THE POLLUTION OF AQUATIC ENVIRONMENT (ESPECIALLY ESTUARIES) BY HEAVY METALS
Analysis of the data using Pearson correlation matrix in the research showed significant correlation between the metals, Fe and Clay suggesting that Fe is the best chemical normalizer for other metals. Different metal assessment indices were applied in order to interpret the sediment’s quality of Qua Iboe River estuary and associated creeks. All the EF’s values of Cr, Fe and Hg were less than 1.5. However, the EF’s values for Cd, Cu, Pb, Zn, and Ni were greater than 1.5 signifying greater percentages from anthropogenic inputs. The sources of pollution were mainly high surface runoffs, domestic effluents from the coastal dwellers and possibly from the oil exploration in the area. The high Igeo values for Ni may be attributed to oil spill and the slow water movement along the creeks. With regards to an overall degree of contamination as proposed by Hakanson (1980) sediment quality equation, the sediments of Qua Iboe River estuary and associated creeks fall between 8 ≤ mCd < 16 indicating high degree of contamination.
1.1 Background of the Study
The pollution of aquatic environment (especially estuaries) by heavy metals has been a source of serious concern to government regulatory agencies, environmentalist and the public at large (Manahan, 1991). This is particularly important because estuaries are rich in nutrient and as a result mothers varieties of fishery resources. Heavy metals play important roles in our society as most of them are vital raw materials in most industries. As trace elements, some heavy metals (e.g. Cu, Se, and Zn etc.) are essential in the maintenance of some metabolic activities in human bodies. However, at certain concentrations they become toxic. They are natural components of the earth’s crust with large variations in concentration. They cannot be degraded nor destroyed due to their persistence in the environment. Their distribution in aquatic environment has been evidenced in human health effects and aquatic life disruptions due to long term exposure and bioaccumulation (Dahilia, Apodaca, Emerson, Tui, & Allyn, 2003). Marine sediments are the ultimate sinks of pollutants in the marine environment and it
constitutes an important medium for scientific research. Like soils in the terrestrial environment, marine sediments in the aquatic ecosystem are the sources of substrate nutrients and become the basis of support to living aquatic organisms (Abdullah, Sidi, & Aris, 2007). The enrichment of metal in a sink is shown mainly by an increase in their concentrations in the bottom sediment. Their occurrence in the environment results primarily from anthropogenic activities. Also, natural processes, such as weathering of rocks and volcanic activities play a significant role in the enrichment of heavy metals in water bodies (Forstner & Wittmann, 1981; Forstner & Wittmann, 1983; Nriagu, 1989).
Heavy metals accumulate in sediments through complex physical and chemical adsorption mechanisms depending on the nature of the sediment matrix and the properties of the adsorbed compounds (Maher & Aislabie, 1992; Leivouri, 1998; Ankley et al., 1992). Several processes enhance the association of heavy metals with solid phase such as direct adsorption by fine-grained inorganic particles of clays, adsorption of hydrous ferric and manganic oxides which may in turn be associated with clays, adsorption on natural organic substances, which may also be associated with inorganic particles and direct precipitation as new solid phases (Gibbs, 1973). The dissolution and adsorption processes are influenced by several physicochemical parameters such as: pH, dissolve
Evaluation of Status of Heavy Metals Pollution of Sediments in Qua-Iboe River Estuary and Associated Creeks, South-Eastern Nigeria.