Adsorbimento-desorbimento di azimsulfuron su suolo

È stato condotto uno studio sull’adsorbimento e il desorbimento dell’AZS su cinque suoli italiani (Vercelli, Fornace, Chilivani, Bassona e Monghidoro) ben classificati e differenti nelle proprietà chimico-fisiche

Il cyhalofop-butile nel comparto suolo-acqua

In questo lavoro si riportano i risultati dell’adsorbimento e della degradazione chimica e fotochimica del cyhalofop-butile, (butil (R)-2-[4-(4-ciano-2- fluorofenossi) fenossi] propionato, CyB), in acqua in presenza di differenti colloidi naturalmente presenti nel suolo e nelle acque superficiali

Direct and indirect photolysis of cyhalofop in aqueous systems

The photodegradation of the aryloxyphenoxy propionic herbicide cyhalofop-butyl (2R)-2-[4-(4-cyano-2-fluorophenoxy)phenoxy]butylpropanoate (CyB), and of its primary metabolite (2R)-2-[4-(4-cyano-2-fluorophenoxy)phenoxy]propanoic acid (CyA) was studied in water at different irradiation wavelengths. The sunlight irradiation was investigated also in the presence of humic acid (HA), Fe oxide, titanium dioxide (TiO2) and zinc oxide (ZnO) as photocatalysts. CyB and CyA were rapidly degraded by UV irradiation. CyB afforded the butyl ester of 2-[3-(4-cyano-2-fluorophenyl)-4-hydroxy-phenoxy]propanoic acid (CyI), a metabolite arising from a photo-Fries rearrangement. Instead, CyA yielded (R)-2-4-(4-carboxyl-2-fluorophenoxy)phenoxypropanoic acid (CyD), a dicarboxylic acid arising from the photo-hydrolysis of cyano group via amide. CyB was stable in simulated sunlight also in the presence of the catalysts tested. The irradiation of a CyA solution, in the presence of HA or Fe oxide, with simulated sunlight did not produce any significant degradation. In the same experimental conditions, CyA was totally mineralized in the presence of TiO2 and ZnO

Soil sorption and leaching of active ingredients of Lumax^® under mineral or organic fertilization

The study describes the soil sorption of the herbicide Lumax®, composed of S-metolachlor (MTC), terbuthylazine (TBZ), and mesotrione (MST), as influenced by mineral and organic fertilizers. The investigation was performed on a sandy soil of an agricultural area designated as a Nitrate Vulnerable Zone, where mineral and organic fertilizers were applied for many years. Two organic fertilizers, cattle manure and slurry, respectively, and a mineral fertilizer with a nitrification inhibitor, Entec®, were compared. According to the experiments, performed with a batch method, the sorption conformed to Freundlich model. The extent of sorption of Lumax® ingredients was closely related to their octanol–water partition coefficient Kow. The respective desorption was hysteretic. Leaching trials were carried out by using water or solutions of DOM or Entec® as the eluants. Only the elution with the mineral fertilizer promoted the leaching of Lumax® active ingredients

Sorption of primisulfuron on soil, and inorganic and organic soil colloids

Inorganic and organic soil colloids are responsible for the sorption of many pesticides. We studied the sorption of the herbicide primisulfuron [methyl 2 N-[[[[[4,6-bis(difluoromethoxy)-2-pyrimidinyl]amino]carbonyl]amino]sulfonyl]benzoate] on Fe3+-, Al3+-, Ca2+- and Na+-exchanged montmorillonite, soil organic matter (H+- and Ca2+-saturated), amorphous iron oxide, and three soils in aqueous media. The sorption on soils was negatively correlated with pH. Ca2+- and Na+-exchanged montmorillonites are ineffective in the sorption of primisulfuron. The sorption on Fe3+- and Al3+-exchanged montmorillonite is rapid and follows the Freundlich equation. Fourier transform infrared (FT-IR) and X-ray powder diffraction studies of the Fe3+- and Al3+-montmorillonite samples after the interaction with primisulfuron in chloroform solution suggest that primisulfuron is adsorbed and degraded in the interlayer. Humic acid is more effective in the sorption than is Ca humate, suggesting that the pH of the suspension (3.5 for humic acid and 6.0 for Ca humate) has a strong influence on the sorption of primisulfuron. Experiments on amorphous iron oxide indicate similar pH dependence. Infrared spectra indicate that the protonation of the pyrimidine nitrogen moiety of herbicide and subsequent hydrogen bonding with the surface hydroxyls of Fe oxide is the mechanism acting in the primisulfuron sorption