Study of the chemical features and geochemical susceptibility of the groundwater system in a typical karst trough valley

REN Kun; SHI Yang; LI Xiao-chun; LAN Jia-cheng; XU Shang-quan

doi:10.3969/j.issn.1001-4810.2014.01.003

Abstract：The karst groundwater system is an important drinking water sources in karst regions.However, with urbanization development,groundwater in China has been widely polluted,especially karst groundwater in southwestern China.It is important to study the degree of response and mechanisms of groundwater fea-tures by external interference in order to guarantee drinking water safety.Using hydrochemical data for A-pril 2012 to March 2013,the geochemical susceptibility of groundwater in Laolongdong subterranean river and Zhaoj iayuanzi epi-karst spring in the river watershed of Nanshan,Chongqing was analyzed,and the prin-cipal cations were Ca2+ and Mg2+ in the epi-karst spring,and Ca2+ and Na+ in the subterranean river.The principal anions were HCO-3 and SO2-4 in both the subterranean river and the epi-karst spring.The values of Mg2+/Ca2+and Na+/Ca2+ were greater in the dry season than in rainy season.The value of HCO-3/SO2-4 was 5.693-8.664 and 3.428-6.524 in dry season,3.428-6.524 and 3.122-5.966 in rainy season.This indicates a high concentration of HCO-3 and low concentration of SO2-4 .Owing to agricultural activities,the rank order of geochemical susceptivity for major elements in the epi-karst spring is HCO-3 > SO2-4 > Ca2+>NO-3 > Mg2+> Na+> K+> Cl-.When agricultural activities,industrial activities as well as urban con-struction activities were all taken into account,the rank order of geochemical susceptivity for maj or elements in the subterranean river became HCO-3 > Na+> Ca2+> K+> Cl-> Mg2+> NO-3 > SO2-4 .With an-thropic activities,each ion is becoming increasingly susceptive.Thus,more attention should be paid to karst groundwater pollution.