Abstract:

Based on the groundwater data obtained from the karst groundwater pollution investigation and evaluation in Southwest China, geochemical characteristics of 30 elements or indicators on 26 karst groundwater samples which have been analyzed and tested are studied in this paper. The type of hydrochemical component, characteristics of ion contents relativity, distribution characteristics and influence factor are described. Results indicate that the hydrochemical type of karst groundwater is Ca-HCO₃ or Ca·Mg-HCO₃；the background values of the items are lower than the values of grade Ⅲ of the National Water Standard. The results show that only several indicators (such as Zn, Se and Hg) in karst groundwater of the study area have changed significantly and are unevenly distributed．Other indicators have changed insignificantly and are evenly distributed in groundwater. All the elements have no correlation with pH, while there is clear positive correlation among HCO^-3, Ca²⁺, Mg²⁺, K⁺, Na⁺, SO^2-₄, NO^-3, I^-,total hardness. HCO^-3, Ca²⁺ and Mg²⁺ play a decisive part on the elemental relationship. The spatial distribution of elements assumes sheet distribution characteristics, which is controlled by the geologic background, geographic condition and human activities.

Key words: geochemical characteristic, groundwater, Chengjiang area in Guangxi