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Acetone is ubiquitous in the troposphere. Several papers have focused in the past on its gas phase reactivity and its impact on tropospheric chemistry. However, acetone is also present in atmospheric water droplets where its behaviour is still relatively unknown. In this work, we present its gas/aqueous phase transfer and its aqueous phase photooxidation. The uptake coefficient of acetone on water droplets was measured between 268 and 281 K ( γ = 0.7 × 10 −2 –1.4 × 10 −2 ), using the droplet train technique coupled to a mass spectrometer. The mass accommodation coefficient α (derived from γ ) was found in the range (1.0–3.0 ± 0.25) × 10 −2 . Henry’s law constant of acetone was directly measured between 283 and 298 K using a dynamic equilibrium system ( H (298K) = (29 ± 5) M atm −1 ), with the Van’t Hoff expression ln H ( T ) = (5100 ± 1100)/ T − (13.4 ± 3.9). A recommended value of H was suggested according to comparison with literature. The OH-oxidation of acetone in the aqueous phase was carried out at 298 K, under two different pH conditions: at pH = 2, and under unbuffered conditions. In both cases, the formation of methylglyoxal, formaldehyde, hydroxyacetone, acetic acid/acetate and formic acid/formate was observed. The formation of small amounts of four hydroperoxides was also detected, and one of them was identified as peroxyacetic acid. A drastic effect of pH was observed on the yields of formaldehyde, one hydroperoxide, and, (to a lesser extent) acetic acid/acetate. Based on the experimental observations, a chemical mechanism of OH-oxidation of acetone in the aqueous phase was proposed and discussed. Atmospheric implications of these findings were finally discussed.

The understandings of atmospheric transport of pesticides need the knowledge of pesticides vapour/particles distribution. Different parameters can influence this equilibrium: total suspended particles (TSP), ambient temperature… vapour/particles (V/P) partitioning of PAHs, OCs and PCBs are well documented. Because of their long life-time, most of the OCs are now prohibited in Europe. They are now replaced by new compounds for which few data are available. In this work it is reported that the influence of TSP, relative humidity of and ambient temperature on the V/P partitioning of different current-used pesticides commonly applied in Alsace region. For this study, a filter-XAD-2 resin plug high-volume air sampler was used to collect simultaneously the particle (P) and vapour (V) phases of pesticides simultaneously on three sites (urban, rural and remote). It can be observed that the cited parameters did not influence individually the V/P partitioning of the studied pesticides. This observation shows that the V/P partitioning is the result of the combined influence of all of the parameters. For all of the pesticides, the vapour phase concentration increases with the decrease of the particle concentration and of the temperature. The influence of the temperature was monitored by the use of the Clausius–Clapeyron equation. From this study, it can be shown that the distribution of alachlor in the gas phase was of local origin while for trifluralin and lindane, results indicate the contribution of long-range transport processes on their gas phase distribution.

Aircraft are prolific sources of particles (soot, liquid aerosols and contrails) that can impact cloudiness and affect the Earth's radiative budget balance. In order to study the formation and evolution of these particles, a numerical approach has been developed combining large-eddy simulation (LES) and a detailed microphysical model. Generally very detailed microphysical models are run along a single average trajectory, without any temperature fluctuation. However, this approach may lead to significant differences in particle properties and particle size distribution as it oversimplifies dynamical and mixing processes compared to multidimensional descriptions of aircraft wakes. This may affect the initialisation of meso-scale models, such as, for example, the formation of cloud condensation nuclei from persistent contrails, and heterogeneous chemical reactions. In this paper, we present the results of detailed microphysical processes calculations applied to a large number of fluid parcels trajectories, generated by a LES two-phase flow solver.

