Abstract: Escalating global copper (Cu) demand and a growing inventory of Cu-bearing mine wastes highlight a mounting environmental liability and potential untapped reserve of alternative Cu resources where re-extraction remains challenging. Electrokinetic in situ leaching (EK-ISL) offers a novel, non-invasive, alternative but its biofunctional consequence on mine tailings remains unknown. Here, we examine the potential impact of citric acid-aided (0.5 M) EK-ISL on microbiome response under laboratory conditions through 16S rRNA metabarcoding. Citric-driven electrokinetically-induced conditions resulted in efficient tailings Cu leaching but altered bacterial ecology, leading to the expansion of copiotrophic (Proteobacteria) over oligotrophic (Chloroflexi) taxa. Functional predictions based on taxonomic information suggested a shift supporting traits linked to rapid growth and niche colonization. Despite microbiome restructuring, our findings support the use of citric acid as a tailings leachate, rather than conventional, chemically aggressive biocidal amendments, that will allow key pedogenic functions such as nitrogen fixation to persist. These novel findings highlight citric acid’s potential to balance efficient metal extraction with ecological recovery which may provide a nature positive option for Cu exploitation with concomitant remediation for the 100bB tonnes of legacy Cu tailing current stored globally.

Keywords: microbiome, metabarcoding, mine waste, heavy metals, ecological succession, microbial ecology, copiotrophy, oligotrophy

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