Impact of wastewater irrigation on groundwater in the Lahore region and contamination source identification

Abstract

Organic pollutants in groundwater samples were analyzed for the very densely populated ‘Lahore’ city and its surrounding ‘Mangamandi’ areas of Punjab-Pakistan, where composite (industrial and urban) wastewater is used for cultivation of crops and vegetables. The samples were pre-concentrated using the Solid Phase Extraction (SPE) technique and analyzed by using High Pressure Liquid Chromatography (HPLC) and a Gas Chromatograph Mass Spectrometer (GC-MS). Organic contaminants like Dichlorodiphenyltrichloroethane (DDT), Dichlorodiphenyldichloroethylene (DDE), Dichlorophenol (DCP), Trichlorophenol (TCP), endrin, and dieldrin were found in certain samples above the permissible limits. Stable isotopes like 13C, 15N and 18O were analyzed to assess the source of shallow groundwater channel contamination. Chemical and isotopic data reveal that contamination of shallow groundwater channels in the area is mainly due to wastewater irrigation and, to some extent, by seepage through unlined wastewater drains in nearby areas. The wastewater containing organic pollutants, used for cultivation, filters through the soil to contaminate the shallow groundwater channels.