Comparative Investigation of Total, Recoverable and Bioavailable Fractions of Sediment Metals and Metalloids in the Lagos Harbour and Lagoon System

Awwal Bamanga,Nnamdi Henry Amaeze,Bader Al-Anzi

doi:10.3390/su11164339

Abstract

This study investigated and characterised concentration of some selected metals and metalloids (As, Cd, Cr, Cu, Co, Fe, Mn, Ni, Pb, Sn, V and Zn) present in surface sediments of the Lagos Harbour (LH) and associated Lagos Lagoon (LG) system using a combination of metal extraction and analytical methods within 26 sampling sites including a control (Apese Lagoon, APL). Sampling was carried out using a Van-veen grab sampler on three occasions (dry seasons 2013, 2014; wet season 2013). The total, recoverable and bioavailable fractions were measured separately by X-ray fluorescence (XRF), Aqua regia (AR) extraction with inductively coupled plasma optical emission spectrometry (ICP-OES) and 1 M hydrochloric acid (1 M HCl) extraction with inductively coupled plasma mass spectrometry (ICP-MS) analysis, respectively. Results were compared with National Oceanic and Atmospheric Administration (NOAA)/Canadian Sediment Quality Guidelines (CSQG) and geochemical spatial distribution maps. Threshold effect level (TEL) were exceeded by total concentration of Cu, Zn and recoverable As across the lagoons. Bioavailable As was below TEL while Ni was associated with the ports in the LH.

Highlights

Heavy metal pollution in sediments of marine ecosystems has gained the increased attention of many environmental researchers over the past few decades
In the Wet Season (WS), As concentrations were higher in the Lagos Harbour (LH) compared to LG and APLwhile the concentrations of Cu exceeded the Threshold effect level (TEL) in the three water bodies (LH, LG and Apese Lagoon (APL))
The results showed that the distributions of heavy metals are influenced by anthropogenic activities, with petroleum tank farm operations and cargo offload being the primary contributors of spills and discharges through which the metals enter the substratum in the LH

Summary

Introduction

Heavy metal pollution in sediments of marine ecosystems has gained the increased attention of many environmental researchers over the past few decades. It is generally known that marine ecosystems are endangered by various contaminants, mostly untreated sewage, waste oils, plastics and industrial effluents that affect the sustainability of living resources and pose global environmental as well as public health risk [5,6]. This can be related to the classical assumption that the marine environment has an infinite capacity to absorb these contaminants without being subjected to undue harm [7]. The continued introduction of wastes into the marine environment can result in a measurable rise in the local level of contamination and this is of growing global concern in view of the threats to coral reefs and marine biota

Methods

Results

Discussion

Conclusion