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Wintertime air pollution affects air quality of Arctic and sub-Arctic urban areas, because of the coupling between strong local emissions for residential heating and energy production and poor atmospheric dispersion associated with a stratified planetary boundary layer. Aerosols represent priority pollutants in such environments, and their behaviour in the Arctic wintertime boundary layer not only impacts air quality but also determines deposition on snow or ice surfaces, leading to chemical and physical modifications in the snowpack. The interactions between boundary layer meteorology and air pollution were the focus of the international ALPACA (Alaskan Layered Pollution and Chemical Analysis) field campaign held in January and February 2022 in Fairbanks (AK, USA). The aim of the present work is to analyse the fluxes of atmospheric particles in at a urban background site in Fairbanks, based on continuous observations of aerosol concentration, size distributions, and size-segregated deposition velocities. The EC system was installed at the suburban site of UAF (University of Alaska Farm), located nearby the foothills bordering the city basin. The main micrometeorological parameters and fluxes (wind field, friction velocity, turbulent kinetic energy, and sensible heat flux) were characterized in terms of boundary layer conditions (occurrence of thermal inversions, dynamic stratifications, vertical wind shear, slope currents, coherent turbulence structures). The aerosol eddy covariance system was based on a condensation particle counter (CPC) - able to measure particles down to 5 nm in diameter - and an Optical Particle Counter Optical Particle Counter (OPC) for evaluating particle fluxes in the accumulation mode (0.25 < dp < 0.8 μm) and quasi-coarse mode (0.8 < dp < 3 μm). The median number concentration was 13 E+3 cm−3, 76 cm−3 and 0.3 cm−3 for ultrafine, accumulation and quasi-coarse particles mode, with higher concentrations found at low wind speeds. The particle fluxes showed a net emission pattern for the ultrafine, accumulation and quasi-coarse dimensional mode, especially in daytime, with average values of 203, 0.3, and 0.02 cm-2 s-1 respectively. Deposition periods were observed most frequently for air masses from the city located to the east, while local emission sources due to traffic lead emission fluxes, especially in the accumulation mode. We discuss the particle flux measurements in the context of parallel aerosol and gaseous pollutants determined by fixed and mobile platforms (a tethered balloon and a car) as well as of determinations of depositions in the snow pack across the Fairbanks area.

Ship emissions of air pollutants in and around ports adversely affect local air quality and human health, especially in harbour cities. In coastal Mediterranean cities, shipping activities are an important contributor to emissions of fine particulate matter (PM2.5) within the urban area. In addition to primary particles emitted in ship exhaust, secondary organic aerosols (SOA) may form in ship plumes through chemical oxidation of volatile organic compounds (VOC) and through condensation of intermediate volatile or semi-volatile organic gases. Shipping also emerges as a major source of ultrafine particles below 100 nm diameter in coastal cities. Ultrafine particles have been estimated to significantly affect human mortality in coastal areas. While a large number of studies investigated the effect of ship-related PM2.5 in coastal areas, currently only few studies deal with the effect of ship emissions on SOA concentrations and number concentrations of ultrafine particles in harbour cities.In this study, we investigate the effect of ship emissions on SOA concentrations and number concentrations of UFP in the harbour city Marseille in southern France, which is an important hub of ferry and cruise ship traffic in the Mediterranean Sea. For city-scale simulations of Marseille, the urban chemistry transport model EPISODE-CityChem (https://doi.org/10.5281/zenodo.1116173) was applied in a coupled setup with the regional-scale Community Multiscale Air Quality Modelling System (CMAQ). EPISODE-CityChem combines a 3-D Eulerian grid model with sub-grid Gaussian plume models and solves the photochemistry of multiple reactive pollutants, including the chemistry of 12 different VOC. New developments in EPISODE-CityChem include the P8P+2 scheme for calculating particle number (PN) concentration and particle number size distribution (PNSD) and the SOA module of the aerosol model MAFOR v2.0 (https://github.com/mafor2/mafor). The STEAM-3 emission inventory for the local shipping in and around the port of Marseille consists of hourly emissions of major pollutants, VOC and particle numbers from ships on 250 m grid resolution. Hourly model output of EPISODE-CityChem for July 2020 was compared to measurements at monitoring stations in Marseille operated by AtmoSud and campaign data recorded at La Major, a site in proximity of the port.Our results show that the potential impact from local shipping to the monthly mean concentration in the urban area of Marseille is only up to 3% for PM2.5, whereas it is up to 42% for total PN. The abundance of ship-related semi-volatile organic vapours is high in the areas of SOA formation, which indicates that volatile organics are mainly in the gas phase because available pre-existing particle surfaces and high ambient temperatures limit their condensation. Ship plumes at La Major were detected based on the difference of total PN concentration between the reference run and a model run excluding ship emissions. The maximum of the modelled and the observed PNSD notably corresponded to the typical size distribution maximum of ship exhaust particles. Total PN should be considered as a more suitable metric for monitoring ship emission impact than PM2.5 because it allows for a better discrimination of ship plumes from the background pollution.

The complex refractive index (CRI) is one of the key parameter driving aerosol spectral optical properties and direct radiative effects (DRE). Its value and spectral variation under different conditions, such as anthropogenic− and biogenic−dominated environments and anthropogenic−biogenic mixing situations, remains not fully understood. As a consequence, oversimplified representations of aerosol optical properties are generally used in climate models. Therefore, measurements of aerosol CRI in different environments and their inclusion in models are needed. The field observations from the ACROSS campaign, performed in June-July 2022 in the Ile de France region, are used in this study to deepen the knowledge of aerosol optical properties, aiming to improve the aerosol representation in the CHIMERE model and provide the best constraint for DRE simulations. Measurements obtained both at the Paris city center and the Rambouilllet rural forest sites during ACROSS are considered, in order to explore the CRI variability from anthropogenic−dominated to biogenic−dominated environments, including anthropogenic−biogenic mixing situations. The CRI retrievals at seven different wavelengths, performed by combining the Mie theory with optical and size distribution measurements, are representative of different atmospheric conditions, aerosol loadings as well as type and chemical compositions. In fact, the June-July 2022 period was characterized by highly diversified weather conditions: 1) two strong heatwaves, promoting SOA build-up and favoring the export of the Paris pollution plume towards the forest site; 2) Saharan dust events transported from the upper atmosphere to the ground; 3) biomass burning episode; 4) periods with reduced anthropogenic influence. The CRI retrievals under these different conditions and their link to particulate chemical composition is investigated. Hence, the CRI dataset presented here constitutes a unique dataset from which models can benefit to validate and constrain simulations and DRE estimations, under both urban and biogenic emissions influence. These data, in conjunction with those from the aircraft observations during ACROSS, are used to initialize and perform sensitivity studies on the aerosol DRE, using the CHIMERE−WRF coupled model, the OPTSIM model for the aerosol optical properties and the Rapid Radiative Transfer Model for GCMs (RRTMG).Keywords: Complex refractive index, direct radiative effect, aerosol mixing, urban, forest

