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.

Use of Several Pollution Indices for Metal Contamination Assessment in Aquatic Ecosystems, A Case Study, Ebrié Lagoon-Côte d’Ivoire

“…Pb concentrations observed at S1 and S5 were higher than the concentrations reported by Ref. [31] in sediments collected in urban bays that are considered to be highly polluted with several organic and metallic compounds [31,32]. The observed Pb contents were below the maximum value reported by Tuo et al [11], and the average value for the study area (64.57 mg/kg) was lower than the world average concentration of Pb (Tables 4 and 5).…”

“…Thus, regarding the obtained results for this study, sediments along ADFMF were free of mercury (Tables 4 and 5). Mn is an essential element due to its biological benefits for both human and marine organisms [32]. As for iron and cadmium contents, the highest concentration of Mn in surface sediments was recorded at S4, the closest to the Abobo-Doume Fish Market (Table 4).…”

Assessment of some key indicators of the physico-chemical and biological quality of an African freshwater lagoon (Aghien Lagoon, Ivory Coast)

“…This means less oxygen would be available for upper forms of aquatic life. The chemical oxygen demand (COD), unlike the BOD5 concerns the whole chemically oxidizable compounds in the analyzed samples [34] . COD values were naturally higher than those of BOD5 according to the fact that the COD takes into account both biodegradable organic compounds (estimated by BOD5) than those which did not.…”

Effet des saisons sur la variation du niveau de pollution organique des eaux de la lagune Ebrié en Côte d’Ivoire

“…Les activités anthropiques menées aux alentours de la lagune Ebrié et sur son plan d'eau entrainent une forte charge de matières oxydables à l'origine de l'eutrophisation qui a pour conséquence la mort de la faune aquatique (Yao et al, 2009 ;Inza et al, 2009 ;Tuo et al, 2015). La connaissance de la distribution spatiale de ces polluants organiques, en lien avec la variation des saisons, est une information capitale dans la prise de décision en vue de la préservation de ce plan d'eau.…”