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HFC-365mfc (1,1,1,3,3-pentafluorobutane) is an industrial chemical used for polyurethane foam blowing. From early 2003, HFC-365mfc has been commercially produced as a substitute for HCFC-141b, whose use in Europe has been banned since January 2004. We describe the first detection of HFC-365mfc in the atmosphere and report on a 2 year long record at the high Alpine station of Jungfraujoch (Switzerland) and the Atlantic coast station of Mace Head (Ireland). The measurements at Jungfraujoch are used to estimate the central European emissions of HFC-365mfc, HCFC-141b, and CFC-11. For HFC-365mfc, we estimate the central European emissions (Germany, France, Italy, Switzerland, The Netherlands, Belgium, and Luxembourg) in 2003 and 2004 as 400-500 tonnes year(-1). These emissions are about one-third lower on a per capita basis than what we estimate from the Mace Head measurements for the total of Europe. The estimated emissions of HCFC-141b for central Europe are higher (i.e., 7.2-3.5 ktonnes year(-1)) with a decreasing trend in the period from 2000 to 2004. Residual emissions of CFC-11 are estimated at 2.4-4.7 ktonnes year(-1) in the same time period. The Po Valley (northern Italy) appears to be a main source region for HFC-365mfc and for the former blowing agents HCFC-141b and CFC-11. In 2004, the emissions of HFC-365mfc arose from a wider region of Europe, which we attribute to an increased penetration of HFC-365mfc into the European market.

Nitrous acid is a major photochemical precursor of the hydroxyl radical, a key oxidant in the degradation of air pollutants in the lower atmosphere. The gas is known to accumulate in the lower troposphere at night, but the recent discovery of enhanced concentrations of nitrous acid measured at various sites both urban and rural during daytime was a surprise. Now the light-induced reaction between soil humic acid and nitrogen dioxide has been put forward as an explanation. The observed reaction rate of nitrous acid formation suggests that this production mechanism could be an important factor in the chemistry of the lower troposphere Nitrous acid is a significant photochemical precursor of the hydroxyl radical1,2,3,4,5,6,7,8,9,10,11,12,13, the key oxidant in the degradation of most air pollutants in the troposphere. The sources of nitrous acid in the troposphere, however, are still poorly understood. Recent atmospheric measurements7,10,11,12,13,14,15,16,17 revealed a strongly enhanced formation of nitrous acid during daytime via unknown mechanisms. Here we expose humic acid films to nitrogen dioxide in an irradiated tubular gas flow reactor and find that reduction of nitrogen dioxide on light-activated humic acids is an important source of gaseous nitrous acid. Our findings indicate that soil and other surfaces containing humic acid exhibit an organic surface photochemistry that produces reductive surface species, which react selectively with nitrogen dioxide. The observed rate of nitrous acid formation could explain the recently observed high daytime concentrations of nitrous acid in the boundary layer, the photolysis of which accounts for up to 60 per cent of the integrated hydroxyl radical source strengths3,6,7,8,9,10,11,12,13. We suggest that this photo-induced nitrous acid production on humic acid could have a potentially significant impact on the chemistry of the lowermost troposphere.

This study presents the first laboratory observation of HNO3 uptake by airborne mineral dust particles. The model aerosols were generated by dry dispersion of Arizona Test Dust (ATD), SiO2, and by nebulizing a saturated solution of calcium carbonate. The uptake of 13N-labeled gaseous nitric acid was observed in a flow reactor on the 0.2–2 s reaction time scale at room temperature and atmospheric pressure. The amount of nitric acid appearing in the aerosol phase at the end of the flow tube was found to be a linear function of the aerosol surface area. SiO2 particles did not show any significant uptake, while the CaCO3 aerosol was found to be more reactive than ATD. Due to the smaller uncertainty associated with the reactive surface area in the case of suspended particles as compared to bulk powder samples, we believe that we provide an improved estimate of the rate of uptake of HNO3 to mineral dust. The fact that the rate of uptake was smaller at a concentration of 1012 than at 1011 was indicative of a complex uptake mechanism. The uptake coefficient averaged over the first 2 s of reaction time at a concentration of 1012 molecules cm-3 was found to increase with increasing relative humidity, from 0.022±0.007 at 12% RH to 0.113±0.017 at 73% RH , which was attributed to an increasing degree of solvation of the more basic minerals. The extended processing of the dust by higher concentrations of HNO3 at 85% RH led to a water soluble coating on the particles and enhanced their hygroscopicity.

