Sampling precautions for the measurement of nitrated polycyclic aromatic hydrocarbons in ambient air

International audienceBecause of the toxicity of polycyclic aromatic hydrocarbons (PAHs) and of their oxidation products, such as nitrated and oxygenated PAHs (NPAHs and OPAHs), the determination of their concentrations is of great interest in terms of atmospheric pollution control. Then, normalisation of sampling procedures appears essential. In this context, this paper presents a comparison of particulate PAH, OPAH and NPAH concentrations determined with two different samplers (cascade impactor and conventional high volume sampler) installed in parallel during several field sampling campaigns carried out under different environmental conditions. For winter and summer periods, the PAH and OPAH concentrations determined with both sampling systems were considered as equivalent. In the summer period, NPAH concentrations quantified with both sampling devices were similar whereas in the winter period, the conventional high volume sampler underestimated their concentrations by a factor of 3-4. This underestimation was observed in the same proportion for all the 17 quantified NPAHs. Analytical error, NPAH formation during the sampling and NPAH degradation by reaction with gaseous oxidants associated to sampling methodology were unable to explain such differences between both samplers used in parallel. A probable hypothesis is that the heating of the PM10 head of the high volume sampler in the winter period generates an increase of the internal sampler temperature that could intensify the chemical degradation of the NPAHs inducing the underestimation of their concentrations in the atmosphere. Further investigations will be necessary to confirm the importance of the temperature on the chemical degradation of these compounds and to understand the different behaviour of PAHs and OPAHs. Consequently, we suggest using oxidant scrubber to prevent chemical degradation of PAHs and derivatives during their sampling. Moreover, we advise against the heating of the sampling head which could induce an increase of these reactions of degradation especially for NPAHs

Detecting and Characterizing Particulate Organic Nitrates with an Aerodyne Long-ToF Aerosol Mass Spectrometer

Particulate organic nitrate (pON) can be a major part of secondary organic aerosol (SOA) and is commonly quantified by indirect means from aerosol mass spectrometer (AMS) data. However, pON quantification remains challenging. Here, we set out to quantify and characterize pON in the boreal forest, through direct field observations at Station for Measuring Ecosystem Atmosphere Relationships (SMEAR) II in Hyytia''la'', Finland, and targeted single precursor laboratory studies. We utilized a long time-of-flight AMS (LToF-AMS) for aerosol chemical characterization, with a particular focus to identify CxHyOzN+ ("CHON+") fragments. We estimate that during springtime at SMEAR II, pON (including both the organic and nitrate part) accounts for similar to 10% of the particle mass concentration (calculated by the NO+/NO2+ method) and originates mainly from the NO3 radical oxidation of biogenic volatile organic compounds. The majority of the background nitrate aerosol measured is organic. The CHON+ fragment analysis was largely unsuccessful at SMEAR II, mainly due to low concentrations of the few detected fragments. However, our findings may be useful at other sites as we identified 80 unique CHON+ fragments from the laboratory measurements of SOA formed from NO3 radical oxidation of three pON precursors (beta-pinene, limonene, and guaiacol). Finally, we noted a significant effect on ion identification during the LToF-AMS high-resolution data processing, resulting in too many ions being fit, depending on whether tungsten ions (W+) were used in the peak width determination. Although this phenomenon may be instrument-specific, we encourage all (LTOF-) AMS users to investigate this effect on their instrument to reduce the possibility of incorrect identifications.Peer reviewe

A really quick easy cheap effective rugged and safe (QuEChERS) extraction procedure for the analysis of particle-bound PAHs in ambient air and emission samples

International audienceA quick easy cheap effective rugged and safe (QuEChERS) like extraction procedure is presented for the measurement of polycyclic aromatic hydrocarbons (PAHs) associated to particulate matter from ambient air or combustion process. The procedure is based on a short mechanical agitation (vortex during 90 s) using a small volume of acetonitrile (7 ml) as extraction solvent. Equivalent extraction efficiencies were obtained when comparing the QuEChERS and the traditional pressurized solvent extraction (ASE) procedures for ambient air and emission (wood combustion) filter samples. The developed QuEChERS extraction protocol was validated with the analysis of a standard reference material (NIST SRM 1649a, urban dust). By comparison to other extraction methods including ASE, the simplicity of the QuEChERS protocol allows to minimize experimental errors, to decrease about a factor 5 the cost per extraction and to increase the productivity per working day by a 10-fold factor. This paper constitutes the first report on the applicability of a QuEChERS-like approach for the quantification of PAHs or other organic compounds in atmospheric particulate matter

