Discussion on the evolution characteristics of phreatic water hydrochemistry of Baoding plain, Hebei, China

It is found that phreatic water quality in study area is poor. The main component and index exceeding standard Ⅲ rate include NO3-, total hardness, Fe2+, NO2- and total dissolved solids, followed by Cl- and SO42-. Among which NO3- exceeds standard Ⅲ rate mainly found in residential areas, agricultural production region and groundwater exploitation region. The increasing of total hardness is closely related to the increasing of Mg2+ and has significant correlation to other anions; the total dissolved solids is closely related to the increasing of SO42- and Na+. Meanwhile the water quality has significant change compared to those of 70-80's, the total hardness, total dissolved solids and pH have a rising trend , and the content increasing range of other components is SO42->Na+>HCO3->Cl->Mg2+>Ca2+. Hydrochemistry type changes from HCO3-Ca·Mg(Ca,Mg·Ca) to other types overall the groundwater has a alkalization trend in study area and the increasing trend of total dissolved solids and total hardness in some places such as Gaoyang, Xiongxian, Anxin is significant. In this paper, we've discussed the reason for this kind of change mainly from ground water exploitation.