Volatile hydrocarbons have been measured for 1 yr at Arosa (2010 m asl) to determine the contribution of European emissions to the trace gas concentrations at this remote site. Results are compared to concurrent hydrocarbon concentrations at the high Alpine background site Jungfraujoch (3580 m asl). Hydrocarbon concentrations at Arosa are generally much higher than at Jungfraujoch. The influence of the Alpine boundary layer air was studied based on the diurnal variation of hydrocarbon concentrations, i.e. rising pollutant concentrations in the morning at Arosa and in the afternoon at Jungfraujoch. Different hydrocarbon emission sources of the uplifting air were found at the two sites. At Jungfraujoch, several transatlantic events were detected from October 2001 to January 2002 based on analysis of hydrocarbon ratios and air parcel trajectories. The OH concentration during the transatlantic transport was estimated to be around 5×10 5 cm −3 , derived from simultaneous hydrocarbon oxidation and dilution in the free troposphere. These transatlantic transport events were tracked back to warm conveyor belts, characterized by uniform dynamics and relatively uniform surface sources. In addition, ozone production in the free tropospheric transport was also documented in these events.

The emissions of 14 C 4 –C 8 VOC species from road traffic have been measured in a highway tunnel (Gubristtunnel) near Zurich, Switzerland in 2002. The investigated traffic situation corresponds to highway driving with an average speed of 90 km h −1 and hot engine conditions. The comparison with measurements in the same tunnel performed in 1993 indicates that the emission factors of the individual hydrocarbons decreased on average by 80% in the 9 years between both investigations. This improvement can mainly be explained by the nearly complete elimination of non-catalyst gasoline-fuelled cars from the Swiss car fleet in the past decade. The relative emission strengths of the quantified individual VOCs were similar in 1993 and 2002. The emission factors reported in this study are the lowest reported from on-road vehicle emission measurements so far, indicating the efficient technology of modern car fleets with respect to VOC emissions. The emission factors derived from the tunnel study are compared to modelled emission factors based on dynamometric test measurements on Swiss passenger cars. The employed model is the Handbuch fur Emissionsfaktoren des Strassenverkehrs; version 1.2 (Umweltbundesamt Berlin and INFRAS AG Bern, 1999). A good agreement between the modelled and measured emissions was found for the investigated traffic situation, indicating that the development of the VOC emissions during the last decade is well understood on the basis of the fleet composition and the dynamometric test measurements. The observed VOC emission reduction corresponds to a traffic situation, where an optimal exhaust gas catalyst performance can be expected. Factors leading to a somewhat less beneficial influence of the catalytic converter technique in other relevant driving situations are therefore additionally discussed.

This study presents the quantification of the emissions of the refrigerants CFC-12 (CCl2F2), HCFC-22 (CHClF2), and HFC-134a (CF3CH2F) from road traffic in Switzerland. These gases are used as refrigerants in car air conditioning systems (A/C-systems) and in cool aggregates for refrigeration transport. All three substances act as greenhouse gases, and CFC-12 and HCFC-22 are in addition stratospheric ozone depleting chemicals. The measurements have been performed in a highway tunnel in the area of Zürich and cover a large number of individual vehicles, which are thought to be representative of a typical European car fleet. The average emission rates per vehicle were found to be 1.0 +/- 0.2 mg h(-1) for CFC-12, 0.6 +/- 0.4 mg h(-1) for HCFC-22, and 6.2 +/- 0.8 mg h(-1) for HFC-134a. These emission factors have been measured for driving vehicles and represent an average emission rate for all types of vehicles regardless of whether they are equipped with an A/C-unit or not. For an average vehicle equipped with an A/C-unit, these results translate into losses of about 14 mg h(-1) for HFC-134a and 20-30 mg h(-1) for CFC-12, when the estimated distribution of HFC-134a-A/C-units (45%) and CFC-12-A/C-units (3-5%) in the car fleet were taken into account. The emissions of CFC-12 and HFC-134a were mainly attributed to the losses from A/C-systems of passenger cars, whereas the emissions of HCFC-22 originate from losses of refrigeration systems of transport trucks. The observed emissions are discussed in respect to their environmental impact and compared to the overall greenhouse gas emissions of road traffic.

