Appraisal of seasonal variation of groundwater quality near an uncontrolled municipal solid waste landfill in Kolkata, India

The present study was aimed to evaluate the impact of leachate derived from uncontrolled municipal landfill on surrounding groundwater quality in Kolkata, India. Seasonal variation of twenty physico-chemical parameters in pre-monsoon (PRM) and post-monsoon (POM) season were analysed in forty groundwater samples around the landfill site. Groundwater pollution was identified by the spatial distribution maps of TDS, Na⁺, Cl⁻, Mn and Fe along with the heavy metals like Pb, Hg andCr in both the seasons. Hydrogeochemical characteristics of groundwater samples showed that the area was dominated by brackish water, [Ca⁺2−Cl⁻], [Mg⁺2−Cl⁻] and [Na⁺−Cl⁻] type in PRM season whereas [Na⁺−HCO3⁻] type dominated in POM season. Hierarchical cluster analysis (HCA) was also applied to identify the source of groundwater pollution. In PRM season, groundwater samples closer to the active landfill site were physico-chemically different from upstream samples but more related to downstream samples. However, in POM season, groundwater samples closer to the active landfill site represented distinctly different physico-chemical characteristics from upstream and downstream samples as a result of high influx of leachate pollutants. In specific, the present study urges for proper pollution control measures along with landfill leachate treatment process to improve the surrounding water quality.