Transfluthrin indoor air concentration and inhalation exposure during application of electric vaporizers

International audienceDifferent household insecticide applications via two electric vaporizers emitting transfluthrin were realized in a full-scale experimental room under controlled air exchange rate conditions. On-line high-time resolved measurements of the gas-phase concentrations of the active substance during and immediately after the spreading periods were performed with a High Sensitivity Proton-Transfer-Reaction Mass Spectrometer (HS-PTR-MS). Experimental and modelled data from the ConsExpo 4.0 software were also compared to evaluate the sources of differences. Different application scenarios were also compared. Averaged inhaled concentrations over 1h, 1week, and 5months were estimated to be 8.3, 1.8, and 1.8μg.m(-3), respectively. Corresponding margins of exposures range from 1000 to 10,000, claiming for the absence of effect. Dermal and dust ingestion pathways, although roughly estimated, seems being non-negligible. This claims for a more in-depth integrated risk assessment

Development of an analytical methodology for obtaining quantitative mass concentrations from LAAP-ToF-MS measurements

Laser ablation aerosol particle-time of flight mass spectrometer (LAAP-ToF-MS) measures the size number of particles, and chemical composition of individual particles in real-time. LAAP-ToF-MS measurements of chemical composition are difficult to quantify, mostly because the instrument sensitivities to various chemical species in the multicomponent atmospheric aerosol particles are unknown. In this study, we investigate a field-based approach for quantitative measurements of ammonium, nitrate, sulfate, OC, and EC, in size-segregated atmospheric aerosols, by LAAP-ToF-MS using concurrent measurements from high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS), and multi-angle absorption photometer (MAAP). An optical particle counter (OPC) and a high-resolution nanoparticle sizer (scanning mobility particle sizer, or SMPS), were used to measure the particle size distributions of the particles in order to correct the number concentrations. The intercomparison reveals that the degree of agreement of the mass concentrations of each compound measured with LAAP-ToF-MS and HR-ToF-AMS/MAAP increases in the following order NH4+ <SO42- <NO3- <EC <OC <Cl- with r2 values in the range of 0.4–0.95 and linear regression slopes ranging between 0.62 and 1.2. The factors that affect the mass concentrations measured by LAAP-ToF-MS are also discussed in details. Yet, the matrix effect remains one of the strongest limiting factor to achieve an absolute quantification of the aerosol chemical composition. In the future we suggest the development of a methodology based on the calculation of the response factors generated by different types of particles, which could possibly resolve certain difficulties associated with the matrix effect

Corrigendum to “Seasonal variations of Quercus pubescens isoprene emissions from an in natura forest under drought stress and sensitivity to futureclimate change in the Mediterranean area”

International audienc

Designing for interaction

At present, the design of computer-supported group-based learning (CS)GBL) is often based on subjective decisions regarding tasks, pedagogy and technology, or concepts such as ‘cooperative learning’ and ‘collaborative learning’. Critical review reveals these concepts as insufficiently substantial to serve as a basis for (CS)GBL design. Furthermore, the relationship between outcome and group interaction is rarely specified a priori. Thus, there is a need for a more systematic approach to designing (CS)GBL that focuses on the elicitation of expected interaction processes. A framework for such a process-oriented methodology is proposed. Critical elements that affect interaction are identified: learning objectives, task-type, level of pre-structuring, group size and computer support. The proposed process-oriented method aims to stimulate designers to adopt a more systematic approach to (CS)GBL design according to the interaction expected, while paying attention to critical elements that affect interaction. This approach may bridge the gap between observed quality of interaction and learning outcomes and foster (CS)GBL design that focuses on the heart of the matter: interaction

Widespread pesticide distribution in the European atmosphere questions their degradability in air

