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Scientific Articles - PTR-MS Bibliography

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Found 83 results
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1995
[Guenther1995] Guenther, A., N. C Hewitt, D. Erickson, R. Fall, C. Geron, T. Graedel, P. Harley, L. Klinger, M. Lerdau, WA. McKay, et al., "A global model of natural volatile organic compound emissions", Journal of Geophysical research, vol. 100, no. D5: American Geophysical Union, pp. 8873–8892, 1995.
Link: http://www.agu.org/pubs/crossref/1995/94JD02950.shtml
Abstract
Numerical assessments of global air quality and potential changes in atmospheric chemical constituents require estimates of the surface fluxes of a variety of trace gas species. We have developed a global model to estimate emissions of volatile organic compounds from natural sources (NVOC). Methane is not considered here and has been reviewed in detail elsewhere. The model has a highly resolved spatial grid (0.5°×0.5° latitude/longitude) and generates hourly average emission estimates. Chemical species are grouped into four categories: isoprene, monoterpenes, other reactive VOC (ORVOC), and other VOC (OVOC). NVOC emissions from oceans are estimated as a function of geophysical variables from a general circulation model and ocean color satellite data. Emissions from plant foliage are estimated from ecosystem specific biomass and emission factors and algorithms describing light and temperature dependence of NVOC emissions. Foliar density estimates are based on climatic variables and satellite data. Temporal variations in the model are driven by monthly estimates of biomass and temperature and hourly light estimates. The annual global VOC flux is estimated to be 1150 Tg C, composed of 44% isoprene, 11% monoterpenes, 22.5% other reactive VOC, and 22.5% other VOC. Large uncertainties exist for each of these estimates and particularly for compounds other than isoprene and monoterpenes. Tropical woodlands (rain forest, seasonal, drought-deciduous, and savanna) contribute about half of all global natural VOC emissions. Croplands, shrublands and other woodlands contribute 10–20% apiece. Isoprene emissions calculated for temperate regions are as much as a factor of 5 higher than previous estimates.
2001
[Rinne2001] Rinne, HJI., AB. Guenther, C. Warneke, JA. De Gouw, and SL. Luxembourg, "Disjunct eddy covariance technique for trace gas flux measurements", Geophysical Research Letters, vol. 28, no. 16, pp. 3139–3142, 2001.
Link: http://www.agu.org/journals/gl/gl0116/2001GL012900/pdf/2001GL012900.pdf
[Karl2001a] Karl, T., A. Guenther, A. Jordan, R. Fall, and W. Lindinger, "Eddy covariance measurement of biogenic oxygenated VOC emissions from hay harvesting", Atmospheric Environment, vol. 35, no. 3: Elsevier, pp. 491–495, 2001.
Link: http://www.sciencedirect.com/science/article/pii/S1352231000004052
Abstract
Biogenic oxygenated volatile organic compound (VOC) fluxes have been directly measured by eddy covariance using the combination of a fast response, real-time \{VOC\} sensor and an acoustic anemometer. \{VOC\} detection is based on proton-transfer reaction mass spectrometry which has currently a response time of ca. 0.8 s and the system is suitable for making nearly unattended, long-term and continuous measurements of \{VOC\} fluxes. The eddy covariance system has a detection limit, for most VOCs, of less than 0.1 mg m−2 h−1. The system was field tested above a hayfield near St. Johann, Austria where cut and drying grasses released a variety of VOCs. High fluxes were observed for about 2 days after cutting and were dominated by methanol (1–8.4 mg m−2 h−1), acetaldehyde (0.5–3 mg m−2 h−1), hexenals (0.1–1.5 mg m−2 h−1) and acetone (0.1–1.5 mg m−2 h−1). The eddy covariance measurements generally agreed with flux estimates based on enclosure measurements and surface layer gradients. The sensitivity and selectivity of the system make it suitable for quantifying the fluxes of the dominant biogenic \{VOCs\} from a variety of landscapes and sources.
2002
[Warneke2002] Warneke, C., SL. Luxembourg, JA. De Gouw, HJI. Rinne, AB. Guenther, and R. Fall, "Disjunct eddy covariance measurements of oxygenated volatile organic compounds fluxes from an alfalfa field before and after cutting", Journal of geophysical research, vol. 107, no. D8: American Geophysical Union, pp. 4067, 2002.
