Distribution And Bioavaiability Of Polycyclic Aromatic Hydrocarbons In Soil Particle-size Separates

Polycyclic aromatic hydrocarbons (PAHs) are a group of organic pollutants with carcinogenic, teratogenic and mutagenic properties, and they are difficult to biodegrade. In this paper, the content, sources and ecological risks of PAHs in topsoil of Quanzhou city were analyzed. Meanwhile,5 field soil samples with relatively high content of PAHs which collected from Xiamen City were choosed for phytoremediation to study the bioavailability of PAHs in soil particle-size separates.The purpose of this study was to provide theoretical data for estimating ecological risks of PAHs and it's bioremediation in soils. The main results are as follow:(1) The total concentrations of 15 kinds of USEPA priority PAHs in Quanzhou different functional areas of the 33 topsoil (0-20 cm) samples ranged from 28.2 to 1432.3μg·kg-1, and 4 to 6 ring PAHs were the dominant compounds. Total concentrations of PAHs in soil samples from different functional zones decreased in the order of industrial areas> residential areas> scenic areas> agricultural fields. PAHs in soils of Quanzhou mainly originated from the combustion of coal, biomass fuels (straw), liquid fossil fuels including gasoline and diesel. The toxic benzo[a]pyrene equivalents (TEQBaP) of the 15 PAHs ranged from 1.57 to 131.6μg·kg-1, with an average value of 38.9μg·kg-1. The total TEQBap of 10 PAHs in 36.4% of the soil samples exceeded the Dutch target reference value, sμggesting that the topsoil in some areas of Quanzhou may have potential ecological risks.(2) The distribution characteristics of 15 kinds of USEPA priority PAHs in different particle-size separates(clay, fine silt, coarse silt, fine and coarse sand)of five field contaminated topsoil samples (0-20 cm) were studied. The results showed that the distribution of PAHs in different soil particle-size separates were very uneven. The average concentrations of total PAHs in particle-size separates to the total PAHs in bulk soils decreased in the order of fine sand> coarse silt> coarse sand> fine silt> clay. The percentages of PAHs in different particle-size separates to the PAHs in bulk soils decreased in the order of fine sand> coarse sand> fine silt> coarse silt> clay.The contribution of 4 rings PAHs to the total PAHs in was highest in all particle-size separates. The enrichment ability of organic matter for PAHs in coarse silt was strongest. (3) A pot experiment was conducted to investigate the bioavailability of PAHs in soils planted with white scrambled eggs tree (Cassia surattensis Burm.F.) in the greenhouse. After 180 d of growth, the plants were havested and the soils were freeze-dried for analysis. The percentage of total PAHs removal was in the range of 28.0%～45.6% for the 5 field contaminated soils. The average degradation rate of PAHs in particle-size separate of coarse sand, fine sand, coarse silt, fine silt and clay was 42.5%,38.0%,21.7%%,54.8% and 59.2%, respectively. The bioavailability of PAHs in coarse silt separates was lower than other separates.