首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 31 毫秒
1.
The Hanjiang River, the largest tributaries of the Changjiang (Yangtze) River, is the water source area of the Middle Route of China’s South-to-North Water Transfer Project. The chemical and strontium isotopic compositions of the river waters are determined with the main purpose of understanding the contribution of chemical weathering processes and anthropogenic inputs on river solutes, as well as the associated CO2 consumption in the carbonate-dominated basin. The major ion compositions of the Hanjiang River waters are characterized by the dominance of Ca2+ and HCO3 −, followed by Mg2+ and SO4 2−. The increase in TDS and major anions (Cl−, NO3 −, and SO4 2−) concentrations from upstream to downstream is ascribed to both extensive influences from agriculture and domestic activities over the Hanjiang basin. The chemical and Sr isotopic analyses indicate that three major weathering sources (dolomite, limestone, and silicates) contribute to the total dissolved loads. The contributions of the different end-members to the dissolved load are calculated with the mass balance approach. The calculated results show that the dissolved load is dominated by carbonates weathering, the contribution of which accounts for about 79.4% for the Hanjiang River. The silicate weathering and anthropogenic contributions are approximately 12.3 and 6.87%, respectively. The total TDS fluxes from chemical weathering calculated for the water source area (the upper Hanjiang basin) and the whole Hanjiang basin are approximately 3.8 × 106 and 6.1 × 106 ton/year, respectively. The total chemical weathering (carbonate and silicate) rate for the Hanjiang basin is approximately 38.5 ton/km2/year or 18.6 mm/k year, which is higher than global mean values. The fluxes of CO2 consumption by carbonate and silicate weathering are estimated to be 56.4 × 109 and 12.9 × 109 mol/year, respectively.  相似文献   

2.
This study focused on the chemical compositions of the rivers around Yulong Mountain, one of the typical monsoonal temperate glacier regions in China. Water samples were collected from Baishui, Sanshu and Geji hydrological stations around Mt. Yulong during rainy season. The chemical analyses indicated that the river water around Mt. Yulong was characterized by high pH values (>8.0) and EC values varied from 36.4 to 71.7 μS/cm with an average of 52.6 μS/cm. Ca2+ and Mg2+ were the dominant cations, together accounting for about 90 % of the total cations. HCO3 ?, followed by SO4 2?, was the dominant anion. Obvious variations had been perceived during the rainy season. River water chemistry in rainy season was mainly influenced by precipitation and rock weathering. The proportions of Na+, K+, Ca2+, Mg2+ and SO4 2? from precipitation in river water were 23.44, 9.66, 3.10, 17.81 and 10.48 %, respectively. In addition, the ion characteristics of river water were mainly influenced by carbonate weathering. The human activities should not be ignored though its influence was little.  相似文献   

3.
The hydrogeochemical study of surface and subsurface water of Mahi River basin was undertaken to assess the major ion chemistry, solute acquisition processes and water quality in relation to domestic and irrigation uses. The analytical results show the mildly acidic to alkaline nature of water and dominance of Na+ and Ca2+ in cationic and HCO3 − and Cl− in anionic composition. In general, alkaline-earth elements (Ca2+ + Mg2+) exceed alkalis (Na+ + K+) and weak acids (HCO3 −) dominate over strong acids (SO4 2+ + Cl−) in majority of the surface and groundwater samples. Ca2+–Mg2+–HCO3 − is the dominant hydrochemical facies both in surface and groundwater of the area. The weathering of rock-forming minerals mainly controlled the solute acquisition process with secondary contribution from marine and anthropogenic sources. The higher concentration of sodium and dissolved silica, high equivalent ratios of (Na+ + K+/TZ+), (Na+ + K+/Cl−) and low ratio of (Ca2+ + Mg2+)/(Na+ + K+) suggest that the chemical composition of the water is largely controlled by silicate weathering with limited contribution from carbonate weathering and marine and anthropogenic sources. Kaolinite is the possible mineral that is in equilibrium with the water, implying that the chemistry of river water favors kaolinite formation. Assessment of water samples for drinking purposes suggests that the majority of the water samples are suitable for drinking. At some sites concentrations of TDS, TH, F−, NO3 − and Fe are exceeding the desirable limit of drinking. However, these parameters are well within the maximum permissible limit except for some cases. To assess the suitability for irrigation, parameters like SAR, RSC and %Na were calculated. In general, both surface and groundwater is of good to suitable category for irrigation uses except at some sites where high values of salinity, %Na and RSC restrict its uses.  相似文献   