Link: http://onlinelibrary.wiley.com/doi/10.1029/2001JD000594/abstract
Abstract
[1] There is interest in and significant uncertainty about the emissions of oxygenated volatile organic compounds (oxVOCs) from vegetation to the atmosphere. Here, we measured the fluxes of selected oxVOCs from an alfalfa field, before, during, and after cutting, using a combination of disjunct eddy covariance and proton-transfer-reaction mass spectrometry. Over the course of 1 day a significant methanol flux of 4 mg m−2 h−1 was observed from undisturbed alfalfa with a maximum at 0800 LT, possibly caused by the evaporation of dew. A smaller release of hexenals during this day (0.04 mg m−2 h−1) demonstrated the sensitivity of the method. Other results suggested that acetaldehyde and acetone were released in the afternoon but were lost by dry deposition in the evening and morning; deposition velocities were estimated to be 0.2 cm s−1 (acetaldehyde) and 0.09 cm s−1 (acetone). After the alfalfa was cut the emissions of methanol, acetaldehyde, acetone, and hexenals were significantly enhanced and remained high for three days during which the alfalfa was drying. After a rainstorm the oxVOC emissions from the cut, wet alfalfa increased even more. Nighttime measurements yielded low oxVOC fluxes in general, but the high variability of the concentrations during the night and the high degree of correlation between different oxVOCs suggest that the nighttime releases of oxVOCs from alfalfa were nonzero. This work suggests that the global source of oxVOCs due to the production of hay is of minor importance. The emission flux of methanol from vegetation during the growing season may be very large on a global basis.
[Karl2002] Karl, TG., C. Spirig, J. Rinne, C. Stroud, P. Prevost, J. Greenberg, R. Fall, and A. Guenther, "Virtual disjunct eddy covariance measurements of organic compound fluxes from a subalpine forest using proton transfer reaction mass spectrometry", Atmospheric Chemistry and Physics, vol. 2, no. 4: Copernicus GmbH, pp. 279–291, 2002.
Link: http://www.atmos-chem-phys.net/2/279/
Abstract
A `virtual' disjunct eddy covariance (vDEC) device was tested with field measurements of biogenic VOC fluxes at a subalpine forest site in the Rocky Mountains of the USA. A PTR-MS instrument was used as the VOC sensor. Daily peak emission fluxes of 2-methyl-3-buten-2-ol (MBO), methanol, acetone and acetaldehyde were around 1.5, 1, 0.8 and 0.4 mg m-2 h-1, respectively. High pass filtering due to long sampling lines was investigated in laboratory experiments, and suggested that VOC losses in PTFA lines are generally governed by diffusion laws. Memory effects and surface reactions did not seem to play a dominant role. Model estimates of MBO fluxes compared well with measured fluxes. The results also suggest that latent heat and sensible heat fluxes are reasonably well correlated with VOC fluxes and could be used to predict variations in VOC emissions. The release of MBO, methanol, acetone and acetaldehyde resulted in significant change of tropospheric oxidant levels and a 10–40% increase in ozone levels, as inferred from a photochemical box model. We conclude that vDEC with a PTR-MS instrument is a versatile tool for simultaneous field analysis of multiple VOC fluxes.
2003
[Karl2003c] Karl, T., A. Guenther, C. Spirig, A. Hansel, and R. Fall, "Seasonal variation of biogenic VOC emissions above a mixed hardwood forest in northern Michigan", Geophysical Research Letters, vol. 30, no. 23: Wiley Online Library, 2003.
Link: http://onlinelibrary.wiley.com/doi/10.1029/2003GL018432/full
Abstract
Fluxes of biogenic volatile organic compounds (VOCs) were measured at a hardwood forest in northern Michigan (UMBS, Prophet research site) over the course of the growing and senescing season. Methanol, acetaldehyde, acetone and isoprene were found to be the most abundant biogenic VOCs with maximum fluxes (mixing ratios in ppbv) of 2.0 mg m−2 h−1 (21.0), 1.0 mg m−2 h−1 (2.7), 1.6 mg m−2 h−1 (5.6) and 7.6 mg m−2 h−1 (6), respectively. The emission patterns show distinct seasonal changes and indicate a spring peak for methanol due to rapid leaf expansion and a fall peak for acetone and acetaldehyde most likely attributed to senescing and decaying biomass; isoprene emissions peaked as expected in the summer. We estimate potential source strengths of 8.9 Tg (C) y−1 methanol, 2.7 Tg (C) y−1 acetaldehyde and 7.0 Tg (C) y−1 acetone for deciduous temperate forests, which is a substantial contribution to the global atmospheric VOC budget.
[Graus2003] Graus, M., J. Kreuzwieser, J. Schnitzler, A. Wisthaler, A. Hansel, and H. Rennenberg, "Xylem-Transported Glucose as an Additional Carbon Source for Leaf Isoprene Formation in Quercus Robur L.", EGS-AGU-EUG Joint Assembly, vol. 1, pp. 10692, 2003.
