Analysis of soil metals and microbial communities in a mining city in D.R. Congo

The mining industry in Katanga specifically in the City of Greater Lubumbashi was initiated in early1900s. Several hydrometallurgical plants and smelters refined Copper and Cobalt and produced zinc,arsenic, and cadmium as by-products. The main objectives of the present study are 1) To determine thedynamics of metal distribution around the Etoile mining site including urban areas and 2) to establishthe microbial profile and bacterial and fungal abundance and diversity in sites with different levels ofmetals. Effects of years of mining activities on the soil microbial abundance and diversity as well as thecurrent levels of total and bioavailable metals has been quantified at different distances from the miningsite. Bacterial and fungal abundance have been characterized in targeted sites. The phytoremediationpotential of Leucaena leucocephala planted in a mine tailing contaminated with copper and cobalt hasbeen established.The soil pH was neutral (pH 7) around the mining sites and acidic at the other sites varying between 4and 6. The highest level of Copper and Cobalt, the main heavy metal contaminants, were found at thetailing and the mining sites. Interestingly, the total levels of these elements in urban areas located at 2km and 4 km from the smelters were low and below government threshold for human risk.There was a wide range of bacterial and fungal genera found to be significantly different among sites.But, there was no link between the level of total Cu and Co and bacterial and fungal abundance. Thealpha diversity indices (Shannon entropy and Pilou eveness) for the sites analyzed were similar for boththe bacterial and fungal communities. Beta diversity indices confirmed the closeness of the sitesanalyzed. The lack of differences in microbial community abundance and diversity between highlycontaminated and less contaminated sites observed in the present study suggested resilience andphysiological adaptation