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Sorption and degradation of azimsulfuron on iron(Ill)-rich soil colloids
No full textThe sorption of N-[[(4,6-dimethoxypyrimidin-2-yl)amino]carbonyl]-1-methyl-4-(2-methyl-2H-tetrazole5-yl)1H-pyrazole-5-sulfonamide (AZS) on an iron oxide, iron(Ill)-humate, and an Fe3+-saturated clay was studied using a batch equilibrium method. Generally, 20 mg of each colloid was equilibrated with 20 mL of AZS solution (1.5-12.7 muM). The sorption on iron-montmorillonite and iron oxide was rapid, and the equilibrium was attained within 1.5 and 5 h, respectively. In the case of Fe-saturated humic acid the equilibrium time was 20 h. After equilibration, the phases were centrifuged (19000g, 15 min) and the supernatant was sampled and analyzed by HPLC. The values of Freundlich constants indicate that iron oxide (K-ads = 199.5) shows the highest sorptive capacity toward AZS, followed by iron(III)-clay (K-ads = 146.6) and iron(III)-humate (K-ads = 108.2). With elapsing time, AZS degradation was observed in all colloidal suspensions. Iron-humate (t(1/2) = 136 h) is most effective in promoting AZS degradation, followed by iron oxide (t(1/2) = 204 h) and iron-clay (t(1/2) = 385 h). The metabolites 2-amino-4,6-dimethoxypyrimidine and 1-methyl-4-(2-methyl-2H-tetrazole-5-yl)-1H-pyrazole-5-sulfonamide, arising from a hydrolytic cleavage of the sulfonylurea bridge, were the only byproducts observed. A Fourier transform infrared study suggests that the sorption of AZS on iron-clay involves the protonation of one of the two basic pyrimidine nitrogens induced by the acidic water surrounding the saturating Fe3+ ions. Instead, the formation of a six-membered chelated complex favors the sorption of AZS on iron oxide
Direct and indirect photolysis of cyhalofop in aqueous systems
No full textThe 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
Hydrolysis and adsorption of cyhalofop-butyl and cyhalofop-acid on soil colloids
No full textA study was undertaken to investigate the stability of cyhalofop-butyl (2R)-2-[4-(4-cyano-2-fluorophenoxy)phenoxy]butylpropanoate (CyB), an aryloxyphenoxy-propionic herbicide, at different pH values. The hydrolysis of CyB was faster in nonsterile than in sterile water. In sterile medium, CyB degraded only to (2R)-2-[4-(4-cyano-2-fluorophenoxy)phenoxy]propanoic acid (CyA), whereas in nonsterile water, also the metabolites (2R)-2-[4-(4-carbamoyl-2-fluorophenoxy)phenoxy]propanoic acid (CyAA) and (2R)-2-[4-(4carboxyl-2-fluorophenoxy)phenoxy]propanoic acid (CyD) were detected. The adsorption of CyB onto clays, iron oxide, and dissolved organic matter (DOM), using a batch equilibrium method, was also studied. A lipophilic bond is responsible for CyB adsorption on DOM. CyB was adsorbed on Fe-III- and Ca-clays through hydrogen bonding between the carbonyl oxygen and water surrounding the exchangeable cations. In the interlayer of K-clay, CyB was hydrolyzed to CyA, which remained adsorbed therein as a monomer. The acid CyA was adsorbed only by the Fe-oxide through complexation. The CyA-Fe-oxide complex was stable and did not undergo degradation
Fenhexamid Adsorption Behavior on Soil Amended with Wine Lees
