北京市平原区地下水有机污染时空分布特征

Temporal and spatial distribution characteristics of organic contamination in groundwater in the Beijing plain

2007～2008年进行的北京市平原区地下水污染调查,发现该地区地下水有机污染具有检出种类多、检出率高、浓度低的特点.主要的有机污染物为三氯甲烷、四氯化碳、1,2-二氯丙烷、1,2-二氯乙烷、三氯乙烯、四氯乙烯、甲苯和苯并[a]芘.对这8种主要有机污染物的时间和空间分布特征进行了研究.研究显示,平面上,有机污染物分布广泛,主要为点状分布,局部地区集中检出.垂向上,随深度增加地下水有机污染减轻（1,2-二氯乙烷除外）.与枯水期相比,丰水期有机物检出率和浓度更高（三氯甲烷除外）,四氯化碳、三氯乙烯、四氯乙烯受枯、丰水期变化影响最小,检出重现性好,污染较严重.与2001年相比,2008年四氯化碳检出率降低,对地下水的污染有所减轻,而三氯甲烷、三氯乙烯、四氯乙烯的检出率变化较小.最后,从污染源、有机物理化特性、水文地质条件等方面对有机污染时空分布特征的成因进行了阐述.

Investigation of groundwater contamination was carried out in the Beijing plain from 2007 to 2008. The results show that the characteristics of organic contamination in groundwater in this area are ＇ diversity of detections＇, ＇high detection rate＇ and ＇low concentration＇ The majority of the organic contaminants are chloroform （ CF ）, carbon tetrachloride （ CT ）, 1,2-dichloropropane （ 1,2-DCA ）, 1,2-dichloroethane （ 1,2- DCP）, trichloroethylene（TCE）, perchloroethylene（PCE）, toluene and benzo （a）pyrene. This study mainly focuses on analyzing the temporal and spatial distribution characteristics of the above-mentioned compounds. In a plan view, the organic contaminants are spread widely in space. They mainly spread in punctate distribution and are concentrated in particular areas. Vertically, the trend of groundwater contamination is lighten（except 1,2-DCP） with increasing depth,. Compared with dry season, concentration and detection rate of organic contamination are higher in rain season （ except chloroform）. The characteristics of CT, TCE and PCE are least affected by different seasons. They have high reappear rate and the pollution is more serious. The detection rate of CT gets lower and the pollution is reduced in the groundwater in 2008, compared with those in the year of 2001. However, the changes in detection rates of CF, TCE and PCE are small. It demonstrates the effect of the temporal and spatial distribution by some factors, including contaminate sources, physical and chemical properties of organic contaminants and hydrogeological conditions.