Petr Vodička

Detailed comparison of OC/EC aerosol at an urban and a rural Czech background site during summer and winter

Winter and summer measurements of organic carbon and elemental carbon (OC and EC) in PM2.5 were performed in parallel at two sites, the rural background station Košetice and the Prague-Suchdol urban background site, with a 2-h time resolution using semi-online field OC/EC analysers. Seasonal and site differences were found in the OC and EC contents of PM2.5. Overall, the highest concentrations of both OC and EC were during winter at the urban site. The average urban impact was 50% for OC and 70% for EC. The summer season gives similar concentrations of OC at both sites. However, higher concentrations of EC, caused by higher traffic, were found at the urban site with an average urban increase of 50%. Moreover, an analysis of four OC fractions depending on the volatility (OC1 - most volatile, OC4 - least volatile) and pyrolytic carbon (PC) is provided. A similar level of each OC fraction at both sites was found in summer, except for higher OC1 at urban and higher PC at the rural site. In winter, the differences between the urban and rural sites were dominated by a large increase of the OC1 fraction in comparison with the rural site. A diurnal pattern of concentration and share of OC1 and PC suggests a prevailing influence of local sources on their concentrations at the urban site in winter. The OC3 and OC4 diurnal cycles suggest their more regional or long range transport origin in both seasons. The prevalent influence of OC1 at any urban site has not been previously reported. The minimisation of semi-volatile carbon losses during semi-continuous sampling and analysis, in comparison with off-line sampling methods, is a probable reason for the observed differences.

The effect of dust particles on cellulose degradation

This study focuses on the changes in properties of cellulose-based paper, which can take place as a consequence of its contamination by dust particles. The PM1 (fine) and PM10 (coarse) fractions of the dust particles from archival repositories were collected on cellulose filters Whatman 41, polytetrafluorethylene, and quartz filters. The latter two types of samples were subsequently analyzed gravimetrically, with ion chromatography, PIXE, and the thermal–optical transmission method, giving mass, ionic, elemental carbon, and organic carbon concentrations. After artificial aging, the viscosity-average degree of polymerization of cellulose (DPv) was measured. It was confirmed that cellulose-based paper can undergo substantial changes when contaminated by dust particles and artificially aged. The decrease of the DPv of cellulose showed a negative correlation with the deposited mass of sulfate ions in the dust particles. Considering the particle size fraction, the results suggest the decisive importance of the fine (PM1) particles. The results provide better understanding of how particulate matter contributes to the chemical degradation of cellulose-based paper. Such knowledge is of importance when considering appropriate conservation measures in archives, libraries, and galleries.

Lead and/or Lead Oxide Nanoparticle Generation for Inhalation Experiments

A method of the continual generation of lead or lead oxide nanoparticles for potential subsequent inhalation experiments with laboratory animals was investigated. We examined the thermal decomposition and oxidation of lead bis(2,2,6,6-tetramethyl-3,5-heptanedionate) in an externally heated tube reactor as well as the evaporation and condensation of metallic lead. The particle production dependence on experimental conditions was investigated using a scanning mobility particle sizer (SMPS), and the particle characteristics were studied using transmission electron microscopy (TEM), high-resolution TEM (HRTEM), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), atomic absorption spectroscopy (AAS), elemental and organic carbon analysis (EC/OC), X-ray photoelectron spectrometry (XPS), and X-ray diffraction (XRD) methods. The evaporation/condensation was evaluated as being the most suitable for inhalation experiments due to its simplicity, high production rate, and the well-defined composition of the nanoparticles. Copyright 2015 American Association for Aerosol Research

Structural and Light-Absorption Characteristics of Complex Water-Insoluble Organic Mixtures in Urban Submicrometer Aerosols

Submicrometer aerosols in the urban atmosphere of Nagoya, Japan, were collected in late winter and early spring, and the water-insoluble organic matter (WISOM) in the samples were fractionated into six subfractions based on their polarities by using solvent and normal-phase solid-phase extractions: nonpolar (F1), low-polar (F2 and F3), and medium-polar (F4, F5, and F6) fractions. The overall structural characteristics of these subfractions were then analyzed using Fourier transform infrared spectroscopy, nuclear magnetic resonance spectroscopy, and high-resolution aerosol mass spectrometry. Quantitative information related to the overall chemical characteristics of the WISOM in the different polarity fractions, including their elemental compositions, the relative abundances of different functional groups and their fragments from electron impact ionization, was obtained. These water-insoluble fractions accounted for half of the total light absorption by the extracted aerosol matter at 400 nm. The contributions of the medium-polar fractions to both the total organic carbon and light absorption by the extracts were dominant among the contributions from the six subfractions. Large molecules with aromatic and heteroatomic (O and N) groups, including charge transfer complexes, might have greatly contributed to the light absorption by the fraction F4, which is the largest fraction of the extracted water-insoluble organic matter.

