show that: (1) The major hydrochemistry types are Ca+Mg-HCO3 and Ca-HCO3, indicate that carbonate weathering is the main source of groundwater chemistry; (2) The results of inverse hydrochemical modeling show that there are two kinds of groundwater-carbonate rock interactions. One is co-dissolution of calcite and dolomite, the other is dedolomitization, and thereinto, dedolomitization is widespread in dolomite aquifers. Furthermore, gypsum has a tendency to dissolve in each aquifer, and the common ion effect of Ca2+ caused by gypsum dissolution promotes dedolomitization. The modeling results suggest that major elements have a good traceability effect on the material source of groundwater. (3) The chemical weathering of carbonate rock is mainly affected by carbonic acid, sulfuric acid and nitric acid. After modifying the impact of evaporite and atmospheric input, the calculations show that the contribution of carbonic acid involved in carbonate weathering is 70.9% (high water period) and 70.0% (low water period). Through statistics of karst springs discharge and contribution of acid involved in carbonate weathering, the two are in a positive relationship. The result can reflect the laws of sulfuric acid and nitric acid under the hydrodynamic condition in different seasons. Therefore, the carbonate weathering should be carefully evaluated in karst areas which have abundant groundwater and the role of groundwater in carbonate weathering is worthy of further study.

scholarly journals Geochemistry of the dissolved loads during high-flow season of rivers in the southeastern coastal region of China: anthropogenic impact on chemical weathering and carbon sequestration

2018 ◽  
Vol 15 (16) ◽  
pp. 4955-4971 ◽  
Author(s):  
Wenjing Liu ◽  
Zhifang Xu ◽  
Huiguo Sun ◽  
Tong Zhao ◽  
Chao Shi ◽  
...  
Keyword(s):  
Nitric Acid ◽  
Acid Deposition ◽  
Anthropogenic Impact ◽  
Chemical Weathering ◽  
Dissolved Inorganic Carbon ◽  
Coastal Region ◽  
High Flow ◽  
Silicate Weathering ◽  
Chemical Compositions ◽  
Co2 Consumption

Abstract. The southeastern coastal region is one of the most developed and populated areas in China. Meanwhile, it has been severely impacted by acid rain over many years. The chemical compositions and carbon isotope compositions of dissolved inorganic carbon (δ13CDIC) in river water in the high-flow season were investigated to estimate the chemical weathering and associated atmospheric CO2 consumption rates as well as the acid-deposition disturbance. Mass balance calculations indicated that the dissolved loads of major rivers in the Southeast Coastal River Basin (SECRB) were contributed to by atmospheric (14.3 %, 6.6 %–23.4 %), anthropogenic (15.7 %, 0 %–41.1 %), silicate weathering (39.5 %, 17.8 %–74.0 %) and carbonate weathering inputs (30.6 %, 3.9 %–62.0 %). The silicate and carbonate chemical weathering rates for these river watersheds were 14.2–35.8 and 1.8–52.1 t km−2 a−1, respectively. The associated mean CO2 consumption rate by silicate weathering for the whole SECRB was 191×103 mol km−2 a−1. The chemical and δ13CDIC evidence indicated that sulfuric and nitric acid (mainly from acid deposition) were significantly involved in the chemical weathering of rocks. There was an overestimation of CO2 consumption at 0.19×1012 g C a−1 if sulfuric and nitric acid were ignored, which accounted for about 33.6 % of the total CO2 consumption by silicate weathering in the SECRB. This study quantitatively highlights the role of acid deposition in chemical weathering, suggesting that the anthropogenic impact should be seriously considered in estimations of chemical weathering and associated CO2 consumption.

scholarly journals Geochemistry of the dissolved loads of rivers in Southeast Coastal Region, China: Anthropogenic impact on chemical weathering and carbon sequestration

2018 ◽  
Author(s):  
Wenjing Liu ◽  
Zhifang Xu ◽  
Huiguo Sun ◽  
Tong Zhao ◽  
Chao Shi ◽  
...  
Keyword(s):  
Sulfuric Acid ◽  
Acid Deposition ◽  
Chemical Weathering ◽  
Dissolved Inorganic Carbon ◽  
Coastal Region ◽  
Carbon Isotope Ratio ◽  
Silicate Weathering ◽  
Chemical Compositions ◽  
Mass Balance Calculation ◽  
Co2 Consumption

