Assessment of heavy metal contamination, mobility and associated risks at a municipal dumpsite using geochemical...

Open dumping of municipal solid waste (MSW) remains a widespread and meagrely regulated waste management practice in many developing nations, resulting in sizeable environmental degradation and increased health risks. This study evaluates the extent of contamination of eight heavy metals silver (Ag), arsenic (As), cadmium (Cd), chromium (Cr), copper (Cu), iron (Fe), lead (Pb), and zinc (Zn) in soils at depths of 0.5 m, 1.0 m, and 1.5 m at the Second Seventh Municipal Solid Waste Dumpsite (SSMSWD) in Lae City, Papua New Guinea. Soil samples were digested using reverse aqua regia and analyzed with Inductively Coupled Plasma-Optical Emission Spectroscopy (ICP-OES). The findings showed that the maximum observed concentrations as µg/g were significantly higher than the recommended values as per World Health Organization (WHO) with Pb-450, Zn-173, Cd-120, Ag-44, As-38, Cu-18, Fe-1.34 and Cr-1.4 respectively. Pollution indices, which classify contamination severity relative to the background concentrations, indicated that Pb, Cd, Zn, As, Ag and Cu fall within the pollution category (PI > 5), while Pollution Load Index (PLI > 1) values reveal the overall deterioration of soil quality. Cumulative Pollution Index (PI_sum) was between 93 and 714, meaning very high overall contamination (PI_sum > 4n), and the average Pollution Index (PI_avg > 1) was between 12 and 89 and this proved that the vertical concentration profiles specify that metal enrichment extending to 1.5 m depth, reflecting downward redistribution inferred from concentration patterns. Findings signify severe multi-metal contamination that degrades soil quality and creates a considerable risk of escape to shallow groundwater, with possible potential repercussions for ecosystem integrity and human health.