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[Cooper2004] Cooper, OR., C. Forster, D. Parrish, M. Trainer, E. Dunlea, T. Ryerson, G. Huebler, F. Fehsenfeld, D. Nicks, J. Holloway, et al., "A case study of transpacific warm conveyor belt transport: Influence of merging airstreams on trace gas import to North America", Journal of geophysical research, vol. 109, no. D23: American Geophysical Union, pp. D23S08, 2004.
Link: http://www.agu.org/pubs/crossref/2004/2003JD003624.shtml
Abstract
The warm conveyor belt (WCB), the major cloud-forming airstream of midlatitude cyclones, is the primary mechanism for rapidly transporting air pollution from one continent to another. However, relatively little has been written on WCB transport across the North Pacific Ocean. To address this important intercontinental transport route, this study describes the life cycle of a WCB associated with the export of a highly polluted air mass from Asia to North America. This event was sampled using in situ measurements from an aircraft platform flying above the North American West Coast during the 2002 Intercontinental Transport and Chemical Transformation (ITCT 2K2) experiment on 5 May. Satellite imagery, trajectory ensembles, in situ measurements, and animations are used to illustrate the formation of the WCB near eastern Asia, its entrainment of polluted air masses, its transport path across the Pacific, and its decay above the eastern North Pacific Ocean and western North America. A major finding is that a WCB can entrain air from a variety of source regions and not just the atmospheric boundary layer. We estimate that 8% of the WCB's mass originated in the stratosphere and 44% passed through the lower troposphere, of which two thirds passed through the lower troposphere above the populated regions of eastern Asia. The remaining 48% traveled entirely within the middle and upper troposphere over the previous 5.5 days. Interestingly, an estimated 18% of the WCB's mass was entrained from an upwind and decaying WCB via a newly discovered but apparently common transport mechanism. Only 9% of the WCB's mass subsequently passed through the lower troposphere of the United States, with the remainder passing over North America in the middle and upper troposphere.
[vonDahl2006] von Dahl}, C. C. {, M. Haevecker, R. Schloegl, and I. T. Baldwin, "Caterpillar-elicited methanol emission: a new signal in plant-herbivore interactions?", Plant J, vol. 46, no. 6: Department of Molecular Ecology, Max Planck Institute for Chemical Ecology, Beutenberg Campus, Hans-Knoell-Strasse 8, 07745 Jena, Germany., pp. 948–960, Jun, 2006.
Link: http://dx.doi.org/10.1111/j.1365-313X.2006.02760.x
Abstract
Plants release into the atmosphere large quantities of volatile organic compounds (VOCs), of which methanol (MeOH), a putative waste product, is the second most abundant. Using online proton-transfer-reaction mass spectrometry (PTR-MS), we demonstrate that when Manduca sexta larvae attack Nicotiana attenuata plants, the wound-induced release of MeOH dramatically increases. The sustained MeOH emission 24 h after herbivore feeding is already substantially greater than the release of the well-characterized green-leaf VOC E-2-hexenal. Herbivore attack and treatment of puncture wounds with larval oral secretions (OS) increased the transcript accumulation and activity of leaf pectin methylesterases (PMEs), and decreased the degree of pectin methylation, as determined by (1)H-NMR; therefore, we propose that the released MeOH originates from the activation of PMEs by herbivore attack. The herbivore- and OS-elicited MeOH results not from the activity of previously characterized elicitors in OS but from a pH shift at the wound site when larval OS (pH 8.5-9.5) are introduced into the wounds during feeding. Applying MeOH to plants in quantities that mimic the herbivory-elicited release decreases the activity of the potent plant defense proteins trypsin proteinase inhibitors (TPI), and increases the performance of the attacking larvae. The pH of lepidopteran larvae regurgitants is commonly very high, and the MeOH released during feeding that is elicited by the pH change at the wound site functions as a quantitative signal that influences the outcome of the plant-herbivore interaction.
[Penuelas2005] Penuelas, J., I. Filella, C. Stefanescu, and J. Llusià, "Caterpillars of Euphydryas aurinia (Lepidoptera: Nymphalidae) feeding on Succisa pratensis leaves induce large foliar emissions of methanol.", New Phytol, vol. 167, no. 3: Unitat Ecofisiologia CSIC-CREAF CREAF, Edifici C, Universitat Autónoma de Barcelona, E-08193 Bellaterra, Barcelona, Spain. josep.penuelas@uab.es, pp. 851–857, Sep, 2005.
Link: http://dx.doi.org/10.1111/j.1469-8137.2005.01459.x
Abstract
A major new discovery made in the last decade is that plants commonly emit large amounts and varieties of volatiles after damage inflicted by herbivores, and not merely from the site of injury. However, analytical methods for measuring herbivore-induced volatiles do not usually monitor the whole range of these compounds and are complicated by the transient nature of their formation and by their chemical instability. Here we present the results of using a fast and highly sensitive proton transfer reaction-mass spectrometry (PTR-MS) technique that allows simultaneous on-line monitoring of leaf volatiles in the pptv (pmol mol(-1)) range. The resulting on-line mass scans revealed that Euphydryas aurinia caterpillars feeding on Succisa pratensis leaves induced emissions of huge amounts of methanol–a biogeochemically active compound and a significant component of the volatile organic carbon found in the atmosphere–and other immediate, late and systemic volatile blends (including monoterpenes, sesquiterpenes and lipoxygenase-derived volatile compounds). In addition to influencing neighboring plants, as well as herbivores and their predators and parasitoids, these large emissions might affect atmospheric chemistry and physics if they are found to be generalized in other plant species.
