Modelling Mercury Dynamics in Soils Impacted by Mercury Emission from Artisanal and Small-Scale Mining Activities.

Soil systems are commonly regarded as receptors of anthropogenic mercury contamination and play an essential role in the containment or dispersion of pollution to surface water, groundwater and the atmosphere. Mercury fate and transport are simulated using a local scale model to evaluate mercury dynamics in a soil system impacted by anthropogenic mercury pollution from artisanal and small-scale gold mining. The model assumes first-order differential equations that describe losses principally by evasion and leaching simulated on a yearly time step from thirty years ago to the present and into the future, where two different scenarios are considered. The model predicts that topsoil mercury concentrations may more than double in the next 50 years. Soil mercury is currently a source of mercury to the atmosphere and water but the leaching flux is less than the evasion flux. The soil would accumulate mercury until emission is curtailed and may require more than 500 years for levels to decrease to background values. If current emission rates are maintained, mercury contents of contaminated soil will keep increasing and will reach levels that poses risk to ecological and human health. [ABSTRACT FROM AUTHOR]