Characteristics of total and methyl mercury in precipitation in Seoul, Korea

Abstract

To investigate the seasonal distribution of mercury (Hg) in precipitation in Seoul, Korea, event based total mercury (THg) and methyl mercury (MeHg) in precipitation samples were collected for one year. During sampling periods, volume weighted mean (VWM) concentration of THg and MeHg were 16.91 and 0.042 ng L-1 and wet deposition flux of THg and MeHg was 5.96 and 0.01 mu g m(-2), respectively. The proportion of MeHg in THg in the rainwater ranged from 0.01% to 2.22% with a mean value of 0.5%. The THg and MeHg concentration in precipitation was the highest in the winter, while wet deposition flux of THg and MeHg were highest in summer. There were significant negative correlations between THg and rain amount (p = 0.034), and between MeHg and the rain amount (p = 0.023), indicating that Hg concentrations in precipitation decreased as the amount of precipitation increased, especially in summer. THg concentration was higher when precipitation amount in one event was less than 20 mm, implying that 20 mm of precipitation can be a threshold value showing the Hg wash-out effect from the atmosphere. A significant correlation was observed between THg and NO3- (r(2) = 0.65) and Cl- ion (r(2) = 0.60), and between MeHg and SO42- ion (r(2) = 0.52) concentrations in precipitation. We also found a weak relationship between MeHg and DOC concentrations in precipitation.