PAHs in Air Adjacent to Two Inland Water Bodies

摘要

Air PAH concentration data have been obtained adjacent to two U.K. water bodies, as part of a study to quantify atmospheric deposition inputs. The sites are 'semiurban' (Castleshaw) and 'rural' (Esthwaite Water, EW), based on PAH air concentrations, compound ratios, and characteristics of the ambient aerosol derived from sorption data analysis. Both sites experienced increased atmospheric loadings of total suspended particulate and PAH in winter. Particle size distributions indicated a seasonal shift in the age of the air mass, suggesting fresher aerosol and increased emissions in winter. Vehicle emissions probably make a greater contribution in non-winter periods, while heating production sources dominate in winter. Particle size data indicate that aging of combustion aerosol occurs by both coagulation and elution of the more volatile compounds to background aerosol of greater mass median diameter (MMD). Precipitation strongly influenced air concentrations'' and phase distributions; particulate scavenging of PAH is more rapid than vapor-phase removal. Consistent with this, statistical analysis indicated that winter air concentrations were more heavily influenced by precipitation rates than temperature; in summer, the reverse was true. There is evidence of a significant source of low molecular weight PAH in the vapor phase in summer months. This is thought to be due to volatilization of PAHs that have previously been deposited from soils and vegetation surfaces.