Assessment of Metal Pollution of Soil and Diagnostic Species Associated with Oil Spills in the Niger Delta, Nigeria

Abstract

An ecological impact assessment of crude-oil spills was carried out on the environment of an oil-rich community in the Niger Delta of Nigeria. Samples of the topsoil (0−15 cm), subsoil (15−25 cm) and the dominant species Gamba grass (Andropogon gayanus) were collected using the transect method from the point of spills. The samples were also collected from an unimpacted location (control). The samples were wet-digested and the concentrations of Pb, Cd, Cu, and Zn were determined by flame atomic absorption spectrophotometry, while the physico-chemical properties of the topsoil were determined by standard methods. The data were subjected to Student t test, ANOVA and Pearson correlation analysis, and the models for pollution assessment were employed to assess the pollution status of the soil and plant species. The results showed that concentrations of Pb, Cu and Zn in the topsoil exceeded international standards at close proximity to point of spills (0−200 m), while Cd concentrations exceeded the international standard at all the locations. Only Cd exceeded the international standard in the subsoil. Contamination (P_i) and integrated pollution (P_c) indices of the topsoil showed reducing trends from the point of pollution, and locations at 0 m and 100 m exhibited high P_c, while those at 200 m showed moderate P_c by all metals. The levels of Pb and Cd in the diagnostic species exceeded the World Health Organization limits and the pollution load index (PLI) portrayed severe contamination. In conclusion, the impact of crude-oil spills in the area was significant; soil remediation is important to avert ecological and human health disasters. Moreover, these findings will be useful for designing strategic measures for environmental control in the area.

DOI: http://dx.doi.org/10.5755/j01.erem.71.3.12474