Abstract. Southeast coastal region is the most developed and populated area in China. Meanwhile, it has been the most severe acid rain impacted region for many years. The chemical compositions and carbon isotope ratio of dissolved inorganic carbon (δ13CDIC) of rivers were investigated to evaluate the chemical weathering and associated atmospheric CO2 consumption rates. Mass balance calculation indicated that the dissolved loads of major rivers in the Southeast Coastal Rivers Basin (SECRB) were contributed by atmospheric (14.4 %, 6.6–23.4 %), anthropogenic (17.8 %, 0–55.2 %), silicate weathering (38.3 %, 10.7–74.0 %) and carbonate weathering inputs (29.4 %, 3.9–62.0 %). The silicate and carbonate chemical weathering rates for these river watersheds were 10.0–29.6 t km−2 a−1 and 1.0–54.1 t km−2 a−1, respectively. The associated mean CO2 consumption rate by silicate weathering for the whole SECRB were 167 × 103 mol km−2 a−1. The chemical and δ13CDIC evidences indicated that sulfuric acid (mainly from acid deposition) was significantly involved in chemical weathering of rocks. The calculation showed an overestimation of CO2 consumption at 0.19 × 1012 g C a−1 if sulfuric acid was ignored, which accounted for about 25 % of the total CO2 consumption by silicate weathering in the SECRB. This study quantitatively highlights that the role of sulfuric acid in chemical weathering, suggesting that acid deposition should be considered in studies of chemical weathering and associated CO2 consumption.

scholarly journals Current estimates of K<sub>1</sub><sup>*</sup> and K<sub>2</sub><sup>*</sup> appear inconsistent with measured CO<sub>2</sub> system parameters in cold oceanic regions

2020 ◽  
Author(s):  
Olivier Sulpis ◽  
Siv K. Lauvset ◽  
Mathilde Hagens
Keyword(s):  
Surface Water ◽  
Ocean Acidification ◽  
Carbonic Acid ◽  
Dissolved Inorganic Carbon ◽  
Dissociation Constants ◽  
Total Alkalinity ◽  
Global Ocean ◽  
Polar Regions ◽  
Carbonate System ◽  
System Variables

Abstract. Seawater absorption of anthropogenic atmospheric carbon dioxide (CO2) has led to a range of changes in carbonate chemistry, collectively referred to as ocean acidification. Stoichiometric dissociation constants used to convert measured carbonate system variables (pH, pCO2, dissolved inorganic carbon, total alkalinity) into globally comparable parameters are crucial for accurately quantifying these changes. The temperature and salinity coefficients of these constants have generally been experimentally derived under controlled laboratory conditions. Here, we use field measurements of carbonate system variables taken from the Global Ocean Data Analysis Project version 2 and the Surface Ocean CO2 Atlas databases to evaluate the temperature dependence of the carbonic acid stoichiometric dissociation constants. By applying a novel iterative procedure to a large dataset of 948 surface-water, quality-controlled samples where four carbonate system variables were independently measured, we show that the set of equations published by Lueker et al. (2000), currently preferred by the ocean acidification community, overestimates the stoichiometric dissociation constants at low temperatures, below ~ 8 °C. We apply these newly derived temperature coefficients to high-latitude Argo float and cruise data to quantify the effects on surface-water pCO2 and calcite saturation states. These findings highlight the critical implications of uncertainty in stoichiometric dissociation constants for future projections of ocean acidification in polar regions, and the need to improve knowledge of what causes the CO2 system inconsistencies in cold waters.

Chemical weathering and CO2 consumption in the Xijiang River basin, South China

Geomorphology ◽  
2009 ◽  
Vol 106 (3-4) ◽  
pp. 324-332 ◽  
Author(s):  
Quanzhou Gao ◽  
Zhen Tao ◽  
Xiakun Huang ◽  
Ling Nan ◽  
Kefu Yu ◽  
...  
Keyword(s):  
River Basin ◽  
South China ◽  
Chemical Weathering ◽  
Xijiang River ◽  
Co2 Consumption ◽  
The Xijiang River
Sign in / Sign up

Export Citation Format

Share Document