Devenir de l'atrazine dans le bassin de Marennes-Oléron (France) - Approche par la modélisation hydrodynamique, hydrosédimentaire et biogéochlmique
Atrazine is the most widely used herbicide on cultured areas. This pesticide is degraded during its transport in rivers and streams, to the coastal area. Marennes Oleron is the main french oyster farming area, receiving the fresh water from the Charente river and all the drainage coming from the coa...
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| Format: | Report |
| Language: | French |
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2001
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| Online Access: | https://archimer.ifremer.fr/doc/00306/41764/40977.pdf https://archimer.ifremer.fr/doc/00306/41764/ |
| Summary: | Atrazine is the most widely used herbicide on cultured areas. This pesticide is degraded during its transport in rivers and streams, to the coastal area. Marennes Oleron is the main french oyster farming area, receiving the fresh water from the Charente river and all the drainage coming from the coastal cultivated marshlands. Agriculture is thus claimed to be responsible for shellfish mortality in the aquaculture area. To simulate the changing fate of atrazine in the environment, a modelling strategy has been selected, a) First, using a two-way hydrodynamic model developped by IFREMER, the atrazine dilution trail in the Marennes Oleron area was simulated.Combined with larvae bioassays of Crassostrea gigas (Japanese oyster), the results show atrazine rates above 800 pg/l in the northern part of the area, inducing larval mortalities from 22 to 48%. a) A one way model perpendicular to the shore and incorporating far more processes than the preceding area was designed.Here, equations for sediment transport, diffusion and degradation in sediment were added to the advection model. Under simulations conditions, the model led us to the conclusion that atrazine transfer fluxs in the sediment (deposit and diffusion) are low in comparaison with advective fiuxs (in the order of 1/400th). The degradation represents 3% of the flux entering the sediment. These preliminary results could be improved by additions to the sediment part of the model and by including phenomena affecting water currents speed. L’atrazine est l’herbicide le plus épandu sur les terres agricoles. Ce produit phytosanitaire lors de son transport dans les cours d’eau est dégradé et véhiculé jusqu’à la zone côtière. Or, le bassin de Marennes- Oléron abrite, avec 100000 tonnes d’huîtres en stock, la production ostréicole française la plus importante. Il reçoit les eaux de la Charente et de la Seudre, ainsi que les effluents agricoles des marais littoraux charentais. L’agriculture est ainsi en parti tenue responsable à chaque accident dans la production des ... |
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