Abstract: A case study was conducted in the Shenfu irrigation area to investigate the effects of long-term PAHs-containing wastewater irrigation on the activities of dehydrogenase, polyphenol oxidase and urease and on the microbial populations in lowland rice soil. The results showed that after a long-term PAHs-containing wastewater irrigation, the PAHs content in test soil ranged from 319.5 to 6 362.8 μg·kg^-1, which surpassed the environmental standard seriously. With the increasing year of freshwater irrigation, soil PAHs content decreased to different degrees, up to the level below environmental standard. Correlation analysis indicated that the quantities of soil microbial and main functional populations were mainly affected by soil physical and chemical properties, and less affected by soil PAHs content. The numbers of soil bacteria had very significantly positive correlations with soil total N, while the test enzyme activities were significantly positively correlated with the contents of soil organic C, total P and PAHs.

Key words: Broadleaved tree species, Seedling, Leaf nutrient contents, Cluster analysis