Spent Engine oil (SEO) is a common environmental pollutant generated after engine services. Disposing SEO is a serious environmental issue in Nigeria as generators end up disposing it in water drain systems, rivers, open vacant plots and agricultural lands. Thus, the need to assess the impact of such disposal on environmental components becomes imperative. Using a completely randomized design, a control and seven treatments of SEO (T0: 0 ml, T1: 5 ml, T2: 10 ml, T3: 15 ml, T4: 20 ml, T5: 25 ml, T6: 50 ml, T7: 75 ml) were applied to potted soil for cowpea planting. Plant height, leave number, yield, heavy metal load and hazard quotient were assessed. Baseline heavy metal analysis showed the SEO contained lead and cadmium at 0.003 mg/kg and 0.462 mg/kg respectively. There was significant reduction in plant height (T0: 50.72 cm, T3: 37.36 cm, T7: 24.33 cm), number of leaves (T0: 25.91, T3: 21.57, T7: 17.67), seed weight (T0: 24.40 g, T3: 16.38 g, T7: 5.03 g) and plant weight (T0: 171.60 g, T3: 136.60 g, T7: 54.70 g) in contaminated soil with increasing SEO concentration (P<0.05). Cowpea grown on contaminated soil accumulated cadmium in seeds (T0: 0.000 mg/kg, T3: 0.057 mg/kg, T7 0.119 mg/kg) and in roots (T0: 0.000 mg/kg, T3: 0.079 mg/kg, T7: 0.263 mg/kg) with hazard quotient ranging from 0.084 to 0.216. This study revealed that increasing environmental pollution through indiscriminate SEO increases the possibility of health risk by elevating hazard quotient and this should therefore be discouraged.
Long-term irrigation with zinc smelter effluent affects important soil properties and heavy metal content in food crops and soil in Rajasthan, India
