Volatilization of mercury from soils in response to simulated precipitation
Increases in mercury volatilization from naturally enriched soils due to precipitation events have been observed in the field, leading to the need for further research on the exact mechanisms responsible for the increase in the observed fluxes. In this research, the effects of precipitation on fluxes were simulated in a controlled laboratory experiment using a dynamic flux chamber system coupled with a Tekran® 2537A Mercury Vapour Analyzer. The experimental results indicate a sharp and rapid spike in the mercury flux, during and immediately following the precipitation event, which is a result of the physical displacement of the Hg-containing interstitial soil air by infiltrating rain water. The enhanced mercury emission flux after a precipitation event is dependent on both the quantity of infiltrating rain and the soil moisture content prior to the rain event, pointing to the mobilization of Hg (II) from soil particle to soil solution phase as the probable controlling process. The critical soil moisture range for surface soil moisture before a precipitation event is between 13% and 15%, above which enhanced mercury emissions do not occur.