QUALITY EVALUATION AND ITS CONTROLLING FACTOR ANALYSES OF SHALLOW GROUNDWATER IN THE URBAN AREA OF SUZHOU, ANHUI PROVINCE, CHINA

摘要

Groundwater is an important source for dinking and irrigation purposes in northern Anhui province, China, and management of this resource is significant to meet the increasing demand of water. In this study, forty-three groundwater samples collected from the First (FA, 20 samples) and Second (SA, 23 samples) loose layer aquifers in the west of Suzhou city, north Anhui Province, China, and their major ion concentrations have been analyzed by a series of chemical indexes (including the Nemerow pollution index, water quality index, sodium adsorption ratio as well as sodium percent) for the evaluation of pollution status, dinking and irrigation suitability. Then the mechanisms controlling the groundwater chemistry have been analyzed. The results indicated that the groundwater samples are neutral to slightly alkaline, 75% and 100% of the FA and SA samples have TDS contents similar to the fresh water (1000mg/L), and the hydrochemical facies of the groundwater samples are classified to be Na-HCO_3, to a lesser extent, Ca-HCO_3 and Mg- HCO_3. Based on Nemerow pollution index, 55% and 26% of samples from the FA and SA are suffered litter pollution, respectively. Water quality index indicated that all of samples can be used for dinking proposes, and approximately 40% of the samples from the two aquifers are good for irrigation according to the analysis of sodium adsorption ratio and sodium percent. Furthermore, the Gibbs diagram, chloro-alkaline indices as well as the relationships between Na~+, Ca~(2+), Mg~(2+) and HCO_3~- indicated that the weathering of silicate minerals and ion exchange are the main process controlling the groundwater chemistry.