Abstract:

Statistics was performed of the data published in the literature during the years of 2004-2007, of the survey of the 16 kinds of PAHs, specified by the US  EPA for priority control, in the surface soil (0-30 cm) of China. The survey encompassed a total of 41 research projects and 2 353 sampling sites, covering 34 cities (or prefectures). According to the geographic locations, the research area was divided into five regions: the northeast region, JingJin and its surrounding region, Yangtse Delta region, Zhujiang Delta region and Midsouthwest region. On the countrywide scale, the amount of total PAHs in the surface soil varied in the range from ND (not detected) to 27 580.9 μg·kg^-1, with mean value being 1 462.55 μg·kg^-1. The contents of 7 carcinogenic PAHs varied in the range from ND to 3 657.67 μg·kg^-1  with mean value being 636.44 μg·kg^-1, which accounted for 44% of the total of the 16 PAHs. On the country wide scale, the proportions of 2-3ringed PAHs, 4ringed PAHs and ≥5 ringed PAHs to the total of PAHs were more or less the same. But the regions varied sharply in content of PAHs. The PAHs in the surface soil of the northeast region, and the JingJin and its surrounding region, both of which are located in North China, and the Yangtse Delta region, which lies in the transition from South to North China, were dominated with 4 ringed and ≥5 ringed PAHs, of which most representative individuals were carcinogenic, while those in the Zhujiang Delta region and the Mid southwest region, which are located in South China, were with 2-3ringed PAHs, of which few representative individuals were carcinogenic. Analysis using the character istic compounds ratio method [Ant/178, Baa/228, Ilp/(Ilp+Bpe) and Fla/(Fla+Pyr)] shows that the PAHs in the surface soil of China come mainly from combustion of grasses, woods and coal, and also from vehicle exhaust and petrol industry, accounting for a comparable proportion. The Ilp/(Ilp+Bpe) and Fla/(Fla+Pyr) ratio analysis reveals that in the JingJin region, the PAHs in the surface soil came mostly from combustion of grasses, woods and coal, while in the Yangtse Delta and the Zhujiang Delta regions they did by a large proportion from vehicle exhaust. In terms of total PAHs in soil, 23% of the soil in the country was not contaminated, 31% little contaminated, 8% contaminated and 38% heavily contaminated. However, the evaluation based on Bap indices indicates that about 20% of the soils in the country was contaminated. Whatever, the two assessments both demonstrate that the proportion of PAHs contaminated soils was obviously higher in North China than in South China.

Key words: PAHs, surface soil, region, ratio of characteristic-compound, source