官厅水库周边蔬菜地表土中多环芳烃的污染

为掌握北京市备用水源地——官厅水库周边的蔬菜地表土中多环芳烃(PAHs)的污染状况及来源,于2008年11月在延庆县小丰营蔬菜产地采集了48个表土样品(0～20cm)测定PAHs含量,并综合特征化合物比值法和因子分析/多元线性回归两种方法推断了土壤中PAHs来源.结果表明,土壤中15种PAHs单体(PAH15)的含量均服从正态分布或对数正态分布,∑15PAH几何均值为(118.71±28.63)ng.g-1(干重含量,下同),算术均值为(139.57±85.65)ng.g-1.以荷兰土壤标准衡量,71%的样点归类PAHs弱污染,与文献报道的大多数国内外农业土壤相比,尚属于较清洁的水平.成分谱分析表明,研究区域土壤中的PAHs分布谱以3环～4环化合物为主,优势化合物为PHE、FLA、FLO、PYR.校正后的FLA/(FLA+PYR),ANT/(ANT+PHE)比值表明该研究区域PAHs主要来自燃烧源.通过因子分析提取了3个主成分,分别代表①燃煤和交通燃油;②生物质燃烧和炼焦;③燃油.多元线性回归分析的结果表明,这3种来源对官厅水库周边蔬菜地表土中PAHs的贡献分别是54.0%,39.9%和6.1%.结合两种源解析方法和排放源分析,除该区域存在明显生物质燃烧源以外,其它来源的PAHs经过了一定距离的大气迁移和沉降.

Polycyclic aromatic hydrocarbons (PAHs) in the surface soils of vegetable plots around the Guanting Reservoir

Guanting Reservoir is a strategic water resource for the city of Beijing. Forty-eight surface soil samples (0~20 cm) around the reservoir were collected from the Xiaofengying vegetable base, Yanqing County, in November 2008 to investigate the sources and contamination status of polycyclic aromatic hydrocarbons (PAHs) in the surface soil. The origins of the PAHs were determined by analyzing the ratio of isomeric PAH species and by factorial analysis/multiple linear regression. The concentrations of 15 PAH compounds (PAH15) in the soil samples showed normal distribution or lognormal distribution. The geometric and arithmetic means were (118.71±28.63) ng·g-1 (dry weight) and (139.57±85.65) ng·g-1, respectively. Based on the Dutch soil quality standard, 71% of the samples were classified into the low-contamination category. These concentrations were lower than many reported in the literature. The PAH compounds were dominated by 3~4 ring compounds, particularly PHE, FLA, FLO and PYR. The corrected isomeric ratio of FLA/(FLA+PYR) and ANT/(ANT+PHE) showed that the PAHs mainly came from combustion sources.Factorial/multiple regression analysis identified three principal sources, representing (1) coal burning/ vehicle exhaust, (2) biomass combustion/coking, and (3) petroleum burning, which account for 54.0%, 39.9% and 6.1% of the PAHs in the soil analysed, respectively. Therefore, apart from the PAHs from biomass burning in the local region, other PAHs were deposited from distant sources via atmospheric transportation.