重庆老龙洞地下河流域氮、磷及微生物污染调查研究

随着城镇化不断发展,我国地下水普遍遭受了不同程度的污染,尤其是西南岩溶区地下水是当地重要的水源,一旦遭受污染将很难恢复.本研究选取NO-3、PO34、NH+4和总细菌(total coliform)、大肠杆菌(total E.coli)、粪大肠杆菌(fecal coliform)作为指标,对重庆南山老龙洞流域进行多年来的调查研究.结果表明,老龙洞流域地下水NO-3、NH+4、PO3-4含量均超过天然水规定值,尤其以NH+4、PO3-4污染较为严重.桂花湾泉NO-3含量为19.78~68.55 mg·L-1,有的月份超过了世界卫生组织规定的标准50 mg·L-1.老龙洞出口NH+4、PO3-4含量分别为2.71~12.92 mg·L-1、0.16~11.22 mg·L-1,是污染最重的地下水.老龙洞地下河NO-3含量低于岩溶表层泉,而NH+4、PO3-4含量则高于表层岩溶泉.城镇化的发展、农田减少以及洞内还原环境是导致老龙洞地下河NO-3含量从2008~2013年降低的原因,而高PO3-4含量污水不断输入地下河使得老龙洞地下河PO3-4含量呈增加趋势.微生物污染极为严重,甚至远超过中国地下水和饮用水规定的Ⅴ类标准,以粪大肠菌为例,地下水中其含量波动范围为3.4×104~3.68×104CFU·mL-1.岩溶区由于特殊的水文地质结构,岩溶洼地、天窗、落水洞导致岩溶地下水极易遭受到污染.农业活动、城镇、企业和居民点生产生活排污,是地下水氮、磷和微生物污染的主要来源.

Investigation of Nitrogen, Phosphorus and Microbial Contamination in Laolongdong Underground River System of Chongqing

With urbanization, groundwater in China has been widely polluted. Karst groundwater is important in southwest China, and would be difficult to recover once contaminated. NO₃^-, PO₄³, NH₄⁺, total coliform, total E. coli and fecal coliform were chosen as indexes in the study of groundwater of Laolongdong Underground River System in Nanshan Mountain, Chongqing. After a few years of survey, the results showed that NO₃^-, NH₄⁺ and PO₄^3- concentrations in the water were all above the nature value, especially NH₄⁺ and PO₄^3-. The NO₃^- concentration of Guihuawan spring ranged from 19.78-68.55 mg·L^-1, in some months, above the recommended water quality guideline (50 mg·L^-1) according to Standards for Drinking Water Quality set by World Health Organization. NH₄⁺ and PO₄^3- concentrations in Laolongdong underground river varied from 2.71-12.92 mg·L^-1 and 0.16-11.22 mg·L^-1. The NO₃^- concentration in Laolongdong underground river was lower than in karst spring; however, the concentrations of NH₄⁺ and PO₄^3- were higher than in the spring. It seemed that the NO₃^- concentration tended to decrease from 2008 to 2013 in the underground river caused by urbanization, reduction of farmland and reducing environment. However, waste water with a high PO₄^3- concentration led to an increasing trend in the PO₄^3- concentration in underground river. Microbial contamination was extremely serious, and even far exceeded class V of water quality standards of China. For example, the concentration of fecal coliform in the groundwater ranged from 3.4×10⁴-3.68×10⁴ CFU·mL^-1. Because of the special hydrogeological structure, karst depressions, skylights and sinkholes can lead pollutants easily to the underground water. Agriculture activity, sewage from towns, enterprises and residential areas were the major sources of nitrogen, phosphorus and microbial contamination.