Adsorption of a triazole antifungal agent, difenoconazole, on soils from a cereal farm: Protective effect of hemp felt

Difenoconazole is a triazole fungicide widely used in agriculture for the protection of various crops. The present study evaluated by batch technique, the high capacity of two soils to adsorb difenoconazole. The Freundlich and Henry models fitted the adsorption data well, suggesting a multi-layer adsorption of difenoconazole. Groundwater ubiquity score (GUS) were between 1.8 and 2.8, indicating that difenoconazole had a moderate risk of contaminating groundwater resources. Adsorption in percolation and leaching experiments were also tested in the laboratory with a soil column. We performed tests on soils alone, on soils covered by hemp felt (raw or chemically modified by the grafting of cyclodextrin molecules) as an adsorbent material for limiting the dissipation of this molecule in the soil, and at the same time on felts alone. Soil alone adsorbed up to 99% of the percolating difenoconazole, whereas the use of modified hemp felt made it possible to limit soil storage to 26%, probably due to the formation of an inclusion complex with cyclodextrins. The trapping of difenoconazole molecules by the felt was not irreversible, as leaching with a CaCl2 solution resulted in the release of 60% of the amount initially fixed on raw hemp. However, only 22% of the amount fixed on modified hemp was released, due to potentially stronger interactions with this material (host/guest type interactions between difenoconazole and cyclodextrin). In conclusion, this study showed that the use of innovative hemp-based materials could permit to limit the accumulation of fungicides in soils. (C) 2021 Elsevier B.V. All rights reserved.