Link: http://adsabs.harvard.edu/abs/2003EAEJA....10692G
Abstract
Isoprene is emitted from mature, photosynthesizing leaves of many plant species, particularly of trees. Current interest in understanding the biochemical and physiological mechanisms controlling isoprene formation is caused by the important role isoprene plays in atmospheric chemistry. Isoprene reacts with hydroxyl radicals (OH) thereby generating oxidizing agents such as ozone and organic peroxides. Ozone causes significant deterioration in air quality and can pose threats to human health therefore its control is a major goal in Europe and the United States. In recent years, much progress has been made in elucidating the pathways of isoprene biosynthesis. Nevertheless the regulatory mechanisms controlling isoprene emission are not completely understood. Light and temperature appear to be the main factors controlling short-term variations in isoprene emission. Exposure of plants to C-13 labeled carbon dioxide showed instantaneous assimilated carbon is the primary carbon source for isoprene formation. However, variations in diurnal and seasonal isoprene fluxes, which cannot be explained by temperature, light, and leaf development led to the suggestion that alternative carbon sources may exist contributing to isoprene emissions. The aim of the present study was to test whether xylem-transported carbohydrates act as additional sources for isoprene biosynthesis. For this purpose, [U-C-13] alpha-D-glucose was fed to photosynthesizing leaves via the xylem of Quercus robur L. seedlings and the incorporation of glucose derived C-13 into emitted isoprene was monitored in real time using Proton-Transfer-Reaction Mass Spectrometry (PTR-MS). A rapid incorporation of C-13 from xylem-fed glucose into single (mass 70) and double (mass 71) C-13 labeled isoprene molecules was observed after a lag phase of approximately 5 to 10 minutes. This incorporation was temperature dependent and was highest (up to 13% C-13 of total carbon emitted as isoprene) at the temperature optimum of isoprene emission (40 - 42°C) when net assimilation was strongly reduced. Fast dark-to-light transitions led to a strong single or double C-13 labeling of isoprene from xylem-fed [U-C-13] glucose. During a time period of 10 - 15 minutes up to 86% of all isoprene molecules became single or double C-13 labeled, resulting in a C-13 portion of up to 30% of total carbon emitted as isoprene. The results provide potential evidence that xylem-transported glucose or its degradation products can be used as additional precursors for isoprene biosynthesis and this carbon source becomes more important under conditions of limited photosynthesis.
2004
[Grabmer2004] Grabmer, W., M. Graus, C. Lindinger, A. Wisthaler, B. Rappenglück, R. Steinbrecher, and A. Hansel, "Disjunct eddy covariance measurements of monoterpene fluxes from a Norway spruce forest using PTR-MS", International Journal of Mass Spectrometry, vol. 239, no. 2: Elsevier, pp. 111–115, 2004.
Link: http://www.sciencedirect.com/science/article/pii/S1387380604003914
Abstract
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.
[Karl2004] Karl, T., M. Potosnak, A. Guenther, D. Clark, J. Walker, J. D. Herrick, and C. Geron, "Exchange processes of volatile organic compounds above a tropical rain forest: Implications for modeling tropospheric chemistry above dense vegetation", Journal of geophysical research, vol. 109, no. D18: American Geophysical Union, pp. D18306, 2004.
Link: http://www.agu.org/pubs/crossref/2004/2004JD004738.shtml
Abstract
Disjunct eddy covariance in conjunction with continuous in-canopy gradient measurements allowed for the first time to quantify the fine-scale source and sink distribution of some of the most abundant biogenic (isoprene, monoterpenes, methanol, acetaldehyde, and acetone) and photooxidized (MVK+MAC, acetone, acetaldehyde, acetic, and formic acid) VOCs in an old growth tropical rain forest. Our measurements revealed substantial isoprene emissions (up to 2.50 mg m−2 h−1) and light-dependent monoterpene emissions (up to 0.33 mg m−2 h−1) at the peak of the dry season (April and May 2003). Oxygenated species such as methanol, acetone, and acetaldehyde were typically emitted during daytime with net fluxes up to 0.50, 0.36, and 0.20 mg m−2 h−1, respectively. When generalized for tropical rain forests, these fluxes would add up to a total emission of 36, 16, 19, 106, and 7.2 Tg/yr for methanol, acetaldehyde, acetone, isoprene, and monoterpenes, respectively. During nighttime we observed strong sinks for oxygenated and nitrogen-containing compounds such as methanol, acetone, acetaldehyde, MVK+MAC, and acetonitrile with deposition velocities close to the aerodynamic limit. This suggests that the canopy resistance (Rc) is very small and not the rate-limiting step for the nighttime deposition of many VOCs. Our measured mean dry deposition velocities of methanol, acetone, acetaldehyde, MVK+MAC, and acetonitrile were a factor 10–20 higher than estimated from traditional deposition models. If our measurements are generalized, this could have important implications for the redistribution of VOCs in atmospheric chemistry models. Our observations indicate that the current understanding of reactive carbon exchange can only be seen as a first-order approximation.
