Mercury isotope signatures of a pre-calciner cement plant in Southwest China

Characterizing the composition of mercury (Hg) isotopes in the atmospheric emissions of cement plants is critical to understand the global circulation of Hg because large quantities of Hg are released from this source annually. A pre-calciner cement plant in Guizhou Province in Southwest China was selected to investigate the mass dependent fractionation (MDF) and mass independent fractionation (MIF) of Hg in the entire production process and the speciated Hg isotope composition in stack gas. Significant MDF and insignificant MIF were observed in this cement plant. Different raw/correction materials have δ202Hg signals ranging from -1.68 to -2.19‰. Raw meal is featured with lighter Hg (δ202Hg = -2.83 ± 0.18‰) as results of Hg circulation and accumulation during the clinker production. Cement products possess negative δ202Hg values (-1.98 ± 0.02‰) due to the input of light δ202Hg isotopes through additives/retarder limestone, and fly ash and gypsum from coal-fired power plant (CFPPs). Speciated Hg isotopes in the stack gas of the kiln tail and kiln head show no significant differences, and δ202Hg and Δ199Hg in the discharged flue gas averaged at -2.03 ± 0. 31‰ and -0.03 ± 0.07‰, respectively, which has negative δ202Hg characteristics with other anthropogenic sources. © 2020 Elsevier B.V.