Contaminant transport from solid waste dumps: Implications for environmental degradation with a focus on capital...

Open dumping of Municipal solid waste is the main method of solid waste management in Pakistan. To investigate the impacts of leachate transportation from these waste dumps on groundwater quality, two sites were selected (I-12 in Islamabad and Lohsar in Rawalpindi), water samples were collected from existing wells during summer, winter, and rainy seasons and were analyzed for physiochemical parameters using standard methods. Most groundwater samples showed contamination and values of various parameters exceeded the desired limits set by the World Health Organization (WHO) and the National Standard for Drinking Water Quality (NSDWQ), especially during the rainy season, whereas the least contamination in groundwater samples was observed during the winter season. The results obtained were, pH: 5.75-7.87, Electrical Conductivity (EC): 103-3460 μS cm^-1, Total Dissolved Solids (TDS): 436-4425 mg L^-1, Total Alkalinity (TA): 190-1330 mg L^-1, Total Hardness (TH): 128-676 mg L^-1, Chlorides (Cl⁻): 56.7-893.3 mg L^-1, Nitrates (NO₃⁻): 7.8-19.9 mg L^-1, Dissolved Oxygen (DO): 6.1-20.8 mg L^-1, Biological Oxygen Demand (BOD): 1.0-44.0 mg L^-1 and Chemical Oxygen Demand (COD): 56-272 mg L^-1. The findings suggest that the magnitude of groundwater contamination from leachate transportation is intricately influenced by factors such as leachate composition, seasonal variations and distance from the dumpsite. The contamination level reduced along the distance from the dumps. Except Copper (Cu) and Zinc (Zn), the concentration of all other heavy metals including, Iron (Fe), Chromium (Cr), Nickel (Ni), Lead (Pb), Cadmium (Cd) was found above standard appreciable limits. The t-test showed a significant difference in parameter concentrations for all seasons except for Cd and Zn. The calculation of water quality index through CCME (Canadian Council of Ministers of Environment) model revealed that all the groundwater samples around both the dump sites were of poor and marginal quality. In general, the groundwater quality of both study areas is not suitable for the drinking purpose. The study suggests regular testing and treating groundwater before use, use of engineered landfills, covering landfills with clay and vegetation and use of alternative strategies like composting and recycling for waste management.