Assessment of Long-Term Soil Contamination Due To Municipal Solid Waste Dumping in Mokokchung, Nagaland: A Pollution Index-Based Approach

Purpose - The purpose of this study is to evaluate the long-term impact of municipal waste dumping on soil quality in Mokokchung, Nagaland, India. It aimed to assess residual contamination levels and evaluate ecological risk using pollution indices. Methods - Soil samples were collected from three distinct ecological zones: a dumpsite (Site1), an undisturbed agroforestry area (Site 2) and a roadside area (Site 3). Atomic absorption spectrophotometry method was used to assess the quantities of heavy metals (Zn, Pb, Cd, Ni, Fe, Cr, and Cu) and for physio-chemical parameters such as pH, EC, organic carbon, nitrogen, phosphorus, and potassium respective methods were used. To describe the level and source of contamination, pollution indices such as the enrichment factor (EF), geo accumulation index (Igeo), contamination factor (CF), and pollution load index (PLI) were calculated. Result - The results showed that the dumpsite had acidic, nutrient-deficient soils and high concentrations of heavy metals, with Cd, Pb, and Cr exhibiting extremely high levels of pollution. While Site 3 shown modest impacts, Site 2 maintained near-background levels and excellent soil conditions. With a PLI of greater than 11.8, the pollution index results further validated the dumpsite's status as highly polluted. Conclusion - These findings underscore the ecological risk of legacy waste dumping and highlight the need for remediation, monitoring, and long-use restriction near former dumpsite.