典型岩溶槽谷区地下水化学特征及地球化学敏感性分析

利用2012年4月—2013年3月的水化学数据研究了重庆老龙洞地下河流域地下水系统地球化学敏感性。结果表明，研究区表层岩溶泉和地下河水化学阳离子分别以Ca2+、Mg2+和Ca2+、Na+为主，阴离子以HCO3-、SO42-为主；表层岩溶泉雨季Mg2+/ Ca2+摩尔比和地下河雨季Na+/ Ca2+摩尔比旱季大于雨季，表层岩溶泉和地下河雨季 HCO3-/SO42- 摩尔比分别为3.428～6.524、3.122～5.966，旱季HCO3-/SO42-摩尔比分别为5.693～8.664、3.428～6.524，表现出低SO42-、高HCO3-的特征，主要受农业活动影响的表层岩溶泉主量元素地球化学敏感性依次为HCO3-> SO42->Ca2+> NO3-> Mg2+> Na+> K+>Cl-，而受农业活动、工业活动、城镇建设活动等多种因子共同影响下的地下河主量元素地球化学敏感性有所变化，依次为HCO3->Na+> Ca2+> K+> Cl-> Mg2+> NO3-> SO42-，随着人类影响的加剧，离子敏感指数将会有增加的趋势。 

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

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 features by external interference in order to guarantee drinking water safety. Using hydrochemical data for April 2012 to March 2013, the geochemical susceptibility of groundwater in Laolongdong subterranean river and Zhaojiayuanzi epi-karst spring in the river watershed of Nanshan, Chongqing was analyzed, and the principal cations were Ca2+ and Mg2+in the epi-karst spring, and Ca2+ and Na+ in the subterranean river. The principal anions were HCO3- and SO42- 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 HCO3- / SO42- 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 HCO3- and low concentration of SO42-. Owing to agricultural activities, the rank order of geochemical susceptivity for major elements in the epi-karst spring is HCO3-> SO42-> Ca2+> NO3- > Mg2+ > Na+ > K+ > Cl-. When agricultural activities, industrial activities as well as urban construction activities were all taken into account, the rank order of geochemical susceptivity for major elements in the subterranean river became HCO3- > Na+ > Ca2+ > K+ > Cl- > Mg2+ > NO3- > SO42-. With anthropic activities, each ion is becoming increasingly susceptive. Thus, more attention should be paid to karst groundwater pollution.