Risk assessment of pesticide impacts on remote ecosystems makes use of model-estimated degradation in air. Recent studies suggest these degradation rates to be overestimated, questioning current pesticide regulation. Here, we investigated the concentrations of 76 pesticides in Europe at 29 rural, coastal, mountain, and polar sites during the agricultural application season. Overall, 58 pesticides were observed in the European atmosphere. Low spatial variation of 7 pesticides suggests continental-scale atmospheric dispersal. Based on concentrations in free tropospheric air and at Arctic sites, 22 pesticides were identified to be prone to long-range atmospheric transport, which included 15 substances approved for agricultural use in Europe and 7 banned ones. Comparison between concentrations at remote sites and those found at pesticide source areas suggests long atmospheric lifetimes of atrazine, cyprodinil, spiroxamine, tebuconazole, terbuthylazine, and thiacloprid. In general, our findings suggest that atmospheric transport and persistence of pesticides have been underestimated and that their risk assessment needs to be improved

Mise au point d un préleveur automatique pour la mesure en continu des composés carbonylés atmosphériques

En raison de leur implication dans les processus photochimiques responsables de la formation de l ozone troposphérique et de leur impact sur la santé humaine, les composés carbonylés font partis des composés organiques volatiles dont il est important de suivre en continu leur concentration atmophérique (fluctuation rapide de leur concentration dans l atmosphère). Ce présent travail de thèse répond à cette demande et deux stratégies de prélèvement ont été explorées dans l optique de disposer d un instrument automatique de mesure en continu des composés carbonylés atmosphériques. Dans un premier temps, le prélèvement par transfert de la phase gazeuse échantillonnée dans une phase liquide associé à une dérivation chimique des composés piégés a été étudié en raison de sa grande spécificité envers les composés carbonylés. Cependant aucun couple dispositif de prélèvement en phase liquide réactifs de dérivation ne permet un piégage quantitatif et/ou une utilisation en continu sur site. Une seconde stratégie, courrament employée dans le prélèvement des composés organiques volatiles (COV) a été étudiée : l adsorption à froid sur un support solide suivie d une thermodesorption couplée à une analyse directe par GC/MS. L efficacité de piégeage des composés carbonylés sur différents adsorbants solides s est révelée superieure à 95% pour les composés carbonylés composés de 1 (formaldéhyde, Pvap(-30C) = 34400 Pa) à 7 carbones (benzaldéhyde, Pvap(-30C) = 0,75 Pa). Fort de ces résultats, ce travail constitue une première étape fructueuse vers l élaboration d un instrument automatique pour la mesure en continu des composés carbonylés atmosphériques.Because of their implication in photochemical processes leadind to the formation of tropospheric ozone and their negative effect on human health, carbonyl compounds are part of the volatile organic compounds which demand a continuous measurement of their atmospheric concentration (fast fluctuation of their atmospheric concentration). The present research meets this requirement and two sampling strategies were studied to have an automatic instrument for the continuous measurement of atmospheric carbonyl compounds. First, sampling by using a tranfer of gaseous phase in a liquid phase associated with a simultaneous chemical derivatization of the trapped compounds was studied because of its high specificity towards carbonyl compounds. However, no couple sampling device-reagent allows a quantitative sampling of carbonyl compounds, nor a continuous measurement in the field. Another strategy was therefore studied: cryogenic adsorption onto solid adsorbent followed by thermodesorption and analysis by GC/MS. Collection efficiency using different solid adsorbents was greater than 95% for carbonyl compounds consisting of 1 (formaldehyde, Pvap (-30C) = 34400Pa) to 7 carbons (benzaldehyde, Pvap (-30C) = 0,75 Pa). This sampling strategy is a successful first step towards the realization of the automatic sampling device for a continuous measurement of atmospheric carbonyls compounds.AIX-MARSEILLE1-BU Sci.St Charles (130552104) / SudocSudocFranceF

Contribution à l'étude de la partition des HAP entre les phases gazeuse et particulaire (validation de la technique de prélèvement par tube denuder annulaire)

