Ecological Risk Link to Trace Metals in Waters and Sediments along the Abobo-Doumé Fish Market in Ebrié Lagoon, Côte d’Ivoire

Abstract

In coastal waters, trace metals continues to be among global threats due to several harmful effects on living organisms. The present study was conducted along the Abobo-Doumé Fish Market (ADFM) to assess metal contamination due to the lack of data despite the influences of several socio-economic activities. Waters (both surface and bottom layers) and surface sediments samples were collected using respectively a Niskin bottle and a Van Venn Steel, at five stations in April 2006.Trace metals concentrations were determined using the ICP-MS Instrument after proper treatment of each sample. Then, the obtained concentrations were used to calculate several pollution indexes such as Contamination Index (CI), Contamination factor (CF), Pollution Load Index (PLI), Enrichment factor (EF) and Muller’s Index of Geo-accumulation (Igeo) to evaluate the contamination of the selected trace metals in waters and sediments. For water samples, apart from Iron that was not detected in any sample, trace metals were found in respective ranges (in µg/L) of ND-0.2 (As), 0.2-2.0 (Cd), 2.0-20.0 (Hg), ND-1.0 (Mn) and 1.0-390.0 (Pb). According the World Health Organization guidelines values, waters were safe for As, Cd, Fe, and Mn. For Hg, apart from waters closed to the ADFM that exhibited a value of 20.0 µg/L, higher than the reference value of 6.0 µg/L, waters were safe elsewhere. Waters were found contaminated with Pb, particularly in bottom layers, with levels nine to thirty times higher than the reference value of 10.0 µg/L. For sediments, the respective ranges (in mg/kg dry weight) were observed: 2.10-4-1668.48 (As), 2.10-4-7.50 (Cd), 1.95-4554.90 (Fe), 10-4-2.070 (Mn) and 0.001-253.50 (Pb). Highest concentrations of As, Cd and Pb were observed in sediments from several sampling stations, indicating a contamination status of these sediments as confirmed by the calculated pollution indexes. In conclusion, waters along the Abobo-Doumé Fish Market were contaminated in Pb, while sediments exhibited highest concentrations in As, Cd and Pb. This area of the Ebrié Lagoon need attention to the exceeded concentrations of toxic elements (As, Cd and Pb) observed. The present study has provided useful data for future environmental assessment along the Abobo-Doumé Fish Market.