Abstract:

The concentration of Cr, As, Fe, Ni and Cd in crude oil impacted soils and cassava plant part samples from Mmahu area in Niger Delta, Nigeria and the phytoremediation potentials of cassava were assessed. The samples were collected from three crude oil exploitation sites. In each of the exploitation site, five farmlands were sampled. Soil samples were collected at the beginning and end of each farmland using soil auger and bulked together to form 15 composite samples. Soil samples were air-dried and sieved to remove root debris. The cassava tubers were collected close to where the soil samples were collected from each sampled farmland. The cassava tuber was peeled and separated into tuber and peel. The plant samples were sundried and ground using ceramic mortar. The tuber and the peel from the two points were also bulked to get a total of 15 cassava tuber samples and 15 cassava peel sampled. All samples were analyzed using Atomic Absorption Spectroscopy (AAS). The results indicated that although, Cr, As, Fe and Ni were found present in the soil, they were below the FAO/WHO soil permissible limits, while Cd value was far above the limit. It was also found that As, Cr and Cd concentrations were higher in cassava peels and tubers in all the three sites sampled when compared to the soil samples. The results of Contamination Factor (CF) and degree of contamination (Cd) showed Cd to be the highest heavy metal element with the highest CF and Cd value followed by Fe which is of moderate contamination, while, Cr, As and Ni had low CF and Cd. The result of Pollution Load Index (PLI) of the cassava samples showed that the cassava peels and tubers in all three sites were polluted. The results of the bioaccumulation factors (BAF) of heavy metals in cassava peel and tuber indicated that cassava has high efficiency in bioaccumulation of these metals. The results obtained on Bio-translocation Factor (BTF) implied that cassava has in-situ phytoremediation potentials but there were variations in the elements translocated across the three sites. These variations might be attributed to the variation in cassava varieties across the three sites.