International audience

Ammonium sulfate (AS) particles are widely used for studying the physical-chemistry processes of aerosols and for instrument calibrations. Small quantities of organic matter can greatly influence the studied properties, as observed by many laboratory studies. In this work, monodisperse particles (from 200 nm to 500 nm) were generated by nebulizing various AS solutions and organic impurities were quantified relative to sulfate using a High-Resolution Time-of-Flight Aerosol Mass Spectrometer (HR-ToF-AMS). The organic content found in AS solutions was also tentatively identified using a Liquid Chromatography–tandem Mass Spectrometry (LC-MS). The results from both analytical techniques were consistent and demonstrated that the organic impurities contained oxygen, nitrogen and/or sulfur, their molecular masses ranged from m/z 69 to 420, they likely originate from the commercial AS crystals. For AS particle sizes ranging from 200 nm to 500 nm, the total mass fraction of organic (relative to sulfate) ranged from 3.8 % to 1.5 % respectively. An inorganic-organic mixture model suggested that the organic impurities were coated on the AS particle surface with a density of 1.1 × 10−3 g m−2. A series of tests were performed to remove the organic content (using pure N2 in the flow, ultrapure water in the solutions, and very high AS quality), showing that at least 40 % of the organic impurities could be removed. In conclusion, it is recommended to use AS seeds with caution, especially when small particles are used, in terms of AS purity and water purity when aqueous solutions are used for atomization.

A seven-week field campaign took place in Fairbanks, Interior of Alaska, during January and February 2022, in the framework of the Alaskan Layered Pollution And Chemical Analysis (ALPACA) international project. A compact Doppler Lidar was deployed (Leosphere WindCube v2) to profile winds in the atmospheric boundary layer from 40 to 290 m above ground level (a.g.l.). The first objective of this project was to study the influence of strong atmospheric stratification and temperature inversion layering on air pollution. For this purpose, the Lidar was first installed in the urban canopy downtown Fairbanks city (~3.5 weeks). The second objective was to study the influence of shallow cold flows (SCF) on surface-based temperature inversions and the energy budget. Therefore, the Lidar was then re-deployed in a suburban site located nearby the foothills bordering the city, at the outlet of a small valley. Measurements on this site also included surface turbulence by eddy-covariance, radiative fluxes and temperature profiles, both in-situ during tethered balloon launches and remote sensing using a Microwave Radiometer.The conditions for operating a near-infrared Doppler Lidar were very stringent, as Arctic environments are generally pristine, except for urban areas in wintertime. However, the wind dataset availability up to 100 m a.g.l. was ~47% at the urban site and ~30% at the suburban site. The relationship between Lidar performance and aerosol size distribution is under evaluation at both sites, using observations from Scanning Mobility Particle Sizers. At the suburban site, the SCF descending from the nearby valley was regularly visible, with wind speeds reaching 5-6 m.s-1 at 40 m a.g.l. Cases of continuous flow lasting for more than 24 hours were observed, during which the SCF depth remained stable and very shallow (40 to 60 m a.gl.). Pulsated episodes also occurred, that could be as short as 2 hours, and were characterized by a more variable SCF depth (up to 100 m a.g.l.). The local and regional conditions triggering the onset, variability and characteristics of the SCF are under investigation. Another unexpected observation was made: at both sites, snow precipitations were always found to be associated with ascending winds (up to 1.2 m.s-1). To improve our understanding of the dynamical processes highlighted by the Lidar wind observations, the Polar-WRF (Weather Research and Forecasting) model will be run at a very high resolution (~1 km). The focus will be to investigate, and potentially improve, the ability of the Polar-WRF surface layer and land-surface model (via the roughness length for momentum and the stability functions) to reproduce the surface energy budget, the very and weakly stable regimes and the transition between the two at the SCF onset in a continental, high-latitude context.

International audience; Bromoform (CHBr3) belongs to very-short-lived substances (VSLSs), which are important precursors of reactive bromine species (BrOx) contributing to tropospheric and stratospheric chemistry. To date, most models calculating bromine product emissions to the atmosphere only consider the natural production of CHBr3 from marine organisms such as macroalgae and phytoplankton. However, CHBr3 has many other anthropogenic sources (coastal industrial sites, desalination and wastewater plants, ballast waters, and seawater toilets) that may drastically increase the amounts emitted in the atmosphere. Here, we report the levels of CHBr3 released in water and air (according to real-time and offline measurements by proton-transfer-reaction time-of-flight mass spectrometry (PTR-ToF-MS) and gas chromatography with electron capture detection (GC-ECD)) in a highly industrialized area where 3 million cubic meters of chlorinated seawater is released each day, which were measured during six field campaigns (at sea and on land) distributed over 3 years. The highest levels found during this survey (which were correlated to the physical–chemical characteristics of the water, meteorological and hydrological conditions, salinity, and temperature gradients along the water column) reached 34.6 μg L–1 in water (100–10 000 times higher than reported natural levels) and 3.9 ppbv in the air (100 times higher than the maximum reported value to date). These findings suggest the need to undertake sampling and analysis campaigns as close as possible to chlorinated discharges, as anthropogenic CHBr3 sources from industrial discharges may be a missing factor in global flux estimates or organic bromine to the atmosphere.

In this work, laboratory chamber experiments of gas-phase methyl iodide photolysis in the presence of ozone at three relative humidity conditions were performed to study the formation and physico-chemical properties of iodine oxide particles. The obtained results revealed significant morphological changes of iodine oxide particles that were observed to depend on relative humidity. The formed iodine oxide particles under dry conditions were supposed to be agglomerates of fine hygroscopic crystals. On the other hand, a humid atmosphere was observed to favor the formation of isomeric, tetragonal and orthorhombic hygroscopic crystals potentially composed of HIO

International audience; Plastic debris in the marine environment are the subject of an extensive literature. According to studies dedicated to the determination of plastic litter abundance and to the characterisation of degradation and fragmentation processes, models were used to estimate the global plastic debris abundance and to simulate their transfer and distribution. Despite these efforts, there is still missing plastic in the models used as areas exist where plastic abundance is less than that estimated. In parallel, microplastics presence in the atmosphere and in remote areas was confirmed suggesting long range atmospheric transport. Potentially addressing both these issues, recent literature suggests that microplastics (MPs) and nanoplastics (NPs) can be transferred from the marine environment to the atmosphere via the bursting of air bubbles at the sea surface. Nevertheless, to date there is no direct evidence of this transfer. In this study, we evaluate plastic particles transfer as a function of MPs/NPs characteristics and water composition by simulating the bubble bursting phenomenon in a laboratory reactor. Size distribution of transferred particles were recorded, and their plastic nature was confirmed using electron microscopy. Results show that under tested conditions, the transfer is possible but limited to particles smaller than 1 μm. The influence of the presence of proxies of components of the sea surface microlayer in the water was evaluated showing a higher particle transfer rate in the presence of a surfactant (sodium dodecyl sulfate) and no significant effect of polysaccharides (xanthan gum and dextran). The surface state of the particles can alter their behaviour in the aqueous phase and thus their transfer to the atmosphere. The effect of bubble size was also evaluated showing a higher transfer rate with the smaller bubble size. In addition, experiments performed with grounded polyethylene (PE) samples showed higher transfer for UV-aged PE than for pristine PE.

