Distribution of heavy metals and total petroleum hydrocarbons in soil and cassava (manihot esculenta) around Omoku, Rivers State, Nigeria

Abstract

Heavy metals and total petroleum hydrocarbon pollution is a worldwide phenomenon which results from both natural and anthropogenic activities. This has resulted in several health and physiological problems. This study investigated the level of heavy metal pollution and total petroleum hydrocarbon content in cassava (Manihot esculenta) and soil of Omoku (Obagi, Obrikom, Ebocha) and a control point in Rivers State. Cassava (Manihot esculenta) and soil samples from different locations were analysed for heavy metals and total petroleum hydrocarbon using atomic absorption spectrophotometer and GC-FID. The data obtained were further subjected to index models (contamination factor, PLI and bioaccumulation factor) of the heavy metals. The data acquired showed that the mean levels of heavy metals (Cr, Cd, Pb, Cu, Fe and Ni) in cassava samples determined ranged from 5.17±0.04 – 7.43±0.00 for Cr, 0.05±0.00– 1.41±0.00 for Cd, 1.70±0.00 – 3.62±0.00 for Pb, 5.86±0.00 – 8.54±0.02 for Cu, 66.032±0.13 – 87.49±0.07 for Fe and 1.723±0.05– 5.801±0.01 for Ni.In soil samples, it was 9.38±0.00– 9.63±0.05 for Cr, 2.61±0.01– 6.78±0.01 for Cd, 7.65±0.00 – 8.56±0.03 for Pb, 7.97±0.01– 8.74±0.02 for Cu, 67.17±0.00 – 87.51±0.08 for Fe and 7.48±0.07 – 8.72±0.05 for Ni. The mean levels of total petroleum hydrocarbon determined in cassava (Manihot esculenta) include 442.00±16.26, 320.67±0.88 and 255.33±6.39 mg/kg for Obagi, Obrikom and Ebocha respectively. In the soil, they include;1095.00±3.00, 895.67±0.88 and 647.33±6.67 mg/kg for Obagi, Obrikom and Ebocha respectively. The results were compared with the standard limits, and it was observed that some of the heavy metals were above the limit, and others were below it. The Pollution load index was also used to ascertain the levels of soil pollution by heavy metals, indicating that all the locations where sampling took place were unpolluted with heavy metals. The highest bioaccumulation factor of the heavy metal in cassava (Manihot esculenta) was Fe and the lowest was discovered to be Cd. It is therefore recommended that emissions from companies into the environment should be minimized.