Effect of pH, iodide, and organic matter on the mobility of mercury(II) in soils

This research attempted to determine the effect of pH, iodide concentration, and organic matter on the mobility of mercury in soils. Initial investigations assessed the impact of the above parameters for three initial mercury concentrations (40, 100, and 200 µg/L) in suspensions of the clay mineral, illite, a major component of the inorganic fraction of Eastern Tennessee soils. Subsequent experiments assessed the capability of large concentrations of iodide (> 1 mM) to extract mercury from contaminated floodplain soils.

Results indicate that iodide affects mercury adsorption in a manner similar to that of chloride, but at much lower concentrations. Iodide is very effective in preventing mercury adsorption by illite. Adsorption is particularly inhibited at low pH values. Organic matter acts to increase mercury adsorption. However, in contaminated soils, iodide was less effective in extracting mercury. Even with high iodide concentrations and extended exposure times, little mercury was extracted from contaminated soils, likely due to the chemical form of mercury in the soil.