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In the frame of the 2019-20 ALIGN-CCUS campaign, the amine plant at the Technology Centre Mongstad (TCM) was operated with the CESAR 1 solvent, i.e. an aqueous solution of 2-amino-2-methylpropan-1-ol (AMP) and piperazine (PZ), for removing carbon dioxide from the flue gas of Equinor’s combined cycle gas turbine plant. An online Proton-Transfer-Reaction Time-of-Flight Mass Spectrometer (PTR-TOF-MS) was used for quantifying atmospheric emissions of AMP and PZ, as well as emissions of amine degradation products and solvent impurities. Mean and median AMP levels emitted to the atmosphere over an operational period of 13 weeks were 562 and 377 ppb, respectively. PZ emissions to the atmosphere were much lower, with mean and median levels being 6.0 and 0.4 ppb, respectively. Three small carbonyl species (formaldehyde, acetaldehyde, acetone) were emitted at levels of tens to hundreds of ppb. Nitrogen-containing degradation products and impurities of solvent amines with mean emission levels >1 ppb included the following compounds: monomethylamine (MMA), formamide (FA), morpholine (MOR), 4,4-dimethyloxazolidine (DMO), 2-methyl-2-(methylamino)propan-1-ol (MeAMP), 4-acetylmorpholine (AMOR) and a compound with a molecular sum formula of C8H14N2, which we tentatively assigned to an alkylated imidazole or pyrazole. Low (

We herein present the chemical-analytical setup used to measure atmospheric emissions of amines and amine degradation products from an amine-based post-combustion carbon capture plant. The emission measurements were carried out at the Technology Centre Mongstad (TCM) in Norway, in the frame of the ALIGN-CCUS campaign from September 2019 to January 2020, when the amine plant was operated with the CESAR 1 solvent. This advanced solvent is an aqueous solution of 2-amino-2-methyl-1-propanol (AMP) and piperazine (PZ). Four chemical-analytical techniques were deployed for characterizing emission of AMP, PZ and their degradation products: online Fourier Transform Infrared (FTIR) Spectroscopy, online Proton-Transfer-Reaction Time-of-Flight Mass Spectrometry (PTR-TOF-MS), online Proton-Transfer-Reaction Quadrupole Mass Spectrometry (PTR-QMS), as well as manual impinger sampling followed by offline Ion Chromatography Mass Spectrometry (IC-MS) analysis. AMP was detected by all four methods, with the results being in reasonably good agreement. PZ was detected by PTR-TOF-MS, PTR-QMS and IC-MS, but because of the low emission levels (single-digit ppb) the latter two methods suffered from a positive bias (due to an interfering compound) and a large measurement uncertainty, respectively. 17 amine degradation products were only detected by the PTR-ToF-MS analyzer. We present exemplary results from the emission measurements carried out during the ALIGN-CCUS 2019-2020 campaign and share some of the lessons learned from this exercise.

South Korea routinely experiences poor air quality with ozone and small particles exceeding air quality standards. To build a better understanding of this problem, in 2016, the KORea-United States cooperative Air Quality (KORUS-AQ) study collected surface and airborne measurements of many chemical species, including the reactive gases hydroxyl (OH) and hydroperpoxyl (HO2). Several different results are reported here. First, OH and HO2 measured on the NASA DC-8 agree to within uncertainties with values calculated by two different box models, both in statistical comparisons and as a function of altitude from the surface to 8 km. These comparisons show substantial scatter, likely due to both variability in instrument performance and the difficulty in interpolating measurements made with frequencies different from those of the model time step. Second, OH and HO2 calculated by a model including HO2 uptake on aerosol particles in the chemical mechanism are inconsistent with observations. Third, in the planetary boundary layer over both ocean and land, measured and model-calculated OH reactivity are sometimes different, and this missing OH reactivity, which is as much as ∼4 s−1, increased from April to June and originated primarily from the Korean peninsula. Fourth, repeated missed approaches at the Seoul Air Base during several days show that the changes in the sum of ozone and nitrogen dioxide are consistent with ozone production rates calculated from HO2 either observed or modeled by the Langley Research Center model.

