Geochemical contamination in the Densu Estuary, Gulf of Guinea, Ghana
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RESEARCH ARTICLE
Geochemical contamination in the Densu Estuary, Gulf of Guinea, Ghana Lailah Gifty Akita 1
&
Jürgen Laudien 3 & Elvis Nyarko 1,2
Received: 4 February 2020 / Accepted: 6 July 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract Chemical contaminants are released from mining, domestic and industrial effluents into an aquatic environment. Sediments (n = 10) were collected with an Eckman grab at ten stations in the Densu Estuary for ecological risk assessment. The spatial distribution of organic characteristics and ecological risk of metals—zinc, lead, copper, mercury, iron, and manganese in sediment—were analyzed using standard methods. The organic parameters occurred in the ranges, as follows: % C, 0.76 to 2.05, % TN, 0.06 to 0.015; % TP, 0.44 to 1.38; and C/N, 12.31 to 34.81. The ranges of metal concentrations (mg/kg) were as follows: Fe, 201.10 to 720.90; Mn, 40.10 to 152.70; Zn, 7.3 to 158.3; Pb, 1.9 to 84.7; Cu 3.4 to 23.0; and Hg, 0.01 to 0.05. The mean concentration of metals in the sediment were Fe > Mn > Pb > Zn > Cu > Hg. The highest mean concentration of Fe suggested redox conditions in the Densu Estuary. There is a low contamination factor (CF) for five metals (Zn, Hg, Fe, Cu, and Mn) (CF < 1) to high contamination of Pb (3 < CF ≤ 6). The average Pb concentration was above local and geological backgrounds, suggesting an anthropogenic source of pollution from industrial and domestic effluents and agrochemicals. The sediment was extremely enriched by Pb (EF > 50) with a positive index of geoaccumulation (0 < Igeo ≤ 2) than other metals. There is considerable to a very high degree of contamination (DC) (3 ≤ DC ≥ 6) of metals in the sediment of Densu Estuary. The potential ecological risk index (≤ 40 PERI < 80) suggested a very low to moderate ecological risk of metal pollution. The study provides baseline knowledge on geochemical contamination in tropical estuarine systems for the development of effective chemical control strategies towards sustainable management of coastal waters. Keywords Metal pollution . Potential ecological risk index . Densu Estuary . Gulf of Guinea
Introduction Uncontrolled population growth, rapid urban development, and rapid industrialization along the coastal areas in Ghana have led to coastal pollution because of anthropogenic inputs such as sewage effluents, municipal waste discharges, and runoff from agricultural and mining activities into the aquatic environment (Armah et al. 1997; Fianko et al. 2007; Monney Editorial Responsibility: Vedula VSS Sarma * Lailah Gifty Akita [email protected] 1
Department of Marine and Fisheries Sciences, University of Ghana, P. O. Box LG 99, Legon, Accra, Ghana
2
Regional Maritime University, P. O. Box GP 1115, Accra, Ghana
3
Alfred Wegner Institute Helmholtz Centre of Polar and Marine Research, Am Alten Hafen 26, 27568 Bremerhaven, Germany
et al. 2013; Mahu et al. 2015). Estuaries act as major carriers and sources of materials including sediment, metals, and organic pollutants and as areas of
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