Bioaccumulation and Translocation Efficiency of Heavy Metals in Vegetables Grown on Long-Term Wastewater Irrigated Soil Near Bindal River, Dehradun

A field study was conducted to the accumulation and translocation efficiency (TE) of heavy metals in vegetables crops grown in the wastewater (WW) irrigated agricultural soil which may be phytotoxic in their high concentrations. The study revealed that WW, being used for irrigation for various vegetable crops near Bindal river, Dehradun, contained lower concentration of Pb (0.36 ± 0.06 mg/l), Cu (0.15 ± 0.01 mg/l), Zn (0.55 ± 0.02 mg/l), Ni (0.32 ± 0.01 mg/l), Cd (0.03 ± 0.00 mg/l), and Cr (1.37 ± 0.09 mg/l) while Hg was below the detection limit (BDL). In WW irrigated soil, the concentration of Pb (70.49 ± 10.54 mg/kg), Cu (54.48 ± 9.63 mg/kg), Zn (244.15 ± 7.19 mg/kg), Ni (27.77 ± 1.50 mg/kg), and Cr (129.52 ± 9.71 mg/kg) was observed to be below than the official Indian standards except that of Cd (17.47 ± 1.20 mg/kg). These concentrations of Pb, Cu, Zn, and Ni were lower than the values reported for tolerable levels except that of Cr (129.52 mg/kg). The enrichment factor calculated for WW irrigated soil was in the order Cr (7.09)[Zn (4.09)[Cu (2.64)[Cd (2.30)[Pb (1.89)[Ni (1.50). Among various corps grown in WW irrigated soil, the maximum concentration of the metals was found in the roots of Brassica juncea (Pb, 33.62 ± 2.41 mg/kg), Phaselous vulgaris (Cu, 31.76 ± 10.92 mg/kg), B. oleracea var. botrytis (Zn, 137.32 ± 9.11 mg/kg), Ni (296.03 ± 70.98 mg/kg); Cd (36.13 ± 5.26 mg/kg); and Cr (165.94 ± 11.70 mg/kg) in P. vulgaris root and Hg was BDL. The bioaccumulation factor (BAF) of metals in vegetables from soils was higher for Pb (0.436) in B. juncea, for Cu (0.213) in P. vulgaris, for Zn (0.195) in B. juncea, for Ni (14.043) and Cd (1.349) in B. oleracea var. botrytis and for Cr (0.822) in Raphanus sativus. The TE was maximum for Pb (67.39 %), Cu (68.76 %), Zn (63.35 %), Ni (70.51 %), Cd (65.99 %), and Cr (60.20 %) in R. sativus. The study concluded that the use of WW for irrigation of crop vegetables has increased the concentration of heavy metals (Pb, Cu, Zn, Ni, Cd, and Cr) in their different parts which may pose a potential threat to human health from this long-term practice of irrigation.