华北平原地下水有机污染特征初步分析

Preliminary analysis on the organic contamination of groundwater in the North China Plain

各种污染造成地下水中有害物质逐年增加,地下水水质逐渐下降,严重危及了饮用水安全。针对此情况,按照相关的要求,采集了245组水样。样品由有资质的测试单位测定。依据对地下水质调查的初步分析,华北平原地下水中已有机物检出。对所有水样测试结果的统计显示:检出的有机污染物共有32种。检出率大于4.5%的有氯仿、甲苯、四氯乙烯、苯并[a]芘、氯苯、苯和1,2-二氯苯,其中个别水样中的四氯化碳、苯并[a]芘和挥发性酚类三项超过了饮用水标准(据地下水质量标准报批稿,中国地质调查局,2007),超标率分别为1.22%、2.45%和1.90%。个别在深层地下水样品中也检出了微量有机污染物,这可能与取样井的混合开采、止水不佳有关。从区域上来看,在人类活动相对强烈的城镇地区地下水中,有机物检出率相对较高,特别是在渗透性好的山前地带,污染物较易进入到地下水中。通过分析发现,地下水有机物的高检出率与地下水硬度的升高有一定相关性。由于地下水有机污染在时间和空间上差异一般较大,建议对已发现的异常点进行重复取样测试,积累水质数据,以利于将来的综合分析。

The groundwater quality is highly influenced by input of contaminants from various sources.In order to acquire the cur-rent status of groundwater quality in the North China Palin（NPC）,245 water samples were collected according to the relating reqirements and standards.The samples were analysed by qualified laboratories.The investigation results showed that there were 32 organic contaminants detected in groundwater in the NPC.Among these compounds,the detection frequencies（ratio of number of samples with organic compound（s） detected to the total number of samples） of chloroform,toluene,tetrachloroethylene,benzo[a]pyrene xylene,chlorobenzene,benzene,and 1,2-dichlorobenzene are higher than 4.5%.According to the standards of groundwater quality（China Geological Survey,2007）,the concentrations of carbon tetrachloride,benzo[a]pyrene,and volatile phe-nols some water samples（2.5% of the total） were higher that that for class III,which corresponds to the drinking water standards.It should be noted that there were organic contaminants detected in some deep groundwater samples.This suggests that further moni-toring work should be carried out for these sites.Normally,the higher detection frequency of organic contaminants corresponds to reagion with intensive human activities,especially in the pediment reagion,due to its high permeability of the geological media.The results preliminarily indicated that there is a correlationship between the organic contaminantion and the increase of the water hard-ness.Due to the high temporal and spatial heterogeneity of groundwater organic contamination,it is suggested that further monitor-ing work should be carried out for these sites where organic contaminants were detected.