兰州市西固区土壤中PAHs污染特征及来源解析

Levels,Source Identification and Contamination Characteristics of PAHs in Soils from Xigu District in Lanzhou,Northwestern China

为了解石油工业区土壤中PAHs（多环芳烃）的污染特征、来源及潜在危害,选择兰州市西固区为研究区域,系统采集表层土壤样品及部分剖面样品,采用GC-MS检测方法,分析了土壤中PAHs的污染水平与分布、来源及潜在致癌风险.结果表明：研究区表层（0-20 cm）土壤中w（∑PAHs）（22种PAHs的总质量分数）在535-32 300μgkg之间;PAHs在土壤剖面的纵向分布上主要集中在5-10 cm,在0-25 cm范围内变化不明显;表层土壤中PAHs主要以2-3环为主.相关性分析显示,土壤中w（∑PAHs）与w（TOC）无显著的相关性,表明TOC并非影响土壤中PAHs持留的重要因素.研究区土壤中PAHs主要来源于石油、生物质和煤炭的燃烧,∑TEQBaP（22种PAHs的毒性当量浓度,以苯并[a]芘等效浓度计）平均值为190μgkg,表明土壤中PAHs的潜在致癌性较低.

PAHs are environmental carcinogens or mutagens. However,information on PAHs contamination in soil from typical petroleum industrial zones of Lanzhou urban areas is not available. In the present study,soil samples were collected from typical petroleum industrial zones in Xigu district in Lanzhou. The contamination levels,spatial distribution,isomeric composition,possible sources and potential carcinogenic risk of PAHs were systematically investigated. The results showed that the total concentrations of 22 PAHs（ ∑PAHs） in topsoil ranged from 535 to 32,300 μgkg in typical petroleum industrial zone. The vertical distribution of the total concentrations in soil had a salient diffusion and transfer. Higher levels of PAHs were found in the soil sites near the petroleum and power plants. The composition of PAHs was characterized by low molecular weight PAHs. Correlation analysis showed that the contents of PAHs were poorly correlated with soil total organic carbon in soil in typical petroleum industrial zone. Principal component analysis and molecular marker ratios of PAHs indicated that PAHs in soil from the study areas mainly originated from combustion sources. Risk assessment suggested that exposure to PAHs needs additional attention given present carcinogenic levels in typical petroleum industrial zones in northwestern China.