An experimental set-up consisting of two parallel absorption cells coupled to a CCD detector was used to determine absolute values of molar absorptivity coefficients ɛ of five herbicides (alachlor, mecoprop-p, pendimethalin, propanil and trifluralin) in methanol. The absorption spectra were measured using a deuterium lamp at room temperature (298 ± 2 K) over the wavelength range 240–340 nm, except for pendimethalin and trifluralin where the wavelength range was extended to 240–550 nm. Absorbances were also measured at 253.7 nm using an Hg-lamp in different concentrations range depending on the studied compound. Except for mecoprop-p where absorbances were too low at this wavelength, the absolute values of molar absorptivity coefficients at 253.7 nm were determined according to the Beer–Lambert's law: ɛ = 381 ± 28 for alachlor, ɛ = 11,240 ± 1030 for pendimethalin, ɛ = 22,220 ± 1850 for propanil and ɛ = 5720 ± 410 for trifluralin (in units of M −1 cm −1 ). The quoted errors correspond to 2 σ obtained from the least square fit analysis and the estimated systematic error of 5% due to the uncertainties in aqueous concentrations. For all the studied compounds, the absorbances measured were lower than two and did not exhibit any deviation from the Beer–Lambert's law.

Quaternary Ammonium Compounds (QACs) are widely found in disinfectants used in hospitals. Benzalkonium chloride (BAC) and didecyldimethylammonium chloride (DDAC) predominate in the disinfecting formulations. These compounds are strong irritants and can play a role in the induction of Occupational Asthma among the professionals of health and cleaning. In order to evaluate the potential health effect of these quaternary ammonium compounds to hospital employers, the development of an analytical method for their quantification in indoor air was developed. DDAC aerosols are trapped by adsorption on XAD-2 resin SKC tube. The air in hospital buildings was sampled using a constant debit Gillian pump at a flow of 1.0 l/min (+/-5%). Ion Chromatography (IC) was chosen for the analysis of DDAC especially for its high sensitivity and specificity. The Limit of Detection (LOD) by IC for DDAC is 0.56 mug/ml. Therefore the LOD of atmospheric DDAC is 28 microg/m(3) with an air volume of 100 l and a desorption volume of 5 ml. All DDAC air samples were lower than the LOD of the analytical method by IC. Under the standard conditions of use of the disinfecting solutions (Surfanios, Ampholysine Plus and Amphospray 41), the insignificant volatility of DDAC would not seem to be able to contaminate the indoor hospital atmosphere during the disinfection process. However, the DDAC can contaminate working atmospheres if it is put in suspension by aerosolisation.

The uptake of dimethyl malonate and dimethyl succinate on aqueous surfaces was measured between 266 and 279 K, using the droplet train technique coupled with mass spectrometric detection. The uptake coefficients A were found to be independent of the aqueous phase composition and of the gas-liquid contact times. In addition, the uptake coefficients and the derived mass accommodation coefficients R show a negative temperature dependence in the temperature ranges studied. The mass accommodations decrease from 7.8 10 -2 to 5.0 10 -2 and from 4.5 10 -2 to 2.3 10 -2 for dimethyl malonate and succinate, respectively. These results are used to discuss the incorporation of oxygenated volatile organic compounds (VOCs) into the liquid using the nucleation theory. Henry’s law constants of both compounds were directly measured between 283 and 298 K using a dynamic equilibrium system. Their values exponentially decrease when temperature increases, from (2.60 ( 0.30) 10 4 to (0.40 ( 0.05) 10 4 and from (1.20 ( 0.10) 10 4 to (0.30 ( 0.03) 10 4 for dimethyl malonate and succinate, respectively (in units of M atm -1 ). The partitioning

In this work, a dynamic system based on the water/air equilibrium at the interface within the length of a microporous tube was used to determine experimentally the Henry's law constants (HLC) of two pesticides: alachlor and dichlorvos. The measurements were conducted over the range 283–298 K. At 298 K, HLC were found to be equal to HLC=(14±2)×103 and HLC=(4.0±0.6)×103 (in units of M atm−1) for alachlor and dichlorvos, respectively. The obtained data were use to derive the following Arrhenius expressions: HLC=(8.0±3.4)×10−10 exp((9200±1600)/T) for alachlor and HLC=(2.8±0.4)×10−13 exp((11 100±1500)/T) for dichlorvos. At a cumulus temperature of 283 K, the fraction of alachlor and dichlorvos in the atmospheric aqueous phase is about 45% and 22%, respectively. Assuming that annual rainfall rate is 1 m/year, the wet deposition lifetimes were then estimated to be of the order of 2.8 days for alachlor and 5.6 days for dichlorvos. These latter are used to compare the relative importance of wet removal towards the lifetime in the gas phase.

