Auflistung nach Autor:in "Paulsen, Dwane"

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Hygroscopic properties of water-soluble matter and humic-like organics in atmospheric fine aerosol
(Copernicus, 22.01.2004) Gysel, Martin; Weingartner, Ernest; Nyeki, Stephan; Paulsen, Dwane; Baltensperger, Urs; Galambos, Ildikó; Kiss, Gyula
Ambient continental-rural fine aerosol (K-puszta, Hungary, PM1.5) was sampled on quartz fibre filters in winter and summer 2001. Water-soluble matter (WSM) was extracted in MilliQ-water, and, in a second step, solid phase extraction was used to isolate the less hydrophilic fraction (ISOM) of the water-soluble organic matter (WSOM) from remaining inorganic salts and "most" hydrophilic organic matter (MHOM). This approach allowed ISOM, which constitutes the major fraction of WSOM, to be isolated from ambient aerosols and investigated in pure form. Hygroscopic properties of both WSM and ISOM extracts as well as of aquatic reference fulvic and humic acids were investigated using a Hygroscopicity Tandem Differential Mobility Analyser (H-TDMA). ISOM deliquesced between 30% and 60% relative humidity (RH), and hygroscopic growth factors at 90% RH ranged from 1.08 to 1.17. The hygroscopicity of ISOM is comparable to secondary organic aerosols obtained in smog chamber experiments, but lower than the hygroscopicity of highly soluble organic acids. The hygroscopic behaviour of investigated fulvic and humic acids had similarities to ISOM, but hygroscopic growth factors were slightly smaller and deliquescence was observed at higher RH (75-85% and 85-95% RH for fulvic acid and humic acid, respectively). These differences probably originate from larger average molecular mass and lower solubility of fulvic and humic acids. Inorganic composition data, measured ISOM hygroscopicity, and a presumed value for the hygroscopicity of the small remaining MHOM fraction were used to predict hygroscopic growth of WSM extracts. Good agreement between model prediction and measured water uptake was observed with differences (by volume) ranging from +1% to -18%. While deliquescence properties of WSM extracts were mainly determined by the inorganic salts (42-53 wt % of WSM), the WSOM accounted for a significant fraction of particulate water. At 90% RH, according to model predictions and measurements, about 80-62% of particulate water in the samples are associated with inorganic salts and about 20-38% with WSOM. The relative contributions of both distinguished WSOM fractions, ISOM and MHOM, remains uncertain since MHOM was not available in isolated form, but the results suggest that the less abundant MHOM is also important due to its presumably larger hygroscopicity.
01A - Beitrag in wissenschaftlicher Zeitschrift
Identification of organic acids in secondary organic aerosol and the corresponding gas phase from chamber experiments
(American Chemical Society, 15.10.2004) Fisseha, Rebeka; Dommen, Josef; Sax, Mirjam; Paulsen, Dwane; Kalberer, Markus; Maurer, Rolf; Höfler, Frank; Weingartner, Ernest; Baltensperger, Urs
Organic acids in the gas and aerosol phase from photooxidation of 1,3,5-trimethylbenzene in the presence of 300 ppb propene and 300 ppb NOx in smog chamber experiments were determined using a wet effluent diffusion denuder/aerosol collector coupled to ion chromatography (IC) with conductivity detection. Behind the IC, the samples were collected using a fraction collector, for identification of unresolved/unidentified organic acids with IC-mass spectrometry (MS). In total, 20 organic acids were found with MS of which 10 were identified. The organic acids identified offline by IC-MS were then further quantified based on the online IC data. The identification was additionally confirmed with gas chromatography-mass spectrometry. At the maximum aerosol concentration, organic acids comprised 20-45% of the total aerosol mass. The method has a detection limit of 10-100 ng/m3 for the identified carboxylic acids.
01A - Beitrag in wissenschaftlicher Zeitschrift
Identification of polymers as major components of atmospheric organic aerosols
(Springer, 2004) Kalberer, Markus; Paulsen, Dwane; Sax, Mirjam; Steinbacher, Martin; Dommen, Josef; Prévôt, André S.H.; Fisseha, Rebeka; Weingartner, Ernest; Frankevich, Vladimir; Zenobi, Renato; Baltensperger, Urs
Results from photooxidation of aromatic compounds in a reaction chamber show that a substantial fraction of the organic aerosol mass is composed of polymers. This polymerization results from reactions of carbonyls and their hydrates. After aging for more than 20 hours, about 50% of the particle mass consists of polymers with a molecular mass up to 1000 daltons. This results in a lower volatility of this secondary organic aerosol and a higher aerosol yield than a model using vapor pressures of individual organic species would predict.
01A - Beitrag in wissenschaftlicher Zeitschrift
Secondary organic aerosol formation by irradiation of 1,3,5-trimethylbenzene−NOₓ-H2O in a new reaction chamber for atmospheric chemistry and physics
(American Chemical Society, 12.03.2005) Paulsen, Dwane; Dommen, Josef; Kalberer, Markus; Prévôt, André S.H.; Richter, René; Sax, Mirjam; Steinbacher, Martin; Weingartner, Ernest; Baltensperger, Urs
A new environmental reaction smog chamber was built to simulate particle formation and growth similar to that expected in the atmosphere. The organic material is formed from nucleation of photooxidized organic compounds. The chamber is a 27 m³ fluorinated ethylene propylene (FEP) bag suspended in a temperature-controlled enclosure. Four xenon arc lamps (16 kW total) are used to irradiate primary gas components for experiments lasting up to 24 h. Experiments using irradiations of 1,3,5-trimethylbenzene−NOₓ−H2O at similar input concentrations without seed particles were used to determine particle number and volume concentration wall loss rates of 0.209 ± 0.018 and 0.139 ± 0.070 1/h, respectively. The particle formation was compared with and without propene.
01A - Beitrag in wissenschaftlicher Zeitschrift
Secondary organic aerosols from anthropogenic and biogenic precursors
(Royal Society of Chemistry, 2005) Baltensperger, Urs; Kalberer, Markus; Dommen, Josef; Paulsen, Dwane; Alfarra, M. Rami; Coe, Hugh; Fisseha, Rebeka; Gascho, Astrid; Gysel, Martin; Nyeki, Stephan; Sax, Mirjam; Steinbacher, Martin; Prévôt, André S.H.; Sjögren, Staffan; Weingartner, Ernest; Zenobi, Renato
Secondary organic aerosol (SOA) formation from the photooxidation of an anthropogenic (1,3,5-trimethylbenzene) and a biogenic (α-pinene) precursor was investigated at the new PSI smog chamber. The chemistry of the gas phase was followed by proton transfer reaction mass spectrometry, while the aerosol chemistry was investigated with aerosol mass spectrometry, ion chromatography, laser desorption ionization mass spectrometry, and infrared spectroscopy, along with volatility and hygroscopicity studies. Evidence for oligomer formation for SOA from both precursors was given by an increasing abundance of compounds with a high molecular weight (up to 1000 Da) and by an increasing thermal stability with increasing aging time. The results were compared to data obtained from ambient aerosol samples, revealing a number of similar features.
01A - Beitrag in wissenschaftlicher Zeitschrift
Volatility measurements of photochemically and nebulizer-generated organic aerosol particles
(Elsevier, 2006) Paulsen, Dwane; Weingartner, Ernest; Alfarra, M. Rami; Baltensperger, Urs
01A - Beitrag in wissenschaftlicher Zeitschrift