[Hayward2004] Hayward, S., A. Tani, S. M. Owen, and N. C Hewitt, "Online analysis of volatile organic compound emissions from Sitka spruce (Picea sitchensis).", Tree Physiol, vol. 24, no. 7: Institute of Environmental and Natural Sciences, Lancaster University, Lancaster, LA1 4YQ, U.K., pp. 721–728, Jul, 2004.
Link: http://treephys.oxfordjournals.org/content/24/7/721.short
Abstract
Volatile organic compound (VOC) emissions from Sitka spruce (Picea sitchensis Bong.) growing in a range of controlled light and temperature regimes were monitored online with a proton transfer reaction-mass spectrometer (PTR-MS) operating at a temporal resolution of approximately 1 min. Isoprene emissions accounted for an average of more than 70% of measured VOCs and up to 3.5% of assimilated carbon. Emission rates (E) for isoprene correlated closely with photosynthetic photon flux (PPF) and temperature, showing saturation at a PPF of between 300 and 400 micromol m(-2) s(-1) and a maximum between 35 and 38 degrees C. Under standard conditions of 30 degrees C and 1000 micromol m(-2) s(-1) PPF, the mean isoprene E was 13 microg gdm(-1) h(-1), considerably higher than previously observed in this species. Mean E for acetaldehyde, methanol and monoterpenes at 30 degrees C were 0.37, 0.78 and 2.97 microg gdm(-1) h(-1), respectively. In response to a sudden light to dark transition, isoprene E decreased exponentially by > 98% over about 3 h; however, during the first 7 min, this otherwise steady decay was temporarily but immediately depressed to approximately 40% of the pre-darkness rate, before rallying during the following 7 min to rejoin the general downward trajectory of the exponential decay. The sudden sharp fall in isoprene E was mirrored by a burst in acetaldehyde E. The acetaldehyde E maximum coincided with the isoprene E minimum (7 min post-illumination), and ceased when isoprene emissions resumed their exponential decay. The causes of, and linkages between, these phenomena were investigated.
[Schade2004] Schade, G. W., and T. G. Custer, "OVOC emissions from agricultural soil in northern Germany during the 2003 European heat wave", Atmospheric Environment, vol. 38, no. 36: Elsevier, pp. 6105–6114, 2004.
Link: http://www.sciencedirect.com/science/article/pii/S1352231004007344
Abstract
Fluxes of methanol and acetone were measured from an agricultural field plot during one of the hottest weeks of the heat wave of the summer of 2003 in Europe. Significant positive fluxes from the bare, plowed soil for these oxygenated volatile organic compounds were found. Methanol fluxes ranged from 0 to 0.20 mg C m−2 h−1 while acetone fluxes ranged from −0.01 to 0.05. Mixing ratios for both methanol and acetone showed significant increases at night, consistent with a ground-based emission source for both the compounds. Methanol emissions were well correlated with sensible heat flux, peaking around noon. Assuming abiological production from soil organic matter in the topsoil, we calculate that 48 kJ mol−1 of energy is required to liberate the methanol from the topsoil. In contrast to methanol, acetone fluxes were not correlated with any measured meteorological parameter. This suggests that acetone has another source and may be produced in the soil subsurface, possibly through biological or moisture-driven processes. Using the flux data, we also simulated relaxed eddy accumulation (REA) experiments and reconfirm that sonic temperature can be used to calculate b-factors for REA analysis of a variety of trace gas fluxes.
[Graus2004] Graus, M., JÖRG-PETER. SCHNITZLER, A. Hansel, C. Cojocariu, H. Rennenberg, A. Wisthaler, and J. Kreuzwieser, "Transient release of oxygenated volatile organic compounds during light-dark transitions in grey poplar leaves", Plant Physiology, vol. 135, no. 4: American Society of Plant Biologists, pp. 1967–1975, 2004.