Changes in engine technologies and after-treatment devices can profoundly alter the chemical composition of the emitted pollutants. To investigate these effects, we characterized the emitted particles' chemical composition of three diesel and four gasoline Euro 5 light-duty vehicles tested at a chassis dynamometer facility. The dominant emitted species was black carbon (BC) with emission factors (EFs) varying from 0.2 to 7.1 mg km−1 for direct-injection gasoline (GDI) vehicles, from 0.02 to 0.14 mg km−1 for port fuel injection (PFI) vehicles, and 0.003 to 0.9 mg km−1 for diesel vehicles. The organic matter (OM) EFs varied from 5 to 103 µg km−1 for GDI gasoline vehicles, from 1 to 8 µg km−1 for PFI vehicles, and between 0.15 and 65 µg km−1 for the diesel vehicles. The first minutes of cold-start cycles contributed the largest PM fraction including BC, OM, and polycyclic aromatic hydrocarbons (PAHs). Using a high-resolution time-of-flight mass spectrometer (HR-ToF-AMS), we identified more than 40 PAHs in both diesel and gasoline exhaust particles including methylated, nitro, oxygenated, and amino PAHs. Particle-bound PAHs were 4 times higher for GDI than for PFI vehicles. For two of the three diesel vehicles the PAH emissions were below the detection limit, but for one, which presented an after-treatment device failure, the average PAHs EF was 2.04 µg km−1, similar to the GDI vehicle's values. During the passive regeneration of the catalysed diesel particulate filter (CDPF) vehicle, we measured particles of diameter around 15 nm mainly composed of ammonium bisulfate. Transmission electron microscopy (TEM) images revealed the presence of ubiquitous metal inclusions in soot particles emitted by the diesel vehicle equipped with a fuel-borne-catalyst diesel particulate filter (FBC-DPF). X-ray photoelectron spectroscopy (XPS) analysis of the particles emitted by the PFI vehicle showed the presence of metallic elements and a disordered soot surface with defects that could have consequences on both chemical reactivity and particle toxicity. Our findings show that different after-treatment technologies have an important effect on the emitted particles' levels and their chemical composition. In addition, this work highlights the importance of particle filter devices' condition and performance.

Biogenic Volatile Organic Compounds (BVOC) are largely accepted to contribute to both atmospheric chemistry and ecosystem functioning. While the forest canopy is recognized as a major source of BVOC, emissions from plant litter have scarcely been explored with just a couple of studies being focused on emission patterns over litter decomposition process. The aim of this study was to quantitatively and qualitatively characterize BVOC emissions (C1–C15) from Pinus halepensis litter, one of the major Mediterranean conifer species, over a 15‐month litter decomposition experiment. Senescent needles of P. halepensis were collected and placed in 42 litterbags where they underwent in situ decomposition. Litterbags were collected every 3 months and litter BVOC emissions were studied in vitro using both online (PTR‐ToF‐MS) and offline analyses (GC‐MS). Results showed a large diversity of BVOC (58 compounds detected), with a strong variation over time. Maximum total BVOC emissions were observed after 3 months of decomposition with 9.18 µg gDM −1 hr−1 mainly composed by terpene emissions (e.g., α‐pinene, terpinolene, β‐caryophyllene). At this stage, methanol, acetone, and acetic acid were the most important nonterpenic volatiles representing, respectively, up to 26%, 10%, and 26% of total emissions. This study gives an overview of the evolution of BVOC emissions from litter along with decomposition process and will thus contribute to better understand the dynamics and sources of BVOC emission in Mediterranean pine forests., We investigated the evolution of the BVOC emissions from the litter of Pinus halepensis during a 15‐month field decomposition experiment. High variability of emissions over decomposition was showed using online and offline measurements performed in vitro. Major compounds observed were monoterpenes, sesquiterpenes, and methanol, and their quantity and quality (terpenic composition) varied over sampling times with a high peak after 3 months of litter decomposition and, for a lesser extent, after 6 months for terpenic emission.

A supersite was recently implemented in Marseille to conduct intensive and advanced measurement studies for ambient aerosols. A Time-of-Flight Aerosol Chemical Speciation Monitor (ToF-ACSM) was deployed to investigate the chemical composition of submicronic aerosol over a 14-month period (1 February 2017–13 April 2018). Parallel measurements were performed with an Aethalometer, an ultrafine particle monitor and a suite of instruments to monitor regulated pollutants (PM2.5, PM10, NOx, O3 and SO2). The averaged PM1 chemical composition over the period was dominated by organics (49.7 %) and black carbon (17.1 %) while sulfate accounted for 14.6 %, nitrate for 10.2 %, ammonium for 7.9 % and chloride for 0.5 % only. Wintertime was found to be the season contributing the most to the annual PM1 mass concentration (30 %), followed by autumn (26 %), summer (24 %) and spring (20 %). During this season, OA and BC concentrations were found to contribute to 32 % and 31 % of their annual concentrations, respectively, as a combined result of heavy urban traffic, high emissions from residential heating, open combustion of green wastes and low planetary boundary layer (PBL) height. In summer, sulfate contribution to PM1 increased with an average and a maximum contribution to the PM1 of 24 % and 66 %. This is partly due to local photochemical production from its precursor SO2, locally emitted by shipping and industrial activities and advected to the city under sea breeze conditions. Results from backtrajectory cluster analysis suggest that, besides local anthropogenic activities, Mediterranean long-range transport contributes the most to the enrichment of the sulfate fraction. Another important feature of the summer season is that half of the most intense SO2 peaks happen at that time of the year and are associated to higher UFPs number. The fifteen days exceeding the target daily PM2.5 concentration value recommended by the World Health Organization (WHO) occurred during the cold period (late autumn-early spring). These episodes contribute to an increase of 6.5 % of the annual PM1 concentration. Local and long-range pollution episodes could be distinguished, accounting for 40 and 60 % of the exceedance days, respectively. Enhanced OA and BC concentrations, mostly originating from domestic wood burning under nocturnal land breeze conditions were observed during local pollution episodes, while high level of oxygenated OA and inorganic nitrate were associated to medium/long-range transported particles. In conclusion this supersite showed a high potential for the study of seasonality and pollution episodes phenomenology in Marseille over multiple geographic scales. The present paper highlights the significant contribution of regional transport of pollutants to the local air pollution that must be considered by local authorities in deploying effective PM abatement strategies.

