Biocrusts significantly affect the bioavailability and ecological risk of heavy metals in gold mine tailings

Jin Fan, Chongfeng Bu, Yangzhou Qi, Wenjuan Zhou, Chun Wang, Yingxin Wei, Kadambot H.M. Siddique

Research output: Contribution to journalArticlepeer-review

3 Citations (Scopus)

Abstract

Aims: Biocrusts are important living covers in ecologically fragile regions that intercept metals entering the soil and indicate heavy metal contamination. This study explored the potential of biocrusts as a novel approach for remediating heavy metal pollution in mining areas. We also investigated the capacity of biocrusts to enrich or degrade heavy metals in gold mine tailings and analyzed the migration, transformation mechanisms, and potential toxic effects of heavy metals in the underlying biocrusts. Methods: We used the BCR sequential extraction procedure to analyze the speciation of heavy metals in the underlying biocrust layer (moss crusts, mixed crusts (moss + algal), and algal crusts). The risk assessment code (RAC) and potential ecological risk index (Er) were used to evaluate the impact of biocrusts on the ecological risk assessment of heavy metals in soil. Results: The results showed that (1) well-developed biocrusts had a strong ability to enrich heavy metals, with these metals accumulating at the surface; (2) biocrust growth facilitated the conversion of heavy metals from an inert state to an active form in the underlying layer, enhancing their bioavailability; (3) Spearman’s correlation and redundancy analysis (RDA) revealed the total amount of heavy metals as the primary factor driving the translocation of soil heavy metals, with soil pH, cationic exchange capacity (CEC) and organic matter content (SOM) exerting varying influences; (4) the comprehensive potential ecological risk index indicated that heavy metals in gold tailings at the strong risk levels, mainly due to arsenic exceeded the standard (~ 7 × background values). However, biocrusts reduced the Er of heavy metals in the underlying layer. The RAC results indicated low mobility and bioavailability of heavy metals in the underlying layer, associated with low ecological risk. Conclusions: As the ‘skin’ of soil, biocrusts could protect soil from heavy metal contamination. Despite enhancing heavy metal bioavailability, their enrichment effect was much greater than their activation effect. As a result, biocrusts hold great promise for remediating heavy metal pollution in degraded ecosystems. Further exploration of the influencing mechanism of biocrusts on heavy metals will help validate their use in mine restoration processes.

Original languageEnglish
Pages (from-to)99-113
Number of pages15
JournalPlant and Soil
Volume493
Issue number1-2
DOIs
Publication statusPublished - Dec 2023

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