Alfons Jordan

Biomass burning as a source of formaldehyde, acetaldehyde, methanol, acetone, acetonitrile, and hydrogen cyanide

Using a novel experimental technique, based on proton transfer reaction mass spectrometry, from measurements of emissions from laboratory scale biomass burning experiments, we have estimated the source strengths of several potential HOx producing gases: formaldehyde, acetaldehyde, methanol and acetone. The derived global average emissions are 5–13; 3.8–10; 1.5-4; 2.3-6.1 Tg y−1, respectively. The resulting global average HOx production from photochemical decay of these gases is 3 × 109 molecules cm−2 s−1. Although relatively small in a global context, these emissions are significant for the photochemistry in fresh fire plumes. From our measurements are also estimated global source strengths from biomass burning for CH3CN and HCN of 0.4-1.0; 0.2-0.6 Tg y−1 respectively. The biomass burning emissions of CH3CN may well dominate the global source of this compound, which thus might well be a unique tracer for biomass burning. Some discrepancies between experimental studies must, however, be resolved.

Volatile organic compounds emitted after leaf wounding: On‐line analysis by proton‐transfer‐reaction mass spectrometry

Volatile organic compounds (VOCs) released from vegetation, including wound-induced VOCs, can have important effects on atmospheric chemistry. The analytical methods for measuring wound-induced VOCs, especially the hexenal family of VOCs (hexenals, hexenols, and hexenyl esters), are complicated by their chemical instability and the transient nature of their formation after leaf and stem wounding. Here we demonstrate that formation and emission of hexenal family compounds can be monitored on-line using proton-transfer-reaction mass spectrometry (PTR-MS), avoiding the need for preconcentration or chromatography. These measurements allow direct analysis of the rapid emission of the parent compound, (Z)-3-hexenal, within 1-2 s of wounding of aspen leaves and then its disappearance and the appearance of its metabolites including (E)-2-hexenal, hexenols, and hexenyl acetates. Similar results were seen in wounded beech leaves and clover. The emission of hexenal family compounds was proportional to the extent of wounding, was not dependent on light, occurred in attached or detached leaves, and was greatly enhanced as detached leaves dried out. Emission of (Z)-3-hexenal from detached drying aspen leaves averaged 500 m gCg 21 (dry leaf weight). Leaf wound compounds were not emitted in a nitrogen atmosphere but were released within seconds of reintroduction of oxygen; this indicates that there are not large pools of hexenyl compounds in leaves. The PTR-MS method also allows the simultaneous detection of less abundant hexanal family VOCs including hexanal, hexanol, and hexyl acetate and VOCs formed in the light (isoprene) or during anoxia (acetaldehyde). PTR- MS may be a useful tool for the analysis of VOC emissions resulting from grazing, herbivory, and other physical damage to vegetation, from harvesting of crops, and from senescing leaves.

Acetone, methanol, and other partially oxidized volatile organic emissions from dead plant matter by abiological processes: Significance for atmospheric HOx chemistry

In this paper, attention is called to the significance of abiological production of partially oxidized volatile organic carbons (POVOCs) from the decay of dead plant material. Measured relative emission of acetone and methanol can be at least 10−4 and 3 - 5 × 10−4 g g−1of decaying dry plant matter, respectively. If these results may be extrapolated, global annual emissions of 6–8 Tg of acetone and 18 – 40 Tg of methanol would result, adding strongly to the estimated total emissions of these compounds to the atmosphere. Because acetone and methanol, through OH and HO2 formation, play significant roles in the chemistry of the atmosphere, further research is strongly needed to quantify the emissions of acetone, methanol, and other POVOCs

Analysing the headspace of coffee by proton-transfer-reaction mass-spectrometry

Abstract An extensive analysis of the headspace (HS) of coffee brew using proton-transfer-reaction mass-spectrometry (PTR-MS) is presented. In particular, we present a set of methods that link mass spectral peaks, as observed in PTR-MS, to chemical compounds in the HS of coffee. Combining all this information, a tentative assignment and rough quantification of liquid coffee HS is presented. Coffee was chosen because it contains a large number of chemically diverse volatile organic compounds (VOCs), representing a challenging system for on-line analysis by PTR-MS.

Eddy covariance measurements of oxygenated volatile organic compound fluxes from crop harvesting using a redesigned proton‐transfer‐reaction mass spectrometer

A redesigned proton-transfer-reaction mass spectrometer was deployed in the field to measure atmospheric fluxes of volatile organic compounds (VOCs) released following the cutting and drying of hay. The instrument has a fast response, around 0.1 s, allowing use of the eddy covariance technique. Measurements were done over a 3-day period in a hay field in the eastern part of Tirol, Austria, in the early growing season and are compared to earlier results obtained using a slower-response instrument in the late growing season [Karl et al., 2000]. Peak upward fluxes of the order of 9.9 × 10−6g m−2 s−1 for methanol, 1.5 × 10−6g m−2 s−1 for acetaldehyde, and 1.5 × 10−6g m−2 s−1 for the sum of hexenals, hexenols, hexanal, pentenols, 3-methylbutanal, and butanone were observed during and after harvesting. Time-integrated values for the first day were of the order of 65±20 mg m−2 (130±40 μg per gram dry weight(gdw)−1) for methanol and 13±4 mg m−2 (26±8 μg gdw−1) for acetaldehyde. VOC fluxes measured in this study were generally higher than in August 1999, which can be explained by higher temperatures and higher photosynthetic productivity. Good agreement with another means for estimating VOC fluxes, the surface gradient method, was achieved. This paper presents measurements of eddy covariance for a wide variety of oxygenated VOCs and shows that hay harvesting can influence the local air quality in many regions in the Alps on a short-term basis.