Changes in engine technologies and after-treatment devices can profoundly alter the chemical composition of the emitted pollutants. To investigate these effects, we characterized the chemical composition of particles emitted from three diesel and four gasoline Euro 5 light duty vehicles on a chassis dynamometer facility. Black carbon (BC) was the dominant emitted species with emission factors (EFs) varying from 0.2 to 7.1 mg km−1 for gasoline cars and 0.003 to 0.08 mg km−1 for diesel cars. For gasoline cars, the organic matter (OM) EFs varied from 5 to 103 µg km−1 for direct injection (GDI) vehicles, and from 1 to 8 µg km−1 for port fuel injection (PFI) vehicles, while for the diesel cars it ranged between 0.15 and 65 µg km−1. Cold-start cycles and more specifically the first minutes of the cycle, contributed the largest fraction of the PM including BC, OM and Polycyclic Aromatic Hydrocarbons (PAHs). More than 40 PAHs, including methylated, nitro, oxygenated and amino PAHs were identified and quantified in both diesel and gasoline exhaust particles using an Aerodyne High Resolution Time-of-Flight Aerosol Mass Spectrometry (HR-ToF-AMS). The PAHs emissions from the GDI technology were a factor of 4 higher compared to the vehicles equipped with a PFI system during the cold start cycle, while the nitro-PAHs fraction was much more appreciable in the GDI emissions. For two of the three diesel vehicles the PAHs emissions were close to the detection limit, but for one, which presented an after-treatment device failure, the average PAHs EF was 2.04 µg km−1. Emissions of nanoparticles (below 30 nm), mainly composed by ammonium bisulfate, were measured during the passive regeneration of the catalyzed diesel particulate filter (CDPF) vehicle. TEM images confirmed the presence of ubiquitous nanometric metal inclusions into soot particles emitted from the diesel vehicle equipped with a fuel borne catalyst – diesel particulate filter (FBC-DPF). XPS analysis of the particles emitted by the PFI car revealed both the presence of heavy elements (Ti, Zn, Ca, Si, P, Cl), and disordered soot surface with a significant concentration of carbon radical defects having possible consequences on both chemical reactivity and particle toxicity. Our findings show that different after-treatment technologies have an important effect on the level and the chemical composition of the emitted particles. In addition, this research highlights the importance of the particle filter devices condition and their regular checking.

Given the toxic nature of many volatile organic compounds (VOCs) present within indoor environments, it is necessary to develop new materials to eliminate them. Photocatalytic paints represent a promising technology to remove the indoor pollutants but they are not optimised yet. Here we evaluate the capacities of one conventional white-wall paint, three photocatalytic paints containing 3.5, 5.25 and 7% of nano-TiO2 PC 500, and two photocatalytic paints with a hybrid cellulose nanocrystals-nano-TiO2 (CNC-nano-TiO2) to eliminate m-xylene from the indoor environment. In particular, we assess the impact of nano-TiO2 content, light intensity, relative humidity (RH), surface temperature (288–320 K) and pigment volume concentration (PVC) on uptake of m-xylene. Uptake coefficients of m-xylene increase by a factor 3, 5 and 3, respectively, as a function of nano-TiO2 content, irradiance and PVC. In contrast, uptakes of m-xylene decrease for a factor of 2 and 3, as a function of RH, and surface, suppressing the photocatalytic activity. The addition of CNC-nano-TiO2 in the binder induces limited binder degradation. These are very promising results which may help to improve the performances of indoor photocatalytic paints aimed to eliminate indoor airborne pollutants.

Photocatalytic materials are a potentially effective remediation technology for indoor air purification. In this paper, we assess the impact of photocatalytic paint porosity on the indoor levels of nitrogen oxides (NOx) and nitrous acid (HONO). We observed that the porosity of photocatalytic paints plays a paramount role in the NO2 removal. The increase of pigment volume concentration (PVC), i.e. porosity, from PVC 53% to PVC 80% leads to an increase of the geometric NO2 uptake coefficient from (3.3 ± 0.5) × 10-6 to (3.2 ± 0.1) × 10-4. At the same time, a high quantity of HONO formed by NO2 conversion on the photocatalytic paint is emitted into the air. The formation of HONO, which is considered as a harmful compound and a major player in the oxidative capacity of indoor air, is reduced as the paint porosity increases. Based on these results, further optimization should be considered for future commercialization of photocatalytic paints aimed for indoor applications.

The capacity of a Quercus pubescens forest to resist recurrent drought was assessed on an in situ experimental platform through the measurement of a large set of traits (ecophysiological and metabolic) studied under natural drought (ND) and amplified drought induced by partial rain exclusion (AD). This study was performed during the 3rd and 4th years of AD, which correspond to conditions of moderate AD in 2014 and harsher AD in 2015, respectively. Although water potential (Ψ) and net photosynthesis (Pn) were noticeably reduced under AD in 2015 compared to ND, trees showed similar growth and no oxidative stress. The absence of oxidative damage could be due to a strong accumulation of α-tocopherol, suggesting that this compound is a major component of the Q. pubescens antioxidant system. Other antioxidants were rather stable under AD in 2014, but slight changes started to be observed in 2015 (carotenoids and isoprene) due to harsher conditions. Our results indicate that Q. pubescens could be able to cope with AD, for at least 4 years, likely due to its antioxidant system. However, growth decrease was observed during the 5th year (2016) of AD, suggesting that this resistance could be threatened over longer periods of recurrent drought.

To reduce the influence of biomass burning on air quality, consumers are encouraged to replace their old woodstove with new and cleaner appliances. While their primary emissions have been extensively investigated, the impact of atmospheric aging on these emissions, including secondary organic aerosol (SOA) formation, remains unknown. Here, using an atmospheric smog chamber, we aim at understanding the chemical nature and quantify the emission factors of the primary organic aerosols (POA) from three types of appliances for residential heating, and to assess the influence of aging thereon. Two, old and modern, logwood stoves and one pellet burner were operated under typical conditions. Emissions from an entire burning cycle (past the start-up operation) were injected, including the smoldering and flaming phases, resulting in highly variable emission factors. The stoves emitted a significant fraction of POA (up to 80%) and black carbon. After ageing, the total mass concentration of organic aerosol (OA) increased on average by a factor of 5. For the pellet stove, flaming conditions were maintained throughout the combustion. The aerosol was dominated by black carbon (over 90% of the primary emission) and amounted to the same quantity of primary aerosol emitted by the old logwood stove. However, after ageing, the OA mass was increased by a factor of 1.7 only, thus rendering OA emissions by the pellet stove almost negligible compared to the other two stoves tested. Therefore, the pellet stove was the most reliable and least polluting appliance out of the three stoves tested. The spectral signatures of the POA and aged emissions by a High Resolution – Time of Flight – Aerosol Mass Spectrometer (Electron Ionization (EI) at 70 eV) were also investigated. The m/z 44 (CO2+) and high molecular weight fragments (m/z 115 (C9H7+), 137 (C8H9O2+), 167 (C9H11O3+) and 181 (C9H9O4+, C14H13+)) correlate with the modified combustion efficiency (MCE) allowing us to discriminate further between emissions generated from smoldering vs flaming conditions.

