Spatial distribution and accumulation of Hg in soil surrounding a Zn/Pb smelter
Nonferrous metal smelting is an important atmospheric mercury (Hg) emission source that has signifificant local and global impacts. To quantify the impact of Hg emission from non-ferrous metal smelter on the surrounding soil, an integrated model parameterizing the processes of smelter emission, air dispersion, atmospheric deposition and Hg accumulation in soil was developed. The concentrations of gaseous elemental Hg (GEM) around the smelter and the spatial distribution of Hg in the surrounding soil were measured and compared with the model results. Atmospheric deposition of Hg emitted from the smelter was identifified as the main source of Hg accumulation in the surrounding soil. From 1960 to 2011, the smelter emitted approximately 105 t of Hg into the atmosphere, of which 15 t deposited locally and resulted in an increase of Hg concentration in soil from 0.12 to 1.77 mg kg−1 . A detailed examination of wind rose and model data suggested that the area within 1.0–1.5 km northwest and southeast of the smelter was most severely impacted. It was estimated that the smelter operation from 1969 to 1990, when large scale emission controls were not implemented, resulted in 6450 μg m−2 yr−1 of Hg net deposition and a model simulated increase of 0.40 mg kg−1 of Hg accumulation in the soil. During the period from 1991 to 2011, atmospheric Hg emission from the smelter alone increased the average concentration in soil from 0.41 mg kg−1 to 0.45 mg kg−1 . In the past 50 years, over 86% of Hg emitted from this smelter went into the global pool, indicating the importance of controlling Hg emissions from non-ferrous metal smelters.