Link: http://www.plantphysiology.org/content/135/4/1967.short
Abstract
In this study, we investigated the prompt release of acetaldehyde and other oxygenated volatile organic compounds (VOCs) from leaves of Grey poplar [Populus x canescens (Aiton) Smith] following light-dark transitions. Mass scans utilizing the extremely fast and sensitive proton transfer reaction-mass spectrometry technique revealed the following temporal pattern after light-dark transitions: hexenal was emitted first, followed by acetaldehyde and other C6-VOCs. Under anoxic conditions, acetaldehyde was the only compound released after switching off the light. This clearly indicated that hexenal and other C6-VOCs were released from the lipoxygenase reaction taking place during light-dark transitions under aerobic conditions. Experiments with enzyme inhibitors that artificially increased cytosolic pyruvate demonstrated that the acetaldehyde burst after light-dark transition could not be explained by the recently suggested pyruvate overflow mechanism. The simulation of light fleck situations in the canopy by exposing leaves to alternating light-dark and dark-light transitions or fast changes from high to low photosynthetic photon flux density showed that this process is of minor importance for acetaldehyde emission into the Earth's atmosphere.
2005
[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.
[Lee2005] Lee, A., GW. Schade, R. Holzinger, and AH. Goldstein, "A comparison of new measurements of total monoterpene flux with improved measurements of speciated monoterpene flux", Atmospheric Chemistry and Physics, vol. 5, no. 2: Copernicus GmbH, pp. 505–513, 2005.
Link: http://www.atmos-chem-phys.net/5/505/2005/acp-5-505-2005.pdf
[Spirig2005] Spirig, C., A. Neftel, C. Ammann, J. Dommen, W. Grabmer, A. Thielmann, A. Schaub, J. Beauchamp, A. Wisthaler, A. Hansel, et al., "Eddy covariance flux measurements of biogenic VOCs during ECHO 2003 using proton transfer reaction mass spectrometry", Atmospheric Chemistry and Physics, vol. 5, no. 2, pp. 465–481, 2005.
Link: http://hal.archives-ouvertes.fr/hal-00295614/
Abstract
Within the framework of the AFO 2000 project ECHO, two PTR-MS instruments were operated in combination with sonic anemometers to determine biogenic VOC fluxes from a mixed deciduous forest site in North-Western Germany. The measurement site was characterised by a forest of inhomogeneous composition, complex canopy structure, limited extension in certain wind directions and frequent calm wind conditions during night time. The eddy covariance (EC) technique was applied since it represents the most direct flux measurement approach on the canopy scale and is, therefore, least susceptible to these non-ideal conditions. A specific flux calculation method was used to account for the sequential multi-component PTR-MS measurements and allowing an individual delay time adjustment as well as a rigorous quality control based on cospectral analysis. The validated flux results are consistent with light and temperature dependent emissions of isoprene and monoterpenes from this forest, with average daytime emissions of 0.94 and 0.3µg m-2s-1, respectively. Emissions of methanol reached on average 0.087µg m-2s-1 during daytime, but fluxes were too small to be detected during night time. Upward fluxes of the isoprene oxidation products methyl vinyl ketone (MVK) and methacrolein (MACR) were also found, being two orders of magnitude lower than those of isoprene. Calculations with an analytical footprint model indicate that the observed isoprene fluxes correlate with the fraction of oaks within the footprints of the flux measurement.
[Jacob2005] Jacob, D. J., B. D. Field, Q. Li, D. R. Blake, J. de Gouw, C. Warneke, A. Hansel, A. Wisthaler, H. B. Singh, and A. Guenther, "Global budget of methanol: Constraints from atmospheric observations", Journal of Geophysical Research: Atmospheres (1984–2012), vol. 110, no. D8: Wiley Online Library, 2005.
Link: http://onlinelibrary.wiley.com/doi/10.1029/2004JD005172/full
Abstract
We use a global three-dimensional model simulation of atmospheric methanol to examine the consistency between observed atmospheric concentrations and current understanding of sources and sinks. Global sources in the model include 128 Tg yr−1 from plant growth, 38 Tg yr−1 from atmospheric reactions of CH3O2 with itself and other organic peroxy radicals, 23 Tg yr−1 from plant decay, 13 Tg yr−1 from biomass burning and biofuels, and 4 Tg yr−1 from vehicles and industry. The plant growth source is a factor of 3 higher for young than from mature leaves. The atmospheric lifetime of methanol in the model is 7 days; gas-phase oxidation by OH accounts for 63% of the global sink, dry deposition to land 26%, wet deposition 6%, uptake by the ocean 5%, and aqueous-phase oxidation in clouds less than 1%. The resulting simulation of atmospheric concentrations is generally unbiased in the Northern Hemisphere and reproduces the observed correlations of methanol with acetone, HCN, and CO in Asian outflow. Accounting for decreasing emission from leaves as they age is necessary to reproduce the observed seasonal variation of methanol concentrations at northern midlatitudes. The main model discrepancy is over the South Pacific, where simulated concentrations are a factor of 2 too low. Atmospheric production from the CH3O2 self-reaction is the dominant model source in this region. A factor of 2 increase in this source (to 50–100 Tg yr−1) would largely correct the discrepancy and appears consistent with independent constraints on CH3O2 concentrations. Our resulting best estimate of the global source of methanol is 240 Tg yr−1. More observations of methanol concentrations and fluxes are needed over tropical continents. Better knowledge is needed of CH3O2 concentrations in the remote troposphere and of the underlying organic chemistry.