Hydrocarbures aromatiques polycycliques et leurs dérivés nitrés et oxygénés dans l'air ambiant : caractérisation physico-chimique et origine

Several studies on the toxicity of the particles in the ambient air show that the polar phase, which contains the oxygenated and nitrated polycyclic aromatic hydrocarbons (OPAHs and NPAHs), is more toxic than the aromatic fraction containing the PAH. In this context, the objective of this study was to chemically characterize the NPAHs and OPAHs in ambient air on various sites (traffic, urban, suburban, rural and altitude). Samplings were performed within the framework of the French research program POllution des Vallées Alpines (POVA) during the winter 2002-2003 and the summer 2003 and in the area of Marseilles in summer 2004. Both, ambient air particulate and gas phases were sampled and particle size distribution was also studied. The results obtained on the OPAHs and the NPAHs contribute to increase the data base even still limited on these compounds. First, we developed a routine analytical method for the simultaneous quantitative determination of NPAHs and OPAHs in complex environmental matrices, using GC/NICI-MS. Results from the field campaigns show that, OPAH concentration levels were of the same order of magnitude as PAHs while NPAH concentrations were one to two orders of magnitude lower. Carcinogenic risk was estimated using toxic equivalent factors. NPAHs could contribute to 20% of the total risk. Study of source specific ratios clearly showed these compounds have a primary origin at the sites close to the sources of pollution whereas production of secondary NPAHs by gas phase reactions was prevalent at the rural sites far to the direct sources of pollution and initiated by OH (day-time reactions). The study of NPAH and OPAH sources suggested that gasoline engines were an important source of such compounds. The OPAH 9,10-anthraquinone presents a double origin: primary diesel emission and photochemical processes without to be able to discriminate when the formation occurred (before or during the sampling). The fraction of PAHs, OPAHs and NPAHs associated with the particle phase was strongly depending on their vapour pressure and the ambient temperature. Sources of these compounds take a part in their gas/particle partitioning which can bring information on their primary or secondary origin. Finally, during both, the winter and summer period, PAHs, OPAHs and NPAHs were mainly associated (>80%) with fine particles (Dp80%) associés à la fraction fine de l'aérosol (Dp<1,3 µm) et ce quelque soit la saison considérée (hiver et été). Les caractéristiques chimiques des différentes classes de composés (polarité…) peuvent néanmoins jouer un rôle quant à leur distribution en taille

De l’importance de la spéciation de la fraction organique pour l’évaluation des sources de particules dans l’air ambiant

PM10 source apportionment was performed by positive matrix factorization (PMF) using specific primary and secondary organic molecular markers on samples collected over a one year period (2013) in Grenoble and at the SIRTA station. This station represents the suburban background air quality conditions of the Paris area (25 km SW from Paris city center) during an intense PM pollution event in March 2015 (PM10 > 50 μg m-3 for several days). Results provided a 9- and 11-factor optimum solution, including sources rarely apportioned such as two types of primary biogenic organic aerosols (fungal spores and plant debris), as well as specific biogenic and anthropogenic secondary organic aerosols (SOA). These sources were identified thanks to the use of key organic markers namely polyols, odd number higher alkanes, and several SOA markers related to the oxidation of isoprene, α-pinene, toluene polycyclic aromatic hydrocarbons (PAHs) and phenolic compounds. Findings of this work demonstrate that the speciation of the organic aerosol fraction and the input of specific molecular markers into source-receptor model are a powerful tool to discriminate OA sources and to get a better understanding of PM origins.La pollution due aux particules (aérosols, PM) présentes dans l’air ambiant est une problématique sanitaire primordiale. La connaissance et l’évaluation de leurs sources sont un enjeu majeur en termes de politiques de gestion de la qualité de l’air. Les travaux menés par l’Ineris, cofinancés par le LCSQA, ont permis de montrer qu’à travers une spéciation fine de la fraction organique de l’aérosol (aérosol organique, AO), et par la mesure de composés clés dits « marqueurs », une évaluation approfondie des sources des particules, incluant des sources primaires ou secondaires généralement non résolues, est réalisable

Simultaneous analysis of oxygenated and nitrated polycyclic aromatic hydrocarbons on standard reference material 1649a (urban dust) and on natural ambient air samples by gas chromatography-mass spectrometry with negative ion chemical ionisation

