Assessment of the level of mercury contamination from some anthropogenic sources in Ulaanbaatar, Mongolia

•Ulaanbaatar (UB) has 3 coal-fired power plants and 100,000 dwellings using coal.•Soil and dust collected in the city were analyzed for Hg by USEPA Method 7473.•The result is classified as “moderately polluted” according to Igeo and/or EF.•It is likely to have good relations between the concentration levels of SO2 and Hg.•It can be proposed that coal combustion is the main source of Hg emission in UB.

Ulaanbaatar (UB), the capital city of Mongolia in the central Asia, is a coal-based city which has 3 coal-fired thermal power plants and about 100,000 dwellings using lumps of lignite for their heating and cooking. So it is possible to be contaminated with mercury (Hg) caused by emission from coal combustion. The purpose of this study is to assess the level of Hg contamination in UB. Soil and dust samples collected from 33 sites within and around the city were analyzed for Hg by following US EPA Method 7473. The concentration level of Hg in soil and dust was in the range of 19.7–672.6 ng/g Hg, and 19.1–161.4 ng/g Hg, respectively. Especially in the urban district of the central part of the city, the median values of Hg in soil and dust are 69.1 ng/g, and 98.7 ng/g, respectively. On the other hand, the levels of Hg in control area were in the range of 16.9–24.3 ng/g in soil, and 28.2–28.9 ng/g in dust. The result of Hg contamination assessment is classified as “moderately polluted” according to the indices of ‘geoaccumulation index (Igeo)’ and ‘enrichment factor (EF).’ The coal combustion of power plants and dwellings is the potential source of Hg contaminations in soil and dust in UB, although the level of Hg in this city is a little lower than the other cities with analogous circumstances. This comes from not only the lower concentration of Hg in used coal (34.0 ng/g and 55.1 ng/g Hg), but also obvious spatial and temporal trends in coal usage in UB. And it is certain that the level of Hg in soil and dust should be increasing year by year owing to upward trend of coal consumption of the city. It is necessary to manage the risk caused by Hg contamination of various environmental compartments, and to control the anthropogenic sources of Hg emission.