[Kohl2013] Kohl, I., J. Herbig, J. Dunkl, A. Hansel, M. Daniaux, and M. Hubalek, "Chapter 6 - Smokers Breath as Seen by Proton-Transfer-Reaction Time-of-Flight Mass Spectrometry (PTR-TOF-MS)", Volatile Biomarkers, Boston, Elsevier, pp. 89 - 116, 2013.
Link: http://www.sciencedirect.com/science/article/pii/B9780444626134000064
Abstract
Abstract Proton-transfer-reaction time-of-flight mass spectrometry has been employed in a 12 months breath gas analysis study to describe the breath composition of 19 cigarette smoking and 53 non-smoking women. The most prevalent constituents were acetone (1.8 ppmv), methanol (310 ppbv), isoprene (280 ppbv), ethanol (130 ppbv), acetaldehyde (90 ppbv) and acetic acid (70 ppbv). Smokers showed the largest signal increase in acetonitrile (ratio smoker/non-smoker 29), benzene (ratio 11), 2-methylfuran (ratio 8) and 2,5-dimethylfuran (ratio 7). Calibration gas measurements allowed the instruments performance regarding precision and accuracy of ion mass-to-charge, m/z, and concentration accuracy measurement to be assessed. The standard deviation of the concentration measurements was 14% or smaller (with the exception of ethanol) with no trend in this variation of sensitivity. The limit of detection (LOD) lay in the sub ppbv range, based on an integration time of 2 s. The m/z accuracy was better than 0.0016 (or less than 29 ppm of the ion mass) throughout the study. The standard deviation of the measured m/z was less than 0.0025 and the coefficient of variation was less than 29 ppm. Keywords PTR-TOF-MS, Smokers’ breath, Breath volatile organic compounds, \{VOCs\}
[Heenan2009] Heenan, S. P., J-P. Dufour, N. Hamid, W. Harvey, and C. M. Delahunty, "Characterisation of fresh bread flavour: Relationships between sensory characteristics and volatile composition", Food Chemistry, vol. 116, no. 1: Elsevier, pp. 249–257, 2009.
Link: http://www.sciencedirect.com/science/article/pii/S0308814609002301
Abstract
The sensory properties and volatile composition of bread flavour were measured to allow improved understanding of perceived bread freshness. Twenty bread varieties consisting of specialty breads (n = 10) and commercial breads (n = 10) were evaluated by descriptive sensory analysis, and volatile composition of all breads was measured by proton transfer reaction mass spectrometry (PTR-MS). The specialty breads (n = 10) studied had been evaluated by consumers, and perceived freshness was known. All sensory attributes and 33 mass ions representative of the PTR-MS spectra significantly (p < 0.05) distinguished between the different breads. Partial least squares regression (PLSR) was used to model and predict sensory profiles as a function of volatile composition for all breads. In addition, a separate model that related volatile composition to known consumer freshness of the 10 specialty breads was created. For each model, accuracy was validated by comparing the differences between predicted and actual, sensory and freshness intensities.
[Beauchamp2010a] Beauchamp, J., J. Frasnelli, A. Buettner, M. Scheibe, A. Hansel, and T. Hummel, "Characterization of an olfactometer by proton-transfer-reaction mass spectrometry", Measurement Science and Technology, vol. 21, no. 2, pp. 025801, 2010.
Link: http://stacks.iop.org/0957-0233/21/i=2/a=025801
Abstract
The performance of a commercial olfactometer instrument, which produces odorant pulses of defined duration and concentration, was characterized using proton-transfer-reaction mass spectrometry (PTR-MS). Direct coupling of the PTR-MS instrument with the olfactometer enabled on-line evaluation of the rapidly delivered aroma pulses. Tests were made with a selection of four odorous compounds: hydrogen sulfide, 2,3-butanedione, ethyl butanoate and ethyl hexanoate. Odour concentrations and stimulus durations for these compounds were monitored directly at the olfactometer delivery port via the respective PTR-MS signals. The performance of the olfactometer was found to be dependent on pulse duration. A decrease over time in maximum intensity for identical pulses over an extended duration showed headspace concentration depletions for compounds sourced from a water solution, indicative of gas/liquid partitioning. Such changes were not present using odours sourced from a cylinder or, presumably, when using liquid odours at neat concentrations. In conclusion, while an olfactometer provides stimuli with good reproducibility, the concept is subject to certain limitations that must be appreciated by the experimenter for accurate application of this technique.
[1566] Stockwell, C.. E., P.. R. Veres, J.. Williams, and R.. J. Yokelson, "Characterization of biomass burning smoke from cooking fires, peat, crop residue and other fuels with high resolution proton-transfer-reaction time-of-flight mass spectrometry", Atmospheric Chemistry and Physics Discussions, vol. 14, pp. 22163–22216, 2014.