International audience; The global impact of aviation on the atmosphere is generally determined using the total amount of gas and particulate matter emitted at the aircraft engine exit but generally ignore some of the physical transformations occurring at much smaller scales in the aircraft wake. In that work, we present an offline alternative method based on the use of a detailed plume aerosol model combined to fluid trajectories calculated from 3D large-eddy simulations (LES). The study has been limited to the first 10 s behind a type Airbus 340 aircraft. The results have been compared to those obtained from a one-way coupling approach including a simple microphysics water vapor deposition model on soot cores. The respective evolutions of average ice particles radius are in good agreement. Furthermore, different types of aerosol properties are examined including the charged volatile particles, the dry and activated soot and the ice crystals from homogeneous and heterogeneous freezing. The variability of the aerosol size distribution clearly illustrates the influence of the mixing, as a function of the position in the aircraft plume. Finally, the volatile particles distribution exhibits a bimodal shape resulting from the presence of charges, in agreement with that observed in literature.

A filter-XAD-2 resin plug high-volume air sampler was used to collect particulate (P) and gaseous (G) phases of seven pesticides (atrazine, terbuthylazine, alachlor, metolachlor, cymoxanil, diflufenicanil, and fenoxaprop- p -ethyl) and two metabolites (de-ethylatrazine (DEA) and de-ethylterbuthylazine (DET)) in downtown Strasbourg (France). Most of the molecules listed above were found to be associated only with particulate aerosols and only four of them were detected regularly in both atmospheric phases (particulate and gaseous). The results presented in this work showed that models developed previously to describe the gas/particle (G/P) partitioning did not work for currently used pesticides. A new partition equation ( K org , m 3 ng −1 ) was defined for the pesticides under study using environmental parameters such as temperature, relative humidity, and organic carbon content of atmospheric aerosols.

Both UV–visible absorption spectrum and Henry's law constants H of S-ethyl dipropylthiocarbamate (EPTC) were investigated in this work. Absolute values of molar absorptivity coefficients ɛ of EPTC in methanol were determined using a deuterium lamp over the wavelength range 233–343 nm at room temperature (298 ± 2 K). Absorbances were also measured at 253.7 nm using an Hg-lamp in the concentration range 10–426 mg L−1. The absolute value of ɛ at this wavelength, ɛ = 45 ± 4 M−1 cm−1, was then determined according to the Beer–Lambert's law. The quoted error corresponds to 2σ obtained from the least square fit analysis and includes an estimated systematic error of 5% due to the uncertainties in aqueous concentrations. The absorbances measured were lower than 1.2 and did not exhibit any deviation from the Beer–Lambert's law. Henry's law constants H of EPTC were determined over the temperature range 278–293 K with a dynamic system based on the existence of an equilibrium at the water/air interface within the length of a microporous tube. The obtained data were used to derive the following Van't Hoff expression: ln H = (9134 ± 1180)/T − (26.6 ± 3.9) leading to a mean value of 91 ± 22 M atm−1 at 293 K. The quoted errors are given at 2σ level from the least-squares analysis and include the estimated systematic error of 5%. It is shown that, at a cumulus cloud temperature of 283 K, the fraction of EPTC in the atmospheric aqueous phase is negligible and therefore this compound will be mainly present in the gas phase.