4.
Weathering of rocks that regulate the water chemistry of the river has been used to evaluate the CO2 consumption rate which exerts a strong influence on the global climate. The foremost objective of the present research is to estimate the chemical weathering rate (CWR) of the continental water in the entire stretch of Brahmaputra River from upstream to downstream and their associated CO2 consumption rate. To establish the link between the rapid chemical weathering and thereby enhance CO2 drawdown from the atmosphere, the major ion composition of the Brahmaputra River that drains the Himalaya has been obtained. Major ion chemistry of the Brahmaputra River was resolved on samples collected from nine locations in pre-monsoon, monsoon and post-monsoon seasons for two cycles: cycle I (2011–2012) and cycle II (2013–2014). The physico-chemical parameters of water samples were analysed by employing standard methods. The Brahmaputra River was characterized by alkalinity, high concentration of Ca2+ and HCO3 ? along with significant temporal variation in major ion composition. In general, it was found that water chemistry of the river was mainly controlled by rock weathering with minor contributions from atmospheric and anthropogenic sources. The effective CO2 pressure (log\({{\text{P}}_{{\text{C}}{{\text{O}}_{\text{2}}}}}\)) for pre-monsoon, monsoon and post-monsoon has been estimated. The question of rates of chemical weathering (carbonate and silicate) was addressed by using TDS and run-off (mm year?1). It has been found that the extent of CWR is directly dependent on the CO2 consumption rate which may be further evaluated from the perspective of climate change mitigation The average annual CO2 consumption rate of the Brahmaputra River due to silicate and carbonate weathering was found to be 0.52 (×106 mol Km?2 year?1) and 0.55 (×106 mol Km?2 year?1) for cycle I and 0.49 (×106 mol Km?2 year?1) and 0.52 (×106 mol Km?2 year?1) for cycle II, respectively, which were significantly higher than that of other Himalayan rivers. Estimation of CWR of the Brahmaputra River indicates that carbonate weathering largely dominates the water chemistry of the Brahmaputra River.  相似文献   

5.
A comprehensive and systematic study to understand various geochemical processes as well as process drivers controlling the water quality and patterns of the hydrochemical composition of river water in Muthirapuzha River Basin, MRB (a major tributary of Periyar, the longest river in Kerala, India), was carried out during various seasons, such as monsoon, post-monsoon and pre-monsoon of 2007–2008, based on the data collected at 15 monitoring stations (i.e., 15 × 3 = 45 samples). Ca2+ and Mg2+ dominate the cations, while Cl? followed by HCO3 ? dominates the anions. In general, major ion chemistry of MRB is jointly controlled by weathering of silicate and carbonate rocks, which is confirmed by relatively larger Ca2+ + Mg2+/Na+ + K+ ratios as well as Ca2+/Na+ vs. Mg2+/Na+ and Ca2+/Na+ vs. HCO3 ?/Na+ scatter plots. The relationship between Cl? and Na+ implies stronger contributions of anthropogenic activities modifying the hydrochemical composition, irrespective of seasons. The water types emerged from this study are transitional waters or waters that changed their chemical character by mixing with waters of geochemically different ionic signatures. However, various ionic ratios, hydrochemical plots and graphical diagrams suggest seasonality over the hydrochemical composition, which is solely controlled by the rainfall pattern. Relatively higher pCO2 indicates the disequilibrium existing in natural waterbodies vis-à-vis the atmosphere, which is an outcome of both the contribution of groundwater to stream discharge and anthropogenic activities. Hence, continuous monitoring of hydrochemical composition of mountain rivers is essential in the context of climate change, which has serious implications on tropical mountain fluvial-hydro systems.  相似文献   