The aim of this series of two publications is to characterise important radical reactions of organic molecules in atmospheric water phases, such as cloud, fog, and rain droplets, or on wetted aerosols. In this first study the reactions occurring in a mixed peroxyl radical system generated from the OH radical attack on a model compound, 2-butoxyethanol, in oxygenated aqueous solution are investigated in the absence of trace compounds typically found in such natural waters. Using gamma-radiation emitted from a Co-60 source, We have produced steady-state concentrations of O-2(-)/HO2- and OH radicals comparable to those predicted for daytime conditions in cloud or fog droplets. The reactions of the peroxyl radicals derived from 2-butoxyethanol (C4H9OCH2CH2OH) in oxygenated aqueous solution have been investigated by measuring detailed product distributions resulting from the oxidation process. The observed and quantified products are mainly esters, ketones, aldehydes and hydroperoxides and accounted for 83% of the removal of 2-butoxyethanol (expressed as a carbon balance). A mechanism for the formation of the reaction products is proposed. It includes the OH attack at four carbon centers of the molecule producing carbon centered radicals, the formation of peroxyl radicals by addition of oxygen to these radicals, the decay of the peroxyl radicals in a reaction system of six different peroxyl radicals and superoxide via bimolecular and unimolecular reactions and the reactions of intermediary produced oxyl radicals. (C) 2000 Elsevier Science Ltd. All rights reserved.

The present study investigates the degradation of atrazine (2-chloro-4-(ethylamino)-6-isopropylamino-s-triazine) by ozone and OH radicals during ozonation and advanced oxidation processes, with the identification of the main degradation products. Besides the dealkylated and amide degradation products(6-amino-2-chloro-4-isopropylamino-s-triazine, 6-amino-2-chloro-4-(ethylamino)-s-triazine, 4-acetamido-2-chloro-6-isopropylamino-s-triazine, 4-acetamido-6-amino-2-chloro-s-triazine, and chlorodiamino-striazine), two new degradation products with an imine group were identified (2-chloro-4-ethylimino-6-isopropylamino-s-triazine and 6-amino-2-chloro-4-ethylimino-s-triazine). The contribution of the different pathways (direct ozone and OH radical reaction) to the overall degradation process has been quantified, and the rate constants of the reactions of atrazine and its main degradation products with both oxidants have been measured. The ethyl group is more reactive than the isopropyl group (i.e. 19 times during ozonation and four times during OH radical attack). The ethyl group reacts in higher proportion through oxidation to acetamide or imine derivates than to dealkylation. In contrast, the isopropyl group reacts mainly through dealkylation to the free amino group. Acetamido and imino groups a re found to be resistant to chemical oxidation. These reactivities were corroborated by the measured values of the rate constants with both oxidants. A combination of product distribution and the kinetic parameters together with ozone and OH radical concentrations allowed us to calculate the evolution of the concentration of the degradation products for a given ozonation process.