We herein report on the adaptation and deployment of a compact and easy-to-use mass spectrometer for online monitoring of amines in industrial flue gas at ppb to ppm levels. The use of ammonia as a source gas in proton-transfer-reaction mass spectrometry (PTR-MS) greatly simplifies the detection of amines, making it possible to use a low-end commercial instrument version (PTR-QMS 300) for the measurements. We characterized the analytical performance of the instrument (sensitivity, limit of detection, precision, matrix effects) for nine solvent amines (monoethanolamine, dimethylaminoethanol, aminomethylpropanol, methyldiethanolamine, diglycolamine, piperazine, aminoethylpiperazine, methylpiperazine, N-(2-hydroxyethyl)piperazine) and three degradation amines (methylamine, dimethylamine, trimethylamine). The new analyzer was tested and validated in side-by-side measurements with established emission monitoring techniques at the Technology Centre Mongstad (TCM) in Norway. After validation, the instrument was permanently installed on top of the absorber tower to deliver real-time amine emission data to the plant information management system.

Laboratory experiments were carried out to study Schiff-base condensation reactions between amines and formaldehyde that occur on inlet lines of emission monitoring instruments. Primary amines and formaldehyde were found to quickly react on inlet surfaces to form the respective Schiff-base condensation products. Secondary and tertiary amines did not react with formaldehyde. Schiff-base condensation reactions between primary amines and formaldehyde were also observed to occur on the ∼110 m long inlet line that connects the absorber stack of the amine-based PCCC facility at Mongstad to the FT-IR and PTR-ToF-MS emission monitors. Emissions of primary amines and formaldehyde may be underestimated if condensation reactions of these species in inlet lines are not taken into account. The PTR-ToF-MS monitor does, however, also quantitatively detect the Schiff-base condensation products, making it straightforward to derive the correct amine and formaldehyde concentrations in the amine wash gas.

Predictions of O_3, CO, total NO_y and individual NO_y species (NO, NO_2, HNO_3, PAN, alkyl nitrates and aerosol nitrate) from a fine resolution regional air quality modeling system for the South Coast Air Basin (SoCAB) and San Joaquin Valley Air Basin (SJVAB) of California are presented and evaluated for the 2008 ARCTAS-CARB campaign. The measurements of the chemical compounds from the fire plumes during the field campaign allow for the evaluation of the model's ability to simulate fire-influenced air masses as well. In general, the model successfully simulated the broad spatial distribution of chemical compounds in both air basins as well as the variation within the basins. Using inventories that reflect 2008 emissions levels, the model performed well in simulating NO_x (NO + NO_2) in SoCAB. Therefore, the under prediction of O_3 over these areas is more likely caused by uncertainties with the VOC emissions, chemistry, or discrepancies in the meteorology. The model did not capture the relatively high levels of O_3, and some reactive nitrogen species that were measured off shore of the SoCAB, indicating potential missing sources or the transport from on shore to off shore was not successfully captured. In SJVAB, the model had good performance in simulating different chemical compounds in the Fresno and Arvin areas. However, enhanced concentrations of O_3, NO_x, HNO_3 and PAN near dairy farms were significantly underestimated in the model. Negative biases also exist for O_3 and HNO_3 near oil fields, suggesting larger uncertainties associated with these emission sources. While the model simulated the total NO_y mixing ratios reasonably well, the prediction for partitioning between individual compounds showed larger uncertainties in the model simulation. Although the fire emissions inventory was updated to include the latest emissions estimates and speciation profiles, our model shows limited improvement in simulating the enhancement of O_3, CO, and PAN under fire impact as compared to a previous version of the modeling system. Further improvements in simulating fire emissions, especially the timing and the plume injection heights, are desired in order to better simulate the impact of fires.

