Mercury emission to atmosphere from Lanmuchang Hg–Tl mining area, Southwestern Guizhou, China

Abstract

In situ mercury emission fluxes from soil in Lanmuchang Hg–Tl mining area, southwestern Guizhou, China, were measured using dynamic flux chamber (DFC) method in December 2002 and May 2003, respectively. Huge mercury emission fluxes from soil were obtained in the mining area, ranging from −623 to 10 544 ng m −2 h −1 ( n = 92 ) with the maximal mean Hg flux of 2283±2434 ng m −2 h −1. Meanwhile, highly elevated total gaseous mercury (TGM) concentrations in the ambient air observed during the sampling periods varied from 35.2±26.1 ng m −3 (7.9–353.8 ng m −3, n = 532 ) in cold season to 111.2 ± 91.8 ng m - 3 ( 12.7 – 468.0 ng m - 3 , n = 903 ) in the warm season, respectively. The correlations between mercury emission fluxes and environmental parameters, such as solar radiation, temperature, TGM concentration in air, relative humidity and soil Hg concentration are studied. The strong Hg emission fluxes resulted in the elevated TGM concentrations in the ambient air in the study area. We acquired a significant Log–Log correlation between the ratio of average Hg flux and average solar radiation and the soil Hg concentrations at all sampling sites in warm and cold seasons. Within the Langmuchang Hg–Tl mining area with a total area of ∼2.9 km 2, the annual Hg emission rate is calculated to be ∼3.54 kg Hg, which is a strong mercury emission source to the local ambient air.