A microbial whole-cell biosensor was developed, and its potential to measure water-dissolved concentrations of middle-chain-length alkanes and some related compounds by bioluminescence was characterized. The biosensor strain Escherichia coli DH5 alpha(pGEc74, pJAMA7) carried the regulatory gene alkS from Pseudomonas oleovorans and a transcriptional fusion of PalkB from the same strain with the promoterless luciferase luxAB genes from Vibrio harveyi on two separately introduced plasmids. In standardized assays, the biosensor cells were readily inducible with octane, a typical inducer of the alk system. Light emission after induction periods of more than 15 min correlated well with octane concentration. In well-defined aqueous samples, there was a linear relationship between light output and octane concentrations between 24 and 100 nM. The biosensor responded to middle-chain-length alkanes but not to alicyclic or aromatic compounds. In order to test its applicability for analyzing environmentally relevant samples, the biosensor was used to detect the bioavailable concentration of alkanes in heating oil-contaminated groundwater samples. By the extrapolation of calibrated light output data to low octane concentrations with a hyperbolic function, a total inducer concentration of about 3 nM in octane equivalents was estimated. The whole-cell biosensor tended to underestimate the alkane concentration in the groundwater samples by about 25%, possibly because of the presence of unknown inhibitors. This was corrected for by spiking the samples with a known amount of an octane standard. Biosensor measurements of alkane concentrations were further verified by comparing them with the results of chemical analyses.

The products formed by the hydroxyl-radical-initiated oxidation of the model ether, isobutyl isopropyl ether [(CH 3 ) 2 CHCH 2 OCH(CH 3 ) 2 ], have been investigated by irradiating synthetic air mixtures containing the substrate, methyl nitrite, and nitric oxide at ppm levels in a Teflon bag reactor at room temperature. The decay of reactant and formation of products were monitored by gas chromatography, mass spectrometry and by HPLC. The molar yields of the major products (mol of product formed/mol of isobutyl isopropyl ether consumed) were as follows: acetone, 0.56 ± 0.04; isopropyl formate, 0.48 ± 0.03; isobutyl acetate, 0.28 ± 0.02; 2-hydroxy-2-methylpropyl acetate [CH 3 C(O)OCH 2 C(OH)(CH 3 ) 2 ], 0.25 ± 0.1. The molar yields of the minor products were as follows: isobutyraldehyde, 0.06 ± 0.05; isopropyl nitrate, 0.09 ± 0.06; 1,1,4-trimethyl-3-oxapentyl nitrate [(CH 3 ) 2 CHOCH 2 C(CH 3 ) 2 (ONO 2 )], 0.07 ± 0.02; isopropyl isobutyrate [(CH 3 ) 2 CHC(O)OCH(CH 3 ) 2 ] ca. 0.01; and isobutyl formate, ca. 0.01. The major products are explained by a mechanism involving initial OH attack at the –CH– and –CH 2 – groups in the alkyl side chains of the ether followed by the subsequent reactions of the resulting carbon-centred, organic peroxy, and organic oxy radicals. The observed products, in conjunction with the proposed reaction pathways, account for a total yield of about 1.15, indicating that all the main routes are accounted for in the degradation of this ether. The major reaction pathways of the three principal organic oxy radicals are summarised as follows (percentage of overall reaction in brackets):(CH3)2C(O˙)OCH2CH(CH3)2 → CH3C(O)OCH2CH(CH3)2]C˙H3 (28%)(CH3)2CHOCH(O˙)CH(CH3)2 → (CH3)2CHOC(O)H]C˙H(CH3)2 (⩽48%)(CH3)2CHOCH2C(O˙)(CH3)2 → (CH3)2C˙OCH2C(OH)(CH3)2 (25%)This study supports the finding that organic oxy radicals generated from ethers and containing the structure RCH(O˙)OR undergo mainly decomposition by C–C bond cleavage, whereas those oxy radicals with the structure RCH(O˙)CH 2 OR undergo preferential 1,5-H-atom transfer isomerisation reactions. The following rate coefficients (10 −12 cm 3 molecule −1 s −1 ) at room temperature for the reactions of OH radicals with the reactant and products have been determined by the relative rate technique: isobutyl isopropyl ether, 19.5 ± 0.4; isobutyl acetate, 6.0 ± 0.5; isobutyraldehyde, 25.8 ± 0.7; isopropyl formate, 2.1 ± 0.1; isopropyl isobutyrate, 6.5 ± 0.4; 1,1,4-trimethyl-3-oxapentyl nitrate, 16.5 ± 0.7; and 2-hydroxy-2-methylpropyl acetate, 9.5 ± 1.6.

