Untersuchungen von Aerosolpartikeln und Wolkenresidualpartikeln mittels Einzelpartikel-Massenspektrometrie und optischen Methoden

Atmosphärische Partikel beeinflussen das Klima durch Prozesse wie Streuung, Reflexion und Absorption. Zusätzlich fungiert ein Teil der Aerosolpartikel als Wolkenkondensationskeime (CCN), die sich auf die optischen Eigenschaften sowie die Rückstreukraft der Wolken und folglich den Strahlungshaushalt auswirken. Ob ein Aerosolpartikel Eigenschaften eines Wolkenkondensationskeims aufweist, ist vor allem von der Partikelgröße sowie der chemischen Zusammensetzung abhängig. Daher wurde die Methode der Einzelpartikel-Laserablations-Massenspektrometrie angewandt, die eine größenaufgelöste chemische Analyse von Einzelpartikeln erlaubt und zum Verständnis der ablaufenden multiphasenchemischen Prozesse innerhalb der Wolke beitragen soll.rnIm Rahmen dieser Arbeit wurde zur Charakterisierung von atmosphärischem Aerosol sowie von Wolkenresidualpartikel das Einzelpartikel-Massenspektrometer ALABAMA (Aircraft-based Laser Ablation Aerosol Mass Spectrometer) verwendet. Zusätzlich wurde zur Analyse der Partikelgröße sowie der Anzahlkonzentration ein optischer Partikelzähler betrieben. rnZur Bestimmung einer geeigneten Auswertemethode, die die Einzelpartikelmassenspektren automatisch in Gruppen ähnlich aussehender Spektren sortieren soll, wurden die beiden Algorithmen k-means und fuzzy c-means auf ihrer Richtigkeit überprüft. Es stellte sich heraus, dass beide Algorithmen keine fehlerfreien Ergebnisse lieferten, was u.a. von den Startbedingungen abhängig ist. Der fuzzy c-means lieferte jedoch zuverlässigere Ergebnisse. Darüber hinaus wurden die Massenspektren anhand auftretender charakteristischer chemischer Merkmale (Nitrat, Sulfat, Metalle) analysiert.rnIm Herbst 2010 fand die Feldkampagne HCCT (Hill Cap Cloud Thuringia) im Thüringer Wald statt, bei der die Veränderung von Aerosolpartikeln beim Passieren einer orographischen Wolke sowie ablaufende Prozesse innerhalb der Wolke untersucht wurden. Ein Vergleich der chemischen Zusammensetzung von Hintergrundaerosol und Wolkenresidualpartikeln zeigte, dass die relativen Anteile von Massenspektren der Partikeltypen Ruß und Amine für Wolkenresidualpartikel erhöht waren. Dies lässt sich durch eine gute CCN-Aktivität der intern gemischten Rußpartikel mit Nitrat und Sulfat bzw. auf einen begünstigten Übergang der Aminverbindungen aus der Gas- in die Partikelphase bei hohen relativen Luftfeuchten und tiefen Temperaturen erklären. Darüber hinaus stellte sich heraus, dass bereits mehr als 99% der Partikel des Hintergrundaerosols intern mit Nitrat und/oder Sulfat gemischt waren. Eine detaillierte Analyse des Mischungszustands der Aerosolpartikel zeigte, dass sich sowohl der Nitratgehalt als auch der Sulfatgehalt der Partikel beim Passieren der Wolke erhöhte. rn

A compact and portable deposition chamber to study nanoparticles in air-exposed tissue