Current-used pesticides commonly applied in Alsace region (Eastern France) on diverse crops (maize, vineyard, vegetables, etc.) were analysed, together with Lindane, in rainwater between January 2002 and June 2003 simultaneously on two sites situated in a typical rural (Erstein, France) and urban area (Strasbourg, France). Rainwater samples were collected on a weekly basis by using two automatic wet only collectors associated with an open collector for the measurement of rainwater height. Pesticides were analysed by GC-MSMS and extracted from rainwater by SPME. Two runs were performed. The first one was performed by using a PDMS (100 μm) fibre for pesticides where direct injection into GC is possible (alachlor, atrazine, azinphos-ethyl, azinphos-methyl, captan, chlorfenvinphos, dichlorvos, diflufenican, α- and β-endosulfan, iprodione, lindane, metolachlor, mevinphos, parathion-methyl, phosalone, phosmet, tebuconazole, triadimefon and trifluralin). The second run was performed by using PDMS/DVB fibre and this run concerns pesticides where a preliminary derivatisation step with pentafluorobenzylbromide (PFBBr) is required for very low volatiles (bromoxynil,2,4-MCPA, MCPP and 2,4-D) or thermo labiles (chlorotoluron, diuron and isoproturon) pesticides. Results showed that the more concentrated pesticides detected were those used as herbicides in large quantities in Alsace region for maize crops (alachlor, metolachlor and atrazine). Maximum concentrations for these herbicides have been measured during intensive applications periods on maize crops following by rapid decrease immediately after use. For Alachlor, most important peaks have been observed between 21 and 28 April 2003 (3327 ng L−1 at Erstein and 5590 ng L−1 at Strasbourg). This is also the case for Metolachlor where most important peak was observed during the same week. Concentrations of pesticides measured out of application periods were very low for many pesticides and some others where never detected during this period. This is the case for diflufenican which was detected only during application. Two important peaks of concentrations were observed; a first one (101 ng L−1) in Erstein in November 2002 (4–11 November) and a second one (762 ng L−1) also in Erstein (28 April–15 May). The same behaviour can be seen for chlorfenvinphos and phosalone which have been detected, respectively, 2 and 4 times in Erstein and Strasbourg at high concentrations (28 April 2003–15 May 2003, 187 ng L−1 of phosalone and 157 ng L−1 of chlorfenvinphos in Erstein). MCPP, 2,4 MCPA and 2,4-D have been detected at high concentrations in rainwater but for the other pesticides very episodically and mainly during their use in agriculture. Maximal concentrations of MCPP and 2,4 MCPA have been measured in Erstein between 28 April and 15 May (904 and 746 ng L−1, respectively). Comparison between rural and urban sites showed that concentrations in rural areas are generally higher except for pesticides commonly applied in urban areas like Diuron. No seasonal phenomenon was observed for Diuron. This herbicide has been detected in practically all of the rainwater samples in Strasbourg (40/41) with a maximum of 1025 ng L−1 (16–23 September 2002) in 38 samples on 41 in Erstein with a maximum of 317 ng L−1 (15–23 October 2002). The total concentration of Diuron measured between 4 March 2002 and 20 July 2003 is of 4721 ng L−1 in Strasbourg and 5025 ng L−1 in Erstein. This result shows that wet deposition of Diuron in urban and rural sites was equivalent and can be explained by the “urban use” of this molecule together with its potential persistence.

By using a dynamic dilution system, the atmospheric measurement of 11 selected toxics VOCs (ethylene, acetylene, propene, 1-butene, 1,3-butadiene, 1-pentene, 1-hexene, benzene, toluene, ethylbenzene, m+p-xylene) from the list WHO of 1996 and TO-14 method of US EPA by preconcentration by thermal desorption (TD), analysis by gas chromatography (GC), identification and quantification with a flame ionisation detector (FID) was developed and validated in term of metrology, especially the techniques of sampling of these VOCs with adsorbents cartridges “Air Toxics” when used with an “UMEG sampler” equipped in the inlet with a nafion® membrane. In particular the influence of climatic conditions (temperature and relative humidity) and the influence of chemical factors like ozone, on the representativity of sampling were studied. Experiments made with various humidities showed that the addition of a nafion® membrane in the inlet of the sampling system was required. Without this membrane, losses of compounds were observed for RH >50%. With this membrane, storage for 2 weeks in a refrigerator, as for canisters, did not induce a loss of compounds. No significative decrease of concentrations of the studied VOCs after 14 days storage, which are known to react with ozone, were observed with an ozone concentrations of 55 ppb. One explanation is that nafion® membrane, placed in the inlet of the sampler, will neutralize ozone before entering the sampling tubes. This observation is in accordance with literature which states that the sampling of VOCs on Carbotrap cartridges without ozone scrubber induce a loss of compounds.

