Total mercury in soil and leachate from municipal solid waste dumping grounds in Mumbai, India

Deonar dumping ground (DeDG) and Mulund dumping ground (MuDG) are two of the three dumping grounds servicing municipal solid waste in Mumbai, India. Total mercury (THg) concentration in top soil samples and leachate were investigated for the two dumping sites. THg concentration of top soil from DeDG and MuDG was in the range of 64.60–2189.30 μg kg−1 and 3.88–1209.93 μg kg−1 respectively. Geoaccumulation index for DeDG and MuDG revealed soils to be moderately contaminated and uncontaminated, respectively. However, some of the individual sampling points showed soils to be strongly contaminated with mercury. THg concentration of leachate from DeDG and MuDG was in the range of 0.50–14.21 μg kg−1 and 0.25–5.43 μg kg−1 respectively. The age, size and quantity of solid waste being dumped were found to be major factors for higher THg concentration in top soil at DeDG. Pearson correlation coefficient revealed THg in leachate to be correlated to THg in soil, chemical oxygen demand (COD), total solids (TS), total suspended solids (TSS), total dissolved solids (TDS) and turbidity of leachate at DeDG and with pH of leachate at MuDG. Cluster analysis showed cluster for sampling points near working face of the landfill. Principal component analysis (PCA) revealed strong loadings between different physicochemical parameters from DeDG and MuDG.