Given toxic nature of many volatile organic compounds (VOCs) present within indoor environments, it is necessary to measure and quantify indoor VOC emissions to better inform and protect the public from possible adverse health effects of indoor air pollution. To better understand and quantify this problem, a horizontal flow tube reactor was used to study VOC emissions from selected paint. Studied paints include mineral silicate binders, acrylic binders and acrylic/siloxane binders with and without incorporated titanium dioxide (nano-TiO2) nanoparticles. Surface emission fluxes of selected VOCs from the tested paints were detected and quantified using a High Sensitivity-Proton Transfer Reaction-Mass Spectrometry (HS-PTR-MS). Low VOC emissions were observed for reference paints (absence of nano-TiO2) in the presence of UV irradiation. On the other hand, important formation of formaldehyde, acetaldehyde and pentanal were observed for photocatalytic paints (impregnated with nano-TiO2). VOC emission fluxes from reference paints and photocatalytic paints were compared to determine the formation of VOCs due to a reaction between the binder and radical reactive species created on photocatalytic surfaces. Different matrix impacts for each paint were studied and an important difference in VOC emission between acrylic binder paints and mineral binder paints was observed under UV irradiation. A 66%, 29% and 88% decreases in formaldehyde, acetaldehyde and pentanal, respectively, emission were observed for mineral binder compared to acrylic binder VOC emission. In majority of the experiments, mineral binder emitted less VOCs compared to acrylic binder. This mineral binder seems to be an important factor in improving indoor air quality.

We have systematically examined the gas and particle phase emissions from seven wood combustion devices. Among total carbon mass emitted (excluding CO2), CO emissions were dominant, together with nonmethane volatile organic compounds (NMVOCs) (10–40%). Automated devices emitted 1–3 orders of magnitude lower CH4 (0.002–0.60 g kg–1 of wood) and NMVOCs (0.01–1 g kg–1 of wood) compared to batch-operated devices (CH4: 0.25–2.80 g kg–1 of wood; NMVOCs: 2.5–19 g kg–1 of wood). 60–90% of the total NMVOCs were emitted in the starting phase of batch-operated devices, except for the first load cycles. Partial-load conditions or deviations from the normal recommended operating conditions, such as use of wet wood/wheat pellets, oxygen rich or deficit conditions, significantly enhanced the emissions. NMVOCs were largely dominated by small carboxylic acids and alcohols, and furans. Despite the large variability in NMVOCs emission strengths, the relative contribution of different classes showed large similarities among d...

International audience; 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 online gas chromatography coupled to mass spectrometry, and particulate chemical composition was analyzed (i) online by thermo-desorption coupled to chemical ionization mass spectrometry and (ii) offline by supercritical fluid extraction coupled to gas chromatography and mass spectrometry. 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 ozonolysis than for 2-methylstyrene ozonolysis at the same reaction advancement. For 2-methylstyrene ozonolysis, formaldehyde and o-tolualdehyde were the two main gaseous phase products while o-toluic acid was the most abundant among six products detected within the particulate phase. For indene ozonolysis, traces of formic and phthalic acids as well as 11 species were detected in the gaseous phase and 11 other products were quantified in the particulate phase, where phthaldialdehyde was the main product. On the basis of the identified products, reaction mechanisms were proposed that highlight specific pathways due to the precursor chemical structure. These mechanisms were finally compared and discussed regarding SOA formation. In the case of 2-methylstyrene ozonolysis, ozone adds mainly on the external and monosubstituted double bond, yielding only one C8- and monofunctionalized Criegee intermediate and hence more volatile products as well as lower SOA mass than indene ozonolysis in similar experimental conditions. In the case of indene, ozone adds mainly on the five-carbon-ring and disubstituted C═C double bond, leading to the formation of two C9- and bifunctionalized Criegee intermediates, which then evolve via different pathways including the hydroperoxide channel and form highly condensable first-generation products.

International audience; In this paper we focus on airborne hyperspectral imaging methodology to characterize PM (Particulate Matter) near industrial emission sources. Two short-term intensive campaigns were carried out in the vicinity of a refinery in the South of France, in September 2015 and February 2016. Different protocols of in-situ PM measurements were performed, at stack measurements (flow rate and offline chemical analysis) and on-line measurement at the refinery border (size distribution, concentration and chemistry of aerosols). A multi temporal methodology to retrieve aerosol type, to map the aerosol concentration and to quantify mass flow rate from airborne hyperspectral data is described in this paper. This method applied to the refinery detected plume from the main stack yields a black carbon to sulfate ratio of 10/90 in mass inside the plume, with an average size distribution smaller than 100 nm. These results are in a good agreement with on-line analysis of aerosols at refinery border. The resulting quantitative map with a metric spatial resolution leads to a flow rate estimated of about 1g/s and is in a good agreement with in-situ stack measurements and modelling.; Ce papier propose une méthodologie de caractérisation des PM (Particulate Matter) proches des sources industrielles par imagerie hyperspectrale aéroportée. Il s’appuie sur deux campagnes de mesures réalisées autour d’une raffinerie dans le sud de la France en Septembre 2015 et Février 2016. Différents protocoles de mesures in-situ des PM ont été réalisées dans ce cadre, mesures au niveau de l’émissaire principal (debit et analyse chimique) et mesures on-line au voisinage de la raffinerie (distribution en taille, concentration et analyse chimique). Une méthodologie multi-temporelle dédiée à l’inversion des types d’aérosols présents dans le panache permettant de fournir une carte en concentration d’aérosols et d’estimer le débit est décrite dans ce papier. Appliquée à ce cas d’étude, les resultats hyperspectraux ont permis d’estimer un rapport suie/sulfate de 10/90 en masse dans le panache avec une distribution en taille inférieure à 100nm. Ces résultats sont en bon accord avec les mesures in-situ. Les cartes en concentration obtenue à une resolution métrique permettent d’estimer un debit de l’ordre de 1g/s en bon accord avec les mesures in-situ au niveau de l’émissaire et avec les résultats de modélisation de dispersion des aerosols.

Earth, as a whole, can be considered as a living organism emitting gases and particles into its atmosphere, in order to regulate its own temperature. In particular, oceans may respond to climate change by emitting particles that ultimately will influence cloud coverage. At the global scale, a large fraction of the aerosol number concentration is formed by nucleation of gas-phase species, but this process has never been directly observed above oceans. Here we present, using semicontrolled seawater-air enclosures, evidence that nucleation may occur from marine biological emissions in the atmosphere of the open ocean. We identify iodine-containing species as major precursors for new particle clusters’ formation, while questioning the role of the commonly accepted dimethyl sulfide oxidation products, in forming new particle clusters in the region investigated and within a time scale on the order of an hour. We further show that amines would sustain the new particle formation process by growing the new clusters to larger sizes. Our results suggest that iodine-containing species and amines are correlated to different biological tracers. These observations, if generalized, would call for a substantial change of modeling approaches of the sea-to-air interactions.

