Mercury emission to atmosphere from primary Zn production in China

Emissions of mercury (Hg) to air have regional and global impacts through long range transport in the atmosphere. Primary Zn production is regarded as an important anthropogenic Hg source in China, but research on its Hg emission is limited. To gain a better understanding of Hg emissions from Zn production activities in China, field investigations at four industrial-scale Zn production plants using electrostatic process with Hg removal (HP-WR), electrostatic process without Hg removal (HP-WOR), retort Zn production (RZ), imperial smelting process (ISP), and one artisanal Zn smelting process (AZ) were carried out. In the investigation, Hg emission factors are defined as how much Hg was emitted to the atmosphere per ton Zn produced during various Zn production methods and were estimated by using mass balance method. The results showed that the estimated Hg emission factors of Zn production were 5.7 ± 4.0 g Hg t−1 Zn for HP-WR, 31 ± 22 g Hg t−1 Zn for HP-WOR, 34 ± 71 g Hg t−1 Zn for RZ, 122 ± 122 g Hg t−1 Zn g t−1 for ISP, and 75 ± 115 g Hg t−1 Zn for AZ. Approximately 80.7–104.2 t year−1 of Hg was emitted to atmosphere from primary Zn production during the period of 2002–2006 in China.