This paper presents airborne measurements of multiple atmospheric trace constituents including greenhouse gases (such as CO2, CH4, O3) and biomass burning tracers (such as CO, CH3CN) downwind of an exceptionally large wildfire. In summer 2013, the Rim wildfire, ignited just west of the Yosemite National Park, California, and burned over 250,000 acres of the forest during the 2-month period (17 August to 24 October) before it was extinguished. The Rim wildfire plume was intercepted by flights carried out by the NASA Ames Alpha Jet Atmospheric eXperiment (AJAX) on 29 August and the NASA DC-8, as part of SEAC4RS (Studies of Emissions, Atmospheric Composition, Clouds and Climate Coupling by Regional Surveys), on 26 and 27 August during its intense, primary burning period. AJAX revisited the wildfire on 10 September when the conditions were increasingly smoldering, with slower growth. The more extensive payload of the DC-8 helped to bridge key measurements that were not available as part of AJAX (e. g. CO). Data analyses are presented in terms of emission ratios (ER), emission factors (EF) and combustion efficiency and are compared with previous wildfire studies. ERs were 8.0 ppb CH4/(ppm CO2) on 26 August, 6.5 ppb CH4 (ppm CO2)1 on 29 August and 18.3 ppb CH4 (ppm CO2)1 on 10 September 2013. The increase in CH4 ER from 6.5 to 8.0 ppb CH4/(ppm CO2) during the primary burning period to 18.3 ppb CH4/(ppm CO2) during the fire's slower growth period likely indicates enhanced CH4 emissions from increased smoldering combustion relative to flaming combustion. Given the magnitude of the Rim wildfire, the impacts it had on regional air quality and the limited sampling of wildfire emissions in the western United States to date, this study provides a valuable dataset to support forestry and regional air quality management, including observations of ERs of a wide number of species from the Rim wildfire.

Data collected during the 2011 DISCOVER-AQ field campaign in the Baltimore Washington region were used to evaluate CO and NO x emissions in the National Emissions Inventory (NEI). The average emissions ratio for the region was seen to be 11.2 ± 1.2 mol CO/mol NO x , 21% higher than that predicted by the NEI. Comparisons between in situ and remote observations and CMAQ model output show agreement in CO emissions of 15 ± 11% while NO x emissions are overestimated by 51–70% in Maryland. Satellite observations of CO by MOPITT show agreement with the Community Multiscale Air Quality (CMAQ) model within 3% over most of the eastern United States. CMAQ NO y mixing ratios were a factor of two higher than observations and result from a combination of errors in emissions and PAN and alkyl nitrate chemistry, as shown by comparison of three CMAQ model runs. Point source NO x emissions are monitored and agree with modeled emissions within 1% on a monthly basis. Because of this accuracy and the NEI assertion that approximately 3/4 of emissions in the Baltimore Washington region are from mobile sources, the MOVES model's treatment of emissions from aging vehicles should be investigated; the NEI overestimate of NO x emissions could indicate that engines produce less NO x and catalytic converters degrade more slowly than assumed by MOVES2010. The recently released 2011 NEI has an even lower CO/NO x emissions ratio than the projection used in this study; it overestimates NO x emissions by an even larger margin. The implications of these findings for US air quality policy are that NO x concentrations near areas of heavy traffic are overestimated and ozone production rates in these locations are slower than models indicate. Results also indicate that ambient ozone concentrations will respond more efficiently to NO x emissions controls but additional sources may need to be targeted for reductions.

In this short technical paper we demonstrate how aging of the micro-channel plate (MCP) detector in a PTR-ToF-MS instrument induces strong mass discrimination and detection non-linearity effects. Based on exemplary data from an 11-week measurement campaign we show how detector aging led to an m/z-dependent loss in detection efficiency in the m/z 33 (−19%) to m/z 205 range (−67%). Ion signals in the upper m/z range did not increase linearly with analyte concentration (0–150 ppbv) when the MCP detector was not operated in the saturation regime. Both effects may lead to large errors in VOC quantification by PTR-ToF-MS if the instrument is not externally calibrated on a frequent basis. We also demonstrate that the current practice of minimizing ion feedback in the MCP detector will trigger the described problems. Our study may serve as a guide for diagnosing and optimizing PTR-ToF-MS detector performance.

Extensive atmospheric emission monitoring has been conducted at the CO2 Technology Centre Mongstad (TCM DA) during amine based post-combustion CO2 capture. The TCM DA amine plant was operated with an aqueous monoethanolamine (MEA) solvent system, treating flue gas from a combined heat and power (CHP) plant. Emission monitoring was conducted by a Fourier Transform Infrared (FTIR) Spectroscopy analyzer, a Proton Transfer Reaction Time-of-Flight Mass Spectrometry (PTR-TOF- MS) analyzer, and manual isokinetic sampling followed by off-line analysis in the laboratory. Atmospheric emissions of MEA were very low throughout the entire campaign, ranging from a few to a few hundred parts per billion (ppb, 1 ppb = 10-9 v/v). Atmospheric emissions of MEA amine based degradation products such as nitrosamines and nitramines were below detectable levels. Atmospheric emissions of ammonia (NH3) were in the low ppm range. Methylamine was emitted at low ppb range. Absorber wash water sections were found to effectively reduce atmospheric emissions from amine based solvent system.

