Heavy Metals Accumulation in Soil and Amaranthus Cruentus L Irrigated with Dye Effluent Polluted Stream Water in Abeokuta, Southwest Nigeria

This study evaluated the quality of Amaranthus cruentus irrigated with dye effluent polluted stream and water from a deep hand-dug surface well (well-water). It also assessed the levels of heavy metals including Manganese, Iron, Copper, Zinc and Chromium in soil and amaranths irrigated with the waters in two dry seasons. The results showed that the pH (9.67) and NO3- (226.76 mg L-1) contents of the dye effluent polluted stream were above maximum limits recommended for irrigation. Manganese, Fe, Cu, Zn and Cr in dye effluent polluted stream water were 0.013, 0.454, 0.041, 0.172 and 0.018 mg L-1, respectively. Soil chemical properties increased significantly with dye effluent polluted stream water over well-water irrigation. Significant amount of metals accumulated in edible shoot of amaranths grown with dye polluted water compared with well-water. In 2010, shoot bioaccumulation of Mn, Fe, Cu, Zn and Cr were 122.47, 426.57, 10.60, 85.90 and 0.002 mg kg-1. Bioaccumulations of the metals were 342.25,518.22, 15.32, 344.31 and 0.003 mg kg-1, respectively in 2011. Iron and Zn values in the vegetable were higher than FAO/WHO/FEPA permissible limits of 500 mg kg-1 Fe and 60-100 mg kg-1 Zn but Mn, Cu and Cr were within allowable limits. Irrigation with dye polluted stream water should be discouraged in this area to prevent build up of toxic metals in food chain.