| Summary: | 碩士 === 國立屏東科技大學 === 環境工程與科學系 === 88 === Wet and dry deposition are two major transport pathways of polycyclic aromatic hydrocarbons(PAHs) to terrestrial and aquatic ecosystems. Based on the remoral efficiency, wet deposition is the more significant process than dry deposition. In this study, wet deposition and air sampling will be investigated in the ambient air of a PCI(petrochemistry industry ) plant and a rural site with automated wet-only collectors and PS-1 samplers. A wet-only collector will be developed to collect large volumes of precipitation and to isolate the particle-associated and dissolved fractions of PAHs during each precipitation event. During periods of no rain or threat of rain, gaseous and particle-bound PAHs will be sampled from the ambient air by using PS-1 samplers. The results of this investigation are as follows: The concentrations of PAHs in the atmosphere of industrial area were higher than those in rural site. So, the concentrations of PAHs that can be scavenged in the rain were relative high. For both PCI and rural sites, the concentrations of particle-bound PAHs in the rain samples were higher than those of dissolved. This is because that the scavenging of particle-bound concentrations of PAHs is more efficient than the scavenging of dissolved concentrations of PAHs in wet deposition. The phenomenon that PAHs deposition flux increase with increasing rainfall intensity implies the significance of below-cloud scavenging because below-cloud scavenging only occurs during precipitation events. Accordingly the presence of PAHs in rain is probably mainly the result of below-cloud scavenging instead of in-cloud scavenging. The efficiencies of particle (Wp) and gas (Wg) washout were higher in rural than those in PCI site. For both PCI and rural sites, the efficiencies of particle washout were higher than those of gas washout in wet deposition of PAHs. For 21 individual PAHs in the rain samples, the high-molecule-weight PAHs, such as COR, BkF and BbC at the rural while COR, BeP and PER at the PCI, had higher gas washout efficiencies. Except COR, the lower-molecule-weight PAHs, such as Nap, BbC, AcPy and Flu at the rural while Nap, Acp, Flu and PA at the PCI, had higher particle washout efficiencies.
The average TC concentration of the particles in precipitation was 186.6 and 462.8 ng/L for the rural and industrial area, respectively. The average EC concentration of the particles was 120.6 and 209.5 ng/L for the rural and industrial area. The average OC concentration in the particle was 65.7 and 235.25 ng/L for the rural and industrial area. The TC , EC and OC concentration in industrial area were 2.48, 1.74 and 3.85 times higher than those in rural area. The average OC/TC and OC/EC ratio were 0.35 and 0.54 for the industrial area, while the average OC/TC and OC/EC ratio are 0.55 and 1.21 for the rural area, respectively. The OC/TC(1:1.57) and OC/EC (1:2.24) ratio for the rural area were less than those for the industrial area. The PAH was related to TC for both of the industrial and rural area. While the PAH was related to EC only in the rural area and was related to EC only in the industrial area.
The information about the wet deposition of PAHs is scattered in the field investigation. The results of this study are important to develop the strategies for controlling of PAHs and understanding the processes that transport and scavenge PAHs from the atmosphere. But it is necessary to get reliable correlativity between the concentrations of PAHs and the concentrations of the relative matter in the rain by more experiment.
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