Sorption of 2,4-d on natural and organic amended soils of different characteristics

The effect of one organic amendment consisting of an urban waste compost (UWC) was assessed on the sorption properties of the herbicide 2,4-D on four soils of different physicochemical characteristics. The soils chosen were a Typic Haphorthod (ST), a Typic Endoaquept (SR), an Entic Pelloxerert (TO), and a Typic Eutrochrept (AL). Adsorption experiments were performed on the original soils, and on mixtures of these soils with UWC at a rate of 6.25% (w/w). These mixtures were used just after preparation, and after aging for 8 and 25 weeks. 2,4-D adsorption was the highest on ST soil, whereas the lowest adsorption was for SR soil. This behavior is related to the high amount of organic matter (OM) and amorphous iron and aluminum oxides content on soil ST, whereas soil SR had the lowest OM content and specific surface area of the soils of this study. Addition of exogenous OM to soils caused an increase in the 2,4-D adsorption by three of the soils treated with UWC, with the only exception being ST soil, due to an observed decrease in its specific surface area. The adsorbed amounts of the herbicide on aged organic fertilized soils diminished in three of the amended soils, but was still greater than on unammended soils. In contrast, the ST soil showed the largest adsorption for unammended soil.     

Carbofuran degraded by iron-doped anatase: Weakening the cholinesterase inhibitory activity in the photoproducts mixture

Carbofuran is a toxic carbamate pesticide, and its use has increased in recent years. While marketing information indicates stability in different chemical media, carbofuran exhibits relative photolability. The aim of this research was to decompose carbofuran and to identify the photoproducts achieved when two different doped titania photocatalysts were employed under UV irradiation. The iron-doped TiO₂ materials were obtained (a) via a hydrothermal method and (b) by an ultrasound-assisted sol–gel method. The precursors were TiOSO₄?xH₂O and Fe₃(NO₃)·9H₂O. X-ray studies confirmed that the anatase phase of the iron-doped TiO₂ resulted from the two preparation methods. The photocatalytic performance of the prepared materials was monitored by LC/ESI-QTOF-MS, enabling the identification of photoproducts: oxo-carbamates, hydroxylated benzofuranes, a carboxamide, and one amine. By using the iron-doped TiO₂ materials, 2,2-dimethyl-2,3-dihydrobenzofuran-3,7-diol was the most abundant photoproduct, and N,2,2-trimethyl-2,3-dihydrobenzofuran-7-amine was the only compound that had not been previously reported in the photolysis and photocatalysis of carbofuran. The product 3-hydroxy carbofuran, a cholinesterase inhibitor, was quantified and was found to be transformed into compounds that lack this inhibitive property.     

Serum levels of organochlorine pesticides in healthy adults from five regions of Spain

The aim of this study was to measure of serum levels of p,p′-dichlorodiphenyl trichloroethane (p,p′-DDT), p,p′-dichlorodiphenyl dichlorethylene (p,p′-DDE), β-hexachlorocyclohexane (β-HCH), and hexachlorobenzene (HCB) in healthy adults in Spain. Furthermore, we also analyzed these levels according to dietary, other lifestyle factors and anthropometric characteristics. We measured the concentrations of such organochlorine pesticides (OCPs) in serum samples collected during 1992–1996 from 953 subjects aged 35–64 years, they were residents of five Spanish regions, they were randomly selected from the European Prospective Investigation into Cancer and Nutrition (EPIC) cohort. OCPs were determined by means of gas chromatography with electron-capture detection (GC-ECD). The most frequent compound found in serum was p,p′-DDE, present in 98% of the samples, followed by HCB and β-HCH, found in 89% and 77% of samples, respectively, while p,p′-DDT could be measured only in 26% of subjects. The geometric means of serum concentrations (ng/g lipid) were 822 for p,p′-DDE, 167 for β-HCH, and 379 for HCB. The concentrations of all OCPs were positively associated with age and body mass index, and decreased along the period of blood collection. No association was found between OCPs levels and dietary factors. The concentrations of p,p′-DDE and β-HCB were higher in Murcia, one of southern regions, most likely associated with intensive past use of pesticides related to agricultural practices, while higher levels of HCB were found in Navarra, located in the north, maybe due to industrial use rather than agricultural application.     

Effect of various cyclodextrins on photodegradation of a hydrophobic herbicide in aqueous suspensions of different soil colloidal components

This paper investigated the photochemical behaviour of the herbicide norflurazon (NFL) in the presence of different soil colloidal components and several cyclodextrins (CDs). The interaction of NFL with CDs yielded the formation of inclusion complexes at 1:1 stoichiometric ratio in solution, with an increase of the herbicide solubility. The irradiation of NFL aqueous solutions in the presence of CDs showed that the higher the formation constant of NFL-CD complexes (Kc) and their solubility, the higher their photocatalytic effects, following the CDs in the order: RAMEB>HPBCD>beta-CD>alpha-CD>gamma-CD. The presence of the different soil colloidal components in aqueous suspension provoked the reduction of the NFL photodegradation rate, due to a screening effect, especially when goethite and humic acids were present. No disappearance of NFL was detected in parallel studies carried out in the dark, except in the case of humic acids, where a 5% adsorption of the initial amount of NFL was adsorbed in the dark control. The presence of the different CDs in such systems showed an inductive photodegradation effect on the herbicide. This could be largely explained by the inclusion effects of CDs in catalyzing interactions between NFL and certain reactive radicals generated by the different colloidal components. Although this work was carried out at laboratory scale and therefore, has limited applications, it reveals that cyclodextrins increase solubilization of hydrophobic herbicides and could lead to their increased photodegradation. This could be a promising method for pesticide-contaminated water remediation. However, it is important to consider the effect of the soil colloidal components in the different aquatic systems and their concentrations, since they can alter the photodegradative effects of the cyclodextrins.     

Differential activity of non-fluorinated and fluorinated analogues of the European corn borer pheromone

Summary.  The differing antagonist activity of (Z)-13-hexadecen-2-one (Z11 – 14 :MK, 1) and its 1,1,1-trifluoro derivative (Z11 –14 :TFMK, 2), two closely related analogues of the European corn borer pheromone Ostrinia nubilalis (Z strain), and their rationale is reported. Both chemicals exhibited some electrophysiological activity, and topical application of 10 pg of pheromone analogue on male antennae was sufficient to induce significantly lower depolarization responses to the pheromone versus untreated insects. In a wind tunnel, the number of European corn borer males attracted to sources containing mixtures of 1 + pheromone in ratios ≥ 1 :1 was significantly lower than the number attracted to a source containing pheromone alone. Source contact behaviour was dramatically impaired when the 1 + pheromone blend reached a ratio of 10 :1, in which only 2% of males displayed source contact in the presence of antagonist. When compound 1 was present at the source, males usually flew upwind with occasional downwind reversals; when compound 2 was present at the lure, males performed wider crosswind reversals, with little progress toward the source. In the field, traps baited with mixtures of both compounds with the pheromone in ratios of 5 :1 and 10 :1 elicited a significantly decreased number of male catches. In esterase inhibition assays, compound 2 was a potent inhibitor (IC₅₀ = 70 nM), whereas the non-fluorinated compound 1 was not. The different activity of both compounds is presumed to be due to different mechanisms of action; considerations for using methyl ketone analogues as new behavioural antagonists of the pheromone are outlined.     

Single adsorption of diclofenac and ronidazole from aqueous solution on commercial activated carbons: effect of chemical and textural properties

Environmental Science and Pollution Research - The importance of the textural and physicochemical characteristics upon the adsorption capacity of the commercial activated carbons (ACs) Coconut,...