The Distribution Variation of Polycyclic Aromatic Hydrocarbons Between Fresh Snow and Seasonal Snowpack in Campus in Changchun City, Northeast China

Polycyclic aromatic hydrocarbons (PAHs) are scavenged from the atmosphere during snowfall, stored in the seasonal snowpack, and exchanged with PAHs in atmosphere. Thus, the PAHs in fresh snow and snowpack could reflect the PAH levels in atmosphere. This study investigated the concentrations and compositions of 16 priority- controlled PAHs in fresh snow and seasonal snowpack, as well as PAH levels in underlying soils before and after snow melting. The total concentrations of PAHs in fresh snow and snowpack ranged from 26.6 +/- 4.2 to 36.9 +/- 1.7 mu g L-1 and from 40.3 +/- 4.4 to 105.9 +/- 6.9 mu g L-1, respectively. The higher concentrations of PAHs in fresh snow compared with other areas indicated a high PAH level in atmosphere in Changchun city, presenting a potential risk to human health. Higher concentrations of total PAHs in snowpack than those in fresh snow indicated the prominent deposition of PAHs from atmosphere to snowpack in winter. In contrast, a specific reduction of five-to sixring PAHs in the snowpack suggested that strong photolysis of five-to six-ring PAHs occurred in snowpack. The variation of PAHs in different snowpacks suggested that the deposition may be largely affected by local environment. The results of diagnostic ratios and principal component analysis (PCA) suggested that the PAHs in fresh snow and snowpack are both from a mixed source of coal combustion and from vehicle emissions. However, nonmetric multidimensional scaling (NMDS) divided fresh snow and snowpack into two groups, indicating the different contributions of coal combustion and vehicle emissions to PAHs in fresh snow and snowpack. After snowpack melting, threeto four-ring PAH levels in underlying soils showed no change, indicating that the three-to four-ring PAHs were volatilized to the atmosphere. This study indicated a risk of atmospheric PAHs in Changchun city in winter and in the beginning of spring.