Abstract: Heavy metals in coal gangue piles spread to the adjacent areas under hydro-mechanical coupling action, resulting in fragile surrounding ecological environment. The resultant ecological risk has received wide concerns. To understand the ecological risk of plant communities and soil pollution in coal gangue piles and the accumulation characteristics of heavy metals in dominant plant species in Southwest China, plant communities and soils of coal gangue piles in three regions of Fuyuan County, Yunnan Province were taken as the research objects. We investigated the characteristics of different plant communities and the heavy metal pollution status of soils (As, Cd, Cr, Cu, Hg, Ni, Pb, Zn). Furthermore, the enrichment and translocation characteristics of heavy metals by dominant species were analyzed. Seven dominant species, namely, Elsholtzia fruticosa, Alnus nepalensis, Buddleja officinalis, Coriaria nepalensis, Artemisia caruifolia, Lespedeza cuneata, Saccharum rufipilum, across nine plant communities were investigated. Alnus nepalensis had strong translocation capacity for Zn and Pb (TF_Zn=2.73, TF_Pb=2.50), while Artemisia caruifolia had the strongest enrichment capacity for Cd (BCF_Cd=0.69). The other dominant species had certain enrichment and translocation capacity for heavy metals. Species richness index was significantly positively correlated with soil total potassium content, and negatively correlated with soil organic matter, total nitrogen, and As content. The proportions of samples with the contents of  Cd, Cr, Cu, Hg, Ni, and Zn in the study area exceeding the background values of corresponding elements in soils in Yunnan Province were 63%， 100%, 100%, 59.3%, 85.2%, 96.3%,  respectively. The ecological risk assessment showed that soil of Saccharum rufipilum community (L1) in Laochang Town was seriously polluted by Hg and As, while the soil of Buddleja officinalis community (H3) in Housuo Town was seriously polluted by Cd. In conclusion, the ecological risks of Hg, Cd, and As in the surface soil were higher than those of other heavy metals, which should be paid attention in future soil environmental risk control. The seven dominant species distributed in the area have certain enrichment and translocation capacity for heavy metals, and can be used for vegetation restoration and ecological restoration of coal gangue piles in the study area.

Key words: coal gangue dump, dominant species, species richness, potential ecological risk assessment, bioconcentration factor, translocation factor