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.

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 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 Hydro-Geochemistry of the River Water in the Jiulongjiang River Basin, Southeast China: Implications of Anthropogenic Inputs and Chemical Weathering

2019 ◽  
Vol 16 (3) ◽  
pp. 440 ◽  
Author(s):  
Xiaoqiang Li ◽  
Guilin Han ◽  
Man Liu ◽  
Kunhua Yang ◽  
Jinke Liu
Keyword(s):  
River Water ◽  
River Basin ◽  
Human Activities ◽  
Chemical Weathering ◽  
Silicate Weathering ◽  
Carbonate Weathering ◽  
Southeast China ◽  
Anthropogenic Inputs ◽  
Weathering Process ◽  
Jiulongjiang River

This study focuses on the chemical weathering process under the influence of human activities in the Jiulongjiang River basin, which is the most developed and heavily polluted area in southeast China. The average total dissolved solid (TDS) of the river water is 116.6 mg/L and total cation concentration ( TZ + ) is 1.5 meq/L. Calcium and HCO 3 − followed by Na + and SO 4 2 − constitute the main species in river waters. A mass balance based on cations calculation indicated that the silicate weathering (43.3%), carbonate weathering (30.7%), atmospheric (15.6%) and anthropogenic inputs (10.4%) are four reservoirs contributing to the dissolved load. Silicates (SCW) and carbonates (CCW) chemical weathering rates are calculated to be approximately 53.2 ton/km2/a and 15.0 ton/km2/a, respectively. When sulfuric and nitric acid from rainfall affected by human activities are involved in the weathering process, the actual atmospheric CO 2 consumption rates are estimated at 3.7 × 105 mol/km2/a for silicate weathering and 2.2 × 105 mol/km2/a for carbonate weathering. An overestimated carbon sink (17.4 Gg C / a ) is about 27.0% of the CO 2 consumption flux via silicate weathering in the Jiulongjiang River basin, this result shows the strong effects of anthropogenic factors on atmospheric CO 2 level and current and future climate change of earth.

scholarly journals Environmental/hydrological problems of the Mekong River Delta

2019 ◽  
Author(s):  
Keyword(s):  
River Basin ◽  
Crop Production ◽  
Anthropogenic Impacts ◽  
World Ocean ◽  
River Delta ◽  
Mekong River ◽  
Water Runoff ◽  
Hydroelectric Power ◽  
Mekong River Delta ◽  
Power Stations

The article shows how anthropogenic impacts on the hydrological regime in the upper part of the river basin together with climatic changes lead to an ecological catastrophe in the delta of the river. We have considered the Mekong River basin, which is located on the territory of six countries, where more than 30 hydroelectric power stations are already operating in the upper part of the basin, and another 10 are under construction. The number of hydroelectric power stations in the basin is planned to be increased to 170. The Mekong River Delta, completely located on the territory of Vietnam, is experiencing huge multifaceted problems. The delta has been growing towards the sea for many centuries, but in recent decades it has been receding, primarily due to a sharp decrease in the inflow of sediment in the delta, which is detained by numerous dams upstream. Uncontrolled until recently the extraction of sand and gravel mixtures from the riverbed also has an impact. On the other hand, the construction of hydraulic structures is not only a very important factor in the economic development of the basin countries, but also an important tool in combating the growing contrast of the climate, when floods are becoming more powerful, and the decline of the runoff in the dry period is becoming lower. Reduction of low-water runoff is exacerbated by the pumping out of groundwater for the needs of water supply. Reduction of the solid flow and low-water flow against the background of the growth of the world ocean level caused by climate change leads to a significant penetration of sea salt waters along the canal and channel systems into the delta. This has an extremely adverse effect on crop production and fish farming. At the same time, the Mekong Delta is the most important agricultural sector in Vietnam, accounting for more than 50% of total rice production and 60% of fish production. An article is devoted to the investigation of these problems and the identification of ways to solve them.

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.

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

scholarly journals Governing Water as a Common Good in the Mekong River Basin: issues of scale

2006 ◽  
Vol 1 (2) ◽  
Author(s):  
Philip Hirsch
Keyword(s):  
River Basin ◽  
Common Good ◽  
Common Property ◽  
Multiple Scales ◽  
Water Governance ◽  
Vice President ◽  
Mekong River ◽  
Transboundary River Basin ◽  
Mekong River Commission ◽  
Basin Scale

Transboundary water governance has received special attention in the wake of the World Bank vice-president Ismail Serageldin’s famous prediction in 1995 that, “if the wars of this century were fought over oil, the wars of the next century will be fought over water”. The water wars scenario ensures that in the world’s more than 260 river basins that flow across national boundaries, primary attention is given to managing water as an international commons. A framework for such transboundary management has been in place more or less continuously in the Mekong for half a century, and it would appear that water has indeed been a force for cooperation even when brutal conflict has torn at the region. Despite the appearance of successful basin-scale management, inter-governmental management of water as an international commons in a transboundary river basin context can also hide some troubling ways in which water as a commons is eroded in the process of development. This paper considers common property dimensions of water and the livelihood systems that they support at multiple scales within the Mekong. It goes on to look at ways in which these are impacted upon by bureaucratisation, infrastructure and commodification processes. Ironically, basin organisations can both enhance and undermine governance for the common good, depending on how they deal with commonality of interest in freshwater at various scales. The paper draws on brief case studies of current trends in water governance including river basin organisations in the Mekong (the Mekong River Commission and River Basin Committees at national levels), of infrastructure (Thailand’s proposed Water Grid and Laos’ Nam Theun 2 dam) and of commodified notions of water (as a development resource and as a scarce commodity to be managed through market mechanisms).

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