The uptake kinetics of ozone (O3) and methyl hydroperoxide (CH3OOH, MHP) by aqueous solutions were studied as a function of temperature using the droplet train technique combined with mass spectrometry detection. The uptake of ozone by pure water was found to be too small to be directly measured. Using NaI as a scavenger increased the uptake coefficient γ from below the detection limit to a range from 0.0037 to 0.0116 for I- activities in the range from 0.3615 to 2.889 at 282 K. From these experiments, we estimated the second-order rate constant for the reaction O3 + I- → products to be in the range 3.2 × 108 to 2.4 × 109 M-1 s-1 for temperature between 275 and 293 K. The activation parameters for this reaction were also estimated. For methyl hydroperoxide, the uptake rate on pure water was fast enough to be directly measured. According to the physicochemical properties of this hydroperoxide, the uptake was mainly due to the diffusion and accommodation processes. It was therefore possible to measure its mass accommodation coefficient α as a function of temperature. The observed values are in the range 0.92 × 10-2 to 2.08 × 10-2 for temperature between 281 and 261 K. The activation parameters for the accommodation were also determined.

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Abstract. Reactive oxygen species (ROS) carried or induced by particulate matter (PM) are suspected of inducing oxidative stress in vivo, leading to adverse health impacts such as respiratory or cardiovascular diseases. The oxidative potential (OP) of PM, displaying the ability of PM to oxidize the lung environment, is gaining strong interest in examining health risks associated with PM exposure. In this study, OP was measured by two different acellular assays (dithiothreitol, DTT, and ascorbic acid, AA) on PM10 filter samples from 15 yearly time series of filters collected at 14 different locations in France between 2013 and 2018, including urban, traffic and Alpine valley site typologies. A detailed chemical speciation was also performed on the same samples, allowing the source apportionment of PM using positive matrix factorization (PMF) for each series, for a total number of more than 1700 samples. This study then provides a large-scale synthesis of the source apportionment of OP using coupled PMF and multiple linear regression (MLR) models. The primary road traffic, biomass burning, dust, MSA-rich, and primary biogenic sources had distinct positive redox activity towards the OPDTT assay, whereas biomass burning and road traffic sources only display significant activity for the OPAA assay. The daily median source contribution to the total OPDTT highlighted the dominant influence of the primary road traffic source. Both the biomass burning and the road traffic sources contributed evenly to the observed OPAA. Therefore, it appears clear that residential wood burning and road traffic are the two main target sources to be prioritized in order to decrease significantly the OP in western Europe and, if the OP is a good proxy of human health impact, to lower the health risks from PM exposure.

The study of the geochemical compositions and K-Ar or Ar-Ar ages of ca. 350Neogene and Quaternary lavas from Baja California, the Gulf of California and Sonora allows us to discuss the nature of their mantle or crustal sources, the conditions of their melting and the tectonic regime prevailing during their genesis and emplacement. Nine petrographic/geochemical groups are distinguished: "regular" calc-alkaline lavas; adakites; magnesian andesites and related basalts and basaltic andesites; niobium-enriched basalts; alkali basalts and trachybasalts; oceanic (MORB-type) basalts; tholeiitic/transitional basalts and basaltic andesites; peralkaline rhyolites (comendites); and icelandites. We show that the spatial and temporal distribution of these lava types provides constraints on their sources and the geodynamic setting controlling their partial melting. Three successive stages are distinguished. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 3 mantle of the Gulf area, generating calc-alkaline lavas as well as adakites derived from slivers of oceanic crust incorporated within this mantle.

The kinetics of sulphur(IV) oxidation by ozone in an aqueous solution were studied in various supporting electrolytes (NaClO4, NaCl, NH4ClO4, Na2SO4), using the stopped flow method. The rate data in perchlorate medium (chosen as reference electrolyte) are empirically correlated by the following expression: r = −d[O3]/dt = k [O3] [S(IV)] [H+]−1/2. For each supporting electrolyte studied, the rate constant varies linearly with the ionic strength. The value of the rate constant is extrapolated to zero ionic strength (1.65 × 104 mol−0.5 L0.5 s−1). The rate constants are shown to be higher mainly when ammonium chloride and sodium sulphate are added to the solution. The effect of temperature is studied between 13 ° and 28 °C. The reaction rate is unaffected by the trace presence of metal ion (Mn2+, Fe2+, Cu2+, Fe3+, Cr3+). The rate of oxidation of dissolved SO2 by O3, in water droplets under atmospheric conditions (presence of [H2O2] = 4.31 × 10−5 mol L−1 and [O3] = 1.17 × 10−9 mol L−1), is calculated as a function of [H+] and compared to the oxidation by H2O2. At zero ionic strength the ozone reaction becomes faster than hydrogen peroxide reaction above −log [H+] = 4.70. This effect appears at higher H+ concentration when the ionic strength increases (−log [H+] = 3 in 4 mol L−1 NaCl or 2 mol L−1 Na2SO4).

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The heterogeneous chemistry of trichloroacetyl chloride was studied using two different techniques allowing direct measurements of the uptake rate by water droplets and of the homogeneous aqueous phase hydrolysis rate. The first technique used was the droplet train technique for the study of the gas/liquid interaction which yielded uptake coefficients lower than 10−3 and estimates of the Henry's law constant H of 2 M atm−1 and of the hydrolysis rate constant kh of 500 s−1 for pH < 3.5. The second technique used was a stopped‐flow method for the homogeneous aqueous phase study. The results led to a hydrolysis rate constant of 150 s−1 in pure water for pH between 4.8 and 5.8 and strongly catalyzed by hydrogen and hydroxide ions. The results show that trichloroacetyl chloride can react readily with water leading to short residence time in the atmosphere.

An original source apportionment study was conducted on atmospheric particles (PM10) collected in Metz, one of the largest cities of Eastern France. A Positive matrix factorization (PMF) analysis was applied to a sampling filter-based chemical dataset obtained for the April 2015 to January 2017 period. Nine factors were clearly identified, showing mainly contributions from anthropogenic sources of primary PM (19.2% and 16.1% for traffic and biomass burning, respectively) as well as secondary aerosols (12.3%, 14.5%, 21.8% for sulfate-, nitrate-, and oxalate-rich factors, respectively). Wood-burning aerosols exhibited strong temporal variations and contributed up to 30% of the PM mass fraction during winter, while primary traffic concentrations remained relatively constant throughout the year. These two sources are also the main contributors during observed PM10 pollution episodes. Furthermore, the dominance of the oxalate-rich factor among other secondary aerosol factors underlines the role of atmospheric processing to secondary organic aerosol loadings which are still poorly characterized in this region. Finally, Concentration-Weighted Trajectory (CWT) analysis were performed to investigate the geographical origins of the apportioned sources, notably illustrating a significant transport of both nitrate-rich and sulfate-rich factors from Northeastern Europe but also from the Balkan region.