Distribution and Fraction of Metal(Loid)s in Antimony Tailings Ponds and Their Effects on Naturally Recovering Local Vegetation and Microorganisms

Abstract

Mining and smelting of antimony ores produce large quantities of tailings that pose significant environmental hazards. Plants and microorganisms exhibit adaptive responses to metal contamination in their habitats. In this study, we selected the Dachang Antimony Mine in Qinglong, Guizhou Province, and collected 0–100 cm samples of tailings/soil and plants from nine sample plots within the tailings site and one adjacent bare soil sampling point (10 sampling locations in total) in and around the tailings site. We analyzed the extent of the metal contamination of the tailings site and its interactions with growing plants/microorganisms, aiming to explore the underlying mechanisms of the natural ecological restoration of this tailings site in the absence of human intervention. The tailing sand/soil in the study area was mainly contaminated by Sb and As, with Sb concentrations up to 7,765 mg/kg (background: 1.21 mg/kg in China) and As concentrations up to 112 mg/kg (background: 11.2 mg/kg in China), far exceeding national soil background levels, and there was also co-contamination of Pb, Cr, Zn, Cu, Ni, and other metals. Pb and As may present high ecological risks. The five dominant plants were more tolerant to the major heavy metals in the study area, and Artemisia argyi showed a notably higher bioconcentration and translocation of major heavy metals than other plants. The vast majority of the plants showed limited capacity to accumulate metal(loid)s but exhibited substantial ability to translocate them from roots to shoots. Their suitability for phytoextraction of heavy metals in the heavy metal-contaminated areas requires further investigation. In addition, the geochemical conditions of the different layers and substrates significantly influenced the microbial community. Among several major heavy metals, there were different degrees of significant positive correlations between higher levels of As, Sb, and Cr and major local microbial communities, which may contribute to the natural ecological recovery of this antimony tailing. This study provides a theoretical basis for the metal pollution of Sb tailings site and its self-recovery situation and ecological remediation in the natural state.