Dry deposition of airborne particles and characteristics of polycyclic aromatic hydrocarbons in Kaohsiung, Taiwan #135

摘要

The concentrations of total suspended particles (TSP) and twenty-one polycyclic aromatic hydrocarbons (PAHs) were measured simultaneously at two sites (Tzuo-Yin and Hsiung-Kong) in Kaohsiung city for four seasons from 2005 to 2006 using high volume air samplers, and the gaseous and particulate phases of individual PAHs were identified. Meanwhile, the deposition fluxes of TSP at the two sites were measured with dry deposition plates. Measured results show that the mean deposition fluxes of TSP were between 182.2 and 195.3 mg/m~2/day, with dry deposition velocity being 2.00-2.04 cm/s. The concentrations of TSP were highest in winter (92.96-164.13 μg/m~3), followed by spring (110.28-171.06 μg/m~3), fall (69.50-128.27 μg/m~3) and summer (44.92-63.02 μg/m~3). The concentrations of total PAHs generally followed the seasonal variations of TSP, being the highest in winter (139.07–190.85 ng/m~3) and the lowest in summer (79.40–104.77 ng/m~3) at both sites. Most PAH species were L-PAHs (low-weight PAHs, about 80.8–82.0%), followed by H-PAHs (high-weight PAHs, 10.5–14.6%) and M-PAHs (medium-weight PAHs, 6.5–6.8%). In particular, NAP (naphthalene), an L-PAH, is the most abundant species, representing about 80.8% and 72.0% of total PAHs at the Tzuo-Yin and the Hsiung-Kong sites, respectively. Furthermore, L-PAHs mostly existed in gaseous form, ranging from 55.9 to 95.9% at Tzuo-Yin and 66.9 to 96.6% at Hsiung-Kong; particularly, over 95% of Nap existed in gaseous phase. The fractions of gaseous PAHs decrease with molecular weight or ring number. On average, about 54.8-70.3% of M-PAHs were in gaseous form, and about 29.7-45.2% of M-PAHs were in particulate form. Particulate phase dominated H-PAHs at both sites, being 60.2-73.5% of H-PAHs were in particulate form and only 26.5-39.8% were in gaseous form. The differences of measured results at the two sites are mainly attributed to the different industry at each site.