Effects of Forest Filtering and Cold Trapping on Polycyclic Aromatic Hydrocarbons Distribution in Southeast Tibet

New pollutants in remote regions have become a global issue of concern. This study collected soil, lichen, moss, and air samples from the high mountain area of southeastern Tibet to analyze the altitude pollution distribution of 16 polycyclic aromatic hydrocarbons(PAHs) and the related influencing factors. The results revealed that the average levels of Σ6PAH in soil, moss, lichen, and air samples were 46.8 ng/g dry weight(dw), 140.6 ng/g dw, 712.0 ng/g dw, and 60.1 ng/m 3 , respectively. Naphthalene and phenanthrene were the most abundant individual isomers, and 2–4 rings PAHs accounted for approximately 90% of the total ΣPAH concentration in the samples. Source apportionment analysis highlighted the impact of atmospheric PAH inputs on this region. Octanol/air distribution factor( K oa ), altitude, plant coverage, and soil organic matter were the key determinants of PAH concentration along the altitudinal gradient. Across all the soil sampling sites, the average contribution of the forest filter effect (FFE) was greater than that of the mountain cold trapping effect based on the principal component analysis and multiple linear regression. The findings of this study strengthened the reasons for the preferential accumulation of organic pollutants in the high-altitude mountainous area, and provided important insights for effective environmental strategies of new pollutants.