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Pose-Juan E.,Nutrition and Bromatology Group | Rial-Otero R.,Nutrition and Bromatology Group | Paradelo M.,Soil and Agricultural Science Group | Simal-Gandara J.,Nutrition and Bromatology Group | And 2 more authors.
Journal of Hazardous Materials | Year: 2010

The objective of this work is to asses the sorption of metalaxyl applied as a copper oxychloride (CO)-metalaxyl formulation, for a set of selected soils devoted to vineyards. The method involved batch incubation of soils suspended with a commercial copper oxychloride-metalaxyl-based fungicide in 0.01 M CaCl2. Afterwards, the metalaxyl concentration remaining in solution was determined by high-performance liquid chromatography (HPLC). The amount of dissolved metalaxyl in the fungicide suspension depends mainly on the soil pH, its potential acidity, and the cation exchange capacity. Of the approx. 20% metalaxyl retained by the solid colloids, the effect of organic matter colloids in soils (15-20 mg kg-1) had a poor contribution (six times lower) than the copper oxychloride colloids (40%, w/w) in the commercial fungicide formulation (100-130 mg kg-1). When comparing these retention data with the behaviour of metalaxyl used as a technical grade fungicide of about 100% purity (10-15 mg kg-1 in solids), it is clear that the commercial formulation increases a 30% retention of metalaxyl by soil (15-20 mg kg-1 in solids). The overall effect of the metalaxyl formulation plus soil show values of 10 times higher retention than technical grade-metalaxyl plus soil. Commercial formulation can decrease the mobility of soluble metalaxyl in agricultural soils with regard to the expected values obtained from batch studies using analytical grade-metalaxyl. Therefore, the effect of surfactants should be considered in the assessment of water contamination by the pesticides used in agriculture. © 2009 Elsevier B.V. All rights reserved.

Pateiro-Moure M.,Soil and Agricultural Science Group | Bermudez-Couso A.,Soil and Agricultural Science Group | Fernandez-Calvino D.,Soil and Agricultural Science Group | Arias-Estevez M.,Soil and Agricultural Science Group | And 2 more authors.
Journal of Chemical and Engineering Data | Year: 2010

The covering of quartz particles (Q) with Fe oxides provides high capacity sorption and immobilization of both paraquat (PQ) and diquat (DQ) as well as phosphates (P), that can be used to remediate contaminated environments due to their persistence. Both PQ and DQ have higher sorption strength on crystalline iron oxide coated quartz particles (QFec) than on amorphous iron oxides (QFea), but the highest is for PQ, which might be due to its strongest interaction. The increasing addition of P contributes to the increase of quat maximum sorption on iron oxide coated quartz particles, because the cosorption of P causes the surface charge to become more negative, facilitating the sorption of positively charged quats, but this happens in a different way for both quats. It was also seen that the formation of phosphate-quat complexes has a lower affinity than P by the coated quartz particles. The characteristics of the coated quartz particles would allow increased sorption of these quaternary ammonium herbicide contaminants. © 2010 American Chemical Society.

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