Abstract: In this study, we determined the contents of 8 soil heavy metals (As, Cd, Cr, Cu, Hg, Ni, Pb and Zn) in surface soils. These soil samples were collected from five different functional areas of Baiyin City, i.e., living area, industrial district, traffic area, park green space and mountain area. We evaluated the level of heavy metal pollution and human health risk by the single pollution index, composite pollution index  and health risk assessment model. The results showed that soil Cu, Cd, Hg, Pb and Zn levels of all functional areas in Baiyin City exceeded the background values of Gansu.  Composite pollution index showed that the pollution levels of the different functional areas decreased in the order of industrial district > traffic area > park green space > living area > mountain area. In addition, soil Hg, Zn, Pb and Cd pollution in all functional areas except mountain area were more serious than other heavy metals, and Hg pollution was the most serious. Health risk assessment model showed that HI and TCR values of heavy metals to children were higher than those to adults. Besides, HI and TCR of different functional areas followed a pattern of industrial district, living area > traffic area > park green space > mountain area. Among the heavy metals, As, Cr and Pb were the three most important factors contributing to HI in all functional areas, and As and Cr were the two most important factors contributing to TCR in all functional areas.

Key words: drought stress, Xanthoceras sorbifolia, protective enzyme., rewatering, gas exchange, chlorophyll fluorescence