关键词: 质量损失率, 高山林线交错带, 凋落物分解, 土壤动物贡献率

Abstract: Here we monitored levels of 8 metals (Cu, Ni, Zn, Cr, As, Cd, Hg and Pb) in 128 soil samples collected from Dongdagou and Xidagou vegetable farms of Baiyin, Gansu, China, and used the anthropogenic influence multiple, principal component analysis, geological accumulation index and potential ecological risk assessment method to evaluate the pollution characteristics and potential risks. The results showed that the soil Cu, Zn, As, Cd, Hg and Pb contents exceeded the background values of Gansu, and the soil Zn, As and Cd contents at Dongdagou and the soil As and Cd contents at Xidagou were higher than the level II of the China’s national soil standards. There were high variations in soil Cd and Hg contents at Dongdagou and in soil Hg and As contents at Xidagou, which were likely impacted by the anthropogenic pollution. Principal component analysis showed that soil Cu, Cd and Pb contents at Dongdagou and soil Zn and Cd contents at Xidagou were controlled by many factors. Geoaccumulation index showed that the soil Cd, As, Hg and Zn contents at vegetable farms of Baiyin were classified as moderate to heavy pollution, the soil Cd content of some samples at Dongdagou even as very heavy pollution, and soil Ni and Cr contents as “no pollution”. The potential ecological risk analysis showed that the single potential ecological risk parameters (E_i) and comprehensive potential ecological risk index (RI) all followed a pattern of Dongdagou>Xidagou, and the single potential ecological risks of Cd, Hg and As were relatively high. Overall, the pollution of heavy metals at Dongdagou was more severe than at Xidagou, and the pollution degree and ecological risk had fallen over the years.

Key words: alpine timberline ecotone, mass loss rate, litter decomposition, contributions of soil fauna