Characterization of Ambient Air Particulates and Particulate Mercury at Sha-Lu, Central Taiwan

Abstract

Ambient air samples were collected between December 9, 2008, and January 14, 2009, at a highway traffic site located in Sha-Lu, central Taiwan. Atmospheric particulates and particulate bound mercury Hg(p) dry deposition, concentrations and dry deposition velocities were also studied. The objective of this study was to: 1) estimate the dry deposition concentrations of ambient air particulates and Hg(p) following 1- and 2-day sampling events using the total suspended particulates (TSP) sampler, and dry deposition plate (DDP) data; and 2) compare Hg(p) concentrations and dry deposition using two different media (i.e., quartz filter and projection film). The results obtained using overhead projection film as collection medium indicated that the average ambient air particulates dry deposition fluxes for the 1- and 2-day periods were 65.99 and 87.88 μ g/min m2, respectively. The corresponding fluxes using quartz filter collection medium were 67.31 and 52.53 μ g/min m2, respectively. Previous Hg related depositional studies have commonly used quartz filter as a collection media; however, in the work reported here overhead projection film was chosen due to its low cost as one of the collection medium, and the results obtained have been compared with the those estimated using quartz. Using the overhead projection collection medium, the average ambient air particulates dry deposition velocities for 1- and 2-day periods were 2.02 and 2.70 cm/sec, respectively, and the corresponding velocities with quartz film collection medium were 1.85 and 1.41 cm/sec, respectively. The overhead projection film collection medium results indicated that the average ambient air particulates bound Hg(p) dry deposition fluxes for the 1- and 2-day periods were 0.16 and 0.09 ng/min m2, respectively, and the corresponding fluxes estimated using the quartz filter collection medium were 0.21 and 0.11 ng/min m2, respectively. The average Hg(p) concentrations ranged from 0.04 to 0.86 ng/m2. The average ambient air particulates bound Hg(p) dry deposition velocities using the overhead projection collection medium for the 1- and 2-day periods were 6.79 and 3.32 cm/sec, respectively, and the corresponding velocities using quartz film collection medium were 8.94 and 4.41 cm/sec, respectively. In addition, the Hg(p) values associated with plant obtained in this study help to establish Hg(p) background concentrations in the air of specific area and also help to establish additional sources of Hg(p) link to distinct pollution events in Taiwan.