Mercury wet deposition and coal-fired power station contributions: An Australian study

Abstract

Regions that have large coal-fired power station regions may be prone to elevated mercury (Hg) deposition fluxes. Total mercury (THg) in daily rainfall samples at a near-field sampling site (Hunter Valley) and a far-field station (Sydney) has been monitored in this study employing ultra-clean sampling techniques and Cold Vapour Atomic Fluorescence Spectrometry (CVAFS) analysis. Measurements of THg range from 0.9 to 16.5 and from 1.2 to 18.9 ng/L for the far-field and near-field sites respectively. Average daily THg wet deposition fluxes were 49.9 and 79.8 ng/m 2 for the far and near-field sites respectively. A two-sample t-test reveals the near-field site to have higher rainfall mercury (significant at the 95% level) and deposition fluxes. At the far-field site, lower Hg deposition occurs during the cooler months, while the Hunter Valley site has higher winter deposition. It is believed that the higher winter values near-field may be due to the combined impact of prevailing wind direction and high pollutant build up brought on by lower mixing height. Based on this study, the first in the Southern Hemisphere, we conclude that rainfall THg concentrations and Hg wet deposition fluxes at the two sites are comparable to rural sites in North America.