New Insight into Atmospheric Mercury Emissions from Zinc Smelters Using Mass Flow Analysis

The mercury (Hg) flow paths from three zinc (Zn) smelters indicated that a large quantity of Hg, approximately 38.0–57.0% of the total Hg input, was stored as acid slag in the landfill sites. Approximately 15.0–27.1% of the Hg input was emitted into water or stored as open-dumped slags, and 3.3–14.5% of the Hg input ended in sulfuric acid. Atmospheric Hg emissions, accounting for 1.4–9.6% of the total Hg input, were from both the Zn production and waste disposal processes. Atmospheric Hg emissions from the waste disposal processes accounted for 40.6, 89.6, and 94.6% of the total atmospheric Hg emissions of the three studied smelters, respectively. The Zn production process mainly contributed to oxidized Hg (Hg²⁺) emissions, whereas the waste disposal process generated mostly elemental Hg (Hg⁰) emissions. When the emissions from these two processes are considered together, the emission proportion of the Hg²⁺ mass was 51, 46, and 29% in smelters A, B, and C, respectively. These results indicated that approximately 10.8 ± 5.8 t of atmospheric Hg emissions from the waste disposal process were ignored in recent inventories. Therefore, the total atmospheric Hg emissions from the Zn industry of China should be approximately 50 t