Pavel Mikuška

Influence of sampling artefacts on measured PM, OC, and EC levels in Carbonaceous aerosols in an urban area

Sampling of particulate matter (PM) with filter media is subject to the influence of positive and negative artefacts. The complexity of these measurements derives from the use of different instrumentation, face velocities, and filter types. Carbonaceous compounds are one of the main PM chemical components affected by these artefacts. In this study, two main types of artefacts were evaluated at an urban site in Ghent (Belgium) during the summer period: those related to the sampling procedure (high- or low-volume samplers) and those related to the adsorption and/or volatilization of carbonaceous species. For their measurement, two high-volume (PM10 and PM2.5) samplers with single quartz fiber filters and two low-volume PM2.5 samplers (one of them coupled to an annular diffusion denuder) with double quartz fiber filters (front and backup) were used. PM2.5 mass concentrations measured by means of the low-volume sampler (front filter) were, on average, 31% higher than those registered with the high-volume sampler. PM2.5 mass concentrations registered with the low-volume sampler coupled to the diffusion denuder represented 88% of the PM2.5 mass collected with the undenuded low-volume sampler. Similar values for organic carbon (OC) were recorded for the high- and low-volume samplers. Front filter OC levels for the denuded samples represented 66% of the front filter OC mass on the undenuded samples. Using the backup filter OC data to apply a correction to the front filter data as suggested by Mader et al. (2003) only marginally reduced the discrepancy between the undenuded and denuded OC data, indicating that such correction does not result in consistent OC data for an urban area in Western Europe during summer.

Ozone flux over a Norway spruce forest and correlation with net ecosystem production.

Daily ozone deposition flux to a Norway spruce forest in Czech Republic was measured using the gradient method in July and August 2008. Results were in good agreement with a deposition flux model. The mean daily stomatal uptake of ozone was around 47% of total deposition. Average deposition velocity was 0.39 cm s(-1) and 0.36 cm s(-1) by the gradient method and the deposition model, respectively. Measured and modelled non-stomatal uptake was around 0.2 cm s(-1). In addition, net ecosystem production (NEP) was measured by using Eddy Covariance and correlations with O3 concentrations at 15 m a.g.l., total deposition and stomatal uptake were tested. Total deposition and stomatal uptake of ozone significantly decreased NEP, especially by high intensities of solar radiation.

Flow-injection chemiluminescence determination of formaldehyde in water.

A modification of the Trautz-Schorigin reaction into a flow-injection analysis configuration is described. Different approaches were used at the optimization of chemiluminescence determination of formaldehyde in water based on the reaction of formaldehyde, gallic acid and hydrogen peroxide in an alkaline solution. Detection system with a 218microl chemiluminescence cell was optimized by both a one-variable-at-a-time method, and a modified simplex method. A calibration graph is linear in the concentration range 4x10(-8) to 1x10(-5)M HCHO. The detection limit of formaldehyde for a signal-to-noise ratio of 3 is 4x10(-8)M. The relative standard deviations for 15 repeated measurements of 1x10(-6) and 5x10(-6)mol l(-1) HCHO are 4.32 and 3.33%, respectively. The analysis time is 1.5min. The method was applied to the determination of formaldehyde in urban rainwater. A comparison of results found by proposed method with those obtained by fluorimetric reference method provided a good agreement.

Study of aerosols generated by 213 nm laser ablation of cobalt-cemented hard metals

Cobalt-cemented hard metals present an example of samples with a complicated matrix consisting of components differing in chemical and physical properties and with extremely low volatility of all components. The purpose of this study was to compare particle formation of a set of real samples with similar matrices but different content of major components. The laser ablation process was studied using a Q-switched quintupled (213 nm) nanosecond Nd:YAG laser. Five samples of Co-cemented tungsten carbides, actually WC-TiC-(Ta,Nb)C-Co with a varied content of main constituents, were selected as representatives of a family of 15 miscellaneous tungsten carbide hard metal products. Physical and chemical properties vary over this specimen selection and therefore the effect on particle size formation and distribution was expected. The size distributions by number of ablated particles in different size ranges were measured using an optical aerosol spectrometer. The results proved the relationship between particle formation and sample composition. The structure of laser generated particles and the properties of ablation-craters were additionally studied by scanning electron microscopy (SEM). Spherical particles in the diameter range of 0.25–2 μm and μm-sized agglomerates composed of primary nano-particles were observed. The W and Co content in the aerosol particles was determined by energy dispersive X-ray spectroscopy (EDS). The volumes of ablation craters were measured by an optical profilometer. The laser ablation study of selected Co-cemented tungsten carbide hard metals indicates a similar total volume of formed particles with composition-dependent particle-size distributions.