International audienceThis study deals with the development of a routine analytical method using gas chromatography-mass spectrometry with negative ion chemical ionisation (GC/NICI-MS) for the determination of 17 nitrated polycyclic aromatic hydrocarbons (NPAHs) and 9 oxygenated polycyclic aromatic hydrocarbons (OPAHs) present at low concentrations in the atmosphere. This method includes a liquid chromatography purification procedure on solid-phase extraction (SPE) cartridge. Application of this analytical procedure has been performed on standard reference material (SRM 1649a: urban dust), giving results in good agreement with the few data available in the literature. The analytical method was also applied on ambient air samples (on both gas and particulate phases) from the French POVA program (POllution des Vallees Alpines). NPAHs concentrations observed for a rural site during the Winter period are about 0.2-100.0 pg m(-3) in the particulate phase and about 0.0-20.0 pg m(-3) in the gas phase. OPAHs present concentrations 10- 100 times higher (0.1-2.0 ng m(-3) and 0.0-1.4 ng m(-3) for the particulate and the gas phases, respectively). These preliminary results show a good correlation between the characteristics of the sampling site and the compound origins (primary or secondary)

Caractérisation chimique de la fraction polaire des particules dans l’air ambiant

Several studies on the toxicity of particles in ambient air show that the polar phase, which contains the oxygenated and nitrated polycyclic aromatic hydrocarbons (OPAHs and NPAHs), is more toxic than the aromatic fraction containing the PAH. In that context, the objective of our study was to chemically characterise the NPAHs and OPAHs in ambient air at various sites (traffic, urban, suburban, rural and altitude). Samplings were performed within the framework of the French research program POllution des Vallées Alpines (POVA) during the winter 2002-2003 and the summer 2003 and in the area of Marseilles in summer 2004. Both, ambient air particulate and gas phases were sampled and particle size distribution was also studied. The results obtained contribute to increase the data base on these compounds. First, we developed an analytical method for the simultaneous quantitative determination of NPAHs and OPAHs in complex environmental matrices, using GC/NICI-MS. Results from the field campaigns show that OPAH concentration levels were of the same order of magnitude as PAHs while NPAH concentrations were one to two orders of magnitude lower. The corresponding carcinogenic risk for NPAH was estimated using toxic equivalent factors (TEF). NPAHs could contribute to 20% of the total risk. No TEF were found for OPAH, which leaves entire the question of the risk they pose. Study of source specific ratios clearly showed that these compounds have a primary origin at the sites close to the sources of pollution whereas the production of secondary NPAHs by gas phase reactions was prevalent at the rural sites far from the direct sources of pollution and initiated by OH (daytime reactions). The study of NPAH and OPAH sources suggested that gasoline engines were an important source of such compounds. The OPAH 9,10-anthraquinone presents a double origin: primary diesel emission and photochemical processes. The fraction of PAHs, OPAHs and NPAHs associated with the particle phase was strongly depending on their vapour pressure and the ambient temperature. Sources of these compounds take a part in their gas/particle partitioning which can bring information on their primary or secondary origin. Finally, during both winter and summer, PAHs, OPAHs and NPAHs were mainly associated with fine particles (Dp<1.3 μm). The differences of chemical properties of the classes of compounds (polarity…) could account for their particle size distribution.Les particules atmosphériques contiennent de nombreux composés organiques toxiques adsorbés à leur surface. Parmi eux, les Hydrocarbures Aromatiques Polycycliques (HAP) émis lors des combustions incomplètes ou de la pyrolyse de la matière organique et des combustibles fossiles, ont des propriétés cancérigènes et/ou mutagènes avérées. Cependant, les produits d’oxydation de ceux-ci, les HAP nitrés (NHAP) et oxygénés (OHAP), semblent plus toxiques que leurs HAP parents, car certains d’entre eux ont été identifiés comme ayant un caractère mutagène direct. Les NHAP et les OHAP sont formés soit, durant le processus de combustion, soit par réaction dans l’atmosphère en phase gazeuse et hétérogène entre les HAP, l’ozone, et les oxydes d’azote initiés par le radical OH ou NO3. Malgré leur caractère hautement toxique, les dérivés polaires des HAP dans l’atmosphère font l’objet de très peu de publications. Le nombre d’études concernant leur formation, leur sources ainsi que leur caractérisation dans l’air ambiant est limité. Ainsi, l’objectif général de ce travail réalisé à l’INERIS était de caractériser chimiquement les NHAP et OHAP dans différents milieux de l’air ambiant : trafic, urbain, péri-urbain, rural et altitude. La répartition entre les phases gazeuse et particulaire de ces composés, leur répartition en fonction de la taille des particules mais aussi leur origine (primaire ou secondaire) ont été étudiées. Ce travail a été réalisé en collaboration avec le Laboratoire de Physico et Toxico-Chimie des systèmes naturels (LPTC) et le Laboratoire de Physico-Chimie Moléculaire (LPCM) de l’Université de Bordeaux 1, notamment en ce qui concerne la réactivité des HA