Link: http://dx.doi.org/10.5194/acpd-14-22163-2014
Abstract
<p>We deployed a high-resolution proton-transfer-reaction time-of-flight mass spectrom-eter (PTR-TOF-MS) to measure biomass burning emissions from peat, crop-residue, cooking fires, and many other fire types during the fourth Fire Lab at Missoula Experi-ment (FLAME-4) laboratory campaign. A combination of gas standards calibrations and 5 composition sensitive, mass dependent calibration curves were applied to quantify gas-phase non-methane organic compounds (NMOCs) observed in the complex mixture of fire emissions. We used several approaches to assign best identities to most major &quot;exact masses&quot; including many high molecular mass species. Using these methods ap-proximately 80&ndash;96 % of the total NMOC mass detected by PTR-TOF-MS and FTIR was 10 positively or tentatively identified for major fuel types. We report data for many rarely measured or previously unmeasured emissions in several compound classes including aromatic hydrocarbons, phenolic compounds, and furans; many of which are suspected secondary organic aerosol precursors. A large set of new emission factors (EFs) for a range of globally significant biomass fuels is presented. Measurements show that 15 oxygenated NMOCs accounted for the largest fraction of emissions of all compound classes. In a brief study of various traditional and advanced cooking methods, the EFs for these emissions groups were greatest for open 3-stone cooking in comparison to their more advanced counterparts. Several little-studied nitrogen-containing organic compounds were detected from many fuel types that together accounted for 0.1&ndash;8.7 % 20 of the fuel nitrogen and some may play a role in new particle formation.</p>
[Guazzotti2003] Guazzotti, SA., DT. Suess, KR. Coffee, PK. Quinn, TS. Bates, A. Wisthaler, A. Hansel, WP. Ball, RR. Dickerson, C. Neusüß, et al., "Characterization of carbonaceous aerosols outflow from India and Arabia: Biomass/biofuel burning and fossil fuel combustion", Journal of geophysical research, vol. 108, no. D15: American Geophysical Union, pp. 4485, 2003.
Link: http://onlinelibrary.wiley.com/doi/10.1029/2002JD003277/abstract
Abstract
A major objective of the Indian Ocean Experiment (INDOEX) involves the characterization of the extent and chemical composition of pollution outflow from the Indian Subcontinent during the winter monsoon. During this season, low-level flow from the continent transports pollutants over the Indian Ocean toward the Intertropical Convergence Zone (ITCZ). Traditional standardized aerosol particle chemical analysis, together with real-time single particle and fast-response gas-phase measurements provided characterization of the sampled aerosol chemical properties. The gas- and particle-phase chemical compositions of encountered air parcels changed according to their geographic origin, which was traced by back trajectory analysis. The temporal evolutions of acetonitrile, a long-lived specific tracer for biomass/biofuel burning, number concentration of submicrometer carbon-containing particles with potassium (indicative of combustion sources), and mass concentration of submicrometer non-sea-salt (nss) potassium are compared. High correlation coefficients (0.84 < r2 < 0.92) are determined for these comparisons indicating that most likely the majority of the species evolve from the same, related, or proximate sources. Aerosol and trace gas measurements provide evidence that emissions from fossil fuel and biomass/biofuel burning are subject to long-range transport, thereby contributing to anthropogenic pollution even in areas downwind of South Asia. Specifically, high concentrations of submicrometer nss potassium, carbon-containing particles with potassium, and acetonitrile are observed in air masses advected from the Indian subcontinent, indicating a strong impact of biomass/biofuel burning in India during the sampling periods (74 (±9)% biomass/biofuel contribution to submicrometer carbonaceous aerosol). In contrast, lower values for these same species were measured in air masses from the Arabian Peninsula, where dominance of fossil fuel combustion is suggested by results from single-particle analysis and supported by results from gas-phase measurements (63 (±9))% fossil fuel contribution to submicrometer carbonaceous aerosol). Results presented here demonstrate the importance of simultaneous, detailed gas- and particle-phase measurements of related species when evaluating possible source contributions to aerosols in different regions of the world.
[1717] Klein, F., S. M. Platt, N. J. Farren, A. Detournay, E. A. Bruns, C. Bozzetti, K. R. Daellenbach, D. Kilic, N. K. Kumar, S. M. Pieber, et al., "Characterization of Gas-Phase Organics Using Proton Transfer Reaction Time-of-Flight Mass Spectrometry: Cooking Emissions.", Environ Sci Technol, vol. 50, pp. 1243–1250, Feb, 2016.
Link: http://dx.doi.org/10.1021/acs.est.5b04618
Abstract
<p>Cooking processes produce gaseous and particle emissions that are potentially deleterious to human health. Using a highly controlled experimental setup involving a proton-transfer-reaction time-of-flight mass spectrometer (PTR-ToF-MS), we investigate the emission factors and the detailed chemical composition of gas phase emissions from a broad variety of cooking styles and techniques. A total of 95 experiments were conducted to characterize nonmethane organic gas (NMOG) emissions from boiling, charbroiling, shallow frying, and deep frying of various vegetables and meats, as well as emissions from vegetable oils heated to different temperatures. Emissions from boiling vegetables are dominated by methanol. Significant amounts of dimethyl sulfide are emitted from cruciferous vegetables. Emissions from shallow frying, deep frying and charbroiling are dominated by aldehydes of differing relative composition depending on the oil used. We show that the emission factors of some aldehydes are particularly large which may result in considerable negative impacts on human health in indoor environments. The suitability of some of the aldehydes as tracers for the identification of cooking emissions in ambient air is discussed.</p>
[1668] Sekimoto, K., S. Inomata, H. Tanimoto, A. Fushimi, Y. Fujitani, K. Sato, and H. Yamada, "Characterization of nitromethane emission from automotive exhaust", Atmospheric Environment, vol. 81, pp. 523–531, Dec, 2013.
