| The water chemistry characteristics of river water can reflect the climate, lithology, atmospheric precipitation, soil, vegetation and human activities in the basin. To a certain degree, it also can reflect the status of water environment quality, the source, distribution and migration of the major elements, can estimate basin chemical weathering process, the weathering rate, consumption of atmospheric CO2 and other relevant information.This article selects Sanchahe River Basin as the research object which located in the karst-dominated terrain of Guizhou province, southwest China.The major ions were determined from the river water to analyze the major ions composition characteristics, the water chemistry characteristics, the spatial and temporal variation characteristics of the major ions.Based on the major ions content and chemical characteristics analysis of the river water,we will identify the possible controls of atmospheric precipitation, human activities and rock weathering. And we will estimate the rock weathering rate and CO2 consumption rate of the basin.The results are showed as follows:The average temperature value of water samples in dry season and wet season of Sanchahe River Basin is 15.6?. The average value of pH is 7.8, slightly alkaline. The average value of conductivity is 467 us/cm. The average concentration of dissolved oxygen is 8.8 mg/L. The average concentration of total dissolved cationic is 4.8 meq/L, it is exceed than the world average value of 1.25 meq/L. The average concentration of total dissolved solid is 340.46 mg/L, excced than the world average value of 100 mg/L.The dominate cation and anion of water samples in dry season and wet season of Sanchahe River Basin is Ca2+, HCO3– and SO42–, respectively. The spatial and temporal distribution characteristic of major ions concentration shows that the dry season is higher than the wet season. The major ions concentration show a trend of increase from upstream to downstream. The major ions concentration of each tributaries show a certain differences.The water chemistry characteristic of Sanchahe River Basin mainly controlled by the carbonate rock weathering. The sulfuric acid participate in the weathering process, it's a obvious feature in the karst terrain of southwest China. The atmospheric precipitation and human activities also have a certain impact. The wet season has large quantities of precipitation, cause a dilution effect. Human activities of industrial influence water chemistry characteristic more than the agricultural.The consumption of CO2 by silicate rock weathering is 325.5×103 mol/?km2·a? in whole year of Sanchahe River Basin. The consumption of CO2 by carbonate rock weathering?carbonic acid and sulfuric acid? in the dry season and wet season are 128.2×103 mol/?km2·a? and 469.2×103 mol/?km2·a?, respectively. In the dry season and wet season, the silicate rock and carbonate rock weathering rate are 2.0 t/?km2·a?, 9.0 t/?km2·a?, 23.4 t/?km2·a? and 85.8 t/?km2·a?, respectively. So the weathering and erosion effect is outstanding. |
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