The products formed by the hydroxyl radical-initiated oxidation of 2-ethoxyethanol (CH3CH2OCH2CH2OH) have been investigated by irradiating synthetic air mixtures containing the substrate, methyl nitrite, and nitric oxide at ppm levels in a Teflon bag reactor at room temperature. The decay of reactants and the formation of products were monitored by gas chro matography and mass spectrometry. The major products ethyl formate [HC(O)OCH2CH3], ethylene glycol monoformate [HC(O)OCH2CH2OH], ethylene glycol monoacetate [CH3C(O)OCH2CH2OH], and ethoxyacetaldehyde [CH3CH2OCH2C(O)H] give a quantitative mass balance with the decay of the substrate molecule. The yields of these products were 34 ± 10%, 36 ± 7%, 7.8 ± 2.4%, and 24 ± 13%, respectively, in terms of percent of 2-ethoxyethanol removed by the OH radical. The product distribution is explained by a mechanism involving initial OH attack at the three CH2 groups in 2-ethoxyethanol followed by the subsequent reac tions of the resulting alkyl and alkoxy radicals. Th...

Different dissolved natural organic materials photosensitize the transformation of a series of methyl and methoxy phenols at pH 8 with a very similar high selectivity (reactivity range 50). This selectivity falls in the range of that achieved using the aromatic ketones benzophenone (BP), 3'-methoxyacetophenone (3'-MAP), and 2-acetonaphthone (2-AN) as model photosensitizers. For both natural and model sensitizers, the photooxidation at pH 8 is not controlled by singlet oxygen. Deuterium isotope effects (k H /k D ) of different phenols are 0.7-1.3 for humic and fulvic acids and 1.1-1.7 for BP, suggesting an electron transfer mechanism. In contrast, the isotope effect for 2-AN of 4 indicates an H-atom abstraction reaction. The results show that reactive excited triplet states are important photooxidants in natural waters and should be considered for assessing the abiotic degradation of chemicals. The reactive triplet state concentration is estimated to be 10 -14 M in the top meter of Lake Greifensee under summer noon sunlight, and this leads to a half-life of 7 h for 2,4,6-trimethylphenol. Further still uncharacterized photooxidants derived from the dissolved organic material are also involved in the phototransformation of the phenols.

Laboratory studies on the heterogeneous conversion of nitrogen dioxide into nitrous acid on irradiated ice films containing humic acid are described. It was found that the presence of light in the visible range of the solar spectrum significantly enhances the rate of nitrous acid release from a humic acid doped ice film. This process might contribute to observed HONO production in snow, where the NO2 is thought to originate from nitrate photolysis. Analysis of the experimental data based on the Langmuir Hinshelwood model framework allowed quantification of the observed dependencies of the nitrous acid production rate on nitrogen dioxide concentration. The observed dependencies on the humic acid concentration as well as on the irradiation intensity were used to estimate light-driven HONO fluxes for environmental snow covers.

D'Anna, Barbara Jammoul, Adla George, Christian Stemmler, Konrad Fahrni, Simon Ammann, Markus Wisthaler, Armin; The interactions of ozone with submicron particles and films consisting of humic acids of various origins were investigated under near-ultraviolet and visible irradiation using aerosol and coated wall flow-tube systems. Ozone loss to these surfaces was strongly activated in the presence of irradiation. Under simulated atmospheric conditions with respect to irradiance, relative humidity, and O-3 mixing ratios, the reactive uptake coefficients of the coatings ranged from gamma similar to 10(-6) (in the dark) to gamma similar to 10(-4) (under near-UVand visible irradiation) and were inversely dependent on the ozone mixing ratio in the 20- to 270-ppbv range. For the aerosol experiment the uptakes were an order of magnitude smaller. Light and ozone exposure promoted emissions of volatile organic compounds including small aldehydes (formaldehyde, acetaldehyde, hexanal, octanal, nonanal), methanol, and acetone. These results together suggest the existence of photoinduced ozone removal at the surface of various humic substances, which may be a potentially important ozone sink in the continental boundary layer and can represent a possible pathway for processing the organic aerosol.