BACKGROUND Epidemiological studies show that elevated levels of particulate matter in ambient air are highly correlated with respiratory and cardiovascular diseases. Atmospheric particles originate from a large number of sources and have a highly complex and variable composition. An assessment of their potential health risks and the identification of the most toxic particle sources would require a large number of investigations. Due to ethical and economic reasons, it is desirable to reduce the number of in vivo studies and to develop suitable in vitro systems for the investigation of cell-particle interactions. METHODS We present the design of a new particle deposition chamber in which aerosol particles are deposited onto cell cultures out of a continuous air flow. The chamber allows for a simultaneous exposure of 12 cell cultures. RESULTS Physiological conditions within the deposition chamber can be sustained constantly at 36-37°C and 90-95% relative humidity. Particle deposition within the chamber and especially on the cell cultures was determined in detail, showing that during a deposition time of 2 hr 8.4% (24% relative standard deviation) of particles with a mean diameter of 50 nm [mass median diameter of 100 nm (geometric standard deviation 1.7)] are deposited on the cell cultures, which is equal to 24-34% of all charged particles. The average well-to-well variability of particles deposited simultaneously in the 12 cell cultures during an experiment is 15.6% (24.7% relative standard deviation). CONCLUSIONS This particle deposition chamber is a new in vitro system to investigate realistic cell-particle interactions at physiological conditions, minimizing stress on the cell cultures other than from deposited particles. A detailed knowledge of particle deposition characteristics on the cell cultures allows evaluating reliable dose-response relationships. The compact and portable design of the deposition chamber allows for measurements at any particle sources of interest.

Responses of lung cells to realistic exposure of primary and aged carbonaceous aerosols

Diesel exhaust and wood burning are important sources of ambient atmospheric particles due to increasing numbers of diesel cars and the importance of wood as a source of renewable energy. Inhalation is the predominant route of entry and uptake for fine and ultrafine particles into the body. Health effects of atmospheric particles are still not completely understood. There is consistent evidence from epidemiology that particle exposure contributes to respiratory and cardiovascular diseases. This study aimed at examining acute responses of airway epithelial cells and luminal macrophages after exposure to freshly emitted and photochemically aged carbonaceous aerosols under realistic atmospheric conditions. In addition to a bronchial epithelial cell line advanced cell cultures namely fully differentiated respiratory epithelia and primary surface macrophages were used. Our results demonstrate that a single exposure of the cells to realistic particle doses of 0.3–3 ng diesel or 3–9 ng wood aerosol per cm2 cell surface induces small, particle-specific responses. The release of interleukin-6 and -8 was found to be decreased in differentiated airway epithelia but not in the other cell models studied. Aerosol exposure decreased macrophage phagocytic activity by 45–90%. Cell and tissue integrity remained unaffected. Overall, primary and aged particles from the same combustion induced similar responses in the cell models tested, whereby particles from diesel exhaust affected the cells more than those from wood combustion.

Arsenic, antimony and selenium in urban soils: potential risks for human health in urban gardening

The benefits of urban agriculture are many and well documented, ranging from health improvement to community betterment, more sustainable urban development and environment protection. On the negative side, urban soils are commonly enriched in toxic trace elements that have accumulated over time through the deposition of atmospheric particles (generated by automotive traffic, heating systems, historical industrial activities and resuspended street dust), and the uncontrolled disposal of domestic, commercial and industrial wastes. This in turn has given rise to concerns about the level of exposure of urban farmers to these elements and the potential health hazards associated with this exposure. Research efforts in this field have started relatively recently and have almost systematically omitted the influence of Sb and Se, and to a lesser extent of As, although all three have proven toxic effects.

PM and material decay: analysis of dry depositions on horizontal and vertical surrogate surfaces through a Deposition Box system

Airborne Particulate Matter (PM), can get removed from the atmosphere through wet and dry mechanisms, and physically/chemically interact with materials and induce premature decay. The effect of dry depositions is a complex issue, especially for outdoor materials, because of the difficulties to collect atmospheric deposits repeatable in terms of mass and homogeneously distributed on the entire investigated substrate. In this work, to overcome these problems by eliminating the variability induced by outdoor removal mechanisms (e.g. winds and rainfalls), a new sampling system called ‘Deposition Box’, was used for PM sampling. Four surrogate materials (Cellulose Acetate, Regenerated Cellulose, Cellulose Nitrate and Aluminum) with different surfaces features were exposed in the urban-marine site of Rimini (Italy), in vertical and horizontal orientations. Homogeneous and reproducible PM deposits were obtained and different analytical techniques (IC, AAS, TOC, VP-SEM-EDX, Vis-Spectrophotometry) were employed to characterize their mass, dimension and composition. Results allowed to discriminate the mechanisms responsible of the dry deposition of atmospheric particles on surfaces with different nature and orientation and to determine which chemical species, and in which amount, tend to preferentially deposit on them. This work demonstrated that “Deposition Box” can represent an affordable tool to study dry deposition fluxes on materials and results obtained will be fundamental in order to extend this kind of exposure to actual building and heritage materials, to investigate the PM contribution in their decay.

