Mercury emissions flux from various land uses in old mining area, Inner Mongolia, China

In this study, the Hg emission flux from various land uses, e.g., coalfield, coal-fired power plants, chlor-alkali plant, and urban areas, was investigated in the Wuda District, Inner Mongolia, China. Mercury emission fluxes were measured using the dynamic flux chamber method coupled with a Lumex multifunctional Hg analyzer RA-915+ (Lumex Ltd., Russia). The results showed that the Hg emission flux in the coalfield ranged from 34 to 318 ng center dot m(-2)center dot h(-1) with an average value of 115 ng center dot m(-2)center dot h(-1). The average flux in the coal-fired power plants, chloralkali plant, and residential area was 71 ng center dot m(-2)center dot h(-1), 77 ng center dot m(-2)center dot h(-1), and 80ng center dot m(-2)center dot h(-1), respectively. The highest flux occurred in coal-fire area in the coalfield. Compared to other regions, the results indicated that the Hg emission flux was normal in the Wuda District. However, the Hg flux emissions from aforementioned land uses were much higher than the background site. We hypothesize that the high flux stemmed from underground coal seam emission of Hg, although we did not observe strong indications of vents, cracks, and smog. Emission of Hg from coal-fired power plants and Hg catalysts used in polyvinyl chloride increased the soil surface Hg concentration and resulted in an Hg emission flux substantially higher than the regional background flux. The Hg emission flux was found to be positively correlated with soil and dust Hg contents, soil surface temperature, atmospheric Hg content, and solar radiation and negatively correlated with relative humidity. Moreover, the effect of Hg dust was stronger than that of soil.