6.
Biogeochemical processes were investigated in alpine river—Kamni?ka Bistrica River (North Slovenia), which represents an ideal natural laboratory for studying anthropogenic impacts in catchments with high weathering capacity. The Kamni?ka Bistrica River water chemistry is dominated by HCO3 ?, Ca2+ and Mg2+, and Ca2+/Mg2+ molar ratios indicate that calcite weathering is the major source of solutes to the river system. The Kamni?ka Bistrica River and its tributaries are oversaturated with respect to calcite and dolomite. pCO2 concentrations were on average up to 25 times over atmospheric values. δ13CDIC values ranged from ?12.7 to ?2.7 ‰, controlled by biogeochemical processes in the catchment and within the stream; carbonate dissolution is the most important biogeochemical process affecting carbon isotopes in the upstream portions of the catchment, while carbonate dissolution and organic matter degradation control carbon isotope signatures downstream. Contributions of DIC from various biogeochemical processes were determined using steady state equations for different sampling seasons at the mouth of the Kamni?ka Bistrica River; results indicate that: (1) 1.9–2.2 % of DIC came from exchange with atmospheric CO2, (2) 0–27.5 % of DIC came from degradation of organic matter, (3) 25.4–41.5 % of DIC came from dissolution of carbonates and (4) 33–85 % of DIC came from tributaries. δ15N values of nitrate ranged from ?5.2 ‰ at the headwater spring to 9.8 ‰ in the lower reaches. Higher δ15N values in the lower reaches of the river suggest anthropogenic pollution from agricultural activity. Based on seasonal and longitudinal changes of chemical and isotopic indicators of carbon and nitrogen in Kamni?ka Bistrica River, it can be concluded that seasonal changes are observed (higher concentrations are detected at low discharge conditions) and it turns from pristine alpine river to anthropogenic influenced river in central flow.  相似文献   

7.
测量了喀斯特地区乌江、沅江两大水系的河流枯水期的主元素、Sr2+离子浓度和Sr同位素比值。这些河流的化学组成代表了流经碳酸盐岩地层的河水的化学组成。这些河流及其支流有高的溶解盐,TZ+变化范围为：2.1～6.3 meq/L,高于全球河流的平均值(TZ+=0.725 meq/L)。河水含有较高的溶质浓度,河水水化学组成以Ca2+和HCO-3为主,其次为Mg2+和SO2-4,Na++K+和Cl-+Si分别只占阳离子和阴离子组成的5%～10%。 这些河流的化学和同位素组成主要受其自流盆地的地质特征控制。流经碳酸盐岩地层的乌江水系河流具有较高的Sr浓度（1.1～9.70 mol/L）和较低的87Sr/86Sr比值（0.7077～0.7110）,与流经碎屑岩地层的沅江水系的清水江河流中较高的87Sr/86Sr比值（0.7090～0.7145）及较低的Sr浓度（0.28～1.32 mol/L）形成鲜明的对比。 流域盆地的地理岩性控制了河水的化学组成和同位素组成。对河水的化学计量分析表明河水化学组成受碳酸盐岩溶解控制,而碳酸盐岩主要受碳酸和硫酸作用而溶解。乌江流域受硫酸作用特别明显,表明硫酸主要来源于燃煤或流域盆地硫化物矿物氧化而形成的大气输入。化学元素和同位素比值之间的相互关系表明3个主要来源为：石灰岩、白云岩和硅酸盐岩的风化。同时估计了碳酸盐岩和硅酸盐岩的化学风化速率,结果表明流域盆地的碳酸盐岩风化速率远远高于许多世界大河。岩石风化过程中硫酸的出现或土地的过度使用或土壤植被的退化等都可能是导致流域的碳酸盐岩风化速率如此高的原因。   相似文献   

8.
River water composition (major ion and 87Sr/86Sr ratio) was monitored on a monthly basis over a period of three years from a mountainous river (Nethravati River) of southwestern India. The total dissolved solid (TDS) concentration is relatively low (46 mg L−1) with silica being the dominant contributor. The basin is characterised by lower dissolved Sr concentration (avg. 150 nmol L−1), with radiogenic 87Sr/86Sr isotopic ratios (avg. 0.72041 at outlet). The composition of Sr and 87Sr/86Sr and their correlation with silicate derived cations in the river basin reveal that their dominant source is from the radiogenic silicate rock minerals. Their composition in the stream is controlled by a combination of physical and chemical weathering occurring in the basin. The molar ratio of SiO2/Ca and 87Sr/86Sr isotopic ratio show strong seasonal variation in the river water, i.e., low SiO2/Ca ratio with radiogenic isotopes during non-monsoon and higher SiO2/Ca with less radiogenic isotopes during monsoon season. Whereas, the seasonal variation of Rb/Sr ratio in the stream water is not significant suggesting that change in the mineral phase being involved in the weathering reaction could be unlikely for the observed molar SiO2/Ca and 87Sr/86Sr isotope variation in river water. Therefore, the shift in the stream water chemical composition could be attributed to contribution of ground water which is in contact with the bedrock (weathering front) during non-monsoon and weathering of secondary soil minerals in the regolith layer during monsoon. The secondary soil mineral weathering leads to limited silicate cation and enhanced silica fluxes in the Nethravati river basin.  相似文献   

