Source Evaluation and Trace Metal Contamination in Benthic Sediments from Equatorial Ecosystems Using Multivariate Statistical Techniques.

Nsikak U Benson,Akan B Williams,Joseph P Essien,Otobong Akpabio,Cyril I Ekong,Francis E Asuquo,Abaas A Olajire,Manuel Reigosa

doi:10.1371/journal.pone.0156485

Abstract

Trace metals (Cd, Cr, Cu, Ni and Pb) concentrations in benthic sediments were analyzed through multi-step fractionation scheme to assess the levels and sources of contamination in estuarine, riverine and freshwater ecosystems in Niger Delta (Nigeria). The degree of contamination was assessed using the individual contamination factors (ICF) and global contamination factor (GCF). Multivariate statistical approaches including principal component analysis (PCA), cluster analysis and correlation test were employed to evaluate the interrelationships and associated sources of contamination. The spatial distribution of metal concentrations followed the pattern Pb>Cu>Cr>Cd>Ni. Ecological risk index by ICF showed significant potential mobility and bioavailability for Cu, Cu and Ni. The ICF contamination trend in the benthic sediments at all studied sites was Cu>Cr>Ni>Cd>Pb. The principal component and agglomerative clustering analyses indicate that trace metals contamination in the ecosystems was influenced by multiple pollution sources.

Highlights

The rapid industrial and socioeconomic development of the Niger Delta of Nigeria has resulted in increasing heavy metal pollution of coastal aquatic ecosystems located in the region [1,2,3,4]
The aquatic ecosystems considered in this study are Douglas Creek (DOU) (4.55°S, 8.00°N), Okorotip Creek (OKT) (4.56°S, 7.93°N), Stubbs Creek (STB) (4.60°S, 7.99°N), Qua Iboe Estuary (QUE) (4.53°S, 7.99°N) and Qua Iboe River (QUR) (4.58°S, 7.93°N)
The total organic carbon (TOC) values ranged from 5.55–10.77, 5.91–11.33, 6.82–11.23, 4.99–6.44, and 5.23 to 14.56% with mean values of 7.05±2.0, 8.46±2.11, 9.45±1.48, 5.24±0.71 and 9.34±3.59% at DOU, OKT, STB, QUE and QUR sites, respectively

Summary

Introduction

The rapid industrial and socioeconomic development of the Niger Delta of Nigeria has resulted in increasing heavy metal pollution of coastal aquatic ecosystems (tidal estuaries and creeks, rivers, mixohaline lagoons and mangrove swamps) located in the region [1,2,3,4]. Most of the equatorial water systems in the Niger Delta serve as primary recipients of petroleum exploration-exploitation wastes, onshore and offshore industrial sewage, chemical contaminants, domestic and office wastes generated by multinational oil companies that are found in the region. These aquatic ecosystems have witnessed the uncontrolled use of banned chemicals by local fishermen for fishing purposes. PLOS ONE | DOI:10.1371/journal.pone.0156485 June 3, 2016

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Conclusion