| In the present study, 131 soil samples were collected from the agricultural topsoil in different land use type within 128 square kilometers surrounding Guiyu twon, and the concentrations of 41 polybrominated diphenyl ether(PBDEs)and 10 Methoxylated Polybrominateddiphenyl ethers(Me O-PBDEs) congeners of each sample were determined. Characterizing the PBDEs and its metabolites in different landuse types,analyzing the sources of contaminants, generating the map of spatial distribution of PBDEs and providingthe high concentration sampling points in administrative map and estimating PBDEs reserves of the region, these above researches were completed,as well as according to the " Technical guidelines for risk assessment of contaminated sites "(HJ25.3-2014), the exposure risk assessments of BDE47, BDE99, BDE153 and BDE209 which are the priority control pollutants by USA Environmental Protection Agency(EPA) were evaluated. The research of absorption, accumulation, degradation and metabolism characteristics of BDE209 in plant rhizosphere soils under middle and low level of BDE209-Cd-Hg compound pollutants were carried out further,trough a 4-kind water spinaches pot experiments. The food exposure assessment was carried out with the reference of the recommended limits of the Food and Sanitation Department of Hong kong. The main conclusions were as follow:(1) The results showed the concentrations of 41 PBDEs congeners varied from30 to 9400 ng?g-1, and the concentrations of deca-polybrominated diphenyl ether(BDE209) changed from no detection to 9200 ng?g-1. The highest detection frequency was found in BDE196 reached 100% among all the 41 congeners. There were 18 PBDEs congeners whose detection frequency reached more than 90%, and the high PBDEs concentrations appeared in Tongmeng town, Gurao town, Chendian town and Guiyu town.(2)The concentrations of BDE209 and the other 40 polybrominated diphenyl ethers congeners(∑40PBDEs) in different land use types of agricultural topsoil showed opposite trends, that is, the concentrations of ∑40PBDEs showed as in paddy rice soil > orchard soil > other paddy soil > vegetable soil >wood field soil > wastefield soil; but the concentrations of BDE209 in soils presented a trend of: waste field soil > vegetable soil > other paddy soil > paddy rice soil > orchard > forest.(3) The results of exposure risk assessment of PBDEs in agricultural topsoil showed the order of contribution was: the skin contact >oral intake > inhalation with soil particles. The 4 PBDEs congeners in the area which were generally considered to be toxic did not exceed the standard of EPA. Except for the exposure of BDE209 in 6sampling points with low risk of cancer, the risk of PBDEs exposure to the agricultural population in the other sampling points were negligible or acceptable risk.(4) Under low level of contamination(≤0.75 mg·kg-1), the concentrations of Hg in leaves of all the 4-kind water spinaches were over the National Food Hygiene Standards. On the other hand, under low level of contamination(≤0.25 mg·kg-1), the concentrations of Cd in leaves of the No.3 and 4 water spinaches were not exceeding the standard. However, under the middle level of contamination of Cd( ≤ 0. 5mg·kg-1), the concentrations of Cd in leaves of the all 4-kind water spinaches were over the National Standards.(5) In the plant rhizosphere soil system, the main catabolites of BDE209 were nona-BDE, and presented a trind like ortho->meta- >para- nona-BDE. In addition,beside the catabolites, there were also metabolites of PBDEs existed, i.e. methyl metabolites of PBDEs(Me O-PBDEs). The concentrations of PBDEs in the edible parts of the 4 kinds of water spinaches were lower than limited standards recommended by Hong kong Food and Environment Hygiene Department. |
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