Hyphenated laser ablation-mass spectrometry instruments have been recognized as useful analytical tools for the detection and chemical characterization of aerosol particles. Here we describe the performances of a Laser Ablation Aerosol Particle-Time-of-Flight Mass Spectrometer (LAAP-ToF-MS) which was designed for aerodynamic particle sizing using two 405 nm scattering lasers and characterization of the chemical composition of single aerosol particle via ablation/ionization by a 193 nm excimer laser and detection in a bipolar time-of flight mass spectrometer with a mass resolving power of m/Δm > 600. A laboratory based optimization strategy is described for the development of an analytical methodology for characterization of atmospheric particles using the LAAP-ToF-MS instrument in combination with a particle generator, a differential mobility analyzer and an optical particle counter. We investigated the influence of a suite of variables (particle number concentration, particle size and particle composition on the detection efficiency). The detection efficiency is a product of the scattering efficiency of the laser diodes and the ionization efficiency or hit rate of the excimer laser. The scattering efficiency was found to vary between 0.6 and 1.9 % with an average of 1.1 %; the relative standard deviation (RSD) was 17.0 %. The hit rate exhibited an excellent repeatability with an average value of 63 % and an RSD of 18 %. In addition to laboratory tests, ambient air was sampled by LAAP-ToF-MS during a period of six days at the campus of Aix-Marseille University, situated in the city center of Marseille, France. The optimized LAAP-ToF-MS methodology enables high temporal resolution measurements of the chemical composition of ambient particles, provides new insights into environmental science, and a new investigative tool for atmospheric chemistry and physics, aerosol science and health impact studies.

The impact of cloud events on isoprene secondary organic aerosol (SOA) formation has been studied from an isoprene/NOx/light system in an atmospheric simulation chamber. It was shown that the presence of a liquid water cloud leads to a faster and higher SOA formation than under dry conditions. When a cloud is generated early in the photooxidation reaction, before any SOA formation has occurred, a fast SOA formation is observed with mass yields ranging from 0.002 to 0.004. These yields are two and four times higher than those observed under dry conditions. When the cloud is generated at a later photooxidation stage, after isoprene SOA is stabilized at its maximum mass concentration, a rapid increase (by a factor of two or higher) of the SOA mass concentration is observed. The SOA chemical composition is influenced by cloud generation: the additional SOA formed during cloud events is composed of both organics and nitrate containing species. This SOA formation can be linked to water soluble volatile organic compounds (VOCs) dissolution in the aqueous phase and to further aqueous phase reactions. Cloud-induced SOA formation is experimentally demonstrated in this study, thus highlighting the importance of aqueous multiphase systems in atmospheric SOA formation estimations.

The vertical profile of new particle formation (NPF) events was studied by comparing the aerosol size number distributions measured aloft and at surface level in a suburban environment in Madrid, Spain, using airborne instruments. The horizontal distribution and regional impact of the NPF events was investigated with data from three urban, urban background, and suburban stations in the Madrid metropolitan area. Intensive regional NPF episodes followed by particle growth were simultaneously recorded at three stations in and around Madrid during a field campaign in July 2016. The urban stations presented larger formation rates compared to the suburban station. Condensation and coagulation sinks followed a similar evolution at all stations, with higher values at urban stations. However, the total number concentration of particles larger than 2.5 nm was lower at the urban station and peaked around noon, when black carbon (BC) levels are at a minimum. The vertical soundings demonstrated that ultrafine particles (UFPs) are formed exclusively inside the mixed layer. As convection becomes more effective and the mixed layer grows, UFPs are detected at higher levels. The morning soundings revealed the presence of a residual layer in the upper levels in which aged particles (nucleated and grown on previous days) prevail. The particles in this layer also grow in size, with growth rates significantly smaller than those inside the mixed layer. Under conditions with strong enough convection, the soundings revealed homogeneous number size distributions and growth rates at all altitudes, which follow the same evolution at the other stations considered in this study. This indicates that UFPs are detected quasi-homogenously in an area spanning at least 17 km horizontally. The NPF events extend over the full vertical extension of the mixed layer, which can reach as high as 3000 m in the area, according to previous studies. On some days a marked decline in particle size (shrinkage) was observed in the afternoon, associated with a change in air masses. Additionally, a few nocturnal nucleation-mode bursts were observed at the urban stations, for which further research is needed to elucidate their origin. © Author(s) 2018., This work was supported by the Spanish Ministry of Agriculture, Fishing, Food and Environment; the Ministry of Economy, Industry and Competitiveness; the Madrid City Council and Regional Government; FEDER funds under the project HOUSE (CGL2016-78594-R); the CUD of Zaragoza (project CUD 2016-05); the Government of Catalonia (AGAUR 2017 SGR44); and the Korean Ministry of Environment through “The Eco-Innovation project”. The funding received by ERA-PLANET (http://www.era-planet.eu, last access: 16 November 2018), the trans-national project SMURBS (http://www.smurbs.eu, last access: 16 November 2018) (Grant agreement No. 689443), and the support of the Academy of Finland via the Center of Excellence in Atmospheric Sciences are acknowledged. These results are part of a project (ATM-GTP/ERC) that has received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation program (Grant agreement No. 742206). The authors also acknowledge the Doctoral program of Atmospheric Sciences at the University of Helsinki (ATM-DP). Markku Kulmala acknowledges the support of the Academy of Finland via his Academy Professorship (no. 302958). We also thank the City Council of Majadahonda for logistic assistance, and the Instituto de Ciencias Agrarias, Instituto de Salud Carlos III, Alava Ingenieros, TSI, Solma Environmental Solutions, and Airmodus for their support.

The charge-transfer-reaction between molecular oxygen ions (O2+) and methyl iodide (CH3I) is studied to investigate if consistent environmental quantification of the gas phase CH3I is possible without prior calibration. The neutral CH3I molecule was chosen because this compound is of atmospheric chemistry and environmental importance in the field of nuclear power plant safety and nuclear energy. Molecular oxygen was used as a reagent ion source in a commercial Proton-Transfer-Reaction Time-of-Flight Mass Spectrometer (PTR-ToF-MS) to produce molecular oxygen ions (O2+). The use of O2+ ions allows for fast, sensitive and specific detection of gas phase CH3I via an electron exchange reaction O2+ + CH3I → CH3I+ + O2. The instrument response was linear in the 0.23–150 ppbv range and its sensitivity was humidity independent. The detection sensitivity of CH3I normalized by the O2+ count rate of 106 cps was found to be S = 22.6 ± 0.3 ncps/ppbv, independent of relative humidity. A typical O2+ primary ion signal was ( 2.0 ± 0.2 ) × 10 6 cps. The lowest measured CH3I concentration was 0.23 ± 0.10 ppb. Error is ±σ. The theoretical collision rate based on the dipole moment and molecular polarizability values is calculated using the Langevin collision rate (kL) approximation, the average-dipole-orientation (ADO) theory and the capture rate coefficient (kCAP) based on trajectory calculations. The experimental rate constant, kexp, for the electron transfer reaction between O2+ ions and CH3I is calculated to be 1.72 ± 0.22 × 10 - 9 cm3s−1. Listed errors are ±σ and represent precision only. The experimentally determined value agrees very well with the theoretical collision rate values, k L = 1.24 × 10 - 9 cm3s-1, k ADO = 1.73 × 10 - 9 cm3s−1 and k CAP = 1.48 × 10 - 9 cm3s-1. The obtained results indicate that the PTR-MS technique is an excellent analytical method to quantify gas phase CH3I.

