| Reclaimed water irrigation is an important aspect of reclaimed water reuse in china and abroad. But its safety has been concerned widely by scholars. Polycyclic aromatic hydrocarbons (PAHs) which are kind of persistent organic pollutants has been proven to widely existed in the sewage and soil of sewage irrigation areas. Does a long-term reclaimed water irrigation cause groundwater contamination? To answer this question, in this study, soil profiles of three typical irrigation areas which are located in southeastern suburb of Beijing were studied. The three typical irrigation areas were irrigated with sewage, reclaimed water, and groundwater respectively. 16 USEPA priority PAHs in soil samples were analyzed by using ultrasonic extraction and gas chromatography/mass. The physical and chemical properties of soil samples and the water quality of irrigation water and groundwater were also analyzed. Vertical distribution of PAHs in soil profile and the effect of irrigation water on soil quality were discussed.The results showed that: PAHs were detected throughout the sampling depth, topsoil was the major accumulation stratum, and the total amounts of PAHs of topsoil in sewage irrigation area, reclaimed water irrigation area and groundwater irrigation area were 726μg/kg, 200μg/kg and 34μg/kg respectively. In stratums blow topsoil, the mean total amounts of PAHs were 290μg/kg, 16.3μg/kg and 8.7μg/kg respectively. All kinds of PAHs were detected in topsoil of three irrigation areas, but the amounts showed significant differences, the sequence of the amount is sewage irrigation area > reclaimed water irrigation area > groundwater irrigation area approximately. The low-ring (2-3 rings) PAHs showed a absolute distribution dominance in stratums blow topsoil, they are the typical pollutants in soil profiles, among which naphthalene and phenanthrene are the main pollutants. The high-ring (4-5 rings) PAHs were only detected in topsoil basically. PAHs composition of topsoil manifested as mixed pollution of heat source and oil source, irrigation water were the main sources.The physical and chemical properties of PAHs have an important impact on their migration capability. Through related analysis and regression analysis between the content of typical PAHs and soil physical and chemical factors, the total organic carbon content of soil (TOC) was the main influencing factor for the vertical migration of PAHs.PAHs detected in irrigation water and groundwater and the typical PAHs of soil profiles were basically the same, naphthalene and phenanthrene were main pollutants, the total amount of PAHs of irrigation water in sewage irrigation area (average = 163.5 ng/L) is the highest, next came irrigation water in reclaimed water irrigation area(average = 81.5 ng/L), the content range of groundwater was 20.8～72.4 ng/L. the total amount of PAHs did not exceed the limit for the National Hygienic Standard for Drinking Water (GB5749-2006).
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