Characteristics of total mercury (TM) wet deposition: Scavenging of atmospheric mercury species

摘要

Total mercury (TM) in precipitation samples were collected with a modified MIC-B sampler on the roof of Graduate School of Public Health building in Seoul, Korea from January 2006 to December 2007 to determine the seasonal variations in TM wet deposition and to identify the contribution of reactive gaseous mercury (RGM) and particulate mercury (Hg_p) scavenging to mercury wet deposition. The volume weighted mean (VWM) TM concentrations in 2006 and 2007 were 10.1 ± 17.0 ng L~(-1) and 16.3 ± 16.5 ng L~(-1), respectively and the TM wet deposition flux in 2006 and 2007 were 16.8 μg m~(-2) and 20.2 μg m~(-2), respectively. Seasonal VWM TM concentrations in 2006 were highest in fall followed by winter, spring, and summer. In 2007, VWM TM concentrations were greatest in winter, followed by spring, summer, and fall. Nonparametric Mann-Whitney test revealed that there was no statistical difference between fall and summer in 2006 (p = 0.10), however, there was a statistical difference between winter and fall in 2007 (p < 0.01). The high VWM TM concentration in spring was probably due to the yellow sand events suggesting that RGM and Hg_p present in the rain were long-range transported from China during this period. The large wet deposition fluxes observed in summers were possibly due to the intense rainfall. Overall there was a significant positive correlation between rainfall depth and wet deposition flux (r~2 = 0.22) (p < 0.01) and a significant negative correlation between rainfall depth and TM concentration in precipitation (r~2 = 0.20) (p<0.01) due to dilution effects. In addition, a weak positive correlation between TM concentration and wet deposition flux was shown (r2 = 0.10) (p < 0.05). Multiple linear regression showed that scavenging coefficient (SC) for RGM was much higher than SC for Hg_p suggesting that RGM was more effectively scavenged by wet deposition than Hg_p (SC_(rgm) = 750 and SC_(hg_p=380).