岩溶区地下水微生物污染特征及来源——以重庆南山老龙洞流域为例

Characteristics and source of microbial contamination of groundwater in Laolongdong basin

文章选取老龙洞地下河流域10个地下水点采集样品,分析水样中的水化学指标和三种重要微生物指标,以了解城市化进程对老龙洞地下河流域水质的影响,探究该地区微生物污染的主要来源。结合岩溶区独特的水文地质条件,利用粪大肠杆菌（FC）与粪链球菌（FS）比值法,初步分析得到该地区微生物污染程度和污染来源。研究结果表明：（1）老龙洞流域地下水存在严重的微生物污染,地下水总细菌数、大肠菌群远超过国家地下水标准规定,分别是国家地下水标准规定的2.3×10^2~5.5×10^4倍、0.8×10^4~0.9×10^6倍,粪大肠菌群数量为100~4.38×10^6 CFU·L^-1;（2）4#、6#采样点微生物污染主要来源于温血动物,1#、7#、8#采样点地下水受城市化进程的影响大;（3）微生物污染主要来源于人类粪便,同时SO2-4、PO3-4、NO-3含量高且与微生物污染相关性密切,说明生活污水引起的次生微生物污染较严重,2#、3#、5#、10#采样点受生活污水和禽畜粪便影响较小,属于单纯的NO-3农业污染型地下水,微生物污染较轻。

Laolongdong basin in Chongqing is a typical karst valley.The groundwater quality is closely linked to above-ground human activity.The study area has a high population density,with the rapid urbanization in the past few years.Sewage from many residents and factories flows through sinkholes into the underground aquifer.Meanwhile,the wastewater treatment and collection system has not been sufficiently developed,causing contamination of the underground river.This study indicates that livestock waste and urban sewage have resulted in high levels of microbial contamination.With social and economic development the groundwater contamination in Laolongdong basin was serious.Hydrogeological changes were monitored at 10 groundwater sampling points,and sewage samples were collected to evaluate their impact on Laolongdong groundwater and track the main sources of groundwater contamination.Taking into consideration the special hydrogeological background of the karst area,membrane filtration was employed and samples were analyzed for chemical composition and three kinds of bacteria used as indicators of the degree of fecal contamination in polluted groundwater.FC/FS was adapted to determine the source of microbial contamination.The results showed that,（1）The microbial contamination was not localized,the total bacteria count（2.3×10^2 to 5.5×10^4）and total coliform（0.8×10^4 to 0.9×10^6）exceeded the National Standard.The number of fecal coliform was 100 to 4.38×10^6 CFU·L-1.（2）The FC/FS ratio indicates that warm-blooded animals were the source of the microbes in samples 4#and 6#.Samples 1#,7#and 8# were affected by urbanization.（3）There was high SO2-4,PO3-4,NO-3content.There was also close correlation among fecal indicator bacteria and SO2-4,PO3-4,NO-3.This indicates that urban sewage led to the serious microbial contamination and the main contamination source was human feces.Samples 2#,3#,5# and 10# were agriculture contamination points,therefore,the pollution was less serious（with NO-3）.