Abstract: Surface (0〖KG-*2〗-〖KG-*7〗20 cm) and subsurface (20〖KG-*2〗-〖KG-*7〗30 or 30〖KG-*2〗-〖KG-*7〗40 cm) soil samples in Baiyangdian area were collected, and their 16 polycyclic aromatic hydrocarbons (PAHs) contents were determined by GC/MS. The total PAHs contents in surface soils varied from 1460 to 6459 ng·g-1, with an average of 4174 ng·g-1, and those in subsurface soils varied from 430 to 3945 ng·g-1, with an average of 1524 ng·g-1. The PAHs contents in surface soils had less correlation with soil total organic carbon (TOC) content, while those in subsurface soils were in adverse, indicating the increasing binding degree of PAHs to TOC in the processes of soil burial and reconstruction, and the differences in the environmental behaviors of different PAHs. In general, low ring (2〖KG-*2〗-〖KG-*7〗3 rings) PAHs such as Nap and Phe transferred from top soil to bottom soil more easily than high ring (≥4 rings) PAHs. The values of PAHs isomer ratios suggested that biomass and coal combustion were the major sources of PAHs in surface soils of Baiyangdian area, which could be related with the human activities such as straw combustion.

Key words: Ecosystem health, Landscape health assessment, Index system, Fuzzy comprehensive evaluation method, Ejin natural oasis