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 Temporary and net sinks of atmospheric CO<sub>2</sub> due to chemical weathering in subtropical catchment with mixing carbonate and silicate lithology

2020 ◽  
Vol 17 (14) ◽  
pp. 3875-3890
Author(s):  
Yingjie Cao ◽  
Yingxue Xuan ◽  
Changyuan Tang ◽  
Shuai Guan ◽  
Yisheng Peng
Keyword(s):  
Acid Deposition ◽  
Chemical Weathering ◽  
Dissolved Inorganic Carbon ◽  
Silicate Weathering ◽  
Carbonate Weathering ◽  
Weathering Rate ◽  
Weathering Rates ◽  
Hypsometric Integral ◽  
Co2 Sink ◽  
Chemical Weathering Rate

Abstract. The study provided the major ion chemistry, chemical weathering rates and temporary and net CO2 sinks in the Bei Jiang, which was characterized as a hyperactive region with high chemical weathering rates, carbonate and silicate mixing lithology, and abundant sulfuric acid chemical weathering agent of acid deposition and acid mining drainage (AMD) origins. The total chemical weathering rate of 85.46 t km−2 a−1 was comparable to that of other rivers in the hyperactive zones between the latitudes 0 and 30∘. A carbonate weathering rate of 61.15 t km−2 a−1 contributed to about 70 % of the total. The lithology, runoff, and geomorphology had a significant influence on the chemical weathering rate. The proportion of carbonate outcrops had a significant positive correlation with the chemical weathering rate. Due to the interaction between dilution and compensation effect, a significant positive linear relationship was detected between runoff and total carbonate and silicate weathering rates. The geomorphology factors such as catchment area, average slope, and hypsometric integral value (HI) had nonlinear correlation with chemical weathering rate and showed significant scale effect, which revealed the complexity in chemical weathering processes. Dissolved inorganic carbon (DIC) apportionment showed that CCW (carbonate weathering by CO2) was the dominant origin of DIC (35 %–87 %). SCW (carbonate weathering by H2SO4) (3 %–15 %) and CSW (silicate weathering by CO2) (7 %–59 %) were non-negligible processes. The temporary CO2 sink was 823.41×103 mol km−2 a−1. Compared with the temporary sink, the net sink of CO2 for the Bei Jiang was approximately 23.18×103 mol km−2 a−1 of CO2 and was about 2.82 % of the “temporary” CO2 sink. Human activities (sulfur acid deposition and AMD) dramatically decreased the CO2 net sink, even making chemical weathering a CO2 source to the atmosphere.

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 Temporary and net sinks of atmospheric CO<sub>2</sub> due to chemical weathering in subtropical catchment with mixing carbonate and silicate lithology

2019 ◽  
Author(s):  
Yingjie Cao ◽  
Yingxue Xuan ◽  
Changyuan Tang ◽  
Shuai Guan ◽  
Yisheng Peng
Keyword(s):  
Acid Deposition ◽  
Chemical Weathering ◽  
Silicate Weathering ◽  
Carbonate Weathering ◽  
Weathering Rate ◽  
Weathering Rates ◽  
Beijiang River ◽  
Hypsometric Integral ◽  
Co2 Sink ◽  
Chemical Weathering Rate

Abstract. The study provides the major ion chemistry, chemical weathering rates and temporary and net CO2 sinks in the Beijiang River, which was characterized as hyperactive region with high chemical weathering rates, carbonate and silicate mixing lithology and abundant sulfuric acid chemical weathering agent with acid deposition and AMD origins. The total chemical weathering rate of 85.46 t km−2 a−1 was comparable to other rivers in the hyperactive zones between the latitude 0–30°. Carbonate weathering rates of 61.15 t km−2 a−1 contributed to about 70 % of the total. The lithology, runoff and geomorphology had significant influence on the chemical weathering rate. The proportion of carbonate outcrops had significant positive correlation with the chemical weathering rate. Due to the interaction between dilution and compensation effect, significant positive linear relationship was detected between runoff and total, carbonate and silicate weathering rates. The geomorphology factors such as catchment area, average slope and hypsometric integral value (HI) had non-linear correlation on chemical weathering rate and showed significant scale effect, which revealed the complexity in chemical weathering processes. DIC-apportionment showed that CCW (Carbonate weathering by CO2) was the dominant origin of DIC (35 %–87 %) and that SCW (Carbonate weathering by H2SO4) (3 %–15 %) and CSW (Silicate weathering by CO2) (7 %–59 %) were non-negligible processes. The temporary CO2 sink was 823.41 103 mol km−2 a−1. Compared with the temporary sink, the net sink of CO2 for the Beijiang River was approximately 23.18 × 103 mol km−2 a−1 of CO2 and was about 2.82 % of the temporary CO2 sink. Human activities (sulfur acid deposition and AMD) dramatically decreased the CO2 net sink and even make chemical weathering a CO2 source to the atmosphere.