9.
The hydrogeochemical and isotope characteristics of the River Idrijca, Slovenia, where the world’s second largest mercury (Hg) mine is located, were investigated. The River Idrijca, a typical steep mountain river, has an HCO3 −–Ca2+–Mg2+ chemical composition. Its Ca2+/Mg2+ molar ratio indicates that dolomite weathering prevails in the watershed. The River Idrijca and its tributaries are oversaturated with respect to calcite and dolomite. The pCO2 pressure is up to 13 times over atmospheric pressure and represents a source of CO2 to the atmosphere. δ18O values in river water indicate primary control from precipitation and enrichment of the heavy oxygen isotope of infiltrating water recharging the River Idrijca from its slopes. The δ13CDIC values range from −10.8 to −6.6‰ and are controlled by biogeochemical processes in terrestrial environments and in the stream: (1) exchange with atmospheric CO2, (2) degradation of organic matter, (3) dissolution of carbonates, and (4) tributaries. The contributions of these inputs were calculated according to steady state equations and are estimated to be—11%:19%:30%:61% in the autumn and 0%:26%:39%:35% in the spring sampling seasons.  相似文献   

10.
The geochemical and isotopic compositions of river water are controlled by different factors. The seasonal and spatial variations in the geochemical composition, δD, δ18O, and δ15N–NO3 of the Kumho River were investigated to reveal the geochemical processes occurring at different seasons. The Kumho River, which runs through different geologic terrains with different land use characteristics, is the largest tributary of the Nakdong River, the longest river in South Korea. The data varied significantly according to the land use and the season. Each monitoring station showed the lowest concentrations of various ions during July, the rainy season, due to the increase of precipitation rate. The ionic concentrations gradually increased downstream by the mineral weathering and anthropogenic activity. At the upper regions of the river, Ca and HCO3, which are closely associated with mineral weathering, were the most dominant cation and anion, respectively. The relatively high Si concentration of the headwater samples, caused by the weathering of volcanic rocks, also showed the importance of weathering in the upper regions mainly composed of volcanic rocks. The downstream regions of the Kumho River are mainly influenced by sedimentary rocks. At the lower reaches of the river, especially near the industrial complexes in Daegu, the third largest city in Korea, Na, Cl, and SO4 became the dominant ions, indicating that the anthropogenic pollution became more important in regulating the chemical composition of the river. The increasing (Ca + Mg + Na + K)/HCO3 ratio downstream also indicates that the anthropogenic effects became more important as the river flows downstream. The isotopic compositions of δD and δ18O indicate that the river waters were significantly affected by evaporation during May and July, but the evaporation effect was relatively low during October. The isotopic composition of δ15N–NO3 increased downstream, also confirming that anthropogenic effects became more significant at the lower reach of the river and near Daegu.  相似文献   

11.
The main ions were measured seasonally during two years at 13 sampling stations in the Salado River and its main tributaries. The importance of each ion was assessed by standard methods used to examine ionic composition and by multivariate methods. The K-means clustering and Principal Component Analysis were applied to the percentages of the major ions. The concentration of the major cations are in the order Na+ > Mg2+ > Ca2+ > K+ and the major anions, Cl− > SO42− > HCO3− > CO32−, and the salinity was high (mean TDS 2,691 mg l−1) due to sodium chloride. Using the proportions of the ions was possible to identify seven types of water within the basin related to discharges of different river sub-catchments and from endorheic catchments (in a sand dune region) actually connected with the basin by canals. The chemical composition of the basin is consequence of surface waters receiving salts from groundwater, evaporation and weathering of Post-Pampeano materials, and of anthropogenic impact by diversion between subcatchments for flood control. These results allowed us to test the marked effects on the ionic balance of basin at the base of a diversion management from endorheic catchments characterized by high salinity waters.  相似文献   

