Distribution Characteristics And Risk Assessment Of Persistent Organic Pollutants In Different Land Use Types

Persistent Organic Pollutants(POPs) are a group of organic compounds, which are toxic, persistent, easy to gather in the living body and carry out long-range transport and deposition。It can cause damage to environment or human beings near or far from POPs’sources. Therefor, it is necessary to carry out POPs’study on acts in the environment.This paper studies the distribution of POPs in soil profiles from Dounan distric. Considering the different land-use types, soil samples were collected from four kinds of land-use types, including greenhouse, open vegetable field, fallow land and residengtial area. The soil samples from greenhouse were also devided into four parts by different planting years. The occurance, source and ecological risk of POPs were analyzed in this paper. Statistical methods were used to study the distribution and contamination of these pollutants in the soils, and the relationship between pollutant residues and environmental factors were also analyzed. Ultrasonic extraction method was used for extracting OCPs and PAHs from soil samples and meaured by GC-MS.OCPs content in soil samples from Dounan district was raning from 32.38-134.42ng/g (dry weight), the average content was 72.79ng/g. DDTs content was raning from 16.29-52.99ng/g, the average content was 27.33ng/g. HCHs content was raning from 13.16-85.15ng/g, the average content of 45.46ng/g. OCPs content in soils of different types from low to high were greenhouse, residential area, fallow land and open vegetable fields. DDTs and HCHs were analyzed on the ratios of isomers, it showed that new HCHs may entered to the soils which maybe affected by the industrial HCH, while DDTs mainly from the pesticide residues. In the soil profiles, the content of DDTs didn’t change with the depth, HCHs has the highest content in the surface and decreased with increasing depth. The distribution of OCPs in the soil profiles has a significant relationship with the TOC content and the percentage of clay. The ecological risks of DDTs and HCHs were assessment, the results showed a low potential ecological risks with HCHs, but DDTs has a certain ecological risk.The content of PAHs in soil samples were ranged in 566.16-2518.25ng/g, with an average of 1641.53ng/g.16 priority PAHs were all detected, PAHs with 3-ring and 4-ring were dominated in the soil samples. Analyzed the content of PAHs in soil samples from different land-use type, the results showed that the residengtial area had the highest concentration. Distribution of PAHs in the soil profiles was influenced by TOC, particle size, human disturbance and other factors. Diagnostic ratio and the principal component analysis were used to determine the origin of PAHs, showing that the PAHs in soils were mainly derived from combustion sources, especially motor vehicle exhaust and emissions from coal-fired. Some resultes indicated the presence of petrogenic. The BaPeq concentration ranged in 92.25～155.22ng/g, compared with the relevant standards and similar studies, the potential risks of Dounan district was low.