Atmospheric deposition of toxics onto Massachusetts Bay—II. Polycyclic aromatic hydrocarbons

Wet and dry atmospheric deposition of polycyclic aromatic hydrocarbons (PAHs) was measured at biweekly intervals from 15 September 1992 to 16 September 1993 at two sites on Massachusetts Bay, Nahant, near Boston and Truro, near the tip of Cape Cod. Wet and dry deposition was measured using a conventional wet/dry collector, except that the dry bucket contained a layer of water in order to simulate the uptake of dry deposition onto a water surface. The PAHs were extracted from the aqueous solution/suspension by methylene chloride, preconcentrated by low-temperature evaporation, and analyzed by GC-MS. Dry and wet depositions of PAHs were significantly greater at Nahant than at Truro, due to the proximity of emission sources in the metropolitan Boston area. Highest deposition of PAHs was observed in the winter season. At Nahant, the following deposition rates (wet + dry) were observed in units of 104 ng m−2 yr−1: fluoroanthene, 13; phenanthrene, 11; pyrene, 9.8; chrysene, 5.3; and the potentially carcinogenic benzo(a) pyrene, 3. At Truro, the deposition rates were several fold lower. Polychlorinated biphenyls (PCBs) were not found above the detection limit of the analytical procedure.