Link: http://dx.doi.org/10.1016/j.atmosenv.2013.09.031
Abstract
<p>We carried out time-resolved experiments using a proton-transfer-reaction mass spectrometer and a chassis dynamometer to characterize nitromethane emission from automotive exhaust. We performed experiments under both cold-start and hot-start conditions, and determined the dependence of nitromethane emission on vehicle velocity and acceleration/deceleration as well as the effect of various types of exhaust-gas treatment system. We found that nitromethane emission was much lower from a gasoline car than from diesel trucks, probably due to the reduction function of the three-way catalyst of the gasoline car. Diesel trucks without a NOx reduction catalyst using hydrocarbons produced high emissions of nitromethane, with emission factors generally increasing with increasing acceleration at low vehicle velocities.</p>
[Zavala2006] Zavala, M., SC. Herndon, RS. Slott, EJ. Dunlea, LC. Marr, JH. Shorter, M. Zahniser, WB. Knighton, TM. Rogers, CE. Kolb, et al., "Characterization of on-road vehicle emissions in the Mexico City Metropolitan Area using a mobile laboratory in chase and fleet average measurement modes during the MCMA-2003 field campaign", Atmospheric Chemistry and Physics, vol. 6, no. 12: Copernicus GmbH, pp. 5129–5142, 2006.
Link: http://www.atmos-chem-phys.net/6/5129/2006/acp-6-5129-2006.html
Abstract
A mobile laboratory was used to measure on-road vehicle emission ratios during the MCMA-2003 field campaign held during the spring of 2003 in the Mexico City Metropolitan Area (MCMA). The measured emission ratios represent a sample of emissions of in-use vehicles under real world driving conditions for the MCMA. From the relative amounts of NOx and selected VOC's sampled, the results indicate that the technique is capable of differentiating among vehicle categories and fuel type in real world driving conditions. Emission ratios for NOx, NOy, NH3, H2CO, CH3CHO, and other selected volatile organic compounds (VOCs) are presented for chase sampled vehicles in the form of frequency distributions as well as estimates for the fleet averaged emissions. Our measurements of emission ratios for both CNG and gasoline powered "colectivos" (public transportation buses that are intensively used in the MCMA) indicate that – in a mole per mole basis – have significantly larger NOx and aldehydes emissions ratios as compared to other sampled vehicles in the MCMA. Similarly, ratios of selected VOCs and NOy showed a strong dependence on traffic mode. These results are compared with the vehicle emissions inventory for the MCMA, other vehicle emissions measurements in the MCMA, and measurements of on-road emissions in U.S. cities. We estimate NOx emissions as 100 600±29 200 metric tons per year for light duty gasoline vehicles in the MCMA for 2003. According to these results, annual NOx emissions estimated in the emissions inventory for this category are within the range of our estimated NOx annual emissions. Our estimates for motor vehicle emissions of benzene, toluene, formaldehyde, and acetaldehyde in the MCMA indicate these species are present in concentrations higher than previously reported. The high motor vehicle aldehyde emissions may have an impact on the photochemistry of urban areas.
[Biasioli2004b] Biasioli, F., F. Gasperi, D. Mott, E. Aprea, F. Marini, and TD. Maerk, "Characterization of Strawberry Genotypes by PTR-MS Spectral Fingerprinting: a Three Year Study", V International Strawberry Symposium 708, pp. 497–500, 2004.
Link: http://www.actahort.org/books/708/708_87.htm
Abstract
Proton Transfer Reaction Mass Spectrometry (PTR-MS) fingerprinting has been used to accurately and rapidly identify the cultivar of single intact strawberry fruits. The technique has been applied in a 3-cultivar experiment with 70 fruits harvested in 2002, 2003 and 2004. The proposed models correctly predicted the cultivar. Cross-validation tests verified 100% correct classification. The data indicated the possibility of correctly characterizing single fruit by fast non-invasive measurements without any pre-treatment and/or concentration of the headspace gas mixture. This is a necessary preliminary step in view of correlation studies of PTR-MS data with genetics and other characterization of fruits, in particular, sensory analysis. Extension to more cultivars is envisaged.
[Herndon2005] Herndon, S. C., J. T. Jayne, M. S. Zahniser, D. R. Worsnop, B. Knighton, E. Alwine, B. K. Lamb, M. Zavala, D. D. Nelson, B. J McManus, et al., "Characterization of urban pollutant emission fluxes and ambient concentration distributions using a mobile laboratory with rapid response instrumentation", Faraday Discussions, vol. 130: Royal Society of Chemistry, pp. 327–339, 2005.
Link: http://pubs.rsc.org/en/content/articlehtml/2005/fd/b500411j
Abstract
A large and increasing fraction of the planet’s population lives in megacities, especially in the developing world. These large metropolitan areas generally have very high levels of both gaseous and particulate air pollutants that have severe impacts on human health, ecosystem viability, and climate on local, regional, and even continental scales. Emissions fluxes and ambient pollutant concentration distributions are generally poorly characterized for large urban areas even in developed nations. Much less is known about pollutant sources and concentration patterns in the faster growing megacities of the developing world. New methods of locating and measuring pollutant emission sources and tracking subsequent atmospheric chemical transformations and distributions are required. Measurement modes utilizing an innovative van based mobile laboratory equipped with a suite of fast response instruments to characterize the complex and “nastier” chemistry of the urban boundary layer are described. Instrumentation and measurement strategies are illustrated with examples from the Mexico City and Boston metropolitan areas. It is shown that fleet average exhaust emission ratios of formaldehyde (HCHO), acetaldehyde (CH3CHO) and benzene (C6H6) are substantial in Mexico City, with gasoline powered vehicles emitting higher levels normalized by fuel consumption. NH3 exhaust emissions from newer light duty vehicles in Mexico City exceed levels from similar traffic in Boston. A mobile conditional sampling air sample collection mode designed to collect samples from intercepted emission plumes for later analysis is also described.
