A Novel Method to Investigate Environmental Risk in Wastewater Toxicity

This is a pioneering study on the main drainage system in Gujranwala District, where untreated mixed wastewater is discharged and subsequently used for vegetable irrigation, leading to potential health and environmental risks. This study seeks to develop the spatial pattern of toxic metal accumulation in soil across an 11 km stretch of land used for vegetable cultivation. By using 90 samples of mixed wastewater and sludge, as well as 10 quadruplicate samples of rhizospheric soils and crops from ten vegetable fields, it was observed that the concentrations of Cr, Cu, Cd, Zn, Fe, Pb, Mg, and Ni in cauliflower (Brassica oleracea var. botrytis L.), coriander (Coriandrum sativum L.), radish (Raphanus sativus L.), mustard (Brassica juncea L.), spinach (Spinacia oleracea L.), meadow clover (Trifolium sp. L.), sorghum (Sorghum bicolour L.), garlic (Allium sativum L.), brinjal (Solanum melongena L.), and mint (Mentha L.) were beyond the permissible limits set by the FAO/WHO, 2001. The declining trend of the toxic metal concentrations in the effluent was Mg > Cr > Ni > Zn > Pb > Cd > Cu > Fe, and in sludge, soil, and plants, it varied in the order of Mg > Fe > Cr > Ni > Zn > Pb > Cd > Cu. Radish, mint, and brinjal had the highest quantities of toxic metals. The spatial pattern of toxic metals was determined by using proximity interpolation, Inverse Distance Weighted (IDW), the fine tuning of the interpolation characteristics, and the kriging of selected sample variograms. Toxic metals were found in the following order: plants > soil > sludge > effluents. The most prevalent cause of metal pollution was soil irrigation with polluted water. This study provides crucial information about the extent of contamination, which could help in the identification of public health risk, the assessment of environmental impacts, and also sustainable water management.