Storage methods extend the postharvest life of apples from weeks to up to one year; however, these methods also alter the production of volatile organic compounds (VOCs), which amongst others, are important for aroma attributes. While the impact of storage on particular aroma components has been established, high throughput methods for determining the storage history during shelf-life are elusive. Here we show the potential of proton transfer reaction-mass spectrometry (PTR-MS), an MS-based metabolic fingerprinting technique, for characterizing fruit in the postharvest chain. The VOC fingerprint of apples (Malus × domestica Borkh. ‘Red Delicious’) was analyzed by PTR-MS during four weeks of shelf-life ripening after storage under four different storage conditions: ULO (ultra-low oxygen), DCA-CF (dynamic controlled atmosphere monitored by chlorophyll fluorescence), RLOS (repeated low oxygen stress) and 1-MCP (1-methylcyclopropene) in ULO. PTR fingerprint mass spectra of the apple headspace, obtained in short time without sample preparation or preconcentration, were sufficient to discriminate the four storage conditions during shelf-life. Moreover, we were able to monitor the changes in quality-critical VOC classes, including esters and terpenes, during shelf-life and observe the differential impact of the storage history on these VOCs. This work emphasizes the potential of PTR-MS as a valuable addition to targeted GC–MS-based approaches in postharvest research.

An instrumented DC-8 aircraft was employed to perform airborne observations in rural and urban environs of California during the summer 2008 NASA ARCTAS-CARB campaign. The fortuitous occurrence of large wildfire episodes in Northern California allowed for studies of fire emissions, their composition, and their interactions with rural and urban air. Relative to CO, emissions of HCN were shown to vary non-linearly with fire characteristics while those of CH 3 CN were nearly unchanged, making the latter a superior quantitative tracer of biomass combustion. Although some fire plumes over California contained little NO x and virtually no O 3 enhancement, others contained ample VOCs and sufficient NO x , largely from urban influences, to result in significant ozone formation. The highest observed O 3 mixing ratios (170 ppb) were also in fire-influenced urban air masses. Attempts to simulate these interactions using CMAQ, a high-resolution state of the art air quality model, were only minimally successful and indicated several shortcomings in simulating fire emission influences on urban smog formation. A variety of secondary oxidation products (e.g. O 3 , PAN, HCHO) were substantially underestimated in fire-influenced air masses. Available data involving fire plumes and anthropogenic pollution interactions are presently quite sparse and additional observational and mechanistic studies are needed.

The sectoral and regional contributions from northern hemisphere anthropogenic and biomass burning emission sectors to black carbon (BC) distributions over the continental United States (CONUS) in summer 2008 are studied using the Sulfur Transport and dEposition Model (STEM). North American (NA) emissions heavily (>70% of total emissions) affect the BC levels from the surface to w5 km, while non-NA plumes compose more than half of the BC above w5 km. Among all sectors, NA and non-NA biomass burning, NA transportation and non-NA residential emissions are the major contributors. The sectoral contributions vary among ten regions defined by the US Environmental Protection Agency (EPA): NA anthropogenic emissions enhance northeastern US BC levels; biomass burning strongly impacts northern California and southeastern US; and the influence of extra-regional plumes is largest in the northwestern US but extends to eastern US. The mean contribution from non-NA sources to US surface BC is w0.05 m gm �3 , with a maximum value of w0.11 m gm �3 in the northwestern US. The non-NA contributions to column BC are higher than to surface BC, ranging from 30% to 80%, depending on region. EPA region 8 is most sensitive to extra-regional BC, partially explaining the observed increasing BC trend there during the past decades associated with the increasing Asian BC emissions. Measurements from the June 24 DC-8 flight during the ARCTAS-CARB field campaign show that BC/(organic matter þ nitrate þ sulfate) mass ratios fairly well represent BC’s warming potential over southern California, which can be approximated by BC/(organic matter þ sulfate) and BC/sulfate for plumes affected and unaffected by fires, respectively. The responses of BC/(organic matter þ sulfate) and BC/sulfate to removing each emission sector are further discussed, indicating that mitigating NA transportation emissions has the highest potential for regional air quality and climate co-benefits.

