Gas-phase and particulate products from the atmospheric degradation of an isoxazole fungicide

[EN] The isoxazole structure is present in several pesticides. However, there is a lack of information about its degradation products after the release to the atmosphere. The main atmospheric reactions of hymexazol (5-methylisoxazol-3-ol), selected as representative model, were investigated at a large outdoor simulation chamber. The predominant products of atmospheric degradations were gaseous nitrogen derivates (nitric acid, nitrogen dioxide, nitrogen oxide, nitrous acid, and peroxyacetylnitrate), ozone, and small oxygenated compounds (formic acid, formaldehyde, and methylglyoxal). The aerosol yields were lower than 5%, and an OH rate-dependence was observed in the nucleation, particle growth, and size distribution. Also, the chemical composition of minor multi-oxygenated products was studied for OH-photooxidations. More than 20 products were detected in the gas or particulate phase. The most abundant were heterocyclic cleavage products with C4-chain and oxygenated moieties at positions 1 and 3, such as 3,4-dioxobutanoic acid, 3-oxobutanoic acid, and 3-oxobutanal. The suggested reaction pathway is the opening of heterocycle ring by the cleavage of N O bond and C N bond, releasing nitrogen oxides.The authors wish to thank the EUPHORE staff and J.T.B. The authors wish to acknowledge Ministerio de Ciencia y Tecnologia for IMPESTAT (CGL2010-18474/CLI) and the European Community's Seventh Framework Program under the Grant agreement no. 228335 (Eurochamp2). The Fundacion CEAM is partly supported by Generalitat Valenciana, and the projects GRACCIE (Consolider-Ingenio 2010) and FEEDBACKS (Prometeo - Generalitat Valenciana). EUPHORE instrumentation is partly funded by the Spanish Ministry of Science and Innovation, through INNPLANTA Project: PCT-440000-2010-003.Tortajada-Genaro, LA.; Borrás García, EM.; Muñoz, A. (2013). Gas-phase and particulate products from the atmospheric degradation of an isoxazole fungicide. Chemosphere. 92(8):1035-1041. https://doi.org/10.1016/j.chemosphere.2013.03.041S1035104192

Gas-phase and particulate products from the atmospheric degradation of the organothiophosphorus insecticide chlorpyrifos-methyl

The phosphorothioate structure is highly present in several organophosphorus pesticides. However, there is insufficient information about its degradation process after the release to the atmosphere and the secondary pollutants formed. Herein, the atmospheric reaction of chlorpyrifos-methyl (o,o-dimethyl o-(3,5,6-trichloropyridin-2-yl) phosphorothioate), is described for semi-urban or rural locations. The photo-oxidation under low NOx conditions (5-55 ppbV) was reproduced in a large outdoor simulation chamber, observing a rapid degradation (lifetime<3.5 h). The formation of gaseous products and particulate matter (aerosol yield 2-8%) was monitored. The chemical composition of minor products (gaseous and particulate) was studied, identifying 15 multi-oxygenated derivatives. The most abundant products were ring-retaining molecules such as o,o-dimethyl o-(3,5,6-trichloropyridin-2-yl) phosphorothioate, dimethyl 3,5,6-trichloropyridin-2-yl phosphate, o-methyl o-(3,5,6-trichloropyridin-2-yl) hydrogen phosphorothioate, 3,5,6-trichloropyridin-2-yl dihydrogen phosphate, 3,5,6-trichloropyridin-2-ol, and 3,5,6-trichloropyridine-2,4-diol. An atmospheric degradation mechanism has been proposed based on an oxidation started with OH-nucleophilic attack to P=S bond. The results have been extrapolated to other organothiophosphorus molecules, such as malathion, parathion, diazinon and methidathion, among many others, to estimate their photo-oxidative degradation and the expected products.The authors wish to thank the EUPHORE staff and J.T.B. The authors wish to acknowledge Ministerio de Economia y Competitividad for IMPLACAVELES (CGL2013-49093-C2-1-R) and IMPESTAT (CGL2010-18474/CLI) projects, and Generalitat Valenciana for the DESESTRES- Prometeo II project. The Fundacion CEAM is partly supported by Generalitat Valenciana - Spain. EUPHORE instrumentation is partly funded by MINECO - Spain, through INNPLANTA Project: PCT-440000-2010-003 and the projects FEDER CEAM10-3E-1301 and CEAM10-3E-1302.Borrás García, EM.; Tortajada-Genaro, LA.; Ródenas, M.; Vera, T.; Coscollá, C.; Yusá, V.; Muñoz, A. (2015). Gas-phase and particulate products from the atmospheric degradation of the organothiophosphorus insecticide chlorpyrifos-methyl. Chemosphere. 138:888-894. https://doi.org/10.1016/j.chemosphere.2014.11.067S88889413