Solid-phase microextraction (SPME) coupled with gas chromatography-mass spectrometry has been used for analysis of four phenols and sixteen nitrophenols in rainwater samples. Analytes were extracted from the water in the immersion mode and derivatised for 5 min during direct desorption in the GC injector. Before desorption, 2 microL N-(t-butyldimethylsilyl)-N-methyltrifluoroacetamide (MDBSTFA) was introduced into the injector, which was maintained at 280 degrees C. Different conditions affecting extraction efficiency were studied, including temperature, type of microextraction fibre, and effect of pH and ionic strength. Five different fibre coatings were tested: 85-mum polyacrylate (PA), 100-microm polydimethylsiloxane (PDMS), 65-mum Carbowax-divinylbenzene (CW-DVB), 75-microm Carboxen-polydimethylsiloxane (CAR-PDMS), and 65-microm polydimethylsiloxane-divinylbenzene (PDMS-DVB). The best conditions were use of PA fibres for 40 min at ambient temperature (75 g NaCl per 100 mL, pH 3.0). MDBSTFA was used as derivatising agent because it enables analysis of phenols derivatives with high confidence in identification, because in electron-impact mode TBDMS-phenol derivatives produce the specific M-57 ion. Quantification was achieved by using 4-nitrophenol-d4, at 1 mg L(-1), as internal standard. Linearity was good, with correlation coefficients in the range 0.9888 (o-cresol) to 0.9987 (dinitro-o-cresol, DNOC). Detection limits varied between 0.208 and 99.3 microg L(-1) and quantification limits between 0.693 and 331 microg L(-1). Uncertainties varied between 8.7% (phenol) and 17.9% (4-methyl-2-nitrophenol). The method was successfully applied to the analysis of rainwater collected at urban and rural sites in Alsace (East of France). Because of derivatisation in the injector and the associated high temperature, the lifetime of the fibre is severely reduced.

The absorption spectra of five pesticides, namely 2,4-dichloro-phenoxy acetic acid (2,4-D), cymoxanil, fenpropidin, isoproturon and pyrimethanil, have been measured in aqueous solution using a set-up consisting of two parallel absorption cells coupled to a CCD detector. The absolute values of their molar absorptivity coefficients epsilon were determined in the wavelength-range 240-344 nm with a deuterium-lamp at room temperature (298+/-2 K). Using the Beer-Lambert law, values of epsilon were also determined at 253.7 nm with a Hg-Lamp: epsilon = 145+/-14 for 2,4-D, epsilon = 7940+/-920 for cymoxanil, epsilon = 196+/-14 for fenpropidin, epsilon = 7330+/-880 for isoproturon, epsilon = 13200+/-1400 for pyrimethanil (in units of M(-1) cm(-1)). The quoted errors correspond to 2 sigma obtained from the least square fit analysis and the estimated systematic error of 5% due to the uncertainties in aqueous concentrations. For all the studied compounds, the absorbances measured were lower than 2.3 and did not exhibit any deviation from the Beer-Lambert's law. Our experimental data are discussed and compared to UV spectra of similar molecules when such data were available in the literature. Based on their UV spectra and the calculated fractions of these pesticides in the aqueous phase, their direct photolysis under sunlight environment could occur, except may be for fenpropidin, either in water surfaces or in aqueous droplets contained in the atmospheric clouds.