[1644] Stojić, A.., S. S Stojić, A.. Šoštarić, L.. Ilić, Z.. Mijić, and S.. Rajšić, "Characterization of VOC sources in an urban area based on PTR-MS measurements and receptor modelling.", Environ Sci Pollut Res Int, May, 2015.
Link: http://dx.doi.org/10.1007/s11356-015-4540-5
Abstract
<p>In this study, the concentrations of volatile organic compounds were measured by the use of proton transfer reaction mass spectrometry, together with NO x , NO, NO2, SO2, CO and PM10 and meteorological parameters in an urban area of Belgrade during winter 2014. The multivariate receptor model US EPA Unmix was applied to the obtained dataset resolving six source profiles, which can be attributed to traffic-related emissions, gasoline evaporation/oil refineries, petrochemical industry/biogenic emissions, aged plumes, solid-fuel burning and local laboratories. Besides the vehicle exhaust, accounting for 27.6&nbsp;% of the total mixing ratios, industrial emissions, which are present in three out of six resolved profiles, exert a significant impact on air quality in the urban area. The major contribution of regional and long-range transport was determined for source profiles associated with petrochemical industry/biogenic emissions (40&nbsp;%) and gasoline evaporation/oil refineries (29&nbsp;%) using trajectory sector analysis. The concentration-weighted trajectory model was applied with the aim of resolving the spatial distribution of potential distant sources, and the results indicated that emission sources from neighbouring countries, as well as from Slovakia, Greece, Poland and Scandinavian countries, significantly contribute to the observed concentrations.</p>
[Boscaini2004] Boscaini, E., T. Mikoviny, A. Wisthaler, E. von Hartungen, and T. D. Märk, "Characterization of wine with PTR-MS", International Journal of Mass Spectrometry, vol. 239, no. 2: Elsevier, pp. 215–219, 2004.
Link: http://www.sciencedirect.com/science/article/pii/S1387380604003537
Abstract
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.
[1465] Sinha, V., V. Kumar, and C. Sarkar, "Chemical composition of pre-monsoon air in the Indo-Gangetic Plain measured using a new PTR-MS and air quality facility: high surface ozone and strong influence of biomass burning", Atmos. Chem. Phys., vol. 14, pp. 5921-5941, 2014.
Link: http://www.atmos-chem-phys.net/14/5921/2014/acp-14-5921-2014.html
Abstract
<p>One seventh of the world population lives in the Indo&ndash;Gangetic Plain (IGP) and the fertile region sustains agricultural food crop production for much of South Asia. Yet it remains one of the most under-studied regions of the world in terms of atmospheric composition and chemistry. In particular, the emissions and chemistry of volatile organic compounds (VOCs) that form surface ozone and secondary organic aerosol through photochemical reactions involving nitrogen oxides is not well understood. In this study, ambient levels of VOCs such as methanol, acetone, acetaldehyde, acetonitrile and isoprene were measured for the first time in the IGP. A new atmospheric chemistry facility that combines India&#39;s first high sensitivity proton transfer reaction mass spectrometer, an ambient air quality station and meteorological station, was used to quantify in-situ levels of several VOCs and air pollutants in May 2012 at a suburban site in Mohali (N. W. IGP). Westerly winds arriving at high wind speeds (5&ndash;20 m s&minus;1) in the pre-monsoon season at the site, were conducive for chemical characterization of regional emission signatures. Average levels of VOCs and air pollutants in May 2012 ranged from 1.2&ndash;1.7 nmol mol&minus;1 for aromatic VOCs, 5.9&ndash;37.4 nmol mol&minus;1 for the oxygenated VOCs, 1.4 nmol mol&minus;1 for acetonitrile, 1.9 nmol mol&minus;1 for isoprene, 567 nmol mol&minus;1 for carbon monoxide, 57.8 nmol mol&minus;1 for ozone, 11.5 nmol mol&minus;1 for nitrogen oxides, 7.3 nmol mol&minus;1 for sulphur dioxide, 104 μg m&minus;3 for PM2.5 and 276 μg m&minus;3 for PM10. By analyzing the one minute in-situ data with meteorological parameters and applying chemical tracers (e.g. acetonitrile for biomass burning) and inter-VOC correlations, we were able to constrain major emission source activities on both temporal and diel scales. Wheat residue burning activity caused massive increases (&gt; 3 times of baseline values) for all the measured VOCs and primary pollutants. Other forms of biomass burning at night were also a significant source for oxygenated VOCs and isoprene (r2 with acetonitrile &ge; 0.5 for night-time data), which is remarkable in terms of atmospheric chemistry implications. Surface ozone exceeded the 8 h national ambient air quality limit of 100 μg O3 m&minus;3 on a daily basis, except for 17 May 2012, when a severe dust storm event (PM2.5 &gt; 800 μg m&minus;3; PM10 &gt; 2700 μg m&minus;3) characterized by long range transport from the west impacted the site. The novel dataset and results point to occurrence of high primary emissions of reactive VOCs. They also highlight the urgent need for establishing more comprehensive observational facilities in the IGP to constrain the spatial and seasonal variability of atmospheric chemical constituents. Such efforts will enable mechanistic level understanding of the in-situ chemical processes controlling formation of surface ozone, a necessary step for effective ozone mitigation and improvement of the regional air quality.</p>
[FeilbergTavsNyord2011] Nyord}, A. {Feilberg, M. N. Ã. ¸rrega Hansen, and S. Lindholst, "Chemical evaluation of odor reduction by soil injection of animal manure.", J Environ Qual, vol. 40, no. 5: Dep. of Biosystem Engineering, Faculty of Science and Technology, Aarhus Univ., Denmark. anders.feilberg@agrsci.dk, pp. 1674–1682, 2011.