Kinetics of superoxide reactions with dissolved organic matter in tropical Atlantic surface waters near Cape Verde (TENATSO)

The decay kinetics of superoxide (O2−) reacting with organic matter was examined in oligotrophic waters at, and nearby, the TENATSO ocean observatory adjacent to the Cape Verde archipelago. Superoxide is the short-lived primary photochemical product of colored dissolved organic matter (CDOM) photolysis and also reacts with CDOM or trace metals (Cu, Fe) to form H2O2. In the present work we focused our investigations on reactions between CDOM and superoxide. O2− decay kinetics experiments were performed by adding KO2 to diethylenetriaminepentaacetic acid (DTPA) amended seawater and utilizing an established chemiluminescence technique for the detection of O2− at nM levels. In Cape Verdean waters we found a significant reactivity of superoxide with CDOM with maximal rates adjacent to the chlorophyll maximum, presumably from production of new CDOM from bacteria/phytoplankton. This work highlights a poorly understood process which impacts on the biogeochemical cycling of CDOM and trace metals in the open ocean

How does exposure to pesticides vary in space and time for residents living near to treated orchards?

This study investigated changes over 25 years (1987-2012) in pesticide usage in orchards in England and Wales and associated changes to exposure and risk for resident pregnant women living 100 and 1000 m downwind of treated areas. A model was developed to estimate aggregated daily exposure to pesticides via inhaled vapour and indirect dermal contact with contaminated ground, whilst risk was expressed as a hazard quotient (HQ) for reproductive and/or developmental endpoints. Results show the largest changes occurred between 1987 and 1996 with total pesticide usage reduced by ca. 25%, exposure per unit of pesticide applied slightly increased, and a reduction in risk per unit exposure by factors of 1.4 to 5. Thereafter, there were no consistent changes in use between 1996 and 2012, with an increase in number of applications to each crop balanced by a decrease in average application rate. Exposure per unit of pesticide applied decreased consistently over this period such that values in 2012 for this metric were 48-65% of those in 1987, and there were further smaller decreases in risk per unit exposure. All aggregated hazard quotients were two to three orders of magnitude smaller than one, despite the inherent simplifications of assuming co-occurrence of exposure to all pesticides and additivity of effects. Hazard quotients at 1000 m were 5 to 30 times smaller than those at 100 m. There were clear signals of the impact of regulatory intervention in improving the fate and hazard profiles of pesticides over the period investigated

Atmospheric fate of pesticides,Distribution between different atmospheric phases and photochemical oxidation