En raison de leur toxicité, les Hydrocarbures Aromatiques Polycycliques (HAP) font partie des polluants atmosphériques devant faire l'objet d'une surveillance (directive cadre européenne 96/62/CE du 27 septembre 1996). De par leurs propriétés physico-chimiques, certains de ces composés sont présents dans l'atmosphère simultanément en phases gazeuse et particulaire. Leur impact sanitaire et environnemental, différent selon la phase considérée, impose le prélèvement et l'analyse séparée des deux phases. Actuellement, la méthode la plus couramment utilisée pour l'échantillonnage simultané et séparé des phases gazeuse et particulaire est les préleveur à haut-débit. Mais de nombreux auteurs ont montré que cette méthode engendrait des artefacts de prélèvement qui induisaient des erreurs dans l'estimation des concentrations. Ce travail de thèse répond à la nécessité de disposer d'un outil de prélèvement HAP dépourvu d'artefact de prélèvement. Dans ce contexte, nos recherches ont porté sur la validation de la méthode de prélèvement par tube denuder multi-annulaire. Cette validation s'est articulée autour de tests en conditions contrôlées (banc à perméation, banc à rouleaux) afin d'évaluer l'impact des principaux paramètres susceptibles d'influer sur les performances du tube (température, humidité, concentration en HAP, taille des particules, conditions de prélèvement), et de prélèvements d'échantillons réels (atmosphériques) pour évaluer l'effet de la matrice environnementale. Elle a été complétée par une comparaison avec le préleveur conventionnel, à partir de prélèvements à l'émission d'un véhicule diesel (banc à rouleaux). Il ressort de l'ensemble de ces tests que le tube denuder multi-annulaire est une méthode adaptée au prélèvement simultané des HAP en phases gazeuse et particulaire, dans une gamme de conditions expérimentales couvrant largement le domaine de conditions généralement rencontrées dans l'environnement. Pour un étude plus précise du phénomène de distribution gaz-particule des HAP, le remplacement des préleveurs conventionnels par des systèmes "tube denuder" est ainsi fortement souhaitable.AIX-MARSEILLE1-BU Sci.St Charles (130552104) / SudocSudocFranceF

Heterogeneous Oxidation of Terbuthylazine by ``Dark'' OH Radicals under Simulated Atmospheric Conditions in a Flow Tube

International audienceIn order to investigate the heterogeneous oxidation kinetics of the herbicide terbuthylazine (TERB), a stable and reproducible generation system of ``dark'' hydroxyl radical in the gas phase was developed and optimized using a PTR-MS. TERB was adsorbed on silica particles, which were coated on the walls of a flow tube. The hydroxyl radical was produced in the dark through the ozonolysis of 2,3-dimethyl-2-butene (DMB). The radical concentration was determined applying two different methods of calculation based on the monitoring of (i) a gaseous compound used as a tracer, m-xylene; (ii) one of the OH radical precursors, DMB. The obtained gaseous OH radical concentration in the reactor was (9.0 +/- 4.0) x 10(7) radical cm(-3). Exposing TERB to the oxidant for 1-14 h, a heterogeneous kinetic constant of k(OH) = (1.5 +/- 0.8) x 10(-13) cm(3) molecule(-1) s(-1) was found at 26 degrees C and RH < 1%. As a result, the heterogeneous oxidation of TERB by OH radicals seems to be much slower (by a factor of 63) when the organic compound is present in the particulate phase than when it reacts in homogeneous gas phase

Etude des artefacts de prélèvement et de la distribution gaz-particules des HAP [Hydrocarbures Aromatiques Polycycliques]

