Rôle des étangs de barrage à vocation piscicole dans la dynamique des micropolluants en têtes de bassins versants

Abstract : In the Lorraine Region, about 7,000 ha of ponds are exploited for fish production. The present work was dedicated to the understanding of micropollutants transfer mechanisms in freshwater fishponds focusing on three issues: (1) evaluate the extent of fishpond (n=45) exposure to trace metals (2) evaluate the influence of fishponds (n=3) on concentrations, potential toxicity and mass flows of pesticides; (3) evaluate the relative importance of transfer pathways of PCBs to fish. (1) The enrichments measured were generally low to moderate with the exception of the sites located in the Vôge and two sites located in the Woëvre. Enrichment was particularly high for Cd and seemed related to the loss of ignition. No relationship between enrichment and land use could however be observed. (2) High pesticide concentrations were generally reduced by more than 90% between upstream and downstream location. The risk of toxicity, evaluated under the toxic unit approach was attenuated downstream of the ponds. When considering the flow of pesticides, the results suggest that, depending on the substances in question, 10 to 100% of the loads of pesticides are retained in fishponds. (3) The oral transfer of polychlorinated biphenyls (PCBs 138, 153, and 180) from a contaminated sediment to a benthic fish (carp) was studied by the in vivo relative bioavailability method. The results show that the contaminated sediment has no effect on the oral bioavailability of the three PCB congeners in common carp. The geosorbing effect of sediment, which explains its role as an environmental reservoir of PCBs, seems insufficient under the conditions of the digestive tract of the common carp, to prevent transfer to fish
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Juliette Gaillard. Rôle des étangs de barrage à vocation piscicole dans la dynamique des micropolluants en têtes de bassins versants. Sciences agricoles. Université de Lorraine, 2014. Français. ⟨NNT : 2014LORR0333⟩. ⟨tel-01751570⟩

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