Accumulation of Cobalt in Soils and Forages Irrigated with City Effluent

Abstract

Despite of its nutrient content, sewage water includes different contaminants responsible for the pollution of soil and plants. In this study,, an experiment was conducted at the University of Sargodha to evaluate the danger of the presence of cobalt in forages irrigated with city effluent. Moreover, the health risks associated with livestock feed on these contaminated forages were evaluated. Cobalt accumulation in different parts of plants was analysed by atomic absorption spectrophotometer (AA-6300 Shimadzu Japan). Some critical indices like pollution load index, bioconcentration factor and health risk index were also determined. The observed cobalt values in water samples used for irrigation were 0.164 mg/L in tap water and 0.191 mg/L in sewage water. The highest cobalt concentration was observed in the root of the winter forage Trifolium alexandrinum (1.560 mg/kg) irrigated with sewage water, while the minimum concentration was recorded in Sorghum bicolor, a summer forage irrigated with tap water (0.085 mg/kg). The maximum bioconcentration factor value for cobalt was 7.7 in the winter crop of T. resupinatum. The maximum pollution load index, daily intake and health risk index values for cobalt were 0.8910, 0.026 and 0.6104, respectively. All of these maximum values were determined for the samples irrigated with sewage water. In summary, the cobalt contents in soil and plant samples significantly increased when the samples were irrigated with sewage water as compared to tap water.