Research on hydrochemical spatio-temporal characteristics of groundwater quality of different aquifer systems in Songhua River Basin, eastern Songnen Plain, Northeast China

Groundwater is often a critical source for industry, agriculture, and many other aspects of life. The Songnen Plain, located in the northeast of China, has been an important base for commodity grain and livestock husbandry in the country, with the groundwater of the Songhua River basin in eastern Songnen Plain playing a major role. Studies of hydrochemical spatio-temporal variation characteristics and evolution rules are carried out in the Songhua River basin. Seventy-three observation wells, including Quaternary unconfined wells, Quaternary confined wells, and Cretaceous confined wells, are analyzed using descriptive statistics, ratios of ions, piper diagrams and regional maps. The results of this study show that (1) HCO3− and Ca2+ are the main anion and cation in the groundwater, respectively, (2) nitrate pollution is relatively serious in unconfined water, (3) variation in chemical composition is greater in confined water than in unconfined water, and (4) the seasonal and regional characteristics of the Songnen groundwater system are controlled by the hydrochemical processes of weathering-dissolution, evaporation, and ion-exchange reactions.