Detection of isoprene in expired air from human subjects using proton-transfer-reaction mass spectrometry

A new analytical method using proton-transfer-reaction mass spectrometry (PTRMS) is described for the determination of trace constituents in human breath. PTRMS is sufficiently sensitive and specific that it does not require preconcentration or separation. At its present stage of development it is capable of detecting trace constituents present in air at the part-per-billion level. These capabilities are illustrated for isoprene, one of the most abundant endogenous hydrocarbons. Our results confirm recent observations of a diurnal level variation associated with sleep or wakefulness; a new finding is that young children have much lower levels of isoprene in breath than adults. To address the metabolic origin of human isoprene, we used PTRMS to analyze expired air for allylic C5 alcohols that have been proposed to be non-enzymatic precursors of isoprene. The lack of correlation between peak breath isoprene and these alcohols suggests that the hydrocarbon is formed by some other mechanism.

The mozzarella cheese flavour profile: a comparison between judge panel analysis and proton transfer reaction mass spectrometry

Described in this paper is a comparison of results obtained in flavour profiling with two different approaches: classical sensory analysis and a novel instrumental technique. The mozzarella cheese flavour profile of seven different brands has been described by a sensory panel of eight judges. The same brands have been studied by means of proton transfer reaction mass spectrometry (PTR-MS), a novel technique well suited for detecting volatile organic compounds (VOCs) down to the pptv level in air, without any need for sample concentration or trapping. The PTR mass spectra of the headspace of mozzarella samples held at 36 °C have been compared with the judge panel flavour profile. Multivariate statistical data analysis shows that the two methods perform comparable sample discrimination. Even though several questions are still open (definition of better instrumental parameters, improvements in sampling set-up, spectral interpretation), the PTR-MS technique appears to be a very promising method for the instrumental evaluation of the flavour sensory profile of food. This opens up new opportunities both in the control of quality and technological processes as well in the fundamental comprehension of the physiological processes of aroma perception. © 2000 Society of Chemical Industry

Dynamic measurements of partition coefficients using proton-transfer-reaction mass spectrometry (PTR–MS)

Abstract Liquid–gas partition coefficients (HLC) of volatile organic compounds (VOCs) in water–air systems are determined using a novel dynamic approach by coupling a stripping cell directly to a proton-transfer-reaction mass spectrometer (PTR–MS). Two complementary set-ups are evaluated, one suited for determining HLCs of highly volatile compounds (

Automobile Emissions of Acetonitrile: Assessment of its Contribution to the Global Source

Based on an estimated global fuel consumption of 2.57 × 1015g(C) y−1 and the assumption thatthe fossil fuel burned in Austria is globallyrepresentative, an upper limit of 0.021 (+150%, −50%)Tg y−1 for global CH3CN emission dueto fossil fuel burning was obtained from the relativeenhancement of the concentrations of toluene, benzene,and acetonitrile (methyl cyanide) during strong,short-term traffic pollution. This is less than 6% ofthe total global budget of CH3CN, which is dominatedby an emission rate of 0.8 Tg y−1 from biomassburning.

Variability-lifetime relationship of VOCs observed at the Sonnblick Observatory 1999—estimation of HO-densities

An extensive dataset of VOC measurements was collected at the Sonnblick Observatory, Austria (3106 m) in Fall/ Winter 1999/2000, showing high mixing ratios of anthropogenic and biogenic VOCs at this high altitude site due to upward mixing of air masses (Geophys. Res. Lett. 2F (2001) 507). Here we give an interpretation of proton-transfer- reaction (PTR-MS) mass scans obtained in November 1999 based on fragmentation data, GC-PTR-MS analysis and the variability-lifetime relationship, described by the power law, sðlnðxÞÞ ¼ Atb : The variability-lifetime plot of anthropogenic VOCs gave a proportionality factor A of 1.40 and a,b exponent (sink term) of 0.44 and allowed an estimate of average HO-densities on the order of (1.570.4) � 10 5 molecules cm � 3 . Additionally we were able to indirectly determine a diurnal HO-profile with peak values of (1.370.5) � 10 6 molecules cm � 3 around midday. HO- reaction rate coefficients for higher aldehydes (heptanal to nonanal) were estimated due to photochemical losses during a stagnant air episode (27 November) and from the variability-lifetime relationship. Combining long term PTR-MS analysis of VOCs and the variability-lifetime method provides a valuable tool for assessing the dominant cause of the variability in VOC concentrations. This information is essential in understanding the sources and photochemical processing of VOCs detected in ambient air at field measurement sites. r 2001 Elsevier Science Ltd. All rights reserved.