International audience; Residential coal combustion is a significant contributor to particulate urban air pollution in Chinese mega cities and some regions in Europe. While the particulate emission factors and the chemical characteristics of the organic and inorganic aerosol from coal combustion is extensively studied, the chemical composition and non methane organic gas (NMOG) emission factors from residential coal combustion are mostly unknown. We conducted 23 individual burns in a traditional Chinese stove used for heating and cooking using five different coals with Chinese origins, characterizing the NMOG emissions using a proton transfer reaction time-of-fight mass spectrometer. The measured emission factors range from 1−15 g/kgcoal for bituminous coals and are below 0.1 g/kgcoal for anthracite coals. The emission factors from the bituminous coals are mostly influenced by the time until the coal is fully ignited. The emissions from the bituminous coals are dominated by aromatic and oxygenated aromatic compounds with a significant contribution of hydrocarbons. The results of this study can help to improve urban air pollution modeling in China and eastern Europe and can be used to constrain a coal burning factor in ambient gas phase positive matrix factorization studies.

A Thermal Desorption Aerosol Gas Chromatograph coupled to a High Resolution – Time of Flight – Aerosol Mass Spectrometer (TAG-AMS) was connected to an atmospheric chamber for the molecular characterization of the evolution organic aerosol (OA) emitted by woodstoves appliances for residential heating. Two logwood stoves (old and modern) and one pellet stove were operated under typical conditions. Emissions were aged during a time equivalent to 5 hours of atmospheric aging. 5 to 7 samples were collected and analyzed with TAG-AMS during each experiment. We detect and quantify over 70 compounds, including levoglucosan and nitrocatechols. We calculate the emission emissions factor (EF) of these tracers in the primary emissions and highlight the influence of the combustion efficiency on these emissions. Smoldering combustion contribute to higher EF and a more complex composition. We also demonstrate the effect of the atmospheric aging on the chemical fingerprint. The tracers are sorted into 3 categories according to the evolution of their concentration: primary compounds, non-conventional primary compounds, and secondary compounds. For each we provide a quantitative overview of their contribution to the OA mass at different times of the photo-oxidative process.

International audience; In this work, the proton transfer reaction between the hydronium ion (H 3 O +) and methyl iodide (CH 3 I) is studied to investigate if consistent quantification of the gas phase CH 3 I is possible in humid air. The neutral CH 3 I molecule was chosen because this compound is of environmental importance in the field of nuclear power plant safety and nuclear energy. Water was used as a reagent ion source in a conventional Insbruck PTR-MS to produce H 3 O + reagent ions. The use of H 3 O + ions allows for fast, sensitive and specific detection of gas phase CH 3 I via a proton-transfer reaction H 3 O + + CH 3 I → [CH 3 I-H] + + H 2 O. The instrument response was linear in the tested 5 to 96 ppbV range and the PTR-MS sensitivity was observed to be humidity dependent. The observed sensitivity was in found to range between 1.6 to 3.3 cps/ppb at relative humidity between 63 and 15% at T= 23 • C. A typical H 3 O + primary ion signal was 10 7 cps and the normalized sensitivity was in the range between 0.16 and 0.33 ncps/ppb. The instrument CH 3 IH + ion background rate was 6.8 ± 1.4 cps and the dwell time was 1 second. The detection limit was calculated as 3 times the standard deviation of the background level and ranged between 1.3 and 3.8 ppb. The theoretical collision rate based on the dipole moment and molecular polarizability is calculated. The theoretical collision rate is compared with the experimentally obtained values. The results indicate that the PTR-MS technique is a good analytical method to detect and quantify gas phase CH 3 I concentrations.

Vapor wall loss has only recently been shown a potentially significant bias in atmospheric chamber studies. Yet, previous works aimed at the determination of the degradation rate of semi-volatile organic compounds (SVOCs) often did not account for this process. Here we evaluate the influence of vapor wall loss on the determination of the gas phase reaction rate kOH of several biomass burning markers (levoglucosan, mannosan, coniferyl aldehyde, 3-guaiacyl propanol, and acetosyringone) with hydroxyl radicals (OH). Emissions from the combustion of beech wood were injected into a 5.5 m3 Teflon atmospheric chamber, and aged for 4 hours (equivalent to 5–8 hours in the atmosphere). The particle phase compound concentrations were monitored using a Thermal Desorption Aerosol Gas Chromatograph coupled to a High-Resolution – Time of Flight – Mass Spectrometer (TAG-AMS). The observed depletion of the concentration was later modeled using two different approaches: the previously published approach which does not take into consideration partitioning and vapor wall loss, and an approach with a more complex theoretical framework which integrates all the processes likely influencing the particle phase concentration. We find that with the first approach one fails to predict the measured markers concentration time evolution. With the second approach, we determine that partitioning and vapor wall loss play a predominant role in the particle phase concentration depletion of all the compounds, while the reactivity with OH has a non-significative effect. Furthermore we show that kOH cannot be determined precisely without a strong constraint of the whole set of physical parameters necessary to formally describe the various processes involved. It was found that the knowledge of the saturation mass concentration C* is especially crucial. Therefore previously published rate constants of levoglucosan and more generally SVOCs with hydroxyl radicals inferred from atmospheric chamber experiments must be, at least, considered with caution.

Photocatalytic paints based on titanium dioxide (TiO2) nanoparticles represent a promising treatment technology for cleaning the air at our dwellings. A few studies have shown that instead of elimination of harmful indoor air pollutants the production of carbonyl compounds occurs from the photocatalytic paints. Herein, we report unexpectedly high concentrations of volatile organic compounds (VOCs) released upon irradiation of photocatalytic paints which are meant to clean the air at our dwellings. The concentrations of the VOCs were measured continuously and online by PTR-ToF-MS (Proton Transfer Reaction-Time of Flight-Mass Spectrometry) connected to a well-established flow tube photoreactor. The PTR-ToF-MS analysis revealed the presence of 52 ions in the mass range between 20 and 490 amu, among which 43 have been identified. In particular very high emission rates were estimated of two relevant indoor air pollutants, formaldehyde and acetaldehyde as 355 μg h–1 and 257 μg h–1 for 1 m2, respectively. We sug...