No full textThe adsorption of fenhexamid (FEN) [N-(2,3-dichloro-4-hydroxyphenyl)-1-methylcyclohexanecarboxamide] on vineyard soil amended with wine lees (WL) produced by vinery was studied. The adsorption extent depends on WL fraction. The addition of the centrifuged solid lees (SWL) increases the FEN adsorption on soil. Most likely, the organic insoluble fraction formed mainly by dead fermentation yeasts is responsible for the observed increase. The adsorption measured on some deactivated yeasts of wine fermentation shows that Saccharomyces cerevisiae are the most active in FEN retention. On the other hand, the soil amendment with whole WL decreases considerably the fungicide adsorption. This opposite effect may be the result of FEN hydrophobic bonds with the dissolved organic matter of lees that keeps fungicide in solution. This hypothesis is substantiated by the increased FEN solubility in the supernatant of centrifuged wine lees (LWL). The results of soil column mobility confirm that the elution with LWL increases the mobility of FEN in soil
Effect of undesalted dissolved organic matter from composts on persistence, adsorption, and mobility of cyhalofop herbicide in solis
No full textThe effect of undesalted dissolved organic matter (DOM) extracted from composts on the degradation, adsorption, and mobility of cyhalofop herbicide in soils was studied. A paddy-field sediment poor in organic matter (OM), an OM-rich forest soil, and DOM from agroindustrial or municipal waste compost were used. DOM increased the cyhalofop-acid but not the cyhalofop-butyl solubility in water. The degradation of cyhalofop-butyl in the sediment was slow, giving cyhalofop-acid as the only metabolite, whereas in forest soil, the process was faster, and three byproducts were detected. Soil pretreatment with DOM did not modify the degradation pattern but only reduced the adsorption of cyhalofop-butyl by soil, whereas it increased the adsorption of cyhalofop-acid. Among the. cationic components of DOM solutions, the potassium ion seems to be related to the increased adsorption of the cyhalofop-acid in both OM-poor and OM-rich soils, yielding reversible complexes with the former and favoring hydrophobic interactions with the latter
Effects of a Municipal Sewage Sludge Amendment on Triasulfuron Soil Sorption and Wheat Growth
No full textThe influence of municipal sewage sludge (SL) as a soil amendment on the sorption and activity of the herbicide triasulfuron (TRS, [2-(2-chloroethoxy)-N-[[(4-methoxy-6-methyl-1,3,5-triazin-2-yl)amino]carbonyl]benzenesulfonamide]) was studied. Weed control was checked in a greenhouse on a wheat (Triticum turgidum L. subsp. durum) crop. At the highest SL amount allowed by Italian regulation, TRS sorption onto soil increased by 7 times and weed control was unaffected. A vegetative bloom and an early heading phase were noted. To compare inorganic fertilization (N, P, and K) and SL amendment, a greenhouse fertilization experiment was carried out. The SL-amended crop developed larger leaf surfaces, higher biomass, and a forward heading compared to that fertilized with N, P, and K. The SL hormone-like activity was evaluated by measuring auxin- and gibberellin-like activity of sewage sludge
Effects of a Municipal Sewage Sludge Amendment on Triasulfuron Soil Sorption and Wheat Growth
No full textThe influence of municipal sewage sludge (SL) as a soil amendment on the sorption and activity
of the herbicide triasulfuron (TRS, [2-(2-chloroethoxy)-N-[[(4-methoxy-6-methyl-1,3,5-triazin-2-yl)amino]-
carbonyl]benzenesulfonamide]) was studied. Weed control was checked in a greenhouse on a wheat
(Triticum turgidum L. subsp. durum) crop. At the highest SL amount allowed by Italian regulation, TRS
sorption onto soil increased by 7 times and weed control was unaffected. A vegetative bloom and an