Link: http://dx.doi.org/10.2134/jeq2010.0499
Abstract
Field application of animal manure is a major cause of odor nuisance in the local environment. Therefore, there is a need for methods for measuring the effect of technologies for reducing odor after manure application. In this work, chemical methods were used to identify key odorants from field application of pig manure based on experiments with surface application by trailing hoses and soil injection. Results from three consecutive years of field trials with full-scale equipment are reported. Methods applied were: membrane inlet mass spectrometry (MIMS), proton-transfer-reaction mass spectrometry (PTR-MS), gold-film hydrogen sulfide (H?S) detection, all performed on site, and thermal desorption gas chromatography with mass spectrometry (TD-GC/MS) based on laboratory analyses of field samples. Samples were collected from a static flux chamber often used for obtaining samples for dynamic olfactometry. While all methods were capable of detecting relevant odorants, PTR-MS gave the most comprehensive results. Based on odor threshold values, 4-methylphenol, H?S, and methanethiol are suggested as key odorants. Significant odorant reductions by soil injection were consistently observed in all trials. The flux chamber technique was demonstrated to be associated with critical errors due to compound instabilities in the chamber. This was most apparent for H?S, on a time scale of a few minutes, and on a longer time scale for methanethiol.
[1513] Holzinger, R.., A.. H. Goldstein, P.. L. Hayes, J.. L. Jimenez, and J.. Timkovsky, "Chemical evolution of organic aerosol in Los Angeles during the CalNex 2010 study", Atmospheric Chemistry and Physics, vol. 13, pp. 10125–10141, Oct, 2013.
Link: http://dx.doi.org/10.5194/acp-13-10125-2013
Abstract
<p>During the CalNex study (15 May to 16 June 2010) a large suite of instruments was operated at the Los Angeles area ground supersite to characterize the sources and atmospheric processing of atmospheric pollution. The thermal-desorption proton-transfer-reaction mass-spectrometer (TD-PTR-MS) was deployed to an urban area for the first time and detected 691 organic ions in aerosol samples, the mean total concentration of which was estimated as 3.3 μg m&minus;3. Based on comparison to total organic aerosol (OA) measurements, we estimate that approximately 50% of the OA mass at this site was directly measured by the TD-PTR-MS. Based on correlations with aerosol mass spectrometer (AMS) OA components, the ions were grouped to represent hydrocarbon-like OA (HOA), local OA (LOA), semi-volatile oxygenated OA (SV-OOA), and low volatility oxygenated OA (LV-OOA). Mass spectra and thermograms of the ion groups are mostly consistent with the assumed sources and/or photochemical origin of the OA components. The mass spectra of ions representing the primary components HOA and LOA included the highest m/z, consistent with their higher resistance to thermal decomposition, and they were volatilized at lower temperatures (&nbsp; 150 &deg;C). Photochemical ageing weakens C-C bond strengths (also resulting in chemical fragmentation), and produces species of lower volatility (through the addition of functional groups). Accordingly the mass spectra of ions representing the oxidized OA components (SV-OOA, and LV-OOA) lack the highest masses and they are volatilized at higher temperatures (250&ndash;300 &deg;C). Chemical parameters like mean carbon number (nC), mean carbon oxidation state (OSC), and the atomic ratios O / C and H / C of the ion groups are consistent with the expected sources and photochemical processing of the aerosol components. Our data suggest that chemical fragmentation gains importance over functionalization as photochemical age of OA increases. Surprisingly, the photochemical age of OA decreases during the daytime hours, demonstrating the importance of rapid production of new (photochemically young) SV-OOA during daytime. The PTR detects higher organic N concentrations than the AMS, the reasons for which are not well understood and cannot be explained by known artifacts related to PTR or the AMS. The median atomic N / C ratio (6.4%) of the ion group representing LV-OOA is a factor 2 higher than N / C of any other ion group. This suggests a multiphase chemical source involving ammonium ions is contributing to LV-OOA.</p>
[Karl2008] Karl, T., A. Guenther, A. Turnipseed, EG. Patton, K. Jardine, and , "Chemical sensing of plant stress at the ecosystem scale", Biogeosciences Discussions, vol. 5, no. 3, pp. 2381–2399, 2008.
