Analysis of characteristic of Hydrogeochemistry in Yinchuan plain

Based on the hydrogeological conditions of Yinchuan plain, the groundwater environmental comprehensive index and groundwater chemical types were analyzed: There is a negative correlation between DO and EC, the study also shows the positive correlation between EC and TDS, the increase of dissolved salts in groundwater leads to the increase of TDS, which makes the conductivity of groundwater and EC increased. The sort of average concentration of cation is Na+>Ca2+>Mg2+>K+>NH+4, and the sort of average concentration of anion is HCO-3>SO2-4>Cl-. The groundwater chemical type of study area mainly include: HCO3·SO4—Ca·Mg, HCO3·SO4—Ca·Na, HCO3·SO4—Na·Mg, SO4·HCO3—Na·Mg. The study shows a negative correlation between activity coefficient and ionic strength: the increase of the ionic strength leads to the increase of the ions concentration and the charge in groundwater, which causes the ion to be reassembled into the solute, which leads to the decrease of activity coefficient of ionic. Calcite is closest to the equilibrium state in the study area, and it may exist in the aquifer environment. Based on the groundwater environmental comprehensive index and the concentration of each component, we can conclude from the groundwater chemical evolution environment of the study area: The No.65 sample locates in the south of study area, and its groundwater chemical type is SO4·Cl—Na, it has a high risk to be contaminated; The sample of No.4, No.83, No.290, which locate in the south of No.65 and the Yellow River irrigation area, surface water has a more significant influence on groundwater, the pollution level of those samples is lower than No.65 sample.