PAHS IN AIR ADJACENT TO 2 INLAND WATER BODIES

Air PAH concentration data have been obtained adjacent to two U.K. wat er bodies, as part of a study to quantify atmospheric deposition input s. The sites are 'semiurban' (Castleshaw) and 'rural' (Esthwaite Water , EW), based on PAH air concentrations, compound ratios, and character istics of the ambient aerosol derived from sorption data analysis. Bot h 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 s ources dominate in winter. Particle size data indicate that aging of c ombustion aerosol occurs by both coagulation and elution of the more v olatile compounds to bac kg round aerosol of greater mass median diame ter (MMD). Precipitation strongly influenced air concentrations and ph ase distributions; particulate scavenging of PAH is more rapid than va por-phase removal. Consistent with this, statistical analysis indicate d that winter air concentrations were more heavily influenced by preci pitation rates than temperature; in summer, the reverse was true. Ther e is evidence of a significant source of low molecular weight PAH in t he vapor phase in summer months. This is thought to be due to volatili zation of PAHs that have previously been deposited from soils and vege tation surfaces.