Les hydrocarbures aromatiques polycycliques (HAP) dans l atmosphère sont largement étudiés depuis de nombreuses années, en raison de l impact sanitaire de ces composés sur l homme. Du fait de leurs propriétés physico-chimiques, les HAP se répartissent dans les phases gazeuses et particulaires. Cette partition gaz-particule influe sur leur devenir (transport et réactivité) et sur leur impact sanitaire. Ceci rend nécessaire le prélèvement simultané dans les deux phases. Par ailleurs le parlement européen (directive fille n2004/107/CE) a récemment décidé qu ils devaient faire l objet d une surveillance et le benzo(a)pyrène (BaP) a été choisi comme étant représentatif de cette classe de composés. Dans les cas d une étude gaz-particule des HAP ou d un suivi réglementaire (du B(a)P en phase particulaire) la mesure est généralement effectuée par préleveur conventionnel haut volume. Or, de nombreux auteurs ont montré que ce type de préleveur engendrait de multiples artefacts. Ce travail a pour objectif d améliorer la mesure biphasique des HAP (et plus généralement des composés organiques semivolatils) en validant un tube dénudeur préalablement calibré en laboratoire. Pour cela nous avons réalisé plusieurs campagnes de terrain afin de comparer le préleveur dénudeur au préleveur conventionnel. Les résultats nous ont permis d observer des différences parfois très importantes entre les préleveurs notamment pour les HAP les plus réactifs (dont le BaP). Ceci semble indiquer une dégradation des HAP particulaires sur le filtre du préleveur conventionnel tandis que le filtre du préleveur dénudeur est protégé des oxydants gazeux par le tube dénudeur. Néanmoins, l ampleur de cette dégradation n est pas une fonction linéaire de la quantité d oxydants. Elle semble être influencé par d autres paramètres, tels que l état de "vieillissement" de la particule. Enfin nous avons conçu et réalisé un dispositif expérimental permettant d étudier la dégradation potentielle des HAP à l intérieur du tube durant le prélèvement. Cette étude a été réalisée pour le naphtalène avec l ozone comme oxydant.Atmospheric polycyclic aromatic hydrocarbons (PAH) has been widely studied since several years because of their human health impact. Due to their physico-chemical properties, PAH in the atmosphere are present in particulate and gaseous phase. This gas-particle partitioning has a strong influence on PAH fate (degradation or deposition) and their health impact. So, for their study, a simultaneous samplig in the two atmospheric phases is necessary. In addition, the European Union (directive n2004/107/CE) has recently decided that PAH should be monitored. Benzo(a)pyrene (BaP) has been chosen as tracer to represent this class of molecule. For both gas-particle partitioning study and for BaP monitoring, samplings are commonly carried out using high volume sampler. Unfortunately, several studies show that this kind of sampler induced sampling artefacts which could disturb the determination of the atmospheric concentrations in the two phases. The aim of this work is to improve the sampling procedure of PAH by the validation of a denuder sampler previously calibrated under laboratory conditions. In this goal several field campaigns were carried out to compare particulate phase sampling and gas-particle partioning with both conventional and denuder samplers. For concentrations in the particulate phase the results showed significant differences between the two samplers which could be important (up to a factor 10), especially for the most reactive PAH such as BaP. This could be the result of degradations occurring on the filter of the conventional sampler during sampling whereas the filter of the denuder sampler is protected from the oxidants by the denuder tube. The importance of the degradation artefact seems more linked to the aged of particle than to the concentrations of oxidant. On the other hand, no relevant differences were observed for the partition study of this kind of semi-volatil coumpounds between the two devices. Finally we conceived and realised an experimental device in order to study the reactivity of PAH occuring in the denuder tube during sampling. The study have been realised for naphthalene with ozone as oxidant.AIX-MARSEILLE1-BU Sci.St Charles (130552104) / SudocSudocFranceF

Heterogeneous degradation of pesticides by OH radicals in the atmosphere: Influence of humidity and particle type on the kinetics

International audiencePesticides can be adsorbed on the surface of atmospheric aerosol, depending on their physicochemical properties. They can be degraded by atmospheric oxidants such as OH radicals but the influence of some environmental parameters on the degradation kinetics, especially relative humidity and particle surface type, is not well understood. Heterogeneous degradation by OH radicals of eight commonly used pesticides (i.e., difenoconazole, tetraconazole, cyprodinil, fipronil, oxadiazon, pendimethalin, deltamethrin, and permethrin) adsorbed on hydrophobic and hydrophilic silicas at a relative humidity ranging from 0% to 70% was studied. Under experimental conditions, only cyprodinil, deltamethrin, permethrin, and pendimethalin were degraded by OH radical in atmospheric relevant concentration. Second-order kinetic constants calculated for the pesticides degraded by OH radicals ranged from (1.93 ± 0.61) × 10−13 cm3 molecule−1 s−1 (permethrin, hydrophobic silica, 30% RH) to (4.08 ± 0.27) × 10−12 cm3 molecule−1 s−1 (pendimethalin, hydrophilic silica, 0% RH). Results obtained can contribute to improve the understanding of the atmospheric fate of pesticides and other semi-volatile organic compounds in the particulate phase and they highlight the importance of taking humidity and particle type into account for the determination of pesticides atmospheric half-lives