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5 p.International audienceThe eruption of the Eyjafjallajökull in April 2010 led to the injection in the troposphere of an important quantity of volcanic ash whose advection towards densely populated areas raised serious concerns regarding potential impacts on air quality. Here we investigate to what extent air quality in France was altered using exclusively quantitative data that was available in near real-time. We rely on a combination of atmospheric dispersion modelling, ground-based remote sensing, and chemical characterization of airborne particles. One week after the onset of the eruption we were able to conclude that the Eyjafjallajökull ash plume was locally responsible for an increase of up to 30 +/- 10 µgm-3 of total PM10 (particulate matter finer than 10 µm) that reached 65 mg m-3 on 18 and 19 April 2010. The methodology presented in this letter offers promising perspectives in terms of emergency response strategy when facing such unforeseen atmospheric dispersion events

A new one-step method for the analysis of highly polar components of secondary organic aerosols (SOA) has been developed. This method should lead to a better understanding of SOA formation and evolution since it enables the compounds responsible for SOA formation to be identified. Since it is based on supercritical fluid extraction coupled to gas chromatography-mass spectrometry, it minimizes the analysis time and significantly enhances sensitivity, which makes it suitable for trace-level compounds, which are constituents of SOA. One of the key features of this method is the in situ derivatisation step: an online silylation allowing the measurement of highly polar, polyfunctional compounds, which is a prerequisite for the elucidation of chemical mechanisms. This paper presents the development of this analytical method and highlights its ability to address this major atmospheric issue through the analysis of SOA formed from the ozonolysis of a biogenic hydrocarbon (sabinene). Ozonolysis of sabinene was performed in a 6 m3 Teflon chamber. The aerosol components were derivatised in situ. More than thirty products, such as sabinaketone, sabinic acid and other multifunctional compounds including dicarboxylic acids and oxoacids, were measured. Nine of them were identified and quantified. The sensitivity and the linearity (0.91

The gas/particle partitioning behaviour of the semi-volatile fraction of secondary organic matter and the associated multiphase chemistry are key features to accurately evaluate climate and health impacts of secondary organic aerosol (SOA). However, today, the partitioning of oxygenated secondary species is rarely assessed in experimental SOA studies and SOA modelling is still largely based on estimated partitioning data. This paper describes a new analytical approach, solvent-free and easy to use, to explore the chemical composition of the secondary organic matter at a molecular scale in both gas and particulate phases. The method is based on thermal desorption (TD) of gas and particulate samples, coupled with gas chromatography (GC) and mass spectrometry (MS), with derivatisation on sampling supports. Gaseous compounds were trapped on Tenax TA adsorbent tubes pre-coated with pentafluorobenzylhydroxylamine (PFBHA) or N-Methyl-N-(<i>t</i>-butyldimethylsilyl)trifluoroacetamide (MTBSTFA). Particulate samples were collected onto quartz or Teflon-quartz filters and subsequently subjected to derivatisation with PFBHA or MTBSTFA before TD-GC/MS analysis. Method development and validation are presented for an atmospherically relevant range of organic acids and carbonyl and hydroxyl compounds. Application of the method to a limonene ozonolysis experiment conducted in the EUPHORE simulation chamber under simulated atmospheric conditions of low concentrations of limonene precursor and relative humidity, provides an overview of the method capabilities. Twenty-five compounds were positively or tentatively identified, nine being in both gaseous and particulate phases; and twelve, among them tricarboxylic acids, hydroxyl dicarboxylic acids and oxodicarboxylic acids, being detected for the first time