12.
The Wujiang River is an important tributary to the Changjiang River that has been intensively impounded for hydropower exploitation. To understand the potential impact of reservoir construction on the riverine inorganic carbon transport, seasonal longitudinal sampling was conducted in four reservoirs Hongjiadu (HJD), Dongfeng (DF), Suofengying (SFY) and Wujiangdu (WJD) along the Wujiang River from April 2006 to January 2007. Results indicated that damming the river induced an obvious discontinuity of water chemistry in the warmer seasons. δ 13C of dissolved inorganic carbon (DIC) ranged from ?3 to ?11.4 ‰, likely as the results of photosynthesis, respiration and carbonate weathering. During periods of thermal stratification, the addition of CO2 from respiration to hypolimnion and the deep water release for hydropower generation led to higher pCO2 downstream, as well as 13C depletion in DIC and undersaturated to calcite. An estimate of DIC budget indicated that only DF reservoir was the sink for DIC while reservoirs HJD, SFY and WJD were the sources for DIC. However, when the retained water was taken into account, for the reason of water storage occurring mainly in HJD and DF, all reservoirs became the sources for DIC with exporting rates of 26.68, 7.97, 6.22 and 11.80 % for HJD, DF, SFY and WJD, respectively.  相似文献   

13.
The major cation and anion compositions of waters from the Lake Qinghai river system (LQRS) in the northeastern Tibetan Plateau were measured. The waters were collected seasonally from five main rivers during pre-monsoon (late May), monsoon (late July), and post-monsoon (middle October). The LQRS waters are all very alkaline and have high concentrations of TDS (total dissolved solids) compared to rivers draining the Himalayas and the southeastern Tibetan Plateau. Seasonal variations in the water chemistry show that, except the Daotang River, the TDS concentration is high in October and low in July in the LQRS waters. The forward models were used to quantify the input of three main rivers (Buha River, Shaliu River, and Hargai River) from rain, halite, carbonates, and silicates. The results suggest that (1) atmospheric input is the first important source for the waters of the Buha River and the Shaliu River, contributing 36–57% of the total dissolved cations, (2) carbonate weathering input and atmospheric input have equal contribution to the Hargai River water, (3) carbonate weathering has higher contribution to these rivers than silicate weathering, and (4) halite is also important source for the Buha River. The Daotang River water is dominated by halite input owing to its underlying old lacustrine sediments. The water compositions of the Heima River are controlled by carbonate weathering and rainfall input in monsoon season, and groundwater input may be important in pre-monsoon and post-monsoon seasons. After being corrected the atmospheric input, average CO2 drawdown via silicate weathering in the LQRS is 35 × 103 mol/km2 per year, with highest in monsoon season, lower than Himalayas and periphery of Tibetan Plateau rivers but higher than some rivers draining shields.  相似文献   

14.
Based on the geological background, R-mode factor statistics, and the analysis of the stability diagram for the corresponding system, five weathering reactions controlling the surface-water chemical composition in the watershed of the Changhuajiang River are deduced. In the mass balance model, the precipitation accounts for some solute input, since the rainwater is dilute without pollution. Most of the Ca2+ and HCO 3 – ions are from the dissolution of calcite, K+, Na+, H4SiO4 and some of the Mg2+ and HCO 3 – come from albite and biotite weathering to kaolinite. The dissolution of dolomite and gypsum controls the mass balances of Mg2+ and SO 4 2– . The dissolution of calcite is the dominant chemical weathering reaction in the watershed because of its reactivity and high concentration. In the watershed in 1986, the chemical weathering rate was 0.073 (kg/m2 a), and the mechanical denudation rate is 0.093 (kg/m2 a). The chemical weathering mass output proportion of carbonate rocks to silicate rocks was about three to one.  相似文献   

15.
Major ions showed high concentrations, ionic strength and chemical activity in the surface waters of Govind Ballabh Pant Sagar reservoir. Various geochemical ratios showed the dominance of silicate over carbonate weathering and major ions such as Na+ + K+ account for about 52 % of the cation budget. The high Na+ and K+ showed sedimentation of rock/coal particles consisting of highly weathered silicate minerals contributed by the discharge of mine water, fly ash mixing during transportation, etc. Further, Ca2+ + Mg2+/Na+ + K+ ratio was <1 (0.92) indicating the occurrence of silicate weathering in the reservoir catchment. The comparative assessment showed that the proportion of Ca2+ + Mg2+/Na+ + K+ tends to be lower along the coal mining belts compared to non-coal mining regions in the world. The Ca2+/SO4 2? ratio <1 revealed not only H2CO3 but H2SO4 also acting as a source of protons for rock weathering. The cause underlying these differences can be related directly to geological substrate and anthropogenic activities.  相似文献   

