Development of an improved dry and wet deposition collector and the atmospheric deposition of PAHs onto Ulsan Bay, Korea

摘要

An improved dry and wet deposition collector was built to monitor the atmospheric deposition of polycyclic aromatic hydrocarbons (PAHs) onto water in lakes or seas. In the improved collector the evaporated solution is replenished from a water supply reservoir by a tubing pump. Water vapor produced by a mini-space heater is sent up to the wet funnel by the vacuum pump (outlet) pressure and the water vapor pressure produced at a given temperature. The condensed water vapor is supplied into the wet funnel with a constant flow rate to prevent the channel formation in the wet adsorption cartridge. In a performance test of the developed deposition collector, the average recovery rate of 16 standard PAHs was 86% when using 30ml of CH_2Cl_2 as an eluent for 10 g of ENVI-18 packed in the adsorption cartridge. The drawbacks, such as evaporation of surrogate solution for dry deposition, channel formation inside wet adsorption cartridge during dry periods and expensive cost for system building, which are commonly faced with measurement of atmospheric deposition of PAHs onto water surfaces have been substantially solved in this improved collector system. The total (dry and wet) atmospheric deposition of PAHs onto Ulsan Bay during the winter was much greater than that during the summer. This was mainly due to a difference in the amounts of fossil fuel used and the prevailing wind characteristics during each season. Dry deposition of PAHs was predominant during the winter, however, wet deposition was the major deposition during the summer. Most of the PAHs deposited onto Ulsan Bay had less than or equal to 4 aromatic rings. The atmospheric deposition of the PAHs with 2, 3 and 4 aromatic rings was 38.0%, 27.8% and 24.1%, respectively.