Cette thèse porte sur le devenir atmosphérique des pesticides. Nous nous sommes plus particulièrement intéressés à leur distribution entre les différentes phases de l'atmosphère et à leur oxydation photochimique.La distribution des pesticides entre les phases aqueuse et gazeuse de l'atmosphère dépend de leur constante de Henry tandis que leur distribution entre les phases gazeuse et particulaires de l'atmosphère dépend de leur pression de vapeur.Les constantes de Henry de pesticides et de composés phénoliques, utilisés comme adjuvants dans les formulations de pesticides, ont été déterminées en fonction de la température (278 301 K). Les résultats obtenus constituent des premières déterminations expérimentales pour un certain nombre de composés, en particulier pour les dépendances en température de la constante de Henry. Des mesures de pression de vapeur du phénol ont permis de vérifier le bon fonctionnement du dispositif de mesures de pression de vapeur.Une autre partie de ce travail a consisté à élaborer, mettre en place et valider un appareillage de mesure des coefficients d'absorption molaire et des spectres d'absorption des pesticides. Le bon fonctionnement du nouveau dispositif expérimental a été vérifié par le bon accord de nos spectres d'absorption de l'acétone avec la littérature. Ce même dispositif a permis de suivre la photolyse en phase aqueuse de plusieurs composés.La constante de photolyse du dichlorvos, la constante de vitesse de réaction du radical OH avec le dichlorvos ainsi que son mécanisme de dégradation par les radicaux OH ont été déterminés dans une chambre de simulation atmosphérique à irradiation naturelle (Euphore, Valence, Espagne). Nos résultats expérimentaux ont mis en évidence la formation de monoxyde de carbone et de phosgène.Les implications atmosphériques sont discutées en terme de durée de vie des pesticides et des phénols étudiés, ceci de manière à évaluer leur impact sur la qualité de l'air.The purpose of this thesis was to determine the atmospheric fate of pesticides: we focused on their atmospheric partitioning and on their photochemical oxidation.The atmospheric partitioning of pesticides between the aqueous and the gaseous phases depends on the Henry s law constant, while their partitioning between the gaseous and the particular phases depends on the vapour pressure.Henry s law constants of pesticides and of phenolic compounds have been measured as a function of temperature (278 301 K) and as a function of salinity. The obtained experimental results are the first temperature dependence for most compounds. Our results have been used to estimate their fractions in both gas and aqueous phases. Experimental vapour pressure measurements of phenol were in good agreement with literature.The molar extinction coefficient of 9 compounds have been measured with a new set-up by UV absorption spectroscopy under deuterium- and mercury-lamp irradiation. Molar extinction coefficient measurements of acetone were carried out to validate the new set-up. Direct photolysis of 8 compounds has been investigated with the same set-up under a Xenon lamp irradiation. Our results have been used to estimate if the studied compounds could be photodissociated in the environment.The photolysis rate constant of dichlorvos, the rate constant of OH reaction with dichlorvos and the oxidation mechanism of dichlorvos with the OH radicals have been determined in the Euphore photoreactor (Valencia, Spain). Phosgen and CO have been found as the major oxidation products of the OH reaction with dichlorvos.The atmospheric implications are discussed in term of lifetimes, in order to assess the impact of these studied pesticides and phenols on air quality

Atmospheric fate of pesticides,Distribution between different atmospheric phases and photochemical oxidation

Cette thèse porte sur le devenir atmosphérique des pesticides. Nous nous sommes plus particulièrement intéressés à leur distribution entre les différentes phases de l'atmosphère et à leur oxydation photochimique.La distribution des pesticides entre les phThe purpose of this thesis was to determine the atmospheric fate of pesticides: we focused on their atmospheric partitioning and on their photochemical oxidation.The atmospheric partitioning of pesticides between the aqueous and the gaseous phases depend

Devenir atmosphérique des pesticides: distribution entre les différentes phases de l'atmosphère et oxydation photochimique

thèse de doctorat ULP Strasbourg soutenue le 7 novembre 2005 (Dir. P. Mirabel, S. Le Calvé

Temperature Dependence of Henry's Law Constants of Fenpropidin and Pyrimethanil: Impact on their Atmospheric Partitionnings and Lifetimes