16.
Alaknanda and Bhagirathi (AB) river basins in the Himalayan region in India expose lithologies comprising mainly of granites, low–high-grade metamorphics, shales and carbonates which, in conjunction with the monsoon rains and glacial melt, control water chemistry and dissolved elemental flux rates. In the present study, we monitored two locations: (a) Srinagar on the Alaknanda river and (b) Maneri on the Bhagirathi river for daily variations in total suspended sediments, major ions and dissolved silica over one complete year (July 2004–June 2005). Based on long-term discharge data, discharge-weighted composition and dissolved elemental flux rates (with respect to Ca, Mg, HCO3, Si) of the river were estimated. The information thus obtained has substantially added up to the existing chemical data of these rivers and has refined the flux rates. Our high-frequency samples provide informations such as (a) water chemical compositions that show a large temporal and spatial variation and (b) carbonate lithology that controls water chemistry predominantly. The dissolution kinetics of various lithologies namely leucogranite, gneiss, quartzite, phyllite and shale of the AB river basins were studied through batch experiments at controlled temperature (25 and 5°C) and pH (8.4) condition. In laboratory, these lithologies undergo slow rates of dissolution (10−13 to 10−15 mol/m2 s), while field weathering rates based on dissolved elemental flux rates in the AB rivers are much higher (10−8 to 10−9 mol/m2 s). Extremely high physical weathering rates in AB rivers, which enhance chemical weathering significantly, mainly attribute this wide discrepancy in laboratory-derived rates of representative basin rocks and dissolved elemental fluxes in the field. However, laboratory-simulated experiments facilitate to quantify elemental release rates, understand the kinetics of the dissolution reactions, and compare their roles at individual level.  相似文献   

17.
To assess the effects of river damming on dissolved inorganic carbon in the Jialing River, a total of 40 water samples, including inflow, outflow, and stratified water in four cascade reservoirs (Tingzikou, Xinzheng, Dongxiguan, Caojie) were collected in January and July, 2016. The major cations, anions, and δ13CDIC values were analyzed. It was found that the dissolved compositions are dominated by carbonate weathering, while sulfuric acids may play a relatively important role during carbonate weathering and increasing DIC concentration. Different reservoirs had variable characteristics of water physiochemical stratification. The DIC concentrations of reservoir water were lower in summer than those in winter due to the dilute effects and intensive aquatic photosynthesis, as well as imported tributaries. The δ13CDIC values in Tingzikou Reservoir were higher during summer than those in winter, which indicated that intensive photosynthesis increased the δ13CDIC values in residual water, but a similar trend was not obvious in other reservoirs. Except for in Xinzheng Reservoir, the δ13CDIC values in inflow and outflow reservoir water were lower than those in the surface water of stratified sampling in summer. For stratified sampling, it could be found that, in summer, the Tingzikou Reservoir δ13CDIC values significantly decreased with water depth due to the anaerobic breakdown of organic matter. The significant correlation (p < 0.01 or 0.05) between the DIC concentrations, the δ13CDIC values and anthropogenic species (Na++K+, Cl–, \({\text{SO}}_{4}^{2 - }\)and \({\text{NO}}_{3}^{ - }\)) showed that the isotope composition of DIC can be a useful tracer of contaminants. In total, Tingzikou Reservoir showed lacustrine features, Xinzheng Reservoir and Dongxiguan Reservoir had “transitional” features, and Caojie Reservoir had a total of “fluvial” features. Generally, cascade reservoirs in the Jialing River exhibited natural river features rather than typical lake features due to characteristics of reservoir water in physiochemical stratification, spatiotemporal variations of DIC concentrations and isotopic compositions. It is evident that the dissolved inorganic carbon dynamics of natural rivers had been partly remolded by dam building.  相似文献   

