Quantitative assessment of cadmium emission from zinc smelting and its influences on the surface soils and mosses in Hezhang County, Southwestern China

Using a mass balance method, we estimated the average Cd emission factors from artisanal zinc smelting using indigenous method in Hezhang, Guizhou, China, to be 1460 and 1240 g Cd t−1 of Zn produced from sulfide ore and oxide ore, respectively. These emission factors are much higher than the literature value used to estimate Cd emission from zinc smelting using pyrometallurgical method in developed countries, which is 50 g Cd t−1 of Zn produced. Based on the average Cd emission factors obtained in the study, annual Cd emission rates from artisanal zinc smelting in this area were calculated from 1989 to 2001. And up to 2003, approximately 450 t of Cd have been released to the ambient air from zinc smelting in a small area (<150 km2) in Hezhang district. Owing to a huge quantity of Cd atmospheric deposition, surface soils and mosses collected around the smelting areas were heavily contaminated. The highest total Cd concentrations in surface soils and naturally growing mosses were found to be 74 and 110 mg kg−1, respectively, exhibiting a local spatial pattern of Cd deposition from atmosphere.