Link: http://hal.archives-ouvertes.fr/hal-00298013/
Abstract
Significant ecosystem-scale emissions of methylsalicylate (MeSA), a semivolatile plant hormone thought to act as the mobile signal for systemic acquired resistance (SAR) (Park et al., 2006), were observed in an agroforest. Our measurements show that plant internal defence mechanisms can be activated in response to temperature stress and are modulated by water availability on large scales. Highest MeSA fluxes (up to 0.25 mg/m2/h) were observed after plants experienced ambient night-time temperatures of  7.5°C followed by a large daytime temperature increase (e.g. up to 22°C). Under these conditions estimated night-time leaf temperatures were as low as  4.6°C, likely inducing a response to prevent chilling injury (Ding et al., 2002). Our observations imply that plant hormones can be a significant component of ecosystem scale volatile organic compound (VOC) fluxes (e.g. as high as the total monoterpene (MT) flux) and therefore contribute to the missing VOC budget (de Carlo et al., 2004; Goldstein and Galbally, 2007). If generalized to other ecosystems and different types of stresses these findings suggest that semivolatile plant hormones have been overlooked by investigations of the impact of biogenic VOCs on aerosol formation events in forested regions (Kulmala et al., 2001; Boy et al., 2000). Our observations show that the presence of MeSA in canopy air serves as an early chemical warning signal indicating ecosystem-scale stresses before visible damage becomes apparent. As a chemical metric, ecosystem emission measurements of MeSA in ambient air could therefore support field studies investigating factors that adversely affect plant growth.
[Yelvington2007] Yelvington, P. E., S. C. Herndon, J. C. Wormhoudt, J. T. Jayne, R. C. Miake-Lye, B. W Knighton, and C. Wey, "Chemical speciation of hydrocarbon emissions from a commercial aircraft engine", Journal of Propulsion and Power, vol. 23, no. 5, pp. 912–918, 2007.
Link: http://arc.aiaa.org/doi/abs/10.2514/1.23520
[1506] Wolfe, G.. M., J.. A. Thornton, N.. C. Bouvier-Brown, A.. H. Goldstein, J.-H.. Park, M.. McKay, D.. M. Matross, J.. Mao, W.. H. Brune, B.. W. LaFranchi, et al., "The Chemistry of Atmosphere-Forest Exchange (CAFE) Model ¬タモ Part 2: Application to BEARPEX-2007 observations", Atmospheric Chemistry and Physics, vol. 11, pp. 1269–1294, Feb, 2011.
Link: http://nature.berkeley.edu/ahg/pubs/Wolf et al acp-11-1269-2011.pdf
Abstract
<p>In a companion paper, we introduced the Chemistry of Atmosphere-Forest Exchange (CAFE) model, a vertically-resolved 1-D chemical transport model designed to probe the details of near-surface reactive gas exchange. Here, we apply CAFE to noontime observations from the 2007 Biosphere Effects on Aerosols and Photochemistry Experiment (BEARPEX-2007). In this work we evaluate the CAFE modeling approach, demonstrate the significance of in-canopy chemistry for forest-atmosphere exchange and identify key shortcomings in the current understanding of intra-canopy processes. CAFE generally reproduces BEARPEX-2007 observations but requires an enhanced radical recycling mechanism to overcome a factor of 6 underestimate of hydroxyl (OH) concentrations observed during a warm (&nbsp;29 &deg;C) period. Modeled fluxes of acyl peroxy nitrates (APN) are quite sensitive to gradients in chemical production and loss, demonstrating that chemistry may perturb forest-atmosphere exchange even when the chemical timescale is long relative to the canopy mixing timescale. The model underestimates peroxy acetyl nitrate (PAN) fluxes by 50% and the exchange velocity by nearly a factor of three under warmer conditions, suggesting that near-surface APN sinks are underestimated relative to the sources. Nitric acid typically dominates gross dry N deposition at this site, though other reactive nitrogen (NOy) species can comprise up to 28% of the N deposition budget under cooler conditions. Upward NO2 fluxes cause the net above-canopy NOy flux to be &nbsp;30% lower than the gross depositional flux. CAFE under-predicts ozone fluxes and exchange velocities by &nbsp;20%. Large uncertainty in the parameterization of cuticular and ground deposition precludes conclusive attribution of non-stomatal fluxes to chemistry or surface uptake. Model-measurement comparisons of vertical concentration gradients for several emitted species suggests that the lower canopy airspace may be only weakly coupled with the upper canopy. Future efforts to model forest-atmosphere exchange will require a more mechanistic understanding of non-stomatal deposition and a more thorough characterization of in-canopy mixing processes.</p>
[1763] Kaser, L.., T.. Karl, B.. Yuan, R.. L. Mauldin, C.. A. Cantrell, A.. B. Guenther, E.. G. Patton, A.. J. Weinheimer, C.. Knote, J.. Orlando, et al., "Chemistry-turbulence interactions and mesoscale variability influence the cleansing efficiency of the atmosphere", Geophysical Research Letters, vol. 42, pp. 10894–10903, Dec, 2015.
Link: http://n2t.net/ark:/85065/d7gq709d
Abstract
<p>The hydroxyl radical (OH) is the most important oxidant in the atmosphere and the primary sink for isoprene, the dominant volatile organic compound emitted by vegetation. Recent research on the atmospheric oxidation capacity in isoprene-dominated environments has suggested missing radical sources leading to significant overestimation of the lifetime of isoprene. Here we report, for the first time, a comprehensive experimental budget of isoprene in the planetary boundary layer based on airborne flux measurements along with in situ OH observations in the Southeast and Central U.S. Our findings show that surface heterogeneity of isoprene emissions lead to a physical separation of isoprene and OH resulting in an effective slowdown in the chemistry. Depending on surface heterogeneity, the intensity of segregation (Is) could locally slow down isoprene chemistry up to 30%. The effect of segregated reactants in the planetary boundary layer on average has an influence on modeled OH radicals that is comparable to that of recently proposed radical recycling mechanisms.</p>
[1645] Ciesa, F., I. Höller, W. Guerra, J. Berger, J. {Dalla Via}, and M. Oberhuber, "Chemodiversity in the Fingerprint Analysis of Volatile Organic Compounds (VOCs) of 35 Old and 7 Modern Apple Cultivars Determined by Proton-Transfer-Reaction Mass Spectrometry (PTR-MS) in Two Different Seasons.", Chem Biodivers, vol. 12, pp. 800–812, May, 2015.
