Heavy metals levels in surface waters and sediments in an oilfield in the Niger Delta, Nigeria

Abstract

Heavy metal levels in the surface waters and sediments from five sampling stations of the Bukuma oilfield, in the Niger Delta, Nigeria were investigated using the AAS technique after standard procedures of storage and extraction. Mean range (mg/l) in the surface waters varied from Zn (0.19 0.64); Pb (ND 0.60); Cd (ND 0.07); Cu (ND - 0.20) to Ni (ND 0.5). Relatively high values (µg/g in dry wt.) were recorded in the sediment samples as follows: Zn (0.18-5.99); Pb (ND 0.68); Cd (ND -0.48); Cu (ND 0.83) to Ni (ND 0.63). The levels of the metals (except Pb) differed significantly (P<0.05) between sediment and the surface water. Regression analysis indicated that the sediment load of the metals contributed to the surface water metal loads. Generally elevated metal levels in both media were recorded at the stations with wellheads, implicating oil-related activities as the main source of contamination. All the metal levels except Zn exceeded the Federal Ministry of Environment (FMENV) limits for aquatic life water quality and other related standards. It is therefore suggested that the use of the inter-tidal mudflats of the area for aquaculture and the fermentation of cassava into fufu' for human consumption as done by the natives should be discouraged to avoid possible heavy metal poisoning.

Keywords: heavy metal, surface water, sediment, Bukuma oilfield, Niger Delta

Global Journal of Pure and Applied Sciences Vol. 12(1) 2006: 79-83