Title: Assessment of environmental and health risks related to soils in the Moanda mining area (Gabon) : study of the quality of cultivated peanuts ( Arachis Hypogea L.)
Abstract:
The exploitation of Manganese in Moanda in the South-East of Gabon leads to the discharge of mining residues into the soil (Mokéa-Niaty, 2019) . The market gardening activities that are developing there expose the populations to the risks of the transfer of metal pollutants to the food chain (Nzengue, 2021) . This study evaluates the transfer of Mn and Pb from mining residues to the different organs of groundnut (Arachis Hypogea L.). Peanut seeds have been pregerminated in the laboratory. The seedlings were transferred to the greenhouse on 5 substrates, 4 of which were enriched with mining residues. Groundnut plant morphometric parameters were estimated every two weeks for four months. Mn and Pb concentrations were determined by ICPAES in peanut substrates and organs. Of the 4 substrates enriched in mining residues, 3 induced visual symptoms of toxicity and a reduction in morphometric parameters compared to the control. The Mn and Pb concentrations in the substrates vary, respectively, from 124590 mg.kg-1 to 539496.67 mg.kg-1 and from 1756 mg.kg-1 to 7518.33 mg.kg-1. In peanut shells, they vary respectively from 63.5 mg.kg-1 to 2713.03 mg.kg-1 and from 0.66 mg.kg-1 to 1.83 mg.kg1. And finally, in the seeds, they vary respectively from 38.97 mg.kg-1 to 299.76 mg.kg-1 and from 0.02 mg.kg-1 to 0.51 mg.kg-1. The hulls seem to play a role of protective barrier which would limit the concentrations of pollutants in the seeds and therefore human exposure. Nevertheless, the concentrations of pollutants measured in groundnuts remain higher than in the case of plants grown on unpolluted reference soils. Precautions should therefore be considered in the Moanda area to limit population exposure. The management of peanut crop residues could also promote soil decontamination.
