Containment and phytoremediation: Complementary roles of vertical plant diversity for heavy metals mitigation in...

Despite decades of mining-driven pollution, the integrated role of vertical plant diversity in mitigating heavy metal risks remains insufficiently explored. Heavy metals (HMs) from mining pose significant environmental risks, with their sources and mitigation by vegetation at Southwest China's mines. This study investigated the sources and environmental risks of HMs in soils surrounding lead-zinc, manganese and limestone mines at the Southwest China and the mitigating role of vertical vegetation in controlling HMs. Manganese mining (24.2%), lead-zinc mining (22.9 %), agriculture plus oil combustion (17.4 %) and limestone mining (11.4 %) were dominant HM sources, accounting for 96 % of total concentrations. Degree of contamination (C-deg), pollution load index (PLI) and potential ecological risk index (PERI) revealed that soils in affected areas exhibited considerable to very high contamination and ecological risks along with significant declines in soil quality. Our findings demonstrate that natural vegetation significantly reduces contamination and ecological risks in vegetated areas (p < 0.05). The high diversity of plants in different vertical layers plays a complementary role in mitigating soil HMs contamination. More diverse tree species can effectively block the spread of HMs, while more diverse herbaceous plants can effectively remediate multiple soil HMs contamination. Vegetated soil exhibited approximately 3.5-fold lower C-deg and significantly reduced PERI (p < 0.05) as compared to adjacent bare soils. These results highlight the importance of native vegetation as a sustainable strategy for mitigating the soil HMs environmental risks of mining activities and the importance of conserving plant diversity in different layers.