[Pegoraro2005] Pegoraro, E., A. Rey, G. Barron-Gafford, R. Monson, Y. Malhi, and R. Murthy, "The interacting effects of elevated atmospheric CO2 concentration, drought and leaf-to-air vapour pressure deficit on ecosystem isoprene fluxes.", Oecologia, vol. 146, no. 1, pp. 120–129, Nov, 2005.
Link: http://dx.doi.org/10.1007/s00442-005-0166-5
Abstract
Isoprene is the most abundant biogenic hydrocarbon released from vegetation and it plays a major role in tropospheric chemistry. Because of its link to climate change, there is interest in understanding the relationship between CO2, water availability and isoprene emission. We explored the effect of atmospheric elevated CO2 concentration and its interaction with vapour pressure deficit (VPD) and water stress, on gross isoprene production (GIP) and net ecosystem exchange of CO2 (NEE) in two Populus deltoides plantations grown at ambient and elevated atmospheric CO2 concentration in the Biosphere 2 Laboratory facility. Although GIP and NEE showed a similar response to light and temperature, their responses to CO2 and VPD were opposite; NEE was stimulated by elevated CO2 and depressed by high VPD, while GIP was inhibited by elevated CO2 and stimulated by high VPD. The difference in response between isoprene production and photosynthesis was also evident during water stress. GIP was stimulated in the short term and declined only when the stress was severe, whereas NEE started to decrease from the beginning of the experiment. This contrasting response led the carbon lost as isoprene in both the ambient and the elevated CO2 treatments to increase as water stress progressed. Our results suggest that water limitation can override the inhibitory effect of elevated CO2 leading to increased global isoprene emissions in a climate change scenario with warmer and drier climate.
[Beauchamp2005] Beauchamp, J., A. Wisthaler, A. Hansel, E. Kleist, M. Miebach, ÜLO. NIINEMETS, U. Schurr, and JÜRGEN. WILDT, "Ozone induced emissions of biogenic VOC from tobacco: relationships between ozone uptake and emission of LOX products", Plant, Cell & Environment, vol. 28, no. 10: Wiley Online Library, pp. 1334–1343, 2005.
Link: http://onlinelibrary.wiley.com/doi/10.1111/j.1365-3040.2005.01383.x/full
Abstract
Volatile organic compound (VOC) emissions from tobacco (Nicotiana tabacum L. var. Bel W3) plants exposed to ozone (O3) were investigated using proton-transfer-reaction mass-spectrometry (PTR-MS) and gas chromatography mass-spectrometry (GC-MS) to find a quantitative reference for plants’ responses to O3 stress. O3 exposures to illuminated plants induced post-exposure VOC emission bursts. The lag time for the onset of volatile C6 emissions produced within the octadecanoid pathway was found to be inversely proportional to O3 uptake, or more precisely, to the O3 flux density into the plants. In cases of short O3 pulses of identical duration the total amount of these emitted C6 VOC was related to the O3 flux density into the plants, and not to ozone concentrations or dose–response relationships such as AOT 40 values. Approximately one C6 product was emitted per five O3 molecules taken up by the plant. A threshold flux density of O3 inducing emissions of C6 products was found to be (1.6 ± 0.7) × 10−8 mol m−2 s−1.
2006
[Klemm2006] Klemm, O., A. Held, R. Forkel, R. Gasche, H-J. Kanter, B. Rappenglück, R. Steinbrecher, K. Müller, A. Plewka, C. Cojocariu, et al., "Experiments on forest/atmosphere exchange: Climatology and fluxes during two summer campaigns in NE Bavaria", Atmospheric Environment, vol. 40: Elsevier, pp. 3–20, 2006.
