Le 28 mai 2018 (amphi ISTE), Lakmini P. Egodawatta, doctorante à l’université de Wollongong (Australie), nous propose un séminaire intitulé "Bioavailability of Arsenic and Antimony co-contamination to vegetable crops in agricultural soils".
résumé :
Antimony (Sb) is an emerging contaminant that is assumed to behave in a similar way to arsenic (As). Sb and As often co-occur because of mining. Although bioaccumulation and phytotoxicity of As has been well studied, little evidence is available on Sb and its interactive effects with As. Metalloid accumulation in agricultural soils may present health risks and hazards to humans and ecosystems through direct ingestion or contact with contaminant soil and food, a reduction in food quality (safety and marketability) via phytotoxicity and reduction in land usability for agricultural production. Plant bioassays allow inferences regarding the potential toxicity of contaminants. The phytotoxicity to plants in the contaminated soils is governed by the bioavailability of the contaminant, which in turn is influenced by soil physical and chemical characteristics, contaminant speciation and the species of plant. However, it is still unclear the impacts of ageing of agricultural lands have on the co-contamination of As and Sb on alternation of crops. The aim of our study was to evaluate the potential use of vegetable crops to identify and assess the bioavailability and toxicity of As and Sb in co-contaminated soils using bioassays. Water spinach and choy sum are herbaceous leafy vegetable belonging to the morning glory (Convolvulaceae) and mustard (Brassicaceae) families, respectively. Our study compares the soil characteristics in terms of total and bioavailable metal fractions with plant accumulation data. Plant toxicity parameters (tissue biomass and lengths) were used to evaluate impacts of contaminant exposure on plant productivity. This information was used to understand the degree of tolerance (Tolerance Index, TI) of plants grown in As and Sb contaminated soils. Moreover, this study investigates the risks associated with As and Sb co-contaminated soils. This was done as single element and mixed metal exposures. Sb contamination in agricultural soils, poses a greater human health risk and hazard, than As only and As and Sb co-contamination, as Sb accumulates in edible crops with no observed phytotoxicity or reduction in the vegetable productivity. However, in soils where Sb co-occur with As (the agricultural lands closer to mining areas), leafy vegetable crop decreases as a result of enhance toxicity in the plant. Therefore, Sb only contaminated agricultural soils pose a significant risk to human health.