Hydrogeochemical characteristics of the shallow pore water in Western Jianghan Plain

Western Jianghan Plain was taken as an example to reveal the migration of groundwater from periphery to the center of Jianghan Plain and complex hydrogeochemical action. Hydrogeochemical characteristics of the shallow pore water in the margin of Western Jianghan Plain were studied by the methods of mathematical statistics, water chemistry, isotope geochemistry and relationships between ions and so on. The results showed that HCO₃-Ca·Mg is the dominant chemical types in flat country. HCO₃-Ca·Mg is the dominant chemical types in hilly and mound land, with small amount HCO₃·SO₄-Ca·Mg. Besides, the HCO₃·NO₃-Ca·Mg is also existent in hilly and mound land and the increasing total dissolved solids is due to the dissolution of carbonate rocks. Shallow pore water is mainly from atmospheric precipitation, and barely influenced by evaporation. The dissolution of calcite, dolomite and gypsum is the dominant hydrogeochemical process, and they are the main source of Ca²⁺ and Mg²⁺. The main source of Na⁺ and K⁺ is by cation exchange adsorption.