Characteristic contaminants in snowpack and snowmelt surface runoff from different functional areas in Beijing, China

Characteristics of physicochemical parameters, dissolved-phase heavy metals, and polycyclic aromatic hydrocarbons (PAHs) were investigated for 68 urban snowmelt surface runoff and snowpack samples collected from five different functional areas in Beijing, including a business area (BA), a cultural and educational area (CEA), a garden area (GA), a residential area (RA), and a roadside area (RSA). Both snowmelt surface runoff and snowpack were significantly polluted by organic matter, as indicated by their high concentrations of chemical oxygen demand (COD) and total organic carbon (TOC). Among the 11 heavy metals analyzed, Zn was the most enriched in all samples, followed by Mn, Fe, and Cu, whereas the concentrations of Pb, Cr, Cd, As, Ni, Sb, and Co were comparatively low. The results suggested that typical traffic emissions, natural events, industrial practices, and human activities were mainly sources of heavy metals. Low molecular-weight (LMW) PAHs were the dominant sources in snowmelt and snowpack. Anthracene (Ant) and fluorene (Flo) were the most enriched PAHs in both snowmelt surface runoff and snowpack. Coal burning for heating and traffic activities were the most important contributors of PAH pollutants in snowmelt surface runoff and snowpack in Beijing in the winter. Ecological risk assessment demonstrated, however, that heavy metals in snowmelt surface runoff pose little risk to downstream aquatic environments. A middle potential ecological risk could be caused by Ant, Flo, benzo[g, h, i]perylene (BghiP), and benzo[a]pyrene (BaA).