early heading phase were noted. To compare inorganic fertilization (N, P, and K) and SL amendment, a
greenhouse fertilization experiment was carried out. The SL-amended crop developed larger leaf
surfaces, higher biomass, and a forward heading compared to that fertilized with N, P, and K. The
SL hormone-like activity was evaluated by measuring auxin- and gibberellin-like activity of sewage
sludge
Gold(III) derivatives with anionic oxygen ligands: mononuclear hydroxo, alkoxo and acetato complexes. Crystal structure of [Au(bpy)(OMe)(2)][PF6]
No full textA variety of gold(III) adducts having sigma-ligated oxygen-donor ligands have been prepared from [Au(bpy)Cl-2][PF6] 1 (bpy = 2,2'-bipyridine) either by partial or total replacement of the chloride ions. The new species comprise hydroxo, [Au(bpy)(OH)Cl][PF6] 2 and [Au(bpy)(OH)(2)][PF6] 3, oxo, [Au-2(bpy)(2)(mu-O)(2)][PF6](2) 4, acetato, [Au(bpy)(O2CMe)(2)][PF6] 5, and alkoxo complexes, [Au(bpy)(OR)Cl][PF6] 6, 7 and [Au(bpy)(OR)(2)][PF6] 8-10 (R = Me 6 and 8; Et 7 and 9; Pr-i 10). The dihydroxo and the oxo complexes can be interconverted by refluxing the former in anhydrous THF and the latter in water. The hydroxides 2 and 3 and the acetato complex 5 undergo sigma-ligand metathesis in ROH solution (R = Me, Et or Pr-i) to give the corresponding alkoxides. The crystal structure of 8, the first of a gold(III) methoxo complex, has been determined by X-ray diffraction analysis.A variety of gold() adducts having σ-ligated oxygen-donor ligands have been prepared from [Au(bpy)Cl2][PF6] 1
(bpy = 2,2-bipyridine) either by partial or total replacement of the chloride ions. The new species comprise hydroxo,
[Au(bpy)(OH)Cl][PF6] 2 and [Au(bpy)(OH)2][PF6] 3, oxo, [Au2(bpy)2(μ-O)2][PF6]2 4, acetato, [Au(bpy)(O2CMe)2][PF6]
5, and alkoxo complexes, [Au(bpy)(OR)Cl][PF6] 6, 7 and [Au(bpy)(OR)2][PF6] 8–10 (R = Me 6 and 8; Et 7 and 9;
Pri 10). The dihydroxo and the oxo complexes can be interconverted by refluxing the former in anhydrous THF and
the latter in water. The hydroxides 2 and 3 and the acetato complex 5 undergo σ-ligand metathesis in ROH solution
(R = Me, Et or Pri) to give the corresponding alkoxides. The crystal structure of 8, the first of a gold() methoxo
complex, has been determined by X-ray diffraction analysi
Replacement of the chloride ligand in [Au(C,N,N)Cl][PF6] cyclometallated complexes by C, N, O and S donor anionic ligands RID D-3096-2011
No full textmu-Oxo and alkoxo complexes of gold(III) with 6-alkyl-2,2 '-bipyridines. Synthesis, characterization and X-ray structures
No full textThe reactivity of a series of gold(III) adducts [Au(HL)Cl-3] 1a-4a with 6-alkyl-2,2'-bipyridines HL (N2C10H7R, R = CH2Me 1, CHMe2 2, CMe3 3 and CH2CMe3 4) has been studied. The reactions of 1a-4a with silver(I) ions or MeCO2Na afford cationic complexes [Au-2(HL)(2)(mu-O)(2)](2+) 1b-4b (as BF4 or PF6 salts) having the gold atom bonded to the nitrogen atoms of the bipyridine and to two oxygen atoms. The crystal structure of Ib[PF6](2), solved by X-ray diffraction, shows that the cation is a centrosymmetric dimer with two oxo (O2-) groups bridging two [Au{N2C10H7(CH2CMe3)-6}] moieties. In the case of 2a, besides the oxo species, mononuclear ionic derivatives [Au(L*)Cl](-)2*c [HL* = N2C10H7(CMe2OH)-6; BF4, PF6 or AuCl4 salts] have been isolated. The latter complexes contain an unexpected Au-O bond. The spectroscopic data and the crystal structure of 2*c[AuCl4] indicate a tridentate N,N,O behaviour of the ligand which forms a [5,5]-fused ring system
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