Along with some research networking programmes, the European Directive 2008/50/CE requires chemical speciation of fine aerosol (PM2.5), including elemental (EC) and organic carbon (OC), at a few rural sites in European countries. Meanwhile, the thermal-optical technique is considered by the European and US networking agencies and normalisation bodies as a reference method to quantify EC-OC collected on filters. Although commonly used for many years, this technique still suffers from a lack of information on the comparability of the different analytical protocols (temperature protocols, type of optical correction) currently applied in the laboratories. To better evaluate the EC-OC data set quality and related uncertainties, the French National Reference Laboratory for Ambient Air Quality Monitoring (LCSQA) organised an EC-OC comparison exercise for French laboratories using different thermaloptical methods (five laboratories only). While there is good agreement on total carbon (TC) measurements among all participants, some differences can be observed on the EC/TC ratio, even among laboratories using the same thermal protocol. These results led to further tests on the influence of the optical correction: results obtained from different European laboratories confirmed that there were higher differences between OCTOT and OCTOR measured with NIOSH 5040 in comparison to EUSAAR-2. Also, striking differences between ECTOT/ECTOR ratios can be observed when comparing results obtained for rural and urban samples, with ECTOT being 50% lower than ECTOR at rural sites whereas it is only 20% lower at urban sites. The PM chemical composition could explain these differences but the way it influences the EC-OC measurement is not clear and needs further investigation. Meanwhile, some additional tests seem to indicate an influence of oven soiling on the EC-OC measurement data quality. This highlights the necessity to follow the laser signal decrease with time and its impact on measurements. Nevertheless, this should be confirmed by further experiments, involving more samples and various instruments, to enable statistical processing. All these results provide insights to determine the quality of EC-OC analytical methods and may contribute to the work toward establishing method standardisation

A new sensitive technique for the quantification of formaldehyde (HCHO) and total aldehydes has been developed in order to monitor these compounds, which are known to be involved in air quality issues and to have health impacts. Our approach is based on a colorimetric method where aldehydes are initially stripped from the air into a scrubbing solution by means of a turning coil sampler tube and then derivatised with 3-methylbenzothiazolinone-2-hydrazone in acid media (pH = -0.5). Hence, colourless aldehydes are transformed into blue dyes that are detected by UV-visible spectroscopy at 630 nm. Liquid core waveguide LCW Teflon® AF-2400 tube was used as innovative optical cells providing a HCHO detection limit of 4 pptv for 100 cm optical path with a time resolution of 15 min. This instrument showed good correlation with commonly used techniques for aldehydes analysis such as DNPH derivatisation chromatographic techniques with off-line and on-line samplers, and DOAS techniques (with deviation below 6%) for both indoor and outdoor conditions. This instrument is associated with simplicity and low cost, which is a prerequisite for indoor monitoring.

The influence of the precursor chemical structure on secondary organic aerosol (SOA) formation was investigated through the study of the ozonolysis of two anthropogenic aromatic alkenes: 2-methylstyrene and indene. Experiments were carried out in three different simulation chambers: ICARE 7300L FEP Teflon chamber (ICARE, Orléans, France), EUPHORE FEP Teflon chamber (CEAM, Valencia, Spain) and CESAM evacuable stainless steel chamber (LISA, Créteil, France). For both precursors, SOA yield and growth were studied on a large range of initial concentrations (from ~60 ppbv to 1.9 ppmv) and the chemical composition of both gaseous and particulate phases was investigated at a molecular level. Gas-phase was described using FTIR spectroscopy and on-line gas chromatography coupled to mass spectrometry and particulate chemical composition was analysed i) on-line by thermo-desorption coupled to chemical ionisation mass spectrometry (TD-API-AMS) and ii) off-line by supercritical fluid extraction coupled to gas chromatography and mass spectrometry (SFE-GC-MS). The results obtained from a large set of experiments performed in three different chambers and using several complementary analytical techniques were in very good agreement. SOA yield was up to 10 times higher for indene

Environmental Context. Volatile organic compounds (VOCs) are a source of ozone and secondary organic aerosols, which have significant effects in the lower troposphere and on human health. The emission rate of VOCs from plants exceeds anthropogenic emissions by a factor of ten. In order to understand how these plant-derived compounds influence global ozone budgets, studies into the atmospheric reactions of these compounds are needed. This study investigates the ozonolysis of sabinene, a VOC abundantly emitted by trees in Europe.Abstract. This work investigates both the gaseous and particulate phase products from the ozonolysis of sabinene in smog chamber experiments. The gaseous phase was analyzed in situ by FTIR. The particulate phase was analyzed after sampling with a supercritical fluid extraction technique directly coupled to gas chromatography and mass spectrometry (SFE-GC-MS) and to an in situ derivatization method. Sabinaketone, formaldehyde, and formic acid have been detected in the gaseous phase. More than 30 products have been observed in the secondary organic aerosol formed from sabinene oxidation and among them 10 have been identified as compounds containing carbonyl, hydroxyl and carboxyl groups. Hypotheses concerning reaction formation pathways have been proposed for each identified product in gaseous and particulate phases.