Enhanced Metal Levels in Vegetables and Farm Soil irrigated with Industrial Waste Water

Abstract

In water stressed Karachi city, waste water is often used for irrigating vegetables fields. Persistent use of waste water causes accumulation of heavy metals in agricultural soils and vegetables. Cd, Cr, Zn and Mn act as essential micronutrients but become toxic after crossing threshold values. To study the effect of waste water on heavy metal concentration in vegetables, soil and water an area irrigated separately with waste water and treated water were selected. Concentrations of Cd, Cr, Zn and Mn in beet, potato and radish were measured by atomic absorption spectrophotometer. The data obtained was tested at 95% (±2s) confidence level for six replicate measurements. The levels of Zn was found higher in both the treated water and vegetables beet, potato and radish irrigated with treated water but Mn was higher in industrial waste water and soil irrigated with industrial waste water and treated water. Soil irrigated with treated water contained (mg.L^-1) 0.007 of Cd; 0.128 Cr; 2.672 Mn and 0.714 Zn. Soil irrigated with waste water seems to accumulate significant concentration of metals. It showed (mg.L^-1) 5.85 of Cd; 84.5 Cr; 480.3 Mn and 305 Zn. Vegetables irrigated with industrial waste water have shown concurrent rise in metal levels. Mn was 0.860 mg.L^-1 in radish, Cr 0.320 mg.L-1 in beet and Cd 0.330 mg.L-1 in potato.