The atmospheric photo-oxidation of 2-aminoethanol (MEA, NH2CH2CH2OH) was studied at the European Photochemical Reactor, EUPHORE, in Valencia (Spain). The experiments were carried out under different atmospherically relevant NOx conditions. The photo-oxidation was monitored in situ by FT-IR and on-line by PTR-TOF-MS, and samples were collected on various adsorbents for subsequent off-line analysis. The formation of particles was monitored by SMPS and AMS on-line instruments and filter sampling followed by LC/HRMS(TOF) analysis. The obtained results suggest that more than 80% of the reaction between MEA and OH radicals takes place at–CH2–, while less than 10% occurs at–NH2 and at–CH2OH, respectively. The major observed products (>80%) in the photo-oxidation were formamide (NH2CHO) and formaldehyde (CH2O). Minor detected products (

We analyze detailed atmospheric gas/aerosol composition data acquired during the 2008 NASA ARCTAS (Arctic Research of the Composition of the Troposphere from Aircraft and Satellites) airborne campaign performed at high northern latitudes in spring (ARCTAS-A) and summer (ARCTAS-B) and in California in summer (ARCTAS-CARB). Biomass burning influences were widespread throughout the ARCTAS campaign. MODIS data from 2000 to 2009 indicated that 2008 had the second largest fire counts over Siberia and a more normal Canadian boreal forest fire season. Near surface arctic air in spring contained strong anthropogenic signatures indicated by high sulfate. In both spring and summer most of the pollution plumes transported to the Arctic region were from Europe and Asia and were present in the mid to upper troposphere and contained a mix of forest fire and urban influences. The gas/aerosol composition of the high latitude troposphere was strongly perturbed at all altitudes in both spring and summer. The reactive nitrogen budget was balanced with PAN as the dominant component. Mean ozone concentrations in the high latitude troposphere were only minimally perturbed (

The sensitivity of biogenic emission estimates and air quality model predictions to the characterization of land use/land cover (LULC) in southeastern Texas was examined using the Global Biosphere Emissions and Interactions System (GloBEIS) and the Comprehensive Air Quality Model with extensions (CAMx). A LULC database was recently developed for the region based on source imagery collected by the Landsat 7 Enhanced Thematic Mapper-Plus sensor between 1999 and 2003, and field data for land cover classification, species identification and quantification of biomass densities. Biogenic emissions estimated from the new LULC data set showed good general agreement in their spatial distribution, but were approximately 40% lower than emissions from the LULC data set currently used by the State of Texas, primarily because of differences in the biomass estimates of key species such as Quercus. Predicted ozone mixing ratios using the biogenic emissions produced from the new LULC data set were as much as 26 ppb lower in some areas on some days, depending on meteorological conditions. Satellite data and image classification techniques provide useful tools for mapping and monitoring changes in LULC. However, field validation is necessary to link species and biomass densities to the classification system used for accurate biogenic emissions estimates, especially in areas such as riparian corridors that contain dense spatial coverage of key species.

Biogenic emissions of hydrocarbons, primarily isoprene, dominate the VOC emission inventory in eastern Texas. Air quality model predictions of isoprene in southeast Texas were evaluated using ground and aircraft measurements collected during the Texas Air Quality Study 2000. The effects of two different vertical mixing schemes on model predictions of isoprene concentrations were also evaluated. The photochemical and biogenic emission estimation models used were the Comprehensive Air Quality Model with Extensions and the Global Biosphere Emissions and Interactions System. Ground level isoprene concentrations predicted by the models showed markedly good agreement with measured diurnal isoprene patterns. The vertical mixing schemes were most influential on surface concentrations, resulting in differences of as much as 270% in modeled isoprene concentrations. The model over predicted observations from airborne canister samples by as much as a factor of two over rural areas, but under predicted observations over urban areas. Modeled isoprene concentrations were also compared with measurements from an airborne Proton Transfer Reaction Mass Spectrometer, and the results indicated under prediction of isoprene by the model over urban areas, but better agreement in rural areas. The impacts of the vertical mixing schemes on isoprene concentrations were less direct aloft than at the surface. The resulting vertical redistribution of isoprene affected transport rates, chemistry, and the accumulation of mass. As a result, differences in concentrations aloft ranged from none to as much as 30%. This study reinforces the challenges of air quality model validation for highly reactive species such as isoprene, and the need for carefully controlled studies of biogenic emissions and chemical processing during different meteorological conditions in regions with spatially heterogeneous land use.

