Abstract: Soil quality of the Sanjiangyuan has an important impact on ecological environment in Tibetan Plateau. With global climate change and intensified human activities, Hg pollution has gradually become a problem in the Sanjiangyuan, due to domestic waste emissions, animal faeces, coal combustion, and transport. The spatial distribution and influencing factors of soil Hg in alpine meadows and grasslands of the Sanjiangyuan were investigated by measuring Hg content, in combination with spatial interpolation and correlation analyses. The results showed that soil Hg contents of the two vegetation types in the Sanjiangyuan were significantly different and decreased with the increase of soil depth. Higher Hg contents were found in the southwestern (0.056±0.013 mg·kg^-1) and southeastern (0.045±0.007 mg·kg^-1) parts of the Sanjiangyuan, while lower Hg contents in the northern (0.007±0.003 mg·kg^-1) and northwestern (0.016±0.001 mg·kg^-1) regions. Pollution and potential ecological risk indices were generally higher in alpine meadows than in alpine grasslands. In most regions, Hg content was relatively low and was mainly concentrated in the surface layer. Mean annual rainfall, altitude, soil organic carbon, soil total nitrogen, soil microbial biomass carbon and nitrogen were the important factors affecting soil Hg contents in both vegetation types. In summary, the southwestern region, represented by Yushu, is an area of high potential ecological risk, and alpine meadows have a stronger enrichment capacity for Hg and higher potential ecological risk. This study is of great significance for the management of Hg and ecological environmental protection in high-altitude grasslands.

Key words: alpine meadow, alpine grassland, soil organic carbon, soil mercury, spatial distribution