Various studies have reported that photochemical nucleation of new ultrafine particles (UFP) in urban environments within high insolation regions occurs simultaneously with high ozone (O3). In this work, we evaluate the atmospheric dynamics leading to summer O3 episodes in the Madrid Air Basin (Central Iberia) by means of measuring a 3D distribution of concentrations for both pollutants. To this end, we obtained vertical profiles (up to 1200 m, above ground level) using tethered balloons and miniaturised instrumentation at a suburban site located to the SW of the Madrid Metropolitan Area (MMA), Majadahonda site (MJDH) in July 2016. Simultaneously, measurements of an extensive number of air quality and meteorological parameters were carried out at 3 supersites across the MMA. Furthermore, data from O3-soundings and daily radio-sounding were also used to interpret the atmospheric dynamics. The results demonstrate the concatenation of venting and accumulation episodes, with relative O3 lows (venting) and peaks (accumulation) in surface levels. Regardless of the episode type, fumigation of high altitude O3-rich layers contributes the major proportion of surface O3 concentrations. Accumulation episodes are characterised by a relatively thinner planetary boundary layer (PBL 2400 m). This orographic-meteorological setting causes the vertical recirculation of air masses and the enrichment of O3 in the lower tropospheric layers. When the highly polluted urban plume from Madrid is affected by these dynamics, the highest Ox (O3 + NO2) concentrations are recorded in the MMA. Vertical O3 profiles during venting episodes, with marked synoptic winds and a deepening of the PBL reaching > 2000 m above sea level, were characterised by an upward gradient in O3 levels, whereas low-altitude O3 concentration maxima due to local/regional production were found during the accumulation episodes. The two contributions to O3 surface levels (fumigation from high altitude strata and local/regional production) require very different approaches for policy actions. In contrast to O3 vertical top-down transfer, UFP are formed in the lowest levels and are transferred upwards progressively with the growth of the PBL.

The capacity of a Quercus pubescens forest to resist recurrent drought was assessed on an in situ experimental platform through the measurement of a large set of traits (ecophysiological and metabolic) studied under natural drought (ND) and amplified drought (AD) induced by partial rain exclusion. This study was performed during the third and fourth years of AD, which correspond to conditions of moderate AD in 2014 and harsher AD in 2015, respectively. Although water potential (Ψ) and net photosynthesis (Pn) were noticeably reduced under AD in 2015 compared to ND, trees showed similar growth and no oxidative stress. The absence of oxidative damage could be due to a strong accumulation of α-tocopherol, suggesting that this compound is a major component of the Q. pubescens antioxidant system. Other antioxidants were rather stable under AD in 2014, but slight changes started to be observed in 2015 (carotenoids and isoprene) due to harsher conditions. Our results indicate that Q. pubescens could be able to cope with AD, for at least 4 years, likely due to its antioxidant system. However, growth decrease was observed during the fifth year (2016) of AD, suggesting that this resistance could be threatened over longer periods of recurrent drought.

Aerosol-cloud interaction contributes to the largest uncertainties in the estimation and interpretation of the Earth's changing energy budget. The present study explores experimentally the impacts of water condensation-evaporation events, mimicking processes occurring, in atmospheric clouds, on the molecular composition of secondary organic aerosol (SOA) from the photooxidation of methacrolein. A range of on and off-line mass spectrometry techniques were used to obtain a detailed chemical characterization of SOA formed in control experiments in dry conditions, in triphasic experiments simulating gas-particle-cloud droplet interactions (starting from dry conditions and from 60% relative humidity (RH)), and in bulk aqueous-phase experiments. We observed that cloud events trigger fast SOA formation accompanied by evaporative losses. These evaporative losses decreased SOA concentration in the simulation chamber by 25-32% upon RH increase, while aqueous SOA was found to be metastable and slowly evaporated after cloud dissipation. In the simulation chamber, SOA composition measured with a high-resolution time-of flight aerosol mass spectrometer, did not change during cloud events compared with high RH conditions (RH > 80%). In all experiments, off-line mass spectrometry techniques emphasize the critical role of 2-methylglyceric acid as a major product of isoprene chemistry, as an important contributor to the total SOA mass (15-20%) and as a key building block of oligomers found in the particulate phase. Interestingly, the comparison between the series of oligomers obtained from experiments performed under different conditions show a markedly different reactivity. In particular, long reaction times at high RH seem to create the conditions for aqueous-phase processing to occur in a more efficient manner than during two relatively short cloud events.

International audience; An undesirable consequence of disinfection is the formation of chemical contaminants known as disinfection byproducts (DBPs). Chronic exposure to DBPs has been linked to adverse health effects. The occurrence of DBPs in chlorinated pools filled with seawater (such as thalassotherapy pools and pools in spas) has received little attention so far. The present study evaluated the speciation and levels of disinfection byproducts in indoor swimming pools filled with seawater and treated with chlorine. Water and air samples were collected from three indoor swimming pools located in Southern France. Several classes of DBPs including trihalomethanes, haloacetic acids, haloacetonitriles, and trihaloacetaldehydes were analyzed in water. Halogenated volatile organic compounds were analyzed in air. Extractable organic halide (EOX) contents were determined using combustion micro-coulometry system. The speciation of DBPs identified in the three pools was predominantly brominated. The mean (arithmetic) concentration of bromoform, dibromoacetic acid, tribromoacetic acid, dibromoacetonitrile and bromal hydrate in the three pools were 79.2, 72.9, 59.9, 26.9 and 10.0 µg/L, respectively. By weight, HAAs represented the most abundant chemical class followed by THMs. In air, bromoform was the most abundant THM occurring at a mean concentration of 133.2 µg/m 3 in the three pools. The mean EOX level was 706 µgCl-/L for the three pools. In average, the quantified DBPs accounted for only 14% of EOX, thus 86% of EOX remained unknown. Further research is warranted to identify the unknown DBPs.

SSCI-VIDE+CARE+RGM:NHY; International audience; 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 mob ility 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+

Newborn altricial mammals need just after birth to locate their mother's nipples for suckling. In this precocious behavior, including for the human baby, maternal odor via the olfactory process plays a major role. Maternal odor emitted by lactating females or by amniotic fluid (AF) attracts pups, but the chemical identity of this attractant has not yet been elucidated. Here, using behavioral tests and gas chromatography coupled with mass spectrometry (GC-MS) techniques, we show that AF extracts from rat pregnant female, nipples, ventral skin, milk, and nest extracts of mother contained 3-6 active substances. AF extracts contained 3 active compounds: ethylbenzene, benzaldehyde, and benzyl alcohol, and their mixture in similar proportions to those found in AF extracts, in a ratio, respectively, of 1:1:12 (700 ng), attracts pups as putative maternal attractant substances (MAS). These 3 AF substances have already been identified in milk, nipples, ventral wash, and nest extracts of mother, but not in feces. Moreover, anethole flavor incorporated in pregnant rat and mother's diet is also detected in AF, nipples, milk, and nest extracts and the pups are attracted to anethole odor, but not in the case of the no-anethole pups. MAS, combined with diet flavors present in the AF bath, represent olfactory signals as "maternal signature odors" (MSO) that are learned by fetus and pups. These findings open the way to improved understanding of the neurobiology of early olfactory learning and of the importance of evolutionarily conserved survival behavior in many mammal species.