Impact of Sahara dust transport on Cape Verde atmospheric element particles

The objectives of this study were to (1) conduct an elemental characterization of airborne particles sampled in Cape Verde and (2) assess the influence of Sahara desert on local suspended particles. Particulate matter (PM10) was collected in Praia city (14°94'N; 23°49'W) with a low-volume sampler in order to characterize its chemical composition by k0-INAA. The filter samples were first weighed and subsequently irradiated at the Portuguese Research Reactor. Results showed that PM10 concentrations in Cape Verde markedly exceeded the health-based air quality standards defined by the European Union (EU), World Health Organization (WHO), and U.S. Environmental Protection Agency (EPA), in part due to the influence of Sahara dust transport. The PM10 composition was characterized essentially by high concentrations of elements originating from the soil (K, Sm, Co, Fe, Sc, Rb, Cr, Ce, and Ba) and sea (Na), and low concentrations of anthropogenic elements (As, Zn, and Sb). In addition, the high concentrations of PM measured in Cape Verde suggest that health of the population may be less affected compared with other sites where PM10 concentrations are lower but more enriched with toxic elements.

Variation of the mixing state of Saharan dust particles with atmospheric transport

Mineral dust is an important aerosol species in the Earth’s atmosphere and has a major source within North Africa, of which the Sahara forms the major part. Aerosol Time of Flight Mass Spectrometry (ATOFMS) is first used to determine the mixing state of dust particles collected from the land surface in the Saharan region, showing low abundance of species such as nitrate and sulphate internally mixed with the dust mineral matrix. These data are then compared with the ATOFMS single particle mass spectra of Saharan dust particles detected in the marine atmosphere in the vicinity of the Cape Verde islands, which are further compared with those from particles with longer atmospheric residence sampled at a coastal station at Mace Head, Ireland. Saharan dust particles collected near the Cape Verde Islands showed increased internally mixed nitrate but no sulphate, whilst Saharan dust particles collected on the coast of Ireland showed a very high degree of internally mixed secondary species including nitrate, sulphate and methanesulphonate. This uptake of secondary species will change the pH and hygroscopic properties of the aerosol dust and thus can influence the budgets of other reactive gases, as well as influencing the radiative properties of the particles and the availability of metals for dissolution.

Focus on high energy particles and atmospheric processes

The letters published in the ‘Focus issue on high energy particles and atmospheric processes’ serve to broaden the discussion about the influence of high energy particles on the atmosphere beyond their possible effects on clouds and climate. These letters link climate and meteorological processes with atmospheric electricity, atmospheric chemistry, high energy physics and aerosol science from the smallest molecular cluster ions through to liquid droplets. Progress in such a disparate and complex topic is very likely to benefit from continued interdisciplinary interactions between traditionally distinct science areas.

Stereochemical transfer to atmospheric aerosol particles accompanying the oxidation of biogenic volatile organic compounds

Asymmetric emission profiles of the stereoisomers of plant-derived volatile organic compounds vary with season, geography, plant type, and stress factors. After oxidation of these compounds in the atmosphere, the low-vapor pressure products ultimately contribute strongly to the particle-phase material of the atmosphere. In order to explore the possibility of stereochemical transfer to atmospheric aerosol particles during the oxidation of biogenic volatile organic compounds, second-order coherent vibrational spectra were recorded of the particle-phase organic material produced by the oxidation of different stereoisomeric mixes of alpha-pinene. The spectra show that the stereochemical configurations are not scrambled but instead are transferred from the gas-phase molecular precursors to the particle-phase molecules. The spectra also show that oligomers formed in the particle phase have a handed superstructure that depends strongly and nonlinearly on the initial stereochemical composition of the precursors. Because the stereochemical mix of the precursors for a material can influence the physical and chemical properties of that material, our findings suggest that chirality is also important for such properties of plant-derived aerosol particles. Citation: Ebben, C. J., S. R. Zorn, S.-B. Lee, P. Artaxo, S. T. Martin, and F. M. Geiger (2011), Stereochemical transfer to atmospheric aerosol particles accompanying the oxidation of biogenic volatile organic compounds, Geophys. Res. Lett., 38, L16807, doi: 10.1029/2011GL048599.

