Complete chemical analysis of aerosol particles in real-time

Real-time mass spectrometry of individual aerosol particles using an ion trap mass spectrometer is described. The microparticles are sampled directly from the air by a particle inlet system into the vacuum chamber. An incoming particle is detected as it passes through two CW laser beams and a pulsed laser is triggered to intercept the particle for laser ablation ionization at the center of the ion trap. The produced ions are analyzed by the ion trap mass spectrometer. Ions of interest are selected and dissociated through collision with buffer gas atoms for further fragmentation analysis. Real-time chemical analyses of inorganic, organic, and bacterial aerosol articles have been demonstrated. It has been confirmed that the velocity and the size of the incoming particles highly correlate to each other. The performance of the inlet system, particle detection, and preliminary results are discussed

Mikroanalytische Untersuchungen zur Wolken- und Nebelbildung mittels laserinduzierter Massenspektroskopie, Roentgenfluoreszenzanalyse, Ionenchromatographie und nasschemischer Methoden

The comparison of the composition of residual cores of drops from clouds and fog with simultaneously collected particles of the interstitial aerosols give information on micro-physical and chemical seletion processes in cloud and fog formation. To collect the residual cores, a virtual counterflow impactor was built up and its suitability for contamination-free separation of the drops from clouds and fog from the particle and gas phase of the interstitial aerosol was checked. The remaining residual cores left over in the virtual counterflow impactor by evaporation of the drops were selectively separated according to size in mini-cascade impactors (for individual particle analysis) and on core pore filters (for the bulk analysis.) By measuring the liquid water content, the number of drops density and the mean drop diameter, fog and cloud physics parameters were collected. The composition of residual cores and of particles of the interstitial aerosol was determined. (orig.)Der Vergleich der Zusammensetzung von Residualkernen von Wolken- und Nebeltropfen mit gleichzeitig gesammelten Partikeln des interstitiellen Aerosols liefert Einblicke in mikrophysikalische und -chemische Selektionsprozesse bei der Wolken- und Nebelbildung. Zur Sammlung der Residualkerne wurde ein virtueller Gegenstromimpaktor aufgebaut und dessen Eignung zur kontaminationsfreien Abtrennung der Wolken- und Nebeltropfen von der Partikel-und Gasphase des interstitiellen Aerosols ueberprueft. Die im virtuellen Gegenstromimpaktor durch Verdampfen der Tropfen uebrig bleibenden Residualkerne wurden groessenselektiv in Mini-Kaskadenimpaktoren (fuer die Einzelpartikelanalyse) und auf Kernporenfiltern (fuer die ''bulk''-Analyse) abgeschieden. Durch Messung des Fluessigwassergehalts, der Tropfenanzahldichte und des mittleren Tropfendurchmessers konnten nebel- und wolkenphysikalische Parameter erfasst werden. Die Zusammensetzung von Residualkernen und von Partikeln des interstitiellen Aerosols wurde bestimmt. (orig.)SIGLEAvailable from TIB Hannover: DW 9945 / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman

Untersuchungen mikrophysikalischer und chemischer Diskriminierungsprozesse bei der Wolkenbildung mittels Einzelpartikelanalyse. Ein Beitrag zum Great Dun Fell Experiment Abschlussbericht

