The impact of forest plant communities on the content of heavy metals in soil profiles of the iron ore mining area, Kryvyi Rih District, Ukraine

The plant-soil interaction plays an important role in maintaining negative effects of soil pollution by heavy metals (HMs). Understanding HMs spatial variability in soils under plant communities is fundamental for soil restoration and predicting contamination by these elements. In this study, HMs content was estimated based on a soil survey conducted in Kryvyi Rih Iron Ore Mining and Metallurgical District, central Ukraine. The distribution of trace metals within a soil profile and their impacts on forest, steppe and agricultural land plant communities were also assessed. During field work, samples were collected from the whole soil profile (in 10 cm layers down to the parent rock). In total, 21 soil pits were sampled and 273 soil samples were collected. The contents of mobile Fe, Mn and Zn were assessed. The results showed that there was a specific pattern of HMs distribution in soil profile at the local background site of Kryvyi Rih District. The accumulation of HMs in soils in the vicinity of an iron ore mining and processing plant was found. Application of individual and integral indices of pollution demonstrated that Fe, Mn and Zn content was related to mining activity. The plant communities had a great impact on the HMs content in soils. According to the values of individual and integrated indices of pollution the plant communities form the following order: agricultural communities > forest communities > steppe communities. The forest plant communities, due to the presence of organic acids in forest leaf litter, promote the mobilization of heavy metals and may contribute to input of Fe, Mn and Zn irons to deeper soil layers. The differences observed between the plant communities located in the contaminated areas provide useful insight clues into the role and relative importance of major factors determining HMs contents in soil. Keywords: plant communities, soil, plant-soil interactions, trace metals, indices of contamination, iron ore mining