Link: http://www.sciencedirect.com/science/article/pii/S1352231006003165
Abstract
During two summer field campaigns in 2001 and 2002, biosphere/atmosphere exchange fluxes of energy, gases, and particles were quantified in a Norway spruce forest in NE Bavaria at 775 m a.s.l. The overall goal of the BEWA campaigns was to study the influence of the emissions of reactive biogenic volatile organic compounds (BVOCs) on chemical and physical processes in the atmosphere, and an overview over the meteorological conditions, experimental frame, and the achieved results is provided. A rigorous quality assurance/quality control plan was implemented. From analysis of meteorological conditions and experimental success, golden day periods were selected for coordinated data analysis. These periods cover typical summertime conditions with various wind directions, NOx mixing ratios between 2 and 10 ppb, and O3 mixing ratios ranging between 13 and 98 ppb. Diurnal patterns of trace gas concentrations resulted from the dynamics of the boundary layer, from regional atmospheric processes (for example production of O3 in the atmosphere), and deposition. Turbulence also exhibited a diurnal pattern indicating thermal production during daytime and calm conditions during nighttime. However, in many cases, turbulence was often well developed during the nights. Horizontal advection of air masses into the trunk space occurred due to the patchiness of the forest. Nevertheless, for most conditions, the application of a one-dimensional model to describe the vertical exchange processes was appropriate. Therefore, the use of one single meteorological tower to study biosphere/atmosphere exchange is valid. Measured turbulent vertical exchange fluxes were estimated to be representative within an error of less than 25%. The results for VOC concentrations and fluxes were rather heterogeneous. Both model and measurements demonstrated that the Norway spruce trees acted as a weak source of formaldehyde.
[Graus2006] Graus, M., A. Hansel, A. Wisthaler, C. Lindinger, R. Forkel, K. Hauff, M. Klauer, A. Pfichner, B. Rappenglück, D. Steigner, et al., "A relaxed-eddy-accumulation method for the measurement of isoprenoid canopy-fluxes using an online gas-chromatographic technique and PTR-MS simultaneously", Atmospheric Environment, vol. 40: Elsevier, pp. 43–54, 2006.
Link: http://www.sciencedirect.com/science/article/pii/S1352231006003190
Abstract
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).
[1501] Holzinger, R.., A.. Lee, M.. McKay, and A.. H. Goldstein, "Seasonal variability of monoterpene emission factors for a ponderosa pine plantation in California", Atmospheric Chemistry and Physics, vol. 6, pp. 1267–1274, Apr, 2006.
Link: http://nature.berkeley.edu/ahg/pubs/seasonal.pdf
Abstract
<p>Monoterpene fluxes have been measured over an 11 month period from June 2003 to April 2004. During all seasons ambient air temperature was the environmental factor most closely related to the measured emission rates. The monoterpene flux was modeled using a basal emission rate multiplied by an exponential function of a temperature, following the typical practice for modelling temperature dependent biogenic emissions. A basal emission of 1.0 μmol h&minus;1 m&minus;2 (at 30&deg;C, based on leaf area) and a temperature dependence (β) of 0.12&deg;C&minus;1 reproduced measured summer emissions well but underestimated spring and winter measured emissions by 60&ndash;130%. The total annual monoterpene emission may be underestimated by &nbsp;50% when using a model optimized to reproduce monoterpene emissions in summer. The long term dataset also reveals an indirect connection between non-stomatal ozone and monoterpene flux beyond the dependence on temperature that has been shown for both fluxes.</p>
[Ammann2006] Ammann, C., A. Brunner, C. Spirig, and A. Neftel, "Technical note: Water vapour concentration and flux measurements with PTR-MS", Atmospheric Chemistry and Physics, vol. 6, no. 12: Copernicus GmbH, pp. 4643–4651, 2006.
Link: http://www.atmos-chem-phys.net/6/4643/2006/acp-6-4643-2006.pdf
[Forkel2006] Forkel, R., O. Klemm, M. Graus, B. Rappenglück, W. R. Stockwell, W. Grabmer, A. Held, A. Hansel, and R. Steinbrecher, "Trace gas exchange and gas phase chemistry in a Norway spruce forest: A study with a coupled 1-dimensional canopy atmospheric chemistry emission model", Atmospheric Environment, vol. 40: Elsevier, pp. 28–42, 2006.
