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Current state of the heavy metal pollution, microbial diversity, and bioremediation experiments around the Qixia Mountain lead–zinc mine in Nanjing, China

Summary

A lead-zinc mine in Nanjing, China has contaminated surrounding soils with dangerous heavy metals like lead, zinc, and cadmium over 70 years of operation. Researchers discovered that combining amaranth plants with a beneficial bacterium called Bacillus velezensis dramatically reduced heavy metal pollution in soil, lowering pollution levels from severely contaminated to acceptable levels. This plant-microorganism approach also improved plant growth while reducing heavy metal uptake in the edible parts of crops, offering a practical solution to make farmland around mines safer for growing food.

Background

Lead-zinc mining operations and ore processing result in severe environmental contamination with heavy metals and tailings. The Qixia Mountain lead-zinc mine in Nanjing, China has operated for over seventy years, causing significant soil pollution in surrounding agricultural and scenic areas. Understanding the current pollution state and microbial community structure is essential for developing effective remediation strategies.

Objective

This study evaluated heavy metal pollution levels and microbial diversity in soils around the Qixia Mountain lead-zinc mine. The research investigated whether plant-microorganism-induced mineralization could effectively remediate contaminated soil through pot experiments using amaranth plants and Bacillus velezensis.

Results

Serious soil pollution was confirmed with Nemerow indices ranging from 4.45 to 26.50. Sphingomonas and other heavy metal-resistant bacteria were dominant in different soil environments. Pot experiments showed that amaranth combined with B. velezensis-induced mineralization significantly reduced pollution levels, decreasing the Nemerow index from 4.5 to approximately 1.0, while promoting plant growth and reducing heavy metal uptake in edible plant parts.

Conclusion

Long-term mining has created severe heavy metal contamination in surrounding soils. Plant-microorganism synergistic remediation, particularly using amaranth and Bacillus velezensis, effectively reduces heavy metal pollution and promotes crop growth. This approach provides a practical solution for remediating contaminated farmland near lead-zinc mines while ensuring food safety.
  • Published in:RSC Advances,
  • Study Type:Field Investigation with Experimental Remediation Study,
  • Source: PMC11926974, PMID: 40124912, DOI: 10.1039/d4ra07920e
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