Abstract: Sixteen US EPA priority polycyclic aromatic hydrocarbons (PAHs) in sewage sludge from 5 wastewater treatment plants in Guiyang City, Southwest China, were analyzed using Soxhletextraction and GCMS method. Possible sources were identified using the diagnostic ratios of PAHs and potential risks were assessed based on the toxic equivalent concentration of BaP (TEQ_BaP). The results showed that total PAHs concentrations in the samples were in the range of 1.90-4.27 mg·kg^-1, which was lower than those of the most of well developed countries and areas. PAHs in the sewage sludge were dominated by 2-4 rings PAHs and mainly stemmed from biomass burning and domestic coal combustion, with some characteristics of vehicle emission. The risk assessment showed that the toxicity equivalent concentration of PAHs (TEQ_BaP16) was in the range of 0.09-0.29 mg·kg^-1, in which 97% of the total TEQ_BaP originated from 7 carcinogenic PAHs. The TEQ_BaP10 was 0.07-0.24 mg·kg^-1, indicating higher carcinogenicity and ecological risk.

Key words: dark loessial soil, water use efficiency., tillage pattern, organic carbon, soil aggregate