[1] Mineral dust contains material such as TiO2 that is well known to have photocatalytic activity. In this laboratory study, mixed TiO2-SiO2, Saharan dust and Arizona Test Dust were exposed to NO2 in a coated wall flow tube reactor. While uptake in the dark was negligible, photoenhanced uptake of NO2 was observed on all samples. For the mixed TiO2-SiO2, the uptake coefficients increased with increasing TiO2 mass fraction, with BET uptake coefficients ranging from 0.12 to 1.9 × 10−6. HONO was observed from all samples, with varying yields, e.g., 80% for Saharan dust. Three-dimensional modeling indicates that photochemistry of dust may reduce the NO2 level up to 37% and ozone up to 5% during a dust event in the free troposphere.

Surface active organic compounds have been observed in marine boundary layer aerosol. Here, we investigate the effect such surfactants have on the uptake of nitric acid (HNO3), an important removal reaction of nitrogen oxides in the marine boundary layer. The uptake of gaseous HNO3 on deliquesced NaCl aerosol was measured in a flow reactor using HNO3 labelled with the short-lived radioactive isotope 13N. The uptake coefficient γ on pure deliquesced NaCl aerosol was γ=0.5±0.2 at 60% relative humidity and 30 ppb HNO3(g). The uptake coefficient was reduced by a factor of 5–50 when the aerosol was coated with saturated linear fatty acids with carbon chain lengths of 18 and 15 atoms in monolayer quantities. In contrast, neither shorter saturated linear fatty acids with 12 and 9 carbon atoms, nor coatings with the unsaturated oleic acid (C18, cis-double bond) had a detectable effect on the rate of HNO3 uptake. It is concluded that it is the structure of the monolayers formed, which determines their resistance towards HNO3 uptake. Fatty acids (C18 and C15), which form a highly ordered film in the so-called liquid condensed state, represent a significant barrier towards HNO3 uptake, while monolayers of shorter-chain fatty acids (C9, C12) and of the unsaturated oleic acid form a less ordered film in the liquid expanded state and do not hinder the uptake. Similarly, high contents of humic acids in the aerosol, a structurally inhomogeneous, quite water soluble mixture of oxidised high molecular weight organic compounds did not affect HNO3 uptake. As surfactant films on naturally occurring aerosol are expected to be less structured due to their chemical inhomogeneity, it is likely that their inhibitory effect on HNO3 uptake is smaller than that observed here for the C15 and C18 fatty acid monolayers.

[1] Ground-based in situ measurements of 1,1-difluoroethane (HFC-152a, CH3CHF2) which is regulated under the Kyoto Protocol are reported under the auspices of the AGAGE (Advanced Global Atmospheric Gases Experiment) and SOGE (System of Observation of halogenated Greenhouse gases in Europe) programs. Observations of HFC-152a at five locations (four European and one Australian) over a 10 year period were recorded. The annual average growth rate of HFC-152a in the midlatitude Northern Hemisphere has risen from 0.11 ppt/yr to 0.6 ppt/yr from 1994 to 2004. The Southern Hemisphere annual average growth rate has risen from 0.09 ppt/yr to 0.4 ppt/yr from 1998 to 2004. The 2004 average mixing ratio for HFC-152a was 5.0 ppt and 1.8 ppt in the Northern and Southern hemispheres, respectively. The annual cycle observed for this species in both hemispheres is approximately consistent with measured annual cycles at the same locations in other gases which are destroyed by OH. Yearly global emissions of HFC-152a from 1994 to 2004 are derived using the global mean HFC-152a observations and a 12-box 2-D model. The global emission of HFC-152a has risen from 7 Kt/yr to 28 Kt/yr from 1995 to 2004. On the basis of observations of above-baseline elevations in the HFC-152a record and a consumption model, regional emission estimates for Europe and Australia are calculated, indicating accelerating emissions from Europe since 2000. The overall European emission in 2004 ranges from 1.5 to 4.0 Kt/year, 5–15% of global emissions for 1,1-difluoroethane, while the Australian contribution is negligible at 5–10 tonnes/year