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 Hydrological and biogeochemical controls on temporal variations of dissolved carbon and solutes in a karst river, South China

2021 ◽  
Vol 33 (1) ◽  
Author(s):  
Jing Liu ◽  
Jun Zhong ◽  
Shuai Chen ◽  
Sen Xu ◽  
Si-Liang Li
Keyword(s):  
Climate Change ◽  
Chemical Weathering ◽  
Inorganic Carbon ◽  
Dissolved Inorganic Carbon ◽  
Global Climate ◽  
Carbon Dynamics ◽  
Temporal Variations ◽  
High Flow ◽  
Dissolved Carbon ◽  
Weathering Processes

Abstract Background Understanding the responses of riverine dissolved carbon dynamics and chemical weathering processes to short-term climatic variabilities is important to understand the Surface-Earth processes under ongoing climate change. Temporal variations of solutes and stable carbon isotope of dissolved inorganic carbon (δ13CDIC) were analysed during a hydrological year in the Guijiang River, South China. We aimed to unravel the chemical weathering processes and carbon dynamics in karst areas under ongoing climate changes. Results Significant positive relationships were found between weathering rates and climatic factors (i.e. temperature and discharge) over the hydrological year. The total flux of CO2 consumption (760.4 × 103 mol/km2/year) in the Guijiang River was much higher than the global mean flux, with a higher CO2 consumption capacity in the Guijiang River relative to most other global rivers. Chemical weathering fluxes in this karst area showed high sensitivity to global climate change. CO2 evasion during the warm–wet seasons was much lower than those during cold–dry seasons. Light δ13CDIC values occurred under high-flow conditions, corresponding with the high temperatures in high-flow seasons. IsoSource modelling revealed that biological carbon could account for 53% of all dissolved inorganic carbon (DIC), controlling the temporal carbon variabilities. Conclusion This study quantitatively evaluated the temporal variations in CO2 fluxes and carbon cycling of karstic river systems and demonstrated that riverine carbon cycling will have a higher sensibility to ongoing global climate change. High discharges accelerate solutes transport, with relatively large quantities of 13C-depleted carbon being flushed into rivers. Meanwhile, high temperatures also accelerate organic carbon mineralisation, producing high content of soil CO2, whose influx can shift the 13C-depleted values in the high-flow seasons. Taken together, biological carbon influx should be responsible for the temporal carbon dynamics.

Mechanisms controlling the chemical weathering flux and CO2 consumption rate of Cauvery river, South India: Role of secondary soil minerals (in weathered profiles) versus primary minerals and anthropogenic sources

2020 ◽  
Author(s):  
Badimela Upendra ◽  
Ciba Manohar ◽  
Aiswarya Aji ◽  
Vinu Dev Vasudevan ◽  
Anoop Krishnan Krishnan
Keyword(s):  
Chemical Weathering ◽  
Anthropogenic Activities ◽  
Anthropogenic Sources ◽  
Silicate Weathering ◽  
Soil Minerals ◽  
Atmospheric Input ◽  
Cauvery River ◽  
Co2 Consumption ◽  
Consumption Rates ◽  
Primary Minerals

&lt;p&gt;Abstract&lt;br&gt;Hydrochemical assessment have been carried out for a tropical, east flowing Western Ghats river Cauvery, southern India, to understand the dissolved load sources, acquisition processes and their controlling factors. Silicate weathering rates (SWR) and associated CO2 consumption rates (CCR) are estimated along with quantification of source wise solute load contribution towards total solute load of the Cauvery River Basin (CRB). Atmospheric input, anthropogenic activities and water-mineral interaction processes are identified as the major solute sources. Using the chemical mass balance forward model, source wise solute load contributions are estimated to be 13%, 32%, 47% and 8% from atmospheric input, anthropogenic activities, silicates and carbonates weathering respectively. It&amp;#8217;s found that, chemical weathering followed by anthropogenic activities are the controlling factors for the solute load of CRB with minor influence of atmospheric input. Weathering index calculated for CRB (Re &gt; 3), suggest incomplete weathering of drainage rocks resulting in formation of secondary soil minerals along the river course. Further, detailed analysis of chemical weathering mechanisms is accomplished via end-member mixing analysis approach (EMMA) by using Ca/Na and Mg/Na ratios of different end-members including primary minerals form country rocks and secondary soil (weathered profile) minerals. End-member mixing diagram referred as modified Na-normalized Ca versus Mg, reveal that chemical weathering of secondary soil minerals is as significant as primary minerals and source wise solute load contribution to the river is almost equal from both sources primary and secondary. At outlet of the basin (Musiri), SWR and associated CCR values are estimated to be 12.9 t.km-2.y-1 and 3.3 &amp;#215; 105 mole.km-2.y-1 respectively. Results indicate that average SWR values estimated for the east flowing Cauvery river are several times (~ 4) lower than the average SWR values of west flowing Western Ghats rivers, even though the associated CO2 consummation rates are comparable for both river systems.&lt;br&gt;Keywords: Cauvery river, solute acquisition mechanisms, chemical weathering, anthropogenic sources, primary minerals, secondary soil minerals, silicate weathering, CO2 consumption rates.&lt;/p&gt;

scholarly journals A Strontium and Hydro-Geochemical Perspective on Human Impacted Tributary of the Mekong River Basin: Sources Identification, Fluxes, and CO2 Consumption

Water ◽  
2021 ◽  
Vol 13 (21) ◽  
pp. 3137
Author(s):  
Shitong Zhang ◽  
Guilin Han ◽  
Jie Zeng ◽  
Xuhuan Xiao ◽  
Fairda Malem
Keyword(s):  
River Basin ◽  
Chemical Weathering ◽  
Anthropogenic Impacts ◽  
Mekong River ◽  
Silicate Weathering ◽  
Sr Isotopes ◽  
Co2 Consumption ◽  
Geological Conditions ◽  
Basin Scale ◽  
Evaporite Dissolution

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.

Contribution of the chemical weathering to the CO2 consumption in a microbasin of Quadrilátero Ferrífero, Brazil

2021 ◽  
Vol 80 (17) ◽  
Author(s):  
Daniela V. Machado ◽  
Camila R. e Silva ◽  
Eduardo D. Marques ◽  
Gabriel S. de Almeida ◽  
Emmanoel V. Silva-Filho
Keyword(s):  
Chemical Weathering ◽  
Co2 Consumption ◽  
Quadrilátero Ferrífero
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