Measurements of atomospheric deposition of polycyclic aromatic hydrocarbons on the Stony Brook Watershed in Westford, Massachusetts

Dry and wet deposition of polycyclic aromatic hydrocarbons (PAHs) was measured at Westford, Massachusetts from October 2001 to July 2002.; Phenanthrene, fluoranthene, and pyrene are the dominant species in wet and dry deposition.; Seasonal variations in both wet and dry deposition rates were observed, with higher deposition rates in the colder months and with lower deposition rates in the warmer months. Noticeably higher deposition rates in the colder months are due to increase of fossil fuel consumption.; In both dry and wet deposition, the heavier molecular weight PAHs are mostly present in undissolved phase whereas low molecular weight species are predominant in dissolved phase. Heavy PAHs are partially dissolved because particles in dry deposition were in contact with much larger volumes of water and for longer period of time than in wet deposition, increasing the probability for the PAHs to leach out from the particles and dissolve in water. (Abstract shortened by UMI.)...