Current status and atmospheric mercury emissions associated with large-scale gold smelting industry in China

Abstract

Mercury, being bound with metal concentrate, is released to atmosphere in the smelting process, and has adverse effects on surrounding ambient air quality and public health. In this study, based on literature and field investigations, onsite measurements of mercury emissions to the atmosphere for four large-scale gold smelters were estimated. Almost all of the atmospheric mercury released from the roasting pretreatment process occurred before acid plants. All the concentrations of mercury emitted from the four tested gold smelters were much lower than the emission standard of air pollutants for GB 9078–1996 Grade II level areas of 1000 μg m–3. The speciation of Hgp took up the largest proportions for the total mercury concentrations. Because of using high mercury oxidation efficiency of double-conversion double absorption (DCDA) technology, the proportions of Hg2+ in the exhaust flue gas was higher than Hg0. Average emission factors of atmospheric mercury for these four tested gold smelters were calculated to be 1.7 kg of Hg per ton gold produced, and the national total amount of mercury emitted from large-scale gold smelting industry in the year of 2014 was estimated to 639.9 kg. However, mercury emission factors obtained from present study were much lower than that in previous research. Thus, with the exact emission factor obtaining from more specific field-test data and the detailed activity data information about gold smelting industry, an accurate inventory of mercury emissions to the atmosphere from large-scale gold smelters in China can be updated in the future.