Description: Das Projekt "Bildung und Umwandlung von Wasserstoffperoxid und organischen Peroxiden in Waeldern" wird vom Umweltbundesamt gefördert und von Gesellschaft zur Förderung der Spektrochemie und Angewandten Spektroskopie, Institut für Spektrochemie und Angewandte Spektroskopie durchgeführt. Achievements: The degradation of natural non methane hydrocarbons (NMHC) (isoprene and terpenes) and formation of peroxides in forest air have been studied. Reliable sampling and determination techniques were developed for the detection of isoprene and monoterpenes. For hydrogen peroxide a previously developed method based on cryosampling and chemiluminescence detection was available. A technique based on the adsorptive preconcentration on 2 adsorbents, combined with an ozone scrubber in front of the sampling tubes was chosen for the measurement of biogenic hydrocarbons. The complexity of the composition of ambient air required the use of a high resolution gas chromatographic analysis coupled with mass spectrometric detection. Several measurement campaigns were carried out at different locations to investigate isoprene and monoterpene concentrations as well as their degradation in and above forests. In addition to the field measurements, Norway spruce saplings were exposed to controlled concentrations of ozone in closed glass chambers to elucidate the influence of ozone, respectively ozone biogenic alkene reaction products, on the monoterpene output of the plant. During ozone fumigation the more reactive monoterpenes d-limonene and beta-phellandrene were found in higher amounts, although a considerable fraction of them was certainly degradated as a consequence of their gas phase reactions. The determination of terpenes in needle tissue from fumigated trees showed results significantly different from those obtained with needles of the control plants. The monoterpene content of current year needles was generally diminished after a fumigation period of about 5 months. Also the amounts of other biogenic hydrocarbons, like sesquiterpenes, diterpenes and oxidized terpenes were reduced in the ozone treated plants. In contrast, recent studies on the monoterpene metabolism investigated in open top chambers have shown no or only slight differences between ozone treated and control plants. Possibly the high air flow through the open top chambers and therefore the low concentrations of products of ozone monoterpene reactions are responsible for these contradictory results. The 2 most widely used techniques for sampling of airborne nonmethane hydrocarbons (NMHC) in remote areas, namely the adsorptive preconcentration on organic polymers or carbon based materials and the whole air sampling in stainless steel canisters, were checked in laboratory studies and field studies regarding their suitability for the collection of unsaturated natural NMHCs, such as isoprene and terpenes. The experiments have shown that ozone scrubbing prior to the preconcentration step is necessary if adsorptive preconcentration is chosen, otherwise an underestimation of some natural alkenes is unavoidable...
Types:
SupportProgram
Origin: /Bund/UBA/UFORDAT
Tags: Gemeine Fichte ? Ozon ? Alken ? Chemilumineszenz ? Fichte ? Ozonwert ? Wasserstoffperoxid ? Peroxid ? Terpene ? Alicyclischer Kohlenwasserstoff ? Naturpolymer ? Baum ? Kohlenwasserstoff ? Isopren ? Polymer ? Adsorptionsmittel ? Außenluft ? Massenspektrometrie ? Messtechnik ? Methan ? Adsorption ? Spektralanalyse ? Organisches Material ? U-Bahn ? Verfahrenskombination ? Edelstahl ? Gasförmiger Stoff ? Gaswäscher ? Luftanalyse ? Nadelwald ? Chromatografie ? Schadstoffabbau ? Studie ? Verfahrenstechnik ? Feldstudie ? Probenahme ? Umweltschutz ? Chemische Reaktion ? Stofftransport ? Wald ? Stoffwechsel ? Konzentrationsmessung ? Nachweisbarkeit ? Auflösungsvermögen ?
Region: Nordrhein-Westfalen
Bounding box: 6.76339° .. 6.76339° x 51.21895° .. 51.21895°
License: cc-by-nc-nd/4.0
Language: Deutsch
Time ranges: 1989-05-01 - 1991-12-31
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