Search

Formaldehyde is a common air pollutant of the indoor environment. It has a potential effect on the respiratory function of people and so studies have been performed to assess this using exposure methods with high concentrations of formaldehyde. However, epidemiology studies have shown its impact on allergic diseases at lower domestic levels. The aim of this study was to develop an exposure chamber to study effects of low controlled concentrations of formaldehyde. Concentrations in the chamber were quantified by a simple DNHP-derivatisation method followed by liquid chromatography coupled to UV detection. Experiments to assess formaldehyde generation yield and reproducibility of formaldehyde levels in the chamber were performed in an empty chamber. The temporal decay of formaldehyde concentration in the exposure chamber was also investigated for more than 2h under different experimental conditions, for example in darkness or with somebody inside the chamber. Actual measured levels of formaldehyde were found to be 78-91% of the calculated value expected. The study of the temporal decay showed that subject’s breathing accounted for the fate of approximately 50% of the formaldehyde lost. Leaks, wall deposition, photolysis and adsorption on clothes were processes identified to explain the remaining 50%. However, this study has shown that both homogeneity and stability of formaldehyde concentration in the gas phase can be maintained acceptably to carry out future human exposure experiments.

Uptake of acetaldehyde on ice surfaces has been investigated over the temperature range 203-253 K using a coated wall flow tube coupled to a mass spectrometric detection. The experiments were conducted on pure ice surfaces and on liquid/solid ice mixture both doped with nitric acid (0.063, 0.63, and 6.3 wt %). Uptake of acetaldehyde on these surfaces was always found to be totally reversible whatever the experimental conditions were. The number of acetaldehyde molecules adsorbed per surface unit was conventionally plotted as a function of acetaldehyde concentration in the gas phase. Although the amounts of acetaldehyde adsorbed on solid ice surfaces (pure and HNO(3)-doped ice) were approximately similar and rather limited, the number of acetaldehyde molecules taken up on the HNO(3)-doped solid ice/liquid mixtures are significantly higher, up to 1 or 2 orders of magnitudes compared to pure ice surfaces. At 213 K for example and for low concentrations of acetaldehyde (

Aldehydes and BTEX concentrations were measured in 20 university libraries in Strasbourg (east of France) using Radiello passive sampling systems containing either DNPH or activated charcoal for aldehydes and BTEX, respectively. For the aldehydes, the conventional DNPH-derivatization method was used, followed by liquid chromatography coupled to UV detection while the BTEX were quantified by GC-PID. Aldehydes levels found inside the libraries ranged from 8.6 to 94.5 μg · m×3 for formaldehyde, 3.7 to 25.9 μg · m-3 for acetaldehyde, 2.1 to 58.8 μg · m-3 for hexanal, 0.2 to 5.3 μg · m-3 for benzaldehyde, and 0.7 to 16.3 μg · m-3 for propionaldehyde. Their mean values are 28.6± 18.8 μg · m-3 (formaldehyde), 10.2 ± 5.8 μg · m-3 (acetaldehyde) and 15.1 ± 12.1 μg · m-3 (hexanal), 1.1 ±1.1 for benzaldehyde and 2.8 ±3.3 for propionaldehyde, where the quoted errors correspond to 1σ level. Total BTEX concentrations were quantified in the same libraries and were usually relatively low ( -3) in all libraries, except for one where unusually high values (~295 μg · m-3) were found. Excluding this latter, the means BTEX concentrations were (in units of μg · m-3): 0.2 ±0.2 (benzene), 3.8 ±2.6 (toluene), 0.8 ±0.5 (ethyl benzene), 1.9 ± 1.2 (m- and p-xylenes), and 0.5 ±0.4 (o -xylene), where the quoted errors correspond again to 1σ.

Aldehydes concentrations were measured in 162 homes in the Strasbourg area (East of France) in the context of a case/control study pairing asthmatic and non-asthmatic people. The surveyed people have completed a questionnaire aiming to characterize the indoor homes and the people life practices. Gaseous aldehyde levels were quantified by a conventional DNHP-derivatization method followed by HPLC/UV. Formaldehyde, acetaldehyde and hexanal were the main encountered aldehydes with mean concentrations of 32.2±14.6, 14.3±9.7 and 8.6±8.1 μg m −3 , respectively, while propionaldehyde and benzaldehyde concentrations were usually −3 . The aldehydes concentrations simultaneously measured in both bedroom and living room were not significantly different except for formaldehyde and were correlated between them meaning that indoor air was quite homogenous in homes. Combination of information collected in our questionnaires and statistical analysis was used to investigate indoor aldehydes determinants. Even if formaldehyde sources are theoretically well identified, they are multiple so that it was difficult to determine the main parameters influencing its concentrations in domestic environment. Higher hexanal concentrations were related to new coatings such as painting, wallpapers and laminate floorings. Hexanal concentration decreased with both coating and furniture ages so that this compound may be considered as a tracer of these emissions.

