[Holzinger2000] "Emissions of volatile organic compounds from Quercus ilex L. measured by proton transfer reaction mass spectrometry under different environmental conditions",
Journal of Geophysical Research
, vol. 105, no. D16, pp. 20573–20579, 2000.
[Crutzen2000] "High spatial and temporal resolution measurements of primary organics and their oxidation products over the tropical forests of Surinam",
, vol. 34, no. 8: Elsevier, pp. 1161–1165, 2000.
Tropical forests with emissions greater than 1015 g C of reactive hydrocarbons per year strongly affect atmospheric chemistry. Here we report aircraft-borne measurements of organics during March 1998 in Surinam, a largely unpolluted region which is optimally located to study chemical processes induced by tropical forest emissions. Isoprene and its degradation products methylvinyl ketone (MVK) and methacrolein (MACR) and possibly isoprene hydroperoxides (ISOHP), were measured in the nmol mol−1 volume mixing ratio (VMR) range, consistent with estimated emissions and model calculations. In addition, high VMRs of some non-isoprene-derived organics were measured, such as acetone (≈2–4 nmol mol1 up to 12 km altitude), an important source of HO and HO2 in the upper troposphere. Moreover, several masses were measured at significant mixing ratios which could not be identified by reference to previous field measurements or gas-phase isoprene chemistry. High VMRs, almost 0.4 nmol mol−1, were also recorded for a compound which is most likely dimethyl sulphide (DMS). If so, boundary layer loss of HO by reactions with hydrocarbons and their oxidation products strongly prolongs the lifetime of DMS, allowing its transport deep into the Amazon forest south of the intertropical convergence zone (ITCZ). We postulate greater sulphate production and deposition north than south of the (ITCZ) with possible consequences for cloud and ecosystem properties.
[Hansel2000] "A method for real-time detection of PAN, PPN and MPAN in ambient air",
Geophysical research letters
, vol. 27, no. 6: Wiley Online Library, pp. 895–898, 2000.
[Yeretzian2000] "On-line monitoring of coffee roasting by proton-transfer-reaction mass-spectrometry",
ACS Symposium Series
, vol. 763: ACS Publications, pp. 112–125, 2000.
[DeGouw2000] "Proton-transfer chemical-ionization mass spectrometry allows real-time analysis of volatile organic compounds released from cutting and drying of crops",
Environmental science & technology
, vol. 34, no. 12: ACS Publications, pp. 2640–2648, 2000.
The wounding and drying of plant material during crop harvest could be a significant source of volatile organic compounds (VOCs) that enter the atmosphere. Here, we show that these primarily oxygenated VOCs can be measured using proton-transfer chemical-ionization mass spectrometry (PT-CIMS), a method that allows online and simultaneous monitoring of oxygenated VOC levels. For clover, alfalfa, and corn, leaf wounding and in particular drying were shown to lead to strongly enhanced emissions of a series of C6 aldehydes, alcohols, and esters derived from (Z)-3-hexenal. Additionally, for the forage crops clover and alfalfa, enhanced emissions of methanol, acetaldehyde, acetone, and butanone were observed. The identities of the measured carbonyl compounds were confirmed using high-pressure liquid chromatography. For clover, initial cutting led to a VOC release of about 175 μg of C (g dry wt)-1, while during drying the cut clover released >1000 μg of C (g dry wt)-1; qualitatively, similar amounts of VOCs were released from alfalfa, the major hay crop in the United States. The atmospheric implications of these findings may include effects on the local air quality in agricultural areas, contributions to long-range transport of pollutants, and effects on the formation of HOx (=OH + HO2) radicals in the upper troposphere.
[Yeretzian2000a] "Time-resolved headspace analysis by proton-transfer-reaction mass-spectrometry",
ACS Symposium Series
, vol. 763: ACS Publications, pp. 58–72, 2000.
A recently developed technique, Proton-Transfer-Reaction Mass-Spectrometry (PTR-MS), is reviewed based on applications on coffee. PTR-MS is a sensitive and fast method for on-line trace gas analysis. It consists of a specially designed chemical ionization cell, where headspace gas is continuously introduced and volatile organic compounds ionized by proton-transfer from H3O+. Protonated compounds are then mass analyzed in a quadrupole mass filter. First a description of the method will be given, with emphasis on the ionization mechanism. We then discuss a series of experiments that allow mass spectral intensities to be related to chemical compounds. Finally, two applications on coffee are discussed.