The interactions of aerosols consisting of humic acids with gaseous nitrogen dioxide (NO2) were investigated under different light conditions in aerosol flow tube experiments at ambient pressure and temperature. The results show that NO2 is converted on the humic acid aerosol into nitrous acid (HONO), which is released from the aerosol and can be detected in the gas phase at the reactor exit. The formation of HONO on the humic acid aerosol is strongly activated by light: In the dark, the HONO-formation was below the detection limit, but it was increasing with the intensity of the irradiation with visible light. Under simulated atmospheric conditions with respect to the actinic flux, relative humidity and NO2-concentration, reactive uptake coefficients γrxn for the NO2→HONO conversion on the aerosol between γrxn −7 (in the dark) and γrxn=6×10−6 were observed. The observed uptake coefficients decreased with increasing NO2-concentration in the range from 2.7 to 280 ppb and were dependent on the relative humidity (RH) with slightly reduced values at low humidity (60% RH). The measured uptake coefficients for the NO2→HONO conversion are too low to explain the HONO-formation rates observed near the ground in rural and urban environments by the conversion of NO2→HONO on organic aerosol surfaces, even if one would assume that all aerosols consist of humic acid only. It is concluded that the processes leading to HONO formation on the Earth surface will have a much larger impact on the HONO-formation in the lowermost layer of the troposphere than humic materials potentially occurring in airborne particles.

Near real-time measurements of light non-methane hydrocarbons (NMHCs) and peroxyacetyl nitrate (PAN) have been performed in the free troposphere using two fast gas chromatography (GC) instruments designed for use on aircraft. A GC-helium ionisation detector (HID) system measured 15 C(2)-C(5) hydrocarbons with 5 min time resolution and a dual channel GC-Electron Capture Detector (ECD) measured PAN with 90 s resolution. Both instruments had low parts per trillion by volume (pptV) detection limits and ran continuously at the remote Jungfraujoch (JFJ) research station in the Swiss Alps (46.55[degree]N, 7.98[degree]E), 3580 m above mean sea level (AMSL), during February/March 2003. Carbon monoxide, ozone, nitrogen oxide and nitrogen dioxide and all odd nitrogen species (NO(y)) were also measured continuously. Hydrocarbons and CO were strongly correlated in all air-masses whilst PAN exhibited both positive and negative correlations with respect to O(3), dependent on age and origin of the air-mass sampled. PAN was found to contribute [similar]20% to the NO(y) sampled on average. The experiment, as well as providing interesting datasets from this remote location, also demonstrated that when optimised, GC techniques have the potential to measure at a time resolution significantly greater than is traditionally considered, with high sensitivity and low uncertainty.

International audience; This submission was created using the RSC Article Template (DO NOT DELETE THIS TEXT) (LINE INCLUDED FOR SPACING ONLY-DO NOT DELETE THIS TEXT) In several recent field campaigns the existence of a strong daytime source of nitrous acid was demonstrated. The mechanism of this source remains unclear. Accordingly, in the present laboratory study, the effect of light (in the range 300-500nm) on the uptake kinetics of NO2 on various surfaces taken as proxies for organic surfaces encountered in the troposphere (as organic aerosol but also ground surfaces) was investigated. In this collaborative study, the uptake kinetics and product formation rate were measured by different flow tube reactors in combination with a sensitive HONO instrument. Uptake on phenolic species was significantly enhanced when irradiated with light of 300 – 420 nm, and HONO was formed with high yield when the gas was humidified. Adding a stronger absorber, such as BBA, further enhanced the reactivity of the substrate. Based on the results reported a mechanism is suggested, in which photosensitised electron transfer are occurring. The results show that HONO can be efficiently formed during the day in the atmosphere at much longer wavelengths compared to the recently proposed nitrate photolysis.