Vom 22.4. bis 12.5.93 fand das Feldexperiment des EUROTRAC-Subprojekts GCE (Ground-based Cloud Experiments) am Great Dun Fell, Cumbria, GB statt. Durch Exposition von fuenfstufigen Kaskadenimpaktoren (Partikeldurchmesser >0,09 #mu#m) wurden Partikeln des intersitiellen Aerosols und Wolkentropfenresiduen gesammelt und mittels Einzelpartikelanalyse untersucht. Zur Gewinnung von Residualkernproben wurde dem Impaktor ein virtueller Gegenstromimpaktor vorgeschaltet. Die externe bzw. interne Mischung maritimer und anthropogener Aerosolkomponenten ermoeglicht eine Charakterisierung von Luftmassen mit Hilfe der Lasermikrosonden-Massenspektrometrie. Als Bildungsprozess kleiner Partikeln ('accumulation mode') wird die heterogene Nukleation von Schwefel- und Methansulfonsaeure auf Partikeln eines Verbrennungsaerosols nahegelegt. Ein vergleichbarer Prozess auf grossen Seesalzkernen wird nicht beobachtet. Typische Wolkentropfenresiduen sind im maritimen Fall Seesalzkerne und sekundaeres Sulfataerosol, intern gemischt mit Methansulfonaten. Als Folge der Partikelalterung aufgewachsene Sulfat- bzw. Nitratschichten haben keinen erkennbaren Einfluss auf die Aufnahme von Seesalzkernen in der Tropfenphase. Die Wolkentropfenresiduen im nicht maritimen Fall bestehen im Wesentlichen aus Sulfaten. In Wolken geringen Fluessigwassergehalts bilden Partikeln aus Krustenmaterial einen signifikanten Anteil der gesammelten Residualkerne. Das vor der Wolkenbildung und nach der Wolkenaufloesung untersuchte Aerosol zeigt sowohl in Bezug auf intern als auch auf extern gemischte Komponenten grosse Aehnlichkeit. Der Einfluss der Wolken ist im wesentlichen an der Bildung von Hydroxymethansulfonaten (gebildet aus geloestem Formaldehyd und Schwefeldioxid) bzw. einer signifikanten Zunahme partikelgebundener Sulfate nachweisbar. Die Sulfatzunahme wird nicht an vergleichsweise grossen Seesalzkernen beobachtet. Die sehr unterschiedliche Aufnahme einzelner Partikelkomponenten in die Wolkentropfen fuehrt zu einer spezifischen Zusammensetzung der Tropfeninhaltsstoffe und der Partikeln des interstitiellen Aerosols. Partikeln aus der Oelverbrennung (Russ) werden in der Regel nur in geringem Umfang in Wolkentropfen inkorporiert. (orig.)From 22nd of April to 12th of Mai 1993 the field campagne of the EUROTRAC subprojekt GCR (Ground-based Cloud Experiments) took place at Great Dun Fell Cumbria, GB. Cloud interstitial particles and cloud droplet residues were collected by five-stage cascade impactors equipped with special inlet systems, e.g. a counterflow virtual impactor (droplet residues) of the University of Rhode Island. Internal as well as external mixtures of marine and anthrophogenic particle constituents which are observed by laser microprobe mass spectrometry enable characterization of air masses. With respect to accumulation mode particles the findings agree with heterogeneous nucleation of MSA and H_2SO_4 on combustion aerosols. This was not observed for large sea salts. Under marine conditions cloud droplet residues mainly consist of sea salt or non sea salt sulphate which was internally mixed with methane sulfonates. Sulphate and nitrate layers formed by aging processes do not significantly influence incorporation of sea salt nuclei into the liquid phase. In case of non marine dominated conditions the cloud droplet residues mainly consists of sulphate species. Clouds of low liquid water content show crystal material as droplet residues. In general the comparison of aerosols examined before cloud formation and after cloud dissipation showed a poor influence of cloud formation on the main chemical particle constituents. Only the formation of HMSA and sulphate was observed. An expected increase of sulphate within cloud droplets containing large sea salt nuclei was missing. Significant change of the chemical cloud droplet inventories from droplet to droplet is a result of incorporation of particle constituents into the liquid phase. Depending on the amount of water soluble trace constituents (e.g. sulphate) soot particles originating from oil combustion remain in the cloud interstitial aerosol when clouds are formed. (orig.)Available from TIB Hannover: F95B976+a / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEBundesministerium fuer Forschung und Technologie (BMFT), Bonn (Germany)DEGerman

Chemical characterization of individual microparticles using an ion trap: real-time chemical analysis of aerosol particles

This paper describes initial experiments to perform laser ablation mass spectrometry in real time on airborne microparticles. The microparticles are sampled directly from the air by a particle inlet system into the vacuum chamber of a mass spectrometer. An incoming particle is detected as it passes through two CW laser beams and a pulsed laser is triggered to intercept the particle for laser ablation/ionization in the mass spectrometer. The initial studies were made with an existing ion trap mass spectrometer with the particle sampling occurring at the center of the trap electrodes. Performance of the inlet system, particle detection, and preliminary results are described

Real-time mass spectrometry of individual airborne bacteria

A method for the real-time detection of individual bacteria is described. Airborne bacteria and bacterial spores are directly sampled by laser ablation in an ion trap mass spectrometer with an atmospheric pressure inlet system. either positive or negative ion mass spectra can be obtained. Ions of a particular value of m/z can be further characterized by tandem mass spectrometry in the ion trap. Spectra averaged from several hundred individual bacteria of the same species appear to differ somewhat from spectra of bacteria of other species and to be readily distinguishable from spectra of nonbiological particles

Phase partitioning of aerosol constituents in cloud based on single-particle and bulk analysis

Single-particle analysis, performed by laser microprobe mass spectrometry and bulk analytical techniques were used to study aerosol-cloud interactions within the third field campaign of the EUROTRAC subproject 'ground-based cloud experiments' at the Great Dun Fell, Cumbria, U.K. in spring 1993. The shape of the ridge made it possible for ground-based instrumentation to sample similar parcels of air before, during and after their transit through the cloud. A single jet five-stage minicascade impactor was used for sampling particles of the interstitial aerosol. A second impactor worked in tandem with a counter-flow virtual impactor and collected residues of cloud droplets. Considering marine conditions largest droplets nucleated on sea-salt particles, whereas smaller droplets were formed on sulphate and methane sulphonate containing particles. This clearly indicates chemical inhomogeneities in the droplet phase. Particles, which were disfavoured by droplet formation, often contained the highest amounts of water-insoluble carbonaceous matter. For the submicron size range we found that the carbonaceous matter was always internally mixed with sulphate. The fraction of carbonaceous matter increased with decreasing size. A detectable fraction of particles remained in the cloud interstitial air, although they were in size as well as in composition suitable to form cloud droplets. The findings confirm that nucleation is the most important process affecting phase partitioning in cloud, but that spatial and temporal variations of water vapour supersaturation have also an influence on the observed phase partitioning. Proton induced X-ray emission analysis and light absorption measurements of filter samples showed that the average scavenged fraction was 0.77 for sulphur and 0.57 for soot in clouds formed by continental influenced air and 0.62 and 0.44, respectively, for marine influenced clouds