Sorption of penconazole applied as a commercial water–oil emulsion in soils devoted to vineyards

Abstract

The objective of this work was to assess the effect of surfactants and oils of a commercial formulation on the potential mobility of penconazole in agricultural soils that have been subjected to a high rate of application of agricultural chemicals. Soil–water partition tests on a commercial water–oil emulsion formulation of penconazole (WOEP) in 0.01 M CaCl 2 containing 35 mg L −1 penconazole, incubated for 24 h, showed a maximum retention of approximately 250–300 mg penconazole kg −1 soil. Approximately 70% of the total penconazole retained by the solid phase was sorbed on the soil (175–200 mg kg −1). The other 30% was retained by the adjuvants present in the commercial formulation. The formulation also influenced the water–soil partition, increasing the sorption in tests on batch studies using technical-grade penconazole (TGP). Soils with high total copper and organic matter had the greatest affinity for penconazole when added as WOEP. Additionally, adsorption of penconazole followed an S-type isotherm, whose behavior was consistent with the ability of the technical-grade penconazole to form aggregates. In the case of the WOEP, the S-type behavior could be attributed to the surfactant present in the formulation, which could be adsorbed onto soil as hemimicelles, which in turn may facilitate adsorption of penconazole.