Abstract
Aquatic ecosystems are increasingly affected by human activities, notably urban sewage and industrial effluent discharges, particularly in rivers. This study assesses heavy metals contamination of sediments of the Mgoua River in Douala, Cameroon. The Geoaccumulation Index (Igeo), the Contamination Factor (FC), the Sediment Pollution Index (SPI), the Enrichment Factor (EF) and the Pollution Load Index (PLI) were used to assess the contamination risk. The mean concentration of Ti, V, Cr, Co, Ni, Cu, As, Cd, Zn, Pb, U, Rb, Sr, Y, Zr, Mo, Mn, Fe, Cs and Ba in sediments was 12601.08, 111.96, 151.93, 9.47, 65.43, 161.81, 7.55, 2.27, 419.30, 248.30, 49.30, 12.65, 89.50, 39.69, 3017.52, 5.95, 313.26, 39667.32, 0.97 and 243.19 µg/l, respectively. Heavy metals concentrations in sediments creased in the following order: U < Cs < Cd < Mo < As < Co < Rb < Y < Ni < Sr < V < Cr < Cu < Ba < Pb < Mn < Zn < Ti < Fe. The Igeo, CF and EF indicate a polymetallic contamination dominated by Cu, Cd and Pb being the most important in all studied sites. The value of SPI varied between 10.95 and 37.84, suggesting that the sediments are moderately to highly polluted, with PLI higher than 1. These indices reveal that the sediments of Mgoua river catchment were polluted with most of the heavy metals. The high concentrations of some of the metals were due to anthropogenic sources particularly the discharge of untreated industrial wastes in to watercourses. This study can therefore be used as a reference to monitor the quality of sediments of the Mgoua river.
Highlights
The significant spike in the number of industries and the high population growth rates recorded in the past decades, in cities, have resulted to serious environmental problems in many industrial regions in the world, notably in developing countries [1]
Many contaminants such as hazardous and toxic metals are accumulated in sediments, which could be extremely harmful to the aquatic environments [3]
The main objective of this work is to assess the level of Trace metals (Ti), Vanadium (V), Chromium (Cr), Cobalt (Co), Nickel (Ni), Copper (Cu), Arsenic (As), Cadmium (Cd), Zinc (Zn), Lead (Pb), Uranium (U), Rubidium (Rb), Strontium (Sr), Yttium (Y), Ziconium (Zr), Molybdenum (Mo), Manganese (Mn), Iron (Fe), Cesium (Cs) and Barium (Ba), as well as the degree of metallic pollution in sediments based on the calculation of indices: Igeo, Enrichment Factor (EF), FC, Sediment Pollution Index (SPI) and Pollution load index (PLI)
Summary
The significant spike in the number of industries and the high population growth rates recorded in the past decades, in cities, have resulted to serious environmental problems in many industrial regions in the world, notably in developing countries [1]. Anthropogenic activities (industrial activities, domestic waste, urbanization and land development...), contribute to polluting rivers with heavy metals, the identification and qualification of the latter in sediments is very important. Sediments are complementary and are vital parts of aquatic environments acting as carriers and potential sink for various pollutants. Many contaminants such as hazardous and toxic metals are accumulated in sediments, which could be extremely harmful to the aquatic environments [3]. Assessing the presence of heavy metals in sediments can be used to understand the potential anthropogenic and industrial risks of direct waste discharges in ecosystems. Heavy metals pollution is a major problem in several developing countries including Cameroon. Pollution in larger rivers has been relatively studied, the geochemistry and the characterization of the sediments of some small catchment areas like that of Mgoua in the Littoral region, which receives considerable quantities of waste from industries and residences has received very few studies [4]
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