Studying Close Approaches for a Cloud of Particles Considering Atmospheric Drag

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Condensational growth of atmospheric aerosol particles in an expanding water saturated air flow

Aerosol particles and water vapour are two important constituents of the atmosphere. Their interaction, i.e. thecondensation of water vapour on particles, brings about the formation of cloud, fog, and raindrops, causing the water cycle on the earth, and being responsible for climate changes. Understanding the roles of water vapour and aerosol particles in this interaction has become an essential part of understanding the atmosphere. In this work, the heterogeneous nucleation on pre-existing aerosol particles by the condensation of water vapour in theflow of a capillary nozzle was investigated. Theoretical and numerical modelling as well as experiments on thiscondensation process were included. Based on reasonable results from the theoretical and numerical modelling, an idea of designing a new nozzle condensation nucleus counter (Nozzle-CNC), that is to utilise the capillary nozzle to create an expanding water saturated air flow, was then put forward and various experiments were carried out with this Nozzle-CNC under different experimental conditions. Firstly, the air stream in the long capillary nozzle with inner diameter of 1.0~mm was modelled as a steady, compressible and heat-conducting turbulence flow by CFX-FLOW3D computational program. An adiabatic and isentropic cooling in the nozzle was found. A supersaturation in the nozzle can be created if the inlet flow is water saturated, and its value depends principally on flow velocity or flow rate through the nozzle. Secondly, a particle condensational growth model in air stream was developed. An extended Mason's diffusion growthequation with size correction for particles beyond the continuum regime and with the correction for a certain particle Reynolds number in an accelerating state was given. The modelling results show the rapid condensational growth of aerosol particles, especially for fine size particles, in the nozzle stream, which, on the one hand, may induce evident `over-sizing' and `over-numbering' effects in aerosol measurements as nozzle designs are widely employed for producing accelerating and focused aerosol beams in aerosol instruments like optical particle counter (OPC) and aerodynamical particle sizer (APS). It can, on the other hand, be applied in constructing the Nozzle-CNC. Thirdly, based on the optimisation of theoretical and numerical results, the new Nozzle-CNC was built. Under various experimental conditions such as flow rate, ambient temperature, and the fraction of aerosol in the total flow, experiments with this instrument were carried out. An interesting exponential relation between the saturation in the nozzle and the number concentration of atmospheric nuclei, including hygroscopic nuclei (HN), cloud condensation nuclei (CCN), and traditionally measured atmospheric condensation nuclei (CN), was found. This relation differs from the relation for the number concentration of CCN obtained by other researchers. The minimum detectable size of this Nozzle-CNC is 0.04?m. Although further improvements are still needed, this Nozzle-CNC, in comparison with other CNCs, has severaladvantages such as no condensation delay as particles larger than the critical size grow simultaneously, low diffusion losses of particles, little water condensation at the inner wall of the instrument, and adjustable saturation --- therefore the wide counting region, as well as no calibration compared to non-water condensation substances.

Atmospheric heterogeneous reactions of N 2 O 5 and NO 3 radicals with mineral dust particles