The European PartEmis project (Measurement and prediction of emissions of aerosols and gaseous precursors from gas turbine engines) was focussed on the characterisation and quantification of exhaust emissions from a gas turbine engine. The combustion aerosol characterisation included on-line measurements of mass and number concentration, size distribution, mixing state, thermal stability of internally mixed particles, hygroscopicity, cloud condensation nuclei (CCN) activation potential, and off-line analysis of chemical composition. Based on this extensive data set, the role of sulphuric acid coating and of the organic fraction of the combustion particles for the CCN activation was investigated. Modelling of CCN activation was conducted using microphysical and chemical properties obtained from the measurements as input data. Coating the combustion particles with water-soluble sulphuric acid, increases the potential CCN activation, or lowers the activation diameter, respectively. The adaptation of a Köhler model to the experimental data yielded coatings from 0.1 to 3 vol-% of water-soluble matter, which corresponds to an increase in the fraction of CCN-activated combustion particles from ≤10−4 to ≌10−2 at a water vapour saturation ratio Sw=1.006. Additional particle coating by coagulation of combustion particles and aqueous sulphuric acid particles formed by nucleation further reduces the CCN activation diameter. In contrast, particles containing a large fraction of non-volatile organic compounds grow significantly less at high relative humidity than particles with a lower content of non-volatile OC. The resulting reduction in the potential CCN activation with an increasing fraction of non-volatile OC becomes visible as a trend in the experimental data. While a coating of water-soluble sulphuric acid increases the potential CCN activation, or lowers the activation diameter, respectively, the non-volatile organic compounds, mainly found at lower combustion temperatures, can partially compensate this sulphuric acid-related enhancement of CCN activation of carbonaceous combustion aerosol particles.

The European PartEmis project (''Measurement and prediction of emissions of aerosols and gaseous precursors from gas turbine engines'') was focussed on the characterisation and quantification of exhaust emissions from a gas turbine engine. A comprehensive suite of aerosol, gas and chemi-ion measurements were conducted under different combustor operating conditions and fuel sulphur concentrations. Combustion aerosol characterisation included on-line measurements of mass and number concentration, size distribution, mixing state, thermal stability of internally mixed particles, hygroscopicity, cloud condensation nuclei (CCN) activation potential, and off-line analysis of chemical composition. Modelling of CCN activation of combustion particles was conducted using microphysical and chemical properties obtained from the measurements as input data. Based on this unique data set, the role of sulphuric acid coatings on the combustion particles, formed in the cooling exhaust plume through either direct condensation of gaseous sulphuric acid or coagulation with volatile condensation particles nucleating from gaseous sulphuric acid, and the role of the organic fraction for the CCN activation of combustion particles was investigated. It was found that particles containing a large fraction of non-volatile organic compounds grow significantly less at high relative humidity than particles with a lower content of non-volatile OC. Also the effect of the non-volatile OC fraction on the potential CCN activation is significant. While a coating of water-soluble sulphuric acid increases the potential CCN activation, or lowers the activation diameter, respectively, the non-volatile organic compounds, mainly found at lower combustion temperatures, can partially compensate this sulphuric acid-related enhancement of CCN activation of carbonaceous combustion aerosol particles.

In this work, a dynamic system based on the water/air equilibrium at the interface within the length of a microporous tube was used to experimentally determine the Henry's law constants (HLC) of phenol and cresols. The measurements were conducted over the range 278–298 K in both deionized water and 35 g l - 1 solution of NaCl. At 293 K and in pure water, HLC were found to be equal to (in units of M atm - 1 ): phenol, HLC = ( 1005 ± 270 ) ; o-cresol, HLC = ( 690 ± 95 ) ; m-cresol, HLC = ( 1324 ± 172 ) ; p-cresol, HLC = ( 1742 ± 360 ) . The obtained data were used to derive the following Arrhenius expressions: HLC = ( 4.1 ± 0.6 ) × 10 - 9 exp ( ( 7684 ± 874 ) / T ) , HLC = ( 1.5 ± 0.1 ) × 10 - 10 exp ( ( 8544 ± 512 ) / T ) , HLC = ( 5.5 ± 0.4 ) × 10 - 11 exp ( ( 9028 ± 508 ) / T ) and HLC = ( 3.3 ± 0.4 ) × 10 - 11 exp ( ( 9258 ± 818 ) / T ) for phenol, o-cresol, m-cresol and p-cresol, respectively. All of the values for HLC in 35 g l - 1 salt solution were 10–30% lower than their respective values in deionized water, depending on the compound and the temperature. These data were then used to estimate the fractions of phenol or of cresols in atmospheric aqueous phase. In order to evaluate the impact of a cloud on the atmospheric chemistry of phenol and cresols, we compare also their atmospheric lifetimes under clear sky ( τ gas ) , and cloudy conditions ( τ multiphase ) . The calculated multiphase lifetimes (in units of days) are significantly lower than those in gas phase at a cumulus temperature of 283 K (in parentheses): phenol, 0.26 (0.45); o-cresol, 0.17 (0.24); m-cresol, 0.13 (0.22); p-cresol, 0.11 (0.23).

