Respiratory exposure of humans to environmental and therapeutic nanoparticles repeatedly occurs at relatively low concentrations. To identify adverse effects of particle accumulation under realistic conditions, monocultures of Calu-3 and A549 cells and co-cultures of A549 and THP-1 macrophages in the air–liquid interphase culture were exposed repeatedly to 2 µg/cm2 20 nm and 200 nm polystyrene particles with different functionalization. Particle accumulation, transepithelial electrical resistance, dextran (3–70 kDa) uptake and proinflammatory cytokine secretion were determined over 28 days. Calu-3 cells showed constant particle uptake without any change in barrier function and cytokine release. A549 cells preferentially ingested amino- and not-functionalized particles combined with decreased endocytosis. Cytokine release was transiently increased upon exposure to all particles. Carboxyl-functionalized demonstrated higher uptake and higher cytokine release than the other particles in the A549/THP-1 co-cultures. The evaluated respiratory cells and co-cultures ingested different amounts and types of particles and caused small (partly transient) effects. The data suggest that the healthy cells can adapt to low doses of non-cytotoxic particles.

In early 2017 high particulate matter (PM) levels were observed across mid-Europe, including Austria. Here we characterize PM pollution in the city of Graz during January to March 2017, a period with substantial exceedances (34 days) of the European Union (EU) PM10 short time limit value. This study evaluates whether the observed exceedances can be attributed to the accumulation of pollutants emitted by local sources or to a larger scale pollution episode including transport. The analyses are based on the ratios of PM10 concentrations determined at an urban and background site, and the analyses of chemical composition of PM2.5 samples (i.e., water soluble ions, organic and elemental carbon, anhydro-sugars, humic-like substances, aluminum, and polycyclic aromatic hydrocarbons). Source apportionment was realized using a macro-tracer model. Overall, the combination of different approaches (PM10 ratios, chemical composition, and macro-tracer derived source apportionment) enabled a conclusive identification of time periods characterized by the accumulation of emissions from local sources or regional pollution episodes.

In the complex situation with the plurality of emissions, the important research task of assessing the air quality and potential sources through aerosol composition analyses remains for Moscow's megacity environment. The light absorption, PM 10 mass concentration, aerosol composition, and meteorological parameters in this urban background were measured during spring 2017, a period characterized by significant changes in the air temperature, mass advection, and solar radiation. The organic and elemental carbon (OC and EC) and 76 organic compounds, e.g., alkanes, polycyclic aromatic hydrocarbons (PAHs), oxidized PAHs, hopanes, anhydrosugars, polyols, primary and secondary saccharides, and HULIS, as well as 13 ions, including K + , a marker of biomass burning, have been quantified to determine the carbonaceous and inorganic chemical profiles of the aerosol. The correlation between the absorption Ångström exponent (AAE) and the levoglucosan concentration reveals the relative contributions of agricultural fires and residential biomass burning (BB) nearby to the urban aerosol composition. Combining detailed analytical and statistical approaches, we have identified and analyzed the specific chemical compounds that most accurately represent the variability of the aerosol composition. Principal component analysis (PCA) highlights the main factors for marker species related to gasoline/diesel traffic, BB, biogenic activity, and secondary formation in the atmosphere. Distinguishing the BB-affected periods allows us to evaluate daily changes in the aerosol composition in relation to the transported air masses and detected fires in the areas surrounding Moscow.

Abstract. Thermal–optical measurement techniques are widely used for the monitoring of carbonaceous aerosols. Although results of different thermal–optical measurement techniques are comparable for total carbon, they can vary widely for values of elemental carbon especially in the presence of brown carbon. Charring of organic material during the inert heating phase of thermal–optical measurements has been found to be a major confounder, but no literature about investigations of structural changes during this process in atmospheric aerosols is available. In a recent study we investigated these structural changes for combustion aerosol standard (CAST) soot. Now we apply this approach to selected atmospheric aerosol filter samples and a subset of eight washed filter samples with low loadings of water-soluble organic carbon (WSOC). To investigate structural changes, Raman spectra were obtained for samples heated to the corresponding temperature levels and gas atmospheres of the EUSAAR2 and NIOSH870 protocols. The temperature levels where changes in the Raman spectra occurred (i.e., changes in structure) varied for different samples. For the washed samples with low WSOC loadings and absence of other water-soluble aerosol components such as inorganic salts, changes in structural ordering and darkening of the samples were not observed. We were able to show for the first time that the darkening of a sample (measured in terms of transmission laser signal) is not necessarily caused by an increase of structural ordering in the sample. Possible transformations at lower temperatures could include a formation of non-graphitic light-absorbing intermediate organic carbon, a release of C−H groups or a decrease of carbonyl groups.

<p>Elemental Carbon (EC), Black Carbon (BC) and Organic Carbon (OC) contribute a large amount to atmospheric aerosols. Due to their significant influence on climate and health, a reliable measurement of these components is essential. Nevertheless, their correct determination is not trivial and results of different measurement techniques show differences by factors up to nine especially in the presence of Brown Carbon (BrC) (e.g. Reisinger et al., 2008; Hitzenberger et al., 2006; Wonaschuetz et al., 2009). EC and OC are usually measured with thermal-optical techniques: The sample is heated stepwise, first in an inert (He) atmosphere, then in an oxidizing (He+O<sub>2</sub>) atmosphere. The darkening of the sample during the heating procedure is traced with a laser transmission/reflection signal. Based on the progress of this signal, the amount of pyrolyzed carbon is calculated and attributed to OC in the subsequent evaluation. Despite this optical correction, the pyrolyzation of OC can lead to uncertainties in the OC/EC split (Cheng et al., 2012). Especially Brown Carbon (BrC) and water soluble organic carbons (WSOC) have a high tendency to pyrolyze and therefore bias the OC/EC split. Moreover several metal salts in the atmospheric aerosol can influence the measurement process and enhance or suppress pyrolysis of OC (Wang et al., 2010). These highly complex chemical and physical reactions are not fully investigated yet but are essential for a profound understanding of the biases in thermal-optical measurement techniques. </p><p>The aim of the present study was to investigate the structural reorganizations of the carbonaceous materials in atmospheric aerosol samples occurring during a thermal-optical heating procedure (EUSAAR2, Cavalli et al., 2010) and to set them in relation with several properties of the samples such as ionic composition, EC, OC, BC and BrC, as well as the air mass origins during sampling of the atmospheric aerosol samples. <br>The changes of the internal structure of the material during the heating procedure of an EC/OC analyzer (Sunset instruments) were analyzed with Raman spectroscopy, which is sensitive to C-C bonding types and to the degree of structural ordering within the sample (Ferrari and Robertson, 2000). Different types of restructuration behavior were defined depending on the temperature levels of the EUSAAR2 protocol where measurable structural changes occur. For all samples ion chromatography was performed with a Dionex Aquion system (Thermo Fisher), BrC and BC were analyzed with the Integrating Sphere method (Wonaschütz et al., 2009) and air mass back trajectories for the respective sampling days were calculated with HYSPLIT.</p>