The experiment presented in this report was performed in a simulated aircraft cabin to evaluate the air cleaning effects of two air purification devices that used photocatalytic oxidation (PCO) technology. Objective physical, chemical and physiological measurements and subjective human assessments were used for the evaluation. Comparisons were made between conditions with and without the PCO units installed in the re-circulated air system. Four groups of 17 subjects were exposed for 7 h to each test condition. Chemical analysis indicates that ethanol, isoprene and toluene were decomposed by oxidation in the PCO units tested. However, some intermediate products, such as formaldehyde and acetaldehyde, were detected. Physiological measurements did not show any significant effects of the two PCO units except that skin dryness was reduced by operating PCO unit 2. Both positive and negative effects of using PCO units on subjective assessments were observed after the first 3 1/4 hours of exposure. After 6 h of exposure, a positive effect of using either PCO unit on symptoms of dizziness and claustrophobia was observed.

Continuous measurements of CO, NO, NO2, PM10, benzene and toluene were conducted over a one-year period at a motorway location in the alpine Inn valley. Diurnal changes in concentrations of detected compounds were observed to vary according to traffic type and frequency, and meteorological conditions of the valley atmosphere, which were both additionally recorded at this location. Seasonal variations were also clearly seen, with lowest levels of compound abundances present in summer and highest levels in winter. Annual mean abundances of compounds were assessed with respect to guideline limits and it was found that NO2 and PM10 exceeded their legislation thresholds. This investigation also included the first continuous year-long measurements of benzene at this location, yielding an annual mean volume mixing ratio of 0.6 ppbV, which is well within the EU guideline limit of 1.5 ppbV. Additionally, benzene abundances were found to correlate well with CO concentrations. A significant correlation was also found between toluene and benzene. However, the ratio toluene:benzene shifted from about 2:1 in summer to approximately 1:1 in winter. This may be explained by a strong evaporative and therefore temperature dependent toluene source, while benzene concentrations mainly result from non-ambient temperature dependent exhaust pipe emissions. This seasonal variation must be taken into account whenever this ratio is used to determine the chemical age of an air mass.

The present communication deals with the improvement of proton transfer reaction mass spectrometry (PTR-MS) wine headspace analyses. In contrast to previous PTR-MS investigations of wine, where wine headspace was ionized by protonated ethanol clusters, the headspace was diluted by a factor of 1:40 with N2 and ionized by H3O+ ions. This method is better suited for routine applications than the previously reported method since it is simpler, faster, and the mass spectra obtained are less complex. A test wine was mixed with ethanol and with water to yield ethanol contents ranging from 10 to 15% (v/v) and these mixtures were analyzed to assess whether any quantitative differences in the composition of volatiles were detectable. The data showed no impact of the ethanol content on the wine headspace composition. The new method was applied to eight different wine samples produced from two different grape varieties: Pinot Noir and Cabernet Sauvignon. Each variety was grown in two different locations in South Tyrol (Northern Italy) and harvested at two different dates. Quantitative (but not qualitative) differences in PTR-MS spectra between the two wine varieties were observed. Using principal component analysis of selected m/z signals differentiation between Pinot Noir and Cabernet Sauvignon samples was achievable.

Oxygen was used as a source gas in a conventional Innsbruck PTR-MS instrument to produce O 2 + ions as chemical ionization (CI) reagents instead of H 3 O + ions. The use of O 2 + ions as CI reagents allows for fast, highly sensitive and specific measurements of gas-phase ammonia (NH 3 ) via the electron transfer reaction O 2 + + NH 3 → NH 3 + + O 2 . The instrument was tested to be linear in the 2–2000 ppbv range. Instrument sensitivity was observed to be humidity-independent and amounted to ∼40 cps/ppbv. The instrumental background was determined by sampling NH 3 -free air from a heated platinum/palladium catalyst. A humidity-dependent increase of the instrumental background from 70 pptv at dry conditions to 470 pptv at humid conditions was observed. The corresponding 2 σ -detection limits at 1 s signal integration time were 90 pptv for dry conditions and 230 pptv for humid conditions, respectively. The observed background may be intrinsically formed in the instrument's ion source but it may also be the result of incomplete NH 3 oxidation in the catalyst used for zeroing. The reported background levels and detection limits are thus to be considered as upper limits. The 1/ e response time of the instrument was in the range of 3–5 s. The PTR-MS instrument was successfully deployed in the field to monitor changes in gas-phase NH 3 concentrations in the few seconds to tens of seconds time range. Laboratory intercomparison measurements between the PTR-MS instrument and a commercial NH 3 analyzer (AiRRmonia) were in good agreement. The use of O 2 + ions as CI reagents will significantly improve the analytical capabilities of the Innsbruck PTR-MS instrument.

