Evolution of groundwater hydrochemical characteristics and origin analysis in middle reaches of Ganjiang River
Ganjiang River is the main water source of Jiangxi Province,studying its groundwater hydrochemical characteristics and genesis mechanism is crucial for the protection of the water quality in the basin.This study selected the Jingkai area of Ji'an City in the middle reaches of the Ganjiang River as the research area and collected 45 sets of shallow groundwater samples during the flood season,normal season,and dry season in 2019.Then,methods such as mathematical statistics,Durov diagrams,Gibbs di-agrams,ion ratio coefficients,and PHREEQC reverse simulation were used to study the hydrochemical distribution characteristics and composition types of shallow groundwater in the region.The main controlling factors and ion sources of the main components were discussed,and hydrogeochemical simulations of typical runoff paths were carried out.The results showed that:the shallow groundwater in the study area belongs to low salinity freshwater,with the main anions and cations being HCO3-and Ca2+.The ab-normal values of NH4+,NO3-,and SO42-in some samples are related to human activities.The main chemical types of groundwater in the study area are HCO3-Ca,HCO3-Ca·Mg,and HCO3·SO4-Ca.The main controlling factor of the formation of ground-water chemistry in the study area is rock weathering.From the ion ratio relationship,it can be concluded that the main source of water components is the dissolution of carbonate minerals,among them,Na+and K+mainly come from the dissolution of salt rocks,SO42-comes from the dissolution of a small amount of evaporite minerals(gypsum),Ca2+and Mg2+come from the dissolu-tion of calcite,dolomite,and silicate minerals.The reverse simulation results of hydrogeochemistry indicated that the dissolution of dolomite,gypsum,and rock salt occurs along the water flow path.Combined with the chlor alkali index,there is a certain degree of reverse cation exchange in groundwater flow.The results can provide some theoretical basis for the development,utilization,and protection of groundwater in the middle reaches of the Ganjiang River.
shallow groundwaterhydrochemical characteristicsion sourcePHREEQCmiddle reaches of Ganjiang River
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