Characterizing spatial distribution of chemical properties and heavy metal contamination in ground-water using GIS

Abstract

Heavy metal contamination poses a significant threat to peri-urban environments, exacerbated by the use of raw sewage and industrial runoff for irrigation. A survey in Lyallpur Town, Faisalabad, utilized ArcGIS 9.1 to assess ground, canal, and wastewater quality. Sixty sites were sampled, with data analyzed for chemical parameters (EC, SAR, RSC) and heavy metal concentrations (Ni, Pb, Cd), highlighting spatial variations in contamination levels.The concentration of Ni, Pb, and Cd were measured using an atomic absorption spectrophotometer. Almost all collected samples were found to be unfit for irrigation due to their high EC, SAR and RSC. Wastewater was highly unfit because of higher values of EC (5.45 dS m^-1), SAR (7.86 mmolc L^-1)^1/2 and RSC (18.95 mmolc L^-1) than permissible limits. In contrast to groundwater and wastewater, canal water was chemically fit for irrigation due to lesser EC (0.72 dS m-1), SAR (2.98 mmol L-1)1/2, and RSC (1.40 mmol L^-1) values. The Cd concentrations (0.04 mg L^-1, 0.03 mg L^-1, and 0.11 mg L^-1) in ground, canal and wastewater, correspondingly, were above the acceptable limit of 0.01 mg L^-1, while Ni and Pb concentrations in all water sources (ground, canal, and waste) found near the permissible limit 0.20 mg L^-1 and 5 mg L^-1, respectively. The irrigation by wastewater results in the increase of heavy metals in the soils, eventually contaminating the groundwater quality. However, it is strongly recommended that wastewater be detoxified and mixed with fresh water before being utilized for the production of crops.