[1] At the high Alpine site of Jungfraujoch (3580 m asl), 23 halogenated greenhouse gases are measured quasi-continuously by gas chromatography-mass spectrometry (GCMS). Measurement data from the years 2000–2002 are analyzed for trends and pollution events. Concentrations of the halogenated trace gases, which are already controlled in industrialized countries by the Montreal Protocol (e.g., CFCs) were at least stable or declining. Positive trends in the background concentrations were observed for substances which are used as CFC-substitutes (hydrofluorocarbons, hydrochlorofluorocarbons). Background concentrations of the hydrofluorocarbons at the Jungfraujoch increased from January 2000 until December 2002 as follows: HFC 134a (CF3CH2F) from 15 to 27 ppt, HFC 125 (CF3CHF2) from 1.4 to 2.8 ppt, and HFC 152a (CHF2CH3) from 2.3 to 3.2 ppt. For HFC 152a, a distinct increase of its concentration magnitude during pollution events was observed from 2000 to 2002, indicating rising European emissions for this compound. Background concentrations of all measured compounds were in good agreement with similar measurements at Mace Head, Ireland. On the other hand, peak concentrations were significantly higher at the Jungfraujoch. This finding is due to the proximity to potent European sources, foremost in southern Europe. The average ratio of halocarbons versus carbon monoxide (CO) concentrations above their baseline values was used to estimate source strengths for the part of Europe which most influences the Jungfraujoch during pollution events. HFCs emission estimates from Jungfraujoch tend to be higher than figures at Mace Head (Ireland) from the end of the 1990s, which either reflects the increased use of these compounds or the closer location of Jungfraujoch to major southern European sources. Transport of polluted European boundary layer air masses to the high Alpine site was observed especially during frontal passages, foehn events, and thermal lifting of air masses in summer. The measurement data during the periods when the Jungfraujoch was under the influence of the polluted boundary layer were used in combination with concurrent air mass trajectories to allocate above baseline halocarbon concentrations to specific European source regions.

The aim of this series of two publications is to characterise radical reactions of organic molecules, occurring in atmospheric water phases. In this second study, the reactions occurring in a mixed peroxyl radical system generated from the OH radical attack on a model compound, 2-butoxyethanol, in oxygenated aqueous solution are investigated in the presence of O-2(-)/HO2 radicals, H2O2, and of copper (I and II)- and iron (II and III) species. A general mechanism of the reactions occurring in such systems is discussed and compared to the formation of organic hydroperoxides and hydrogen peroxide from this oxidation reactions. The main features of the mechanism are as follows: (i) production of peroxyl radicals following OH-attack on the model compound; (ii) cycling of the transition metals between the oxidation states given above, arising from a reduction reaction with superoxide, O-2(-) and oxidation reactions by organic peroxyl radicals, organic hydroperoxides, superoxide, and oxygen; (iii) reactions of organic peroxyl radicals, in contrast to superoxide radicals, occur only with the reduced forms of the transition metals and lead to the formation of organic hydroperoxides: (iv) the reaction of organic peroxyl radicals with Cu (I) is fast (k > 10(8) M-1 s(-1)); (v) the reaction of organic hydroperoxides with Cu (I) can he much faster (2 orders of magnitude) than the analogous reaction of hydrogen peroxide and leads to the production of oxyl radicals: and (vi) oxalate, a strong ligand for Cu (II), reduces the activity of copper, owing to its stabilisation of the copper (II) complex. The mechanism is discussed in relation to atmospheric conditions. (C) 2000 Elsevier Science Ltd. All rights reserved.