Seasonal Distribution, Bioavailability and Ecological Risk Assessment of Heavy Metals in Sediments from Gold Mining in the Northern Part of Côte d’Ivoire, West Africa

Abstract

This study aimed to evaluate the spatial and seasonal distribution, bioavailability and potential risk of metal in surface sediment from Korhogo and Tengrela gold mines in the Savanah District, one of the main mining areas of Côte d’Ivoire. Lead (Pb), cadmium (Cd), and mercury (Hg) concentrations in surface sediments collected were evaluated using inductive coupled plasma-optical emission spectrometer (ICP-OES). Bioavailability was evaluated according to the Community Bureau Reference (BCR) sequential extraction protocol and Risk assessment Code (RAC) was calculated to appreciate the potential risks. The results revealed that sediments from Korhogo and Tengrela were contaminated with Pb, Cd, and Hg. Except for Cd, seasonal variation indicated that metal concentrations decreased from dry season to rainy season. The extractable fractions showed that the largest metals were bound to the crystalline structure of the sediments with a quantitative percentage ranging from 56.1 to 85.9 %, indicating their low mobility. Regarding the potential mobility and availability of lead, cadmium, and mercury in sediments, the mean concentrations of the sum of the non-residual fractions varied from 1.087 to 20.917 µg.g-1, from 0.082 to 0.238 µg.g-1, and from 0.011 to 0.267 µg.g-1 for Pb, Cd and Hg, respectively Overall, the surface sediments are at a low to medium toxicity-risk level with RAC values lower than or equal to 15%, indicating that metals could not cause a threat to organisms in the sediments and to humans via consumption to crops irrigated with water around the Korhogo and Tengrela gold mine sites.