Saturn's moon Titan has been considered as one of the few places in our Solar System, where atmospheric and surface conditions could have produced organic compounds essential as precursors for an evolution of life. The Cassini–Huygens mission has provided new data on Titan's atmosphere and surface, which enabled us to simulate the chemical processes occurring under these conditions. Possible lightning events on Titan cannot only produce higher hydrocarbons, but also allow surface water ice to participate in the reaction scenario, resulting in C H O, C H N, and C H O N compounds including several molecules relevant for the formation of amino acids and nucleic acids.

During the 2002 summer intensive field campaign of BEWA2000 a proton-transfer-reaction mass spectrometer (PTR-MS) was used for online determination of volatile organic compounds (VOC) emitted by Norway spruce ( Picea abies L. [Karst]) twigs in a dynamic sampling enclosure. Emissions of isoprenoids (isoprene and monoterpenes) and oxygenated VOC (OVOC; acetaldehyde, acetone, methanol, and ethanol) were investigated. Emissions showed clear diurnal patterns with high daytime emission rates amounting to 1.8 μg C g −1 dwt h −1 for the sum of monoterpenes and in the range of 0.1 to 0.6 μg C g −1 dwt h −1 for isoprene>acetone>ethanol>methanol. Data were used to validate existing models on isoprene and monoterpene emissions and to discuss environmental and physiological factors affecting VOC emissions. Isoprene and acetaldehyde emission rates were best modelled applying the Guenther 1993 temperature and solar radiation algorithm. Emissions of monoterpenes, acetone and ethanol were best described by a temperature-only exponential algorithm. Using these model approaches a maximum emission variability of 66% was covered (isoprene). Poor r 2 values ranging from 0.15 to 0.42 were typical for oxygenated VOC emission modelling indicating the need for model improvement e.g. development of process-based models describing the emission as a result of biochemical de novo synthesis as well as physico-chemical transport properties inside the leaves.

Diurnal mixing ratios of aldehydes and ketones were investigated during two joint experiments in summer months to identify biogenic contributions from coniferous forests to tropospheric chemistry. In a Norway spruce forest, the diurnal variation of carbonyl compounds was measured at 12 m (in the treetop) and at 24 m (above the canopy). The main findings of the experiment are that acetone (up to 9.1 ppbv), formaldehyde (up to 6.5 ppbv), acetaldehyde (up to 5.5 ppbv) and methyl ethyl ketone (MEK, up to 1.8 ppbv) were found in highest concentrations. For all major compounds with the exception of MEK, primary emissions are supposed. From α-pinene oxidation, pinonaldehyde was found with its peak concentrations (up to 0.15 ppbv) during the early morning hours. The diurnal variation of concentrations for most other compounds shows maximum concentrations near midday in 2,4-dinitrophenylhydrazine (DNPH) measurements but not for proton-transfer reaction mass spectrometry (PTR-MS) measurements of acetaldehyde and acetone. A clear correlation of carbonyl compound concentration to the radiation intensity and the temperature (R2=0.66) was found. However, formaldehyde did not show distinct diurnal variations. A very high correlation was observed for both heights between mixing ratios of acetaldehyde and acetone (R2=0.84), acetone and MEK (R2=0.90) as well as acetaldehyde and MEK (R2=0.88) but not for formaldehyde and the others. For the most time, the observed carbonyl compound concentrations above the canopy are higher than within the forest stand. This indicates an additional secondary formation in the atmosphere above the forest. The differences of acetone and acetaldehyde mixing ratios detected by DNPH technique and the PTR-MS could not be fully clarified by a laboratory intercomparison.