Die heterogenen Reaktionen von N2O5 bzw. NO3 auf mineralischen Staubpartikeln wurden untersucht, um deren Einfluss auf den Abbau atmosphärischer Stickoxide (NOx) sowie auf die chemische Veränderung der Staubpartikel während ihres Transportes durch die Atmosphäre besser verstehen zu können. Die experimentellen Studien wurden bei Atmosphärendruck, Raumtemperatur und unterschiedlichen relativen Luftfeuchten durchgeführt. Der Aufnahmekoeffizient γ(N2O5) von N2O5 auf dispergiertem Staub aus der Sahara wurde zu 0,020 ± 0,002 (1σ) bestimmt, unabhängig von der relativen Feuchte (0 - 67 %) sowie der N2O5-Konzentration (5x1011 - 3x1013 Moleküle cm-3).rnDie Analyse der Reaktionsprodukte in der Gasphase sowie auf der Partikeloberfläche führt zu der Annahme, dass N2O5 auf der Staubpartikeloberfläche zu Nitrat hydrolysiert wird. Es konnte kein Einfluss der relativen Feuchte auf den Aufnahmekoeffizienten ermittelt werden, was durch das vorhandene interlamellare Wasser, welches bis zu 10 % der Partikelmasse betragen kann, erklärbar ist. Der gemessene Wert des Aufnahmekoeffizienten ist unabhängig von der Eingangs-N2O5-Konzentration, was sich über die sehr große innere Oberfläche der Partikel erklären lässt. Dennoch ließ sich durch eine vorherige Konditionierung der Partikel mit gasförmigem HNO3, was eine Nitratanreicherung an der Oberfläche bewirkt, die Effizienz der N2O5-Aufnahme auf die Staubpartikel reduzieren. Zusätzliche Studien befassten sich mit der Bestimmung des Aufnahmekoeffizienten von N2O5 auf Illit-Partikeln und auf Teststaub aus Arizona. Bei einer relativen Luftfeuchte von 0 % wurden für γ(N2O5) Werte von 0,084 ± 0,019 (1σ) für Illit und von 0,010 ± 0,001 (1σ) für Arizona Teststaub ermittelt.rnUnter Anwendung einer neuartigen Messmethode, die auf der zeitgleichen Messung der Konzentrationsabnahme von NO3 und N2O5 relativ zueinander beruht, wurde das Verhältnis γ(NO3)/γ(N2O5) der Aufnahmekoeffizienten von NO3 und N2O5 auf Saharastaub zu 0,9 ± 0,4 (1σ) bestimmt. Dieser Wert war unabhängig von der relativen Feuchte, den NO3- und N2O5-Konzentrationen sowie der Reaktionszeit, obwohl eine Oberflächendeaktivierung für beide Spurenstoffe beobachtet wurde.

Hygroscopic growth of atmospheric aerosol particles based on active remote sensing and radiosounding measurements: selected cases in southeastern Spain

A new methodology based on combining active and passive remote sensing and simultaneous and collocated radiosounding data to study the aerosol hygroscopic growth effects on the particle optical and microphysical properties is presented. The identification of hygroscopic growth situations combines the analysis of multispectral aerosol particle backscatter coefficient and particle linear depolarization ratio with thermodynamic profiling of the atmospheric column. We analyzed the hygroscopic growth effects on aerosol properties, namely the aerosol particle backscatter coefficient and the volume concentration profiles, using data gathered at Granada EARLINET station. Two study cases, corresponding to different aerosol loads and different aerosol types, are used for illustrating the potential of this methodology. Values of the aerosol particle backscatter coefficient enhancement factors range from 2.1 ± 0.8 to 3.9 ± 1.5, in the ranges of relative humidity 60–90 and 40–83%, being similar to those previously reported in the literature. Differences in the enhancement factor are directly linked to the composition of the atmospheric aerosol. The largest value of the aerosol particle backscatter coefficient enhancement factor corresponds to the presence of sulphate and marine particles that are more affected by hygroscopic growth. On the contrary, the lowest value of the enhancement factor corresponds to an aerosol mixture containing sulphates and slight traces of mineral dust. The Hänel parameterization is applied to these case studies, obtaining results within the range of values reported in previous studies, with values of the γ exponent of 0.56 ± 0.01 (for anthropogenic particles slightly influenced by mineral dust) and 1.07 ± 0.01 (for the situation dominated by anthropogenic particles), showing the convenience of this remote sensing approach for the study of hygroscopic effects of the atmospheric aerosol under ambient unperturbed conditions. For the first time, the retrieval of the volume concentration profiles for these cases using the Lidar Radiometer Inversion Code (LIRIC) allows us to analyze the aerosol hygroscopic growth effects on aerosol volume concentration, observing a stronger increase of the fine mode volume concentration with increasing relative humidity.