Spatio-seasonal dynamics of bacteria and metal composition of a platinum mine tailings dam, Rustenburg, South Africa

Abstract

Seasonal variations and proximity to polluted sites, among other factors, play a vital role in soil composition. The impact of spatio-seasonal changes on bacterial and heavy metal content on and around the platinum mine tailings dam, Rustenburg, South Africa, was assessed. Tailings and topsoils collected during summer and winter were examined for bacterial abundance, physicochemical parameters and metal contents using standard methods. Data were analysed using ANOVA, correlation and cluster analyses. Bacteria counts were 2.5 × 105 to 1.0 × 106 and 3.5 × 105 to 7.8 × 105 CFU g−1 in summer and winter, respectively. Molecular identification revealed the presence of the bacterial species Paenibacillus lautus and Stenotrophomonas maltophilia. Significant (p < 0.05) differences were obtained between chromium (Cr), copper (Cu) and nickel (Ni) concentrations in both seasons but not with bacterial counts. Although higher bacterial abundance was observed on sites 1 and 2 in both seasons. Relative abundance of Ni > Cu > Cr was observed with significantly (p < 0.05) higher concentrations in winter. Pearson's correlation (p < 0.05) and cluster (r = 0.60, p < 0.05) analyses confirmed strong positive correlations between bacteria and Cr, Cu and Ni concentrations. The high bacterial presence on sites in proximity to the dam may indicate metal tolerance of these species