Assessment of soil and vegetation condition in Zakamensk town (Buryatia): the consequences of operating Dzhida tungsten-molybdenum plant
The state of soil and vegetation in residential and surrounding landscapes at the Zakamensk town was assessed after the dismantling the former Dzhidinski tungsten-molybdenum combine (DTMC) in 1997 and carrying out the first stage of rehabilitation measures. It was shown that the soil contamination of urban territory, established according to the results of ecological-geochemical survey 2005, continued to increase until 2012. Stale sulfide bearing tailings are the main sources of soil contamination, and the content of mobile (acid-soluble) forms of heavy metals (Pb, Zn, Cu) migrating from tailings ponds to nearby landscapes increases with time in the surface layer. Content of mobile Zn and Cu in soils correlates positively with the total content of these metals in soils and the general level of soil contamination. Pb mobile form was registered in the areas of strong and the maximal soil contamination. Pb is poorly soluble in the less contaminated soils and it concentrates in the humus layer of soils. The plants in the town of Zakamensk and the adjacent areas are strongly polluted (Zc > 10). Accumulation of elements by plants is directly linked to the level of soil contamination and the content of mobile forms of elements in soil, except for Pb and Cu. The concentration of chemical elements of first and second classes of environmental hazard in plants form the following decreasing succession: birch leaf - poplar leaf - potato leaf - herbaceous vegetation - lettuce leaf - cabbage leaf - potato tuber. The first stage of measures aimed at partial removal of ore tailings outside of the urban area resulted in increasing the general content of heavy metals in the surface of the main source of pollution, i.e., the former hydraulic tailings.