Trace metals in intertidal sediment of mangrove-sheltered creeks in Niger Delta, Nigeria: Variability before and after crude oil spillage

Abstract

Trace metals (Zn, Cu and Pb) fluxes were studied in five intertidal flats at Bodo Creek, Eastern Niger
Delta, Nigeria in 2006, and re- evaluated in 2010 following two major oil spills that occurred in the creek.
This study is the first to look at trace metal loads in the interstitial sediments of Bodo creek. Standard
methods were employed in the sampling campaign and analysis. The concentration of all metals under
study were higher than stipulated limit by WHO (2006) during post spill analysis. Concentration of Zn
did not vary between stations and months pre-spill but did in post-spill, having values slightly higher
than WHO (2006) stipulated limit. During the pre-spill sediment analysis, Pb concentrations ranged from
no detection to 0.0012 mg/kg in 2006, increasing to 0.169 mg/kg post spill in 2010. Cu content ranged
from 0.1312 - 0.1858 and 0.3374 - 0.4504 mg/kg pre- and post-spill, respectively. In addition to oil
induced metal loadings, the metals concentration dynamics show strong correlation with season.
Metals had higher concentrations during the dry season due to reduced water volume in the creek and
consequently less dilution. Implication for uptake, bioaccumulation and biotransformation by food
species in the creek catchment above biosafety limits for user population is stressed and measures to
avert public health consequences are advocated.