Uptake of ethanol either on pure frozen ice surfaces or supercooled solutions doped with HNO3 (0.63 and 2.49 wt %) has been investigated using a coated wall flow tube coupled to a mass spectrometric detection. The experiments were conducted over the temperature range of 213-243 K. Uptake of ethanol on these surfaces was always found to be totally reversible whatever were the experimental conditions. The number of ethanol molecules adsorbed per surface unit was conventionally plotted as a function of ethanol concentration in the gas phase and subsequently analyzed using Langmuir's model. The amount of ethanol molecules taken up on nitric acid doped-ice surfaces was found to increase largely with increasing nitric acid concentrations. For example at 223 K, and for an ethanol gas-phase concentration of 1x10(13) molecules cm3, the number of adsorbed molecules are (in units of molecules cm-2): approximately 1.3x10(14) on pure ice; approximately 1.4x10(15) on ice doped with HNO3 0.63 wt %; approximately 7.5x10(15) on ice doped with HNO3, 2.49 wt %, i.e. 60 times larger than on pure ice. Since, according to the shape of the isotherms, the adsorption did not proceed beyond monolayer coverage, the enormous increase of ethanol uptake was explained by considering its dissolution in either a supercooled liquid layer (T230 K) or a liquid solution (T230 K). The formation of both was indeed favored by the presence of the HNO3. Our experimental results suggest that the amount of ethanol dissolved in such supercooled solutions follows Henry's law and that the Henry's law constants at low temperatures, i.e., 223-243 K, can be estimated by extrapolation from higher temperatures. Such supercooled solutions which exist in the troposphere either in deep convective clouds or in mixed clouds for temperature above 233 K, might be responsible for the scavenging of large amounts of soluble species, such as nitric and sulfuric acids, oxygenated VOCs including alcohols, carboxylic acids, and formaldehyde.

Formaldehyde and acetaldehyde concentrations have been measured in indoor environments of various public spaces (railway station, airport, shopping center, libraries, underground parking garage, etc.) of Strasbourg area (east of France). In addition, formaldehyde, acetaldehyde propionaldehyde and hexanal concentrations have been measured in 22 private homes in the same area. In most of the sampling sites, indoor and outdoor formaldehyde and acetaldehyde concentrations were measured simultaneously. Gaseous aldehydes levels were quantified by a conventional DNHP-derivatization method followed by liquid chromatography coupled to UV detection. Outdoor formaldehyde and acetaldehyde concentrations were both in the range 1–10 μg m −3 , the highest values being measured at the airport and railway station. Indoor concentrations were strongly dependant upon the sampling sites. In homes, the average concentrations were 37 μg m −3 (living rooms) and 46 μg m −3 (bedrooms) for formaldehyde, 15 μg m −3 (living rooms) and 18 μg m −3 (bedrooms) for acetaldehyde, 1.2 μg m −3 (living rooms) and 1.6 μg m −3 (bedrooms) for propionaldehyde, 9 μg m −3 (living rooms) and 10 μg m −3 (bedrooms) for hexanal. However, concentrations as high as 123, 80 and 47 μg m −3 have been found for formaldehyde, acetaldehyde and hexanal respectively. In public spaces, the highest formaldehyde concentration (62 μg m −3 ) was found in a library and the highest concentration of acetaldehyde (26 μg m −3 ) in the hall of a shopping center. Additional measurements of formaldehyde and acetaldehyde were made inside a car both at rest or in a fluid or heavy traffic as well as in a room where cigarettes were smoked. Our data have been discussed and compared with those of previous studies.