18.
The silicon isotopic composition of dissolved silicon and suspended particulate matter (SPM) were systematically investigated in water samples from the mainstem of the Yellow River and 4 major tributaries. The SPM content of the Yellow River varied from 1.4 to 38,560 mg/L, averaging 3568 mg/L, and the δ30Si of suspended particulate matter (δ30SiSPM) varied from 0.3‰ to −0.4‰, averaging −0.02‰. The major factors affecting the SPM content and the δ30SiSPM values in the Yellow River were inferred to be the mineralogical, chemical and isotopic characteristics of the sediments from the Loess Plateau and a combination of the climate and the flow discharge of the river.The major ions in the Yellow River water were Na+, Ca2+, Mg2+, HCO3−, SO42− and Cl−. High salt concentration was observed in samples from the middle and lower reaches, likely reflecting the effects of evaporation and irrigation because the Na+, Mg2+, SO42− and K+ concentrations were correlated with the Cl− concentration. The dissolved Si concentration (DSi) increased downstream, varying from 0.016 to 0.323 mM. The δ30Si of dissolved Si (δ30SiDiss) varied from 0.4‰ to 2.5‰, averaging 1.28‰. The major processes controlling the DSi and δ30SiDiss of the Yellow River are (a) the weathering of silicate rocks, (b) the formation of phytoliths in plants, (c) the evaporation of water from and the addition of meteoric water to the river system, which only affects concentrations, (d) the adsorption and desorption of aqueous monosilicic acid on iron oxide, and (e) the dissolution of phytoliths in soils.The DSi and δ30SiDiss values of global rivers vary spatially and temporally in response to changes in climate, chemical weathering intensity and biological activity. The moderately positive δ30SiDiss values observed in the Yellow River may be attributed to the higher rates of chemical weathering and biological activities that have been observed in this catchment in comparison with those of other previously studied catchments, excluding the Yangtze River. Human activities may also potentially influence chemical weathering and biological activities and affect the DSi and δ30SiDiss values of the major rivers of the world. Further river studies should be performed to gain a better understanding of the global Si isotope budget.  相似文献   

19.
A detailed investigation of the fluvial geochemistry of the Han River system allows to estimate the rates of chemical weathering and the consumption of CO2. The Han River drains approximately 26,000 km2 and is the largest river system in South Korea in terms of both water discharge and total river length. It consists of two major tributaries: the North Han River (NHR) and the South Han River (SHR). Distinct differences in basin lithology (silicate vs. carbonate) between the NHR and SHR provide a good natural laboratory in which to examine weathering processes and the influence of basin geology on water quality. The concentrations of major elements and the Sr isotopic compositions were obtained from 58 samples collected in both summer and winter along the Han River system in both 2000 and 2006. The concentrations of dissolved loads differed considerably between the NHR and SHR; compared with the SHR, the NHR had much lower total dissolved solids (TDS), Sr, and major ion concentrations but a higher Si concentration and 87Sr/86Sr ratio. A forward model showed that the dissolved loads in the NHR came primarily from silicate weathering (55 ± 11%), with a relatively small portion from carbonates (30 ± 14%), whereas the main contribution to the dissolved loads in the SHR was carbonate weathering (82 ± 3%), with only 11 ± 4% from silicates. These results are consistent with the different lithologies of the two drainage basins: silicate rocks in the NHR versus carbonate rocks in the SHR. Sulfuric acid derived from sulfide dissolution in coal-containing sedimentary strata has played an important role in carbonate weathering in the SHR basin, unlike in the NHR basin. The silicate weathering rate (SWR) was similar between the NHR and SHR basins, but the rate of CO2 consumption in the SHR basin was lower than in the NHR basin due to an important role of sulfuric acid derived from pyrite oxidation.  相似文献   

20.
Water samples collected from the six reservoirs of Damodar River basin in pre- and post-monsoon, have been analysed, to study the major ion chemistry and the weathering and geochemical processes controlling the water composition. Ca, Na and HCO3 dominate the chemical composition of the reservoir water. The seasonal data shows a minimum concentration of most of the ions in post-monsoon and a maximum concentration in pre-monsoon seasons, reflecting the concentrating effects due to elevated temperature and increased evaporation during the low water level period of the pre-monsoon season. Water chemistry of the reservoirs strongly reflects the dominance of continental weathering aided by atmospheric and anthropogenic activities in the catchment area. Higher concentration of SO4 and TDS in Panchet, Durgapur and Tenughat reservoirs indicate mining and anthropogenic impact on water quality. The high contribution of (Ca+Mg) to the total cations, high concentration of dissolved silica, relatively high (Na+K)/TZ+ ratio (0.3) and low equivalent ratio of (Ca+Mg)/(Na+K) suggests combined influence of carbonate and silicate weathering. Kaolinite is the possible mineral that is in equilibrium with the water, implying that the chemistry of reservoir water favours kaolinite formation. The calculated values of SAR, RSC and sodium percentage indicate the ‘excellent to good quality’ of water for irrigation uses.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号