Link: http://www.sciencedirect.com/science/article/pii/S1352231006003189
Abstract
Numerical modelling is an efficient tool to investigate the role of chemical degradation of biogenic volatile organic compounds (BVOC) and the effect of dynamical processes on BVOC and product mixing ratios within and above forest canopies. The present study shows an application of the coupled canopy-chemistry model CACHE to a Norway spruce forest at the Waldstein (Fichtelgebirge, Germany). Simulated courses of temperature, trace gas mixing ratios, and fluxes are compared with measurements taken during the BEWA2000 field campaigns. The model permits the interpretation of the observed diurnal course of ozone and VOC by investigating the role of turbulent exchange, chemical formation and degradation, emission, and deposition during the course of the day. The simulation results show that BVOC fluxes into the atmosphere are 10–15% lower than the emission fluxes on branch basis due to chemical BVOC degradation within the canopy. BVOC degradation by the NO3 radical was found to occur in the lower part of the canopy also during daytime. Furthermore, the simulations strongly indicate that further research is still necessary concerning the emission and deposition of aldehydes and ketones.
2007
[Sinha2007] Sinha, V., J. Williams, M. Meyerhöfer, U. Riebesell, AI. Paulino, and A. Larsen, "Air-sea fluxes of methanol, acetone, acetaldehyde, isoprene and DMS from a Norwegian fjord following a phytoplankton bloom in a mesocosm experiment", Atmospheric Chemistry and Physics, vol. 7, no. 3: Copernicus GmbH, pp. 739–755, 2007.
Link: http://www.atmos-chem-phys.net/7/739/2007/acp-7-739-2007.html
Abstract
{The ocean's influence on volatile organic compounds (VOCs) in the atmosphere is poorly understood. This work characterises the oceanic emission and/or uptake of methanol, acetone, acetaldehyde, isoprene and dimethyl sulphide (DMS) as a function of photosynthetically active radiation (PAR) and a suite of biological parameters. The measurements were taken following a phytoplankton bloom, in May/June 2005 with a proton transfer reaction mass spectrometer (PTR-MS), from mesocosm enclosures anchored in the Raunefjord, Southern Norway. The net flux of methanol was always into the ocean, and was stronger at night. Isoprene and acetaldehyde were emitted from the ocean, correlating with light (ravcorr
[1488] Karl, T., A. Guenther, R. J. Yokelson, J. Greenberg, M. Potosnak, D. R. Blake, and P. Artaxo, "The tropical forest and fire emissions experiment: Emission, chemistry, and transport of biogenic volatile organic compounds in the lower atmosphere over Amazonia", Journal of Geophysical Research: Atmospheres, vol. 112, pp. n/a–n/a, 2007.
Link: http://dx.doi.org/10.1029/2007JD008539
Abstract
<p>Airborne and ground-based mixing ratio and flux measurements using eddy covariance (EC) and for the first time the mixed layer gradient (MLG) and mixed layer variance (MLV) techniques are used to assess the impact of isoprene and monoterpene emissions on atmospheric chemistry in the Amazon basin. Average noon isoprene (7.8 &plusmn; 2.3 mg/m2/h) and monoterpene fluxes (1.2 &plusmn; 0.5 mg/m2/h) compared well between ground and airborne measurements and are higher than fluxes estimated in this region during other seasons. The biogenic emission model, Model of Emissions of Gases and Aerosols from Nature (MEGAN), estimates fluxes that are within the model and measurement uncertainty and can describe the large observed variations associated with land-use change in the region north-west of Manaus. Isoprene and monoterpenes accounted for &sim;75% of the total OH reactivity in this region and are important volatile organic compounds (VOCs) for modeling atmospheric chemistry in Amazonia. The presence of fair weather clouds (cumulus humilis) had an important impact on the vertical distribution and chemistry of VOCs through the planetary boundary layer (PBL), the cloud layer, and the free troposphere (FT). Entrainment velocities between 10:00 and 11:30 local time (LT) are calculated to be on the order of 8&ndash;10 cm/s. The ratio of methyl-vinyl-ketone (MVK) and methacrolein (MAC) (unique oxidation products of isoprene chemistry) with respect to isoprene showed a pronounced increase in the cloud layer due to entrainment and an increased oxidative capacity in broken cloud decks. A decrease of the ratio in the lower free troposphere suggests cloud venting through activated clouds. OH modeled in the planetary boundary layer using a photochemical box model is much lower than OH calculated from a mixed layer budget approach. An ambient reactive sesquiterpene mixing ratio of 1% of isoprene would be sufficient to explain most of this discrepancy. Increased OH production due to increased photolysis in the cloud layer balances the low OH values modeled for the planetary boundary layer. The intensity of segregation (Is) of isoprene and OH, defined as a relative reduction of the reaction rate constant due to incomplete mixing, is found to be significant: up to 39 &plusmn; 7% in the &sim;800-m-deep cloud layer. The effective reaction rate between isoprene and OH can therefore vary significantly in certain parts of the lower atmosphere.</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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