International audienceHenry's law constants (HLC) play a key role in the environmental fate of pesticides and their distribution between the different phases, i.e., between air, water and soil. For certain compounds such as fenpropidin and pyrimethanil, HLC values are poorly documented in the literature and in particular their temperature dependence. This work reports the experimental HLC values of two pesticides, namely fenpropidin and pyrimethanil, determined by means of a dynamic equilibrium system coupled to an off-line analysis performed by Gas Chromatography–Photoionisation Detection (GC–PID). The measurements were conducted over the range 278–293 K.In pure water, the experimental average values of HLC at 293 K were: HLC293K(fenpropidin) = (10.0 ± 3.1) × 104 M atm–1, HLC293K(pyrimethanil) = (8.2 ± 0.7) × 104 M atm–1. The obtained data were used to derive the following Arrhenius expressions where the quoted errors represent 2σ: ln HLC (fenpropidin) = (6060 ± 2420)/T – (9.1 ± 8.3); ln HLC (pyrimethanil) = (14570 ± 1800)/T – (38.4 ± 6.2). The environmental implications are then discussed in terms of lifetime or partitionning between the different atmospheric compartments

Devenir atmosphérique des pesticides (Distribution entre les différentes phases de l'atmosphère et oxydation photochimique)

Cette thèse porte sur le devenir atmosphérique des pesticides. Nous nous sommes plus particulièrement intéressés à leur distribution entre les différentes phases de l atmosphère et à leur oxydation photochimique.La distribution des pesticides entre les phases aqueuse et gazeuse de l atmosphère dépend de leur constante de Henry tandis que leur distribution entre les phases gazeuse et particulaires de l atmosphère dépend de leur pression de vapeur.Les constantes de Henry de pesticides et de composés phénoliques, utilisés comme adjuvants dans les formulations de pesticides, ont été déterminées en fonction de la température (278 301 K). Les résultats obtenus constituent des premières déterminations expérimentales pour un certain nombre de composés, en particulier pour les dépendances en température de la constante de Henry. Des mesures de pression de vapeur du phénol ont permis de vérifier le bon fonctionnement du dispositif de mesures de pression de vapeur.Une autre partie de ce travail a consisté à élaborer, mettre en place et valider un appareillage de mesure des coefficients d absorption molaire et des spectres d absorption des pesticides. Le bon fonctionnement du nouveau dispositif expérimental a été vérifié par le bon accord de nos spectres d absorption de l acétone avec la littérature. Ce même dispositif a permis de suivre la photolyse en phase aqueuse de plusieurs composés.La constante de photolyse du dichlorvos, la constante de vitesse de réaction du radical OH avec le dichlorvos ainsi que son mécanisme de dégradation par les radicaux OH ont été déterminés dans une chambre de simulation atmosphérique à irradiation naturelle (Euphore, Valence, Espagne). Nos résultats expérimentaux ont mis en évidence la formation de monoxyde de carbone et de phosgène.Les implications atmosphériques sont discutées en terme de durée de vie des pesticides et des phénols étudiés, ceci de manière à évaluer leur impact sur la qualité de l air.The purpose of this thesis was to determine the atmospheric fate of pesticides: we focused on their atmospheric partitioning and on their photochemical oxidation.The atmospheric partitioning of pesticides between the aqueous and the gaseous phases depends on the Henry s law constant, while their partitioning between the gaseous and the particular phases depends on the vapour pressure.Henry s law constants of pesticides and of phenolic compounds have been measured as a function of temperature (278 301 K) and as a function of salinity. The obtained experimental results are the first temperature dependence for most compounds. Our results have been used to estimate their fractions in both gas and aqueous phases. Experimental vapour pressure measurements of phenol were in good agreement with literature.The molar extinction coefficient of 9 compounds have been measured with a new set-up by UV absorption spectroscopy under deuterium- and mercury-lamp irradiation. Molar extinction coefficient measurements of acetone were carried out to validate the new set-up. Direct photolysis of 8 compounds has been investigated with the same set-up under a Xenon lamp irradiation. Our results have been used to estimate if the studied compounds could be photodissociated in the environment.The photolysis rate constant of dichlorvos, the rate constant of OH reaction with dichlorvos and the oxidation mechanism of dichlorvos with the OH radicals have been determined in the Euphore photoreactor (Valencia, Spain). Phosgen and CO have been found as the major oxidation products of the OH reaction with dichlorvos.The atmospheric implications are discussed in term of lifetimes, in order to assess the impact of these studied pesticides and phenols on air quality.STRASBOURG-Sc. et Techniques (674822102) / SudocSudocFranceF