Link: http://dx.doi.org/10.1002/cbdv.201400384
Abstract
<p>Volatile organic compounds (VOCs) are chemical species that play an important role in determining the characteristic aroma and flavor of fruits. Apple (Malus &times; domestica Borkh.) cultivars differ in their aroma and composition of VOCs. To determine varietal differences in the aroma profiles, VOCs emitted by 7 modern and 35 old apple cultivars were analyzed using Proton Transfer Reaction Mass Spectrometry (PTR-MS). PTR-MS is a rapid, reproducible, and non-destructive spectrometric technique for VOC analysis of single fruits, developed for direct injection analysis. In the present study, we analyzed the differences in the emission of VOCs from single fruits at harvest and after a storage period of 60&plusmn;10 days, followed by 3 d of shelf life. Our results show that VOC profile differences among apple cultivars were more pronounced after storage than at harvest. Furthermore, chemodiversity was higher in old cultivars compared to modern cultivars, probably due to their greater genetic variability. Our data highlight the importance of storage and shelf life are crucial for the development of the typical aroma and flavor of several apple cultivars. The validity of the method is demonstrated by comparison of two different harvest years.</p>
[1716] Schuhfried, E., J. {Sánchez Del Pulgar}, M. Bobba, R. Piro, L. Cappellin, T. D. Märk, and F. Biasioli, "Classification of 7 monofloral honey varieties by PTR-ToF-MS direct headspace analysis and chemometrics.", Talanta, vol. 147, pp. 213–219, Jan, 2016.
Link: http://dx.doi.org/10.1016/j.talanta.2015.09.062
Abstract
<p>Honey, in particular monofloral varieties, is a valuable commodity. Here, we present proton transfer reaction-time of flight-mass spectrometry, PTR-ToF-MS, coupled to chemometrics as a successful tool in the classification of monofloral honeys, which should serve in fraud protection against mispresentation of the floral origin of honey. We analyzed 7 different honey varieties from citrus, chestnut, sunflower, honeydew, robinia, rhododendron and linden tree, in total 70 different honey samples and a total of 206 measurements. Only subtle differences in the profiles of the volatile organic compounds (VOCs) in the headspace of the different honeys could be found. Nevertheless, it was possible to successfully apply 6 different classification methods with a total correct assignment of 81-99% in the internal validation sets. The most successful methods were stepwise linear discriminant analysis (LDA) and probabilistic neural network (PNN), giving total correct assignments in the external validation sets of 100 and 90%, respectively. Clearly, PTR-ToF-MS/chemometrics is a powerful tool in honey classification.</p>
[1605] Taiti, C., C. Costa, P. Menesatti, D. Comparini, N. Bazihizina, E. Azzarello, E. Masi, and S. Mancuso, "Class-modeling approach to PTR-TOFMS data: a peppers case study.", J Sci Food Agric, May, 2014.
Link: http://dx.doi.org/10.1002/jsfa.6761
Abstract
<p>Proton transfer reaction-mass spectrometry (PTR-MS), in its recently developed implementation based on time-of-flight mass spectrometry (PTR-TOFMS), was used to rapidly determine the volatile compounds present in fruits of Capsicum spp.We analyzed the volatile organic compounds emission profile of freshly cut chili peppers belonging to three species and 33 different cultivars. PTR-TOFMS data, analyzed with appropriate and advanced multivariate class-modeling approaches, perfectly discriminated among the three species (100% correct classification in validation set). VIP (variable importance in projection) scores were used to select the 15 most important volatile compounds in discriminating the species. The best candidates for Capsicum spp. were compounds with measured m/z of 63.027, 101.096 and 107.050, which were, respectively, tentatively identified as dimethyl sulfide, hexanal and benzaldehyde.Based on the promising results, the possibility of introducing multivariate class-modeling techniques, different from the classification approaches, in the field of volatile compounds analyses is discussed. &copy; 2014 Society of Chemical Industry.</p>

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Selected PTR-MS related Reviews

F. Biasioli, C. Yeretzian, F. Gasperi, T. D. Märk: PTR-MS monitoring of VOCs and BVOCs in food science and technology, Trends in Analytical Chemistry 30 (7) (2011).
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J. de Gouw, C. Warneke, T. Karl, G. Eerdekens, C. van der Veen, R. Fall: Measurement of Volatile Organic Compounds in the Earth's Atmosphere using Proton-Transfer-Reaction Mass Spectrometry. Mass Spectrometry Reviews, 26 (2007), 223-257.
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W. Lindinger, A. Hansel, A. Jordan: Proton-transfer-reaction mass spectrometry (PTR–MS): on-line monitoring of volatile organic compounds at pptv levels, Chem. Soc. Rev. 27 (1998), 347-375.
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Lists with PTR-MS relevant publications of the University of Innsbruck can be found here: Atmospheric and indoor air chemistry, IMR, Environmental Physics and Nano-Bio-Physics

 

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