Adsorption study of acetic acid on ice surfaces was performed by combining experimental and theoretical approaches. The experiments were conducted between 193 and 223 K using a coated wall flow tube coupled to a mass spectrometric detection. Under our experimental conditions, acetic acid was mainly dimerized in the gas phase. The surface coverage increases with decreasing temperature and with increasing concentrations of acetic acid dimers. The obtained experimental surface coverages were fitted according to the BET theory in order to determine the enthalpy of adsorption deltaH(ads) and the mololayer capacity N(M(dimers)) of the acetic acid dimers on ice: deltaH(ads) = (-33.5 +/- 4.2) kJ mol(-1), N(M(dimers)) = (l1.27 +/- 0.25) x 10(14) dimers cm(-2). The adsorption characteristics of acetic acid on an ideal ice I(n)(0001) surface were also studied by means of classical molecular dynamics simulations in the same temperature range. The monolayer capacity, the configurations of the molecules in their adsorption sites, and the corresponding adsorption energies have been determined for both acetic acid monomers and dimers, and compared to the corresponding data obtained from the experiments. In addition, the theoretical results show that the interaction with the ice surface could be strong enough to break the acetic acid dimers that exist in the gas phase and leads to the stabilization of acetic acid monomers on ice.

International audience; Adsorption study of ethanol on ice surfaces were performed by combining experimental and theoretical approaches. The experiments were conducted using a coated wall flow tube coupled to a mass spectrometric detection. The surface coverage increases with decreasing temperature and with increasing ethanol concentrations. The obtained experimental surface coverages were fitted according to the B.E.T. theory in order to determine the enthalpy of adsorption ∆H ads and the monolayer capacity N M : ∆H ads =-57 ± 8 kJ mol-1 , N M = (2.8 ± 0.8)×10 14 molecule cm-2. The adsorption characteristics of ethanol on a proton disordered Ih(0001) ice surface were also jointly studied by performing classical molecular dynamics simulations. More specifically, the configurations of the molecules in their adsorption sites and the corresponding adsorption energies have been studied as a function of temperature and coverage. In the simulations, the saturation coverage is around N M = 3.2×10 14 molecule cm-2 , and corresponds to an adsorption energy equal to-56.6 kJ mol-1 , in good agreement with the experimental value. The results are discussed and compared with previous determinations for alcohols.

Adsorption studies of acetone and of 2,3-butanedione on ice surfaces were performed using a new vertical coated wall flow tube coupled to a mass spectrometric detection. Adsorption of acetone on ice was found to be totally reversible for ice temperatures ranging from 193 to 223 K and for gas phase acetone concentrations varying between 5.4 × 1010 and 6.4 × 1013 molecules cm−3. Adsorption of 2,3-butanedione was also reversible at 213 and 223 K but partially irreversible at 193 and 203 K when its concentrations were larger than 1 × 1013 molecules cm−3. It was shown that, at 203 K, the surface coverage increases when the ice surface contains large and dense cracks but is independent of the presence of cracks at 223 K. The surface coverage also increases with decreasing temperature and with increasing acetone or 2,3-butanedione concentrations. The obtained experimental surface coverages were fitted according to the Langmuir and BET theories in order to determine the enthalpy of adsorption ΔHads and the monolayer capacity NM. The following values of NM were derived (in units of 1014 molecule cm−2): NM = 1.3 ± 0.2 for acetone and NM = 1.2 ± 0.5 for 2,3-butanedione. The corresponding enthalpies of adsorption are (in kJ mol−1): −49 ± 7 for acetone and −59 ± 8 for 2,3-butanedione. The results are discussed and compared with previous determinations for acetone. Finally, the obtained results are used to estimate the partitioning of acetone between the ice and gas phases in clouds of the upper troposphere.

Uptake measurements of ethanol were performed to provide experimental values for a theoretical approach of its incorporation into a water droplet. The uptake coefficients of ethanol on pure water w...

In this article, a model which examines the formation and evolution of chemiions in an aircraft engine is proposed. This model which includes chemiionisation, electron thermo-emission, electron attachment to soot particles and to neutral molecules, electron-ion and ion-ion recombination, ion-soot interaction, allows the determination of the ion concentration at the exit of the combustor and at the nozzle exit of the engine. It also allows the determination of the charge of the soot particles. For the engine considered, the upper limit for the ion emission index EIi is of the order of (2-5) x1016 ions/kg-fuel if ion-soot interactions are ignored and the introduction of ion-soot interactions lead about to a 50% reduction. The results also show that most of the soot particles are either positively or negatively charged, the remaining neutral particles representing approximately 20% of the total particles. A comparison of the model results with the available ground-based experimental data obtained on the ATTAS research aircraft engines during the SULFUR experiments (Schumann, 2002) shows an excellent agreement.