Polycyclic aromatic hydrocarbons in fresh snow in the city of Harbin in northeast China

Characterizing levels of polycyclic aromatic hydrocarbons (PAHs) in snow and their toxicity is important for understanding snow scavenging of PAHs and associated human health and environmental risks in cold regions. A total of 48 fresh snow samples were collected from six precipitation events during the winter of 2014–2015 at eight (5 urban, 2 suburban and 1 rural) sites across the heavily industrialized and agricultural city of Harbin in northeast China, and were analyzed for the USEPA priority 16 PAHs. Concentrations of the sum of the 16 PAHs from individual snow samples ranged from 0.3 to 2549.6 μg L⁻¹ or nearly four orders of magnitude. The arithmetic mean concentration (±standard deviation) of the 48 samples was 218.1 ± 623.7 μg L⁻¹, and the median value was 10.7 μg L⁻¹. The most abundant PAHs averaged from all the samples were Pyrene (17.1%), followed by Phenanthrene (14.9%), Naphthalene (14.4%), and Fluoranthene (10.2%). The important carcinogenic ∑₇PAH_s accounted for 58.4% of the total PAHs at locations directly impacted by road traffic. Source apportionment analysis using diagnostic ratios coupled with principal component analysis (PCA) indicated that coal and biomass combustion and vehicle exhausts are the major sources of PAHs in winter. Concentrations of PAHs in snow were significantly correlated with measured levels of PAHs in airborne particulate matter (PM_2.5 (R = 0.857, p < 0.05); PM₁₀ (R = 0.831, p < 0.05)), as well as with ambient temperature (R = −0.851, p < 0.05). Almost all (99%) of PAHs measured in the snow were present in particulate phase. The practice of clearing snow by removing it from urban areas and disposing it in suburban and rural areas may create a new pathway of exposure, which needs to be assessed further.