Some local environmental effects on mercury emission and absorption at a soil surface

The purpose of this study was to quantify effects of some local environmental variables on the soil surface exchanges of total gaseous mercury (TGM), under controlled conditions. A dynamic flux chamber with a Tekran mercury analyzer was used to quantify TGM emissions from, and absorption by, a clean, fine sandy loam soil with very low mercury content inside of a building and in a low TGM environment, outside. Simultaneous measurements of mercury flux, air and soil temperatures, ozone concentration, humidity, soil moisture and solar radiation were made. Controlled applications of water were made to change soil H2O content and measure the response of mercury flux. Air-soil exchanges were highly dependent on soil temperature (r2 = 0.78) and the mercury concentration gradient between the TGM in the soil pores and the ambient TGM above the soil surface (r2 = 0.98 for absorption and r2 = 0.408 for emissions). Correlations with air temperature and ozone levels are explained by the relationships of these variables with soil temperature. No detectable correlation was found with solar radiation or humidity. Wet soil maintained higher rates of soil TGM emission and decreased soil absorption. Emissions increased with increasing soil H2O, peaked at approximately field capacity, and then decreased slightly until saturation.