On the use of the field Sunset semi-continuous analyzer to measure equivalent black carbon concentrations

ABSTRACT This study describes a method to calculate equivalent black carbon (EBC) concentrations comparable to those obtained from optical filter-based EBC instrumentation from data obtained with a semi-continuous thermo-optical analyzer (Sunset Laboratory Inc., USA) without any need of instrument alterations or extra costs. A correction for the reflection of the Sunset analyzer laser beam by the walls of the sampling tube is introduced. EBCSunset concentrations obtained during two intensive campaigns in Prague (one in winter and one in summer) were compared also to EBC measured by an AE31 Aethalometer (EBCaeth), an AE51 MicroAethalometer (EBCmicro), and a Multi Angle Absorption Photometer (EBCMAAP). Good agreement was observed in both campaigns. The EBCSunset data were also corrected for loading effects in two ways—a simple loading correction and a total correction using data also from the MAAP and a nephelometer. The loading corrections gave similar results for EBCSunset and the aethalometer data except for the simple correction for summer EBCSunset data. The multiple scattering correction factors computed for EBCSunset agreed well with those calculated for EBCaeth. The wall reflection correction for the Sunset analyzer data further improves the agreement between EBCSunset and EBCMAAP. Copyright

Seasonal study of stable carbon and nitrogen isotopic composition in fine aerosols at a Central European rural background station

A study of the stable carbon isotope ratios (δ13C) of total carbon (TC) and the nitrogen isotope ratios (δ15N) of total nitrogen (TN) was carried out for fine aerosol particles (PM1) and was undertaken every 2 days with a 24 h sampling period at a rural background site in Košetice (Central Europe) from 27 September 2013 to 9 August 2014 (n= 146). We found a seasonal pattern for both δ13C and δ15N. The seasonal variation in δ15N was characterized by lower values (average of 13.1± 4.5 ‰) in winter and higher values (25.0±1.6 ‰) in summer. Autumn and spring were transition periods when the isotopic composition gradually changed due to the changing sources and ambient temperature. The seasonal variation in δ13C was less pronounced but more depleted in 13C in summer (−27.8± 0.4 ‰) as compared to winter (−26.7± 0.5 ‰). A comparative analysis with water-soluble ions, organic carbon, elemental carbon, trace gases and meteorological parameters (mainly ambient temperature) has shown major associations with the isotopic compositions, which has provided greater knowledge and understanding of the corresponding processes. A comparison of δ15N with NO−3 , NH + 4 and organic nitrogen (OrgN) revealed that although a higher content of NO−3 was associated with a decrease in the δ 15N of TN, NH+4 and OrgN caused increases. The highest concentrations of nitrate, mainly represented by NH4NO3 related to the emissions from biomass burning leading to an average δ15N of TN (13.3 ‰) in winter. During spring, the percentage of NO−3 in PM1 decreased. An enrichment of 15N was probably driven by the equilibrium exchange between the gas and aerosol phases (NH3(g)↔NH+4 (p)), which is supported by the increased ambient temperature. This equilibrium was suppressed in early summer when the molar ratios of NH+4 /SO 2− 4 reached 2, and the nitrate partitioning in aerosol was negligible due to the increased ambient temperature. Summertime δ15N values were among the highest, suggesting the aging of ammonium sulfate and OrgN aerosols. Such aged aerosols can be coated by organics in which 13C enrichment takes place by the photooxidation process. This result was supported by a positive correlation of δ13C with ambient temperature and ozone, as observed in the summer season. During winter, we observed an event with the lowest δ15N and highest δ13C values. The winter event occurred in prevailing southeast air masses. Although the higher δ13C values probably originated from biomass-burning particles, the lowest δ15N values were probably associated with agriculture emissions of NH3 under low-temperature conditions (< 0 C).

Single Usage of a Kitchen Degreaser Can Alter Indoor Aerosol Composition for Days

To the best of our knowledge, this study represents the first observation of multiday persistence of an indoor aerosol transformation linked to a kitchen degreaser containing monoethanol amine (MEA). MEA remaining on the cleaned surfaces and on a wiping paper towel in a trash can was able to transform ammonium sulfate and ammonium nitrate into (MEA)2SO4 and (MEA)NO3. This influence persisted for at least 60 h despite a high average ventilation rate. The influence was observed using both offline (filters, impactors, and ion chromatography analysis) and online (compact time-of-flight aerosol mass spectrometer) techniques. Substitution of ammonia in ammonium salts was observed not only in aerosol but also in particles deposited on a filter before the release of MEA. The similar influence of other amines is expected based on literature data. This influence represents a new pathway for MEA exposure of people in an indoor environment. The stabilizing effect on indoor nitrate also causes higher indoor exposure to fine nitrates.