The concentrations and fluxes of total gaseous mercury in a western coastal area of Korea during late March 2001

Factors affecting the distribution and exchange of total gaseous mercury (Hg) were investigated over a bare paddy field at Hari, a relatively clean district at Kang Hwa Island, Korea in late March 2001. The Hg concentrations were quantified at two heights (1 and 5 m above the ground), and then combined with micrometeorological measurements of turbulent exchange coefficients for flux computation. During the 8-day period of measurements, mean concentrations of Hg (3.72 ng m−3, N=164) were lower than those reported from urbanized/industrialized areas but higher than the background concentration (i.e., 1–2 ng m−3). The Hg fluxes, however, were comparable to those reported in the literature for polluted environments and showed clear diurnal pattern with maximum ( 600 ng m−2 h−1) during midday and the minimum ( 100 ng m−2 h−1) at nighttime. Occasionally, at nighttime when the turbulent mixing was weak under stable conditions, a deposition of Hg was observed at much lower rates (about −32.3 ng m−2 h−1). The rate of Hg emission tended to increase with increasing air/soil temperatures and pollutant levels under enhanced turbulent mixing. By contrast, dry deposition of Hg seemed to be related to the increase of certain pollutants such as fine particles (PM 2.5) and CO. Overall, the bare paddy field was a strong source of Hg with the daily net Hg emission of 4.4 μg m−2 during the measurement period.