International audience; A modelling study of the formation of volatile particles in a combustor exhaust has been carried out in the frame of the PartEmis European project. A kinetic model has been used in order to investigate nucleation efficiency of the H2O-H2SO4 binary mixture in the sampling system. A value for the fraction of the fuel sulphur S(IV) converted into S(VI) has been indirectly deduced from comparisons between model results and measurements. In the present study, ranges between roughly 2.5% and 6%, depending on the combustor settings and on the value assumed for the parameter describing sulphuric acid wall losses. Soot particles hygroscopicity has also been investigated as their activation is a key parameter for contrail formation. Growth factors of monodisperse particles exposed to high relative humidity (95%) have been calculated and compared with experimental results. The modelling study confirms that the growth factor increases as the soot particle size decreases.

A dynamic system based on the water/air equilibrium at the interface within the length of a microporous tube has been used to determine experimentally the Henry's law constants (HLC) of two pesticides: metolachlor and diazinon. The measurements were conducted over the temperature range 283-301 K. At 293 K, HLCs values are (42.6+/-2.8) x 10(3) (in units of M atm(-1)) for metolachlor and (3.0+/-0.3)x10(3) for diazinon. The obtained data were used to derive the following Arrhenius expressions: HLC=(3.0+/-0.4) x 10(-11) exp((10,200+/-1,000)/T) for metolachlor and (7.2+/-0.5) x 10(-15) exp((11,900+/-700)/T) for diazinon. At a cumulus cloud temperature of 283 K, the fractions of metolachlor and diazinon in the atmospheric aqueous phase are about 57% and 11% respectively. In order to evaluate the impact of a cloud on the atmospheric chemistry of both studied pesticides, we compare also their atmospheric lifetimes under clear sky (tau(gas)), and cloudy conditions (tau(multiphase)). The calculated multiphase lifetimes (in units of hours) are significantly lower than those in gas phase at a cumulus temperature of 283 K (in parentheses): metolachlor, 0.4 (2.9); diazinon, 1.9 (5.0).

A model which considers the formation and evolution of combustion ions in a combustor of an aircraft engine in dependence on the electron detachment efficiency from negative ions is presented. It is a further development of the model reported by (Sorokin et al., 2003). The model allows to consider the effect of the transformation of primary negative ions to more stable secondary negative ions with a much higher electron affinity and as a consequence a greater stability with respect to electron thermal detachment. The formed stable negative ions most probably are sulfur-bearing ions. This effect slows down the charged particle neutralization rate leading to an increase of the concentration of positive and negative ions at the combustor exit. The results of the simulation and their comparison with the ground-based experimental data obtained within the framework of the project PartEmis (Particle emission, measurements and predictions of emission of aerosols and gaseous precursors from gas turbine engines; coordinator: C. Wilson) at the QinetiQ test facility at Pyestock, UK (Wilson et al., 2003) support the above hypothesis, i.e. the increase of the fuel sulfur content leads to an increase of the ion concentration at the combustor exit.

With the exception of a few pioneering studies such as the work of Albert Levy (1877-1907, in Ulrich and Williot 1993) at the turn of the last century, precipitation chemistry monitoring in rural areas really began in France at the end of the 1970s (BAPMON and EMEP networks), as a result of international studies showing the negative impact of precipitation acidity on surface waters and the possibilities of long-range pollution transport (Gorham and Gordon 1960; Zephoris et al. 1984). No dense deposition network covering the whole country was organized until the end of the 1980s, but a large number of local studies were initiated, the results of which were often never published.