A relaxed-eddy-accumulation set-up using an online gas-chromatographic technique and proton-transfer-reaction mass spectrometry was applied to determine isoprenoid fluxes above a Norway spruce forest in July 2001/2002. The system was quality assured and its suitability for determination of canopy fluxes of isoprenoids was demonstrated. Flux measurements of oxygenated hydrocarbons failed the data quality check due to artefacts presumably arising from line and ozone-scrubber effects. Observations of turbulent fluxes of isoprenoids during the two field experiments show good agreements with primary flux data derived from enclosure measurements and modelling results using a canopy-chemistry emission model (CACHE). For monoterpenes maximum daytime fluxes of more than 2 nmol m - 2 s - 1 were observed, isoprene fluxes reached 1– 1.5 nmol m - 2 s - 1 .

Interest in reliable quantification of organic trace compounds released from terrestrial ecosystems stems from their impact on oxidant levels such as ozone and hydroxyl radicals and on secondary organic aerosol formation. In an attempt to quantify these emissions, a disjunct sampler (DS) was coupled to a PTR-MS instrument. In the disjunct eddy covariance (DEC) technique, an instantaneous grab sample is taken at intervals of tens of seconds and vertical wind speed is recorded at the instant of sample collection. The intermittent periods are used for sample analysis by a moderately fast chemical sensor, in this case a PTR-MS instrument, which allows for fast and sensitive detection of biogenic volatile organic compounds. The vertical turbulent transport of a trace compound is then calculated from the covariance of the fluctuations in vertical wind speed and compound mixing ratio. Fluxes of monoterpenes from a Norway spruce forest were measured during the 2002 summer intensive field campaign of BEWA2000 and results compared well with data obtained using relaxed eddy accumulation (REA) and the enclosure approach. In addition to this field experiment, a laboratory test was carried out to validate the disjunct sampling procedure.

A new method for measuring volatile profiles of alcoholic beverages (or other ethanol-containing analytes such as perfumes or herbs) has been developed. The method is based on proton transfer reaction mass spectrometry (PTR-MS). However, instead of hydronium ions (H3O+) protonated ethanol clusters (C2H5OH2+(C2H5OH)n = 1,2) are used as chemical ionization reagent ions. A stable reagent ion distribution is obtained by a 10-fold dilution of analyte headspace into ethanol-saturated nitrogen. Samples with different ethanol content can thus be directly compared. Characteristic mass spectral fingerprints have been obtained for four wine varieties. Principal component analysis discriminates between different wine varieties and shows specific correlations between wine variety and selected ions.

Proton-transfer-reaction mass spectrometry (PTR-MS) was used as an analytical tool to measure gas-phase concentrations of short-chain fatty acids. Chemical ionisation of C2 C6 carboxylic acids by PTR-MS produced intense protonated molecular ions (with traces of hydrates) along with acylium ion fragments. Gas-phase concentrations were derived using the established method for calculating PTR-MS sensitivity factors. Henry's law constants of carboxylic acids for aqueous solutions at 40 °C were determined. Direct monitoring of volatile fatty acids, known to be associated with secretions from the human axilla, was performed via a specially designed transfer device situated in the axilla. Mass spectral data corresponded with the findings of a sensory assessor.

In situ measurements of CO, NO x , PM 10 and certain organic compounds took place over an 11 day period encompassing a 12 h motorway blockade. Located within the Inn valley (Tirol, Austria), the monitoring site experiences varying meteorological conditions and traffic frequency throughout the day which both strongly influence air pollutant levels. Early morning increases of NO x , PM 10 and aromatic hydrocarbons were clearly correlated with rising traffic. Midday minima and afternoon maxima may be explained by changing wind conditions and varying inversion layer dynamics. Night time lows in concentrations can be explained by minimal traffic activity. Classification of compound sources was made through grouping of data, separated into times when heavy duty vehicles (HDV) were permitted to use the motorway and HDV-ban periods. Increased levels of NO x and PM 10 were observed from data that included periods of high HDV numbers, with levels decreasing significantly during HDV-ban periods. In contrast, the aromatic hydrocarbons and CO displayed only minor variations between these two periods. Furthermore, on typical workdays NO x levels reached a maximum that corresponded to a peak in HDV numbers, whereas the aromatic compounds peaked later when LDV numbers had reached their maximum. Our findings give strong evidence that increased NO x and PM 10 levels can be predominantly attributed to HDV traffic. Principal components analyses for the separated data further support this conclusion.