Recent distribution and sources of polycyclic aromatic hydrocarbons in surface soils from Yangtze river delta

Abstract

采集长江三角洲区域11个地市范围内的243个样点的表层土壤样品,针对29种多环芳烃（polycyclic aromatic hydrocarbons,PAHs）浓度的空间分布模式、组分谱特征以及初步排放源进行分析.结果表明,研究区域内总PAHs浓度范围在21.03 578.5 ng·g-1,算术均值310.6 ng·g-1,标准偏差459.1 ng·g-1.区域PAHs浓度表现出较大的空间分布差异.此外,表土PAHs浓度与表土总有机碳分数TOC呈现正相关.研究涉及的11个地市中,表土PAHs浓度的高值主要集中在苏州辖区,可达759.0 ng·g-1±1 132.9 ng·g-1;而无锡(565.3 ng·g-1±705.5 ng·g-1)、上海(349.4 ng·g-1±220.1 ng·g-1)两市表土的PAHs平均含量仅次于苏州.全区域表土中PAHs组分以24环的中、低环组分为主,其中低环比例最高.利用特征比值与主成分分析,可初步判断长江三角洲地区表土中PAHs的近期主要排放源为混合源,即工业燃煤和生物质的燃烧过程同时,局部区域还涉及交通尾气排放. A total of 243 surface soil samples collected from 11 cities in the Yangtze River Delta region were analyzed for the concentrations, spatial distribution, component profiles and emission sources of 29 PAH species. The analytical results indicated the total concentrations of PAHs in Yangtze River Delta fell in the range from 21.0 ng·g-1 to 3578.5 ng·g-1 with an arithmetic mean and standard deviation of 310.6 ng·g-1 and 459.1 ng·g-1, respectively. Our data showed spatial distribution of PAHs concentrations varied greatly in the region. In addition, the contents of PAHs were positively correlated with the total organic carbon fractions in topsoil. The sites with the highest levels of PAHs in the 11 cities studied were located in Suzhou with 759.0 ng·g-1±1132.9 ng·g-1, followed by the areas of Wuxi and Shanghai, with the total PAHs concentrations of 565.3 ng·g-1±705.5 ng·g-1 and 349.4 ng·g-1±220.1 ng·g-1 respectively. The profiles of different components pointed to a predominant role of the species with 2-4 rings, and especially for the low molecular weight components with 2-3 rings. A preliminary identification on emission sources of local PAHs was performed by the specific ratios of isomeric species and principal component analysis (PCA). The results designated industrial coal and biomass combustion as the main mixed emission sources of PAHs in surface soils from Yangtze River Delta, and tail gas from transport as another major source in some areas.