Annular diffusion denuder for simultaneous removal of gaseous organic compounds and air oxidants during sampling of carbonaceous aerosols

A specially designed annular diffusion denuder for simultaneous removal of organic gaseous compounds and atmospheric oxidants in carbonaceous aerosol sampling is presented. Various kinds of denuder coatings were compared with respect to the collection efficiency of both organic gaseous compounds and NO(2) and ozone. The optimum sorbent is a mixture of activated charcoal and sulfite on molecular sieve. To ensure high collection efficiency over long-term field operation, two annular diffusion denuders are combined in series. The first half of the first denuder is filled with Na(2)SO(3) on molecular sieve (23 cm long layer) while the second half of the first denuder and the whole second denuder are filled with activated charcoal (the total length of the charcoal section is 67 cm). At a flow rate of 16.6 L min(-1), the collection efficiency of organic gaseous compounds and atmospheric oxidants in the annular diffusion denuder is better than 95%. Only small losses of aerosol particles (<3.6% in number concentration) were observed in the size range 0.12-2.26 μm. The annular diffusion denuder is compatible with the collection of aerosols on 47-mm diameter quartz fiber filters at a flow rate of 16.6 L min(-1). The use of this denuder enables one to sample carbonaceous aerosols on filters without positive sampling artefacts from volatile organic compounds and interferences from atmospheric oxidants. The annular diffusion denuder has been applied successfully for the sampling of carbonaceous aerosols during field campaigns of typically 1 month each at urban and forested sites in Europe.

A portable device for fast analysis of explosives in the environment

A novel portable device for fast and sensitive analysis of explosives in environmental samples is presented. The developed system consists of miniaturized microcolumn liquid chromatograph, photolytic converter and chemiluminescence detector. The device is able to determine selectively nitramine- and nitroester- and most of nitroaromates-based explosives as well as inorganic nitrates at trace concentrations in water or soil extracts in less than 8 min. The device allows to analyze various environmental samples such as soils or water materials without previous preconcentration. Because of internal power supply, the device ensures 12h of continuous operation. Limits of detection of compounds of interest are in the range of concentrations from 5.0 × 10(-9)M to 8.0 × 10(-5)M for a signal-to-noise ratio of 3. Limits of quantification are in the range of concentrations from 1.7 × 10(-8)M to 2.7 × 10(-4)M for a signal-to-noise ratio of 10. The repeatability of the method (RSD=2.9-5.6%) was determined by repeated injections (n=10) of the standard samples during 4h.

Inhaled Cadmium Oxide Nanoparticles: Their in Vivo Fate and Effect on Target Organs

The increasing amount of heavy metals used in manufacturing equivalently increases hazards of environmental pollution by industrial products such as cadmium oxide (CdO) nanoparticles. Here, we aimed to unravel the CdO nanoparticle destiny upon their entry into lungs by inhalations, with the main focus on the ultrastructural changes that the nanoparticles may cause to tissues of the primary and secondary target organs. We indeed found the CdO nanoparticles to be transported from the lungs into secondary target organs by blood. In lungs, inhaled CdO nanoparticles caused significant alterations in parenchyma tissue including hyperemia, enlarged pulmonary septa, congested capillaries, alveolar emphysema and small areas of atelectasis. Nanoparticles were observed in the cytoplasm of cells lining bronchioles, in the alveolar spaces as well as inside the membranous pneumocytes and in phagosomes of lung macrophages. Nanoparticles even penetrated through the membrane into some organelles including mitochondria and they also accumulated in the cytoplasmic vesicles. In livers, inhalation caused periportal inflammation and local hepatic necrosis. Only minor changes such as diffusely thickened filtration membrane with intramembranous electron dense deposits were observed in kidney. Taken together, inhaled CdO nanoparticles not only accumulated in lungs but they were also transported to other organs causing serious damage at tissue as well as cellular level.

Elemental mapping of structural materials for a nuclear reactor by means of LA-ICP-MS

Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) was applied to the study of the interaction of molten LiF–NaF salts with candidate structural materials for a nuclear reactor-transmutor cooling circuit. At a working temperature of 680 °C structural materials of heat exchangers are attacked and the melt–alloy interaction provokes microstructural and composition changes of the contact surface. The resulting corrosion-influenced zones were studied by LA-ICP-MS and the maps of elemental distribution were created on the semiquantitative level using the procedure based on the normalization of particular isotopic signals to the sum of signals of all isotopes present in the examined zone. Consequently, LA-ICP-MS signals were measured for structural material constituents (Ni, Cr, Fe, W, Mo, Ti, and Mn) and for cationic constituents of the cooling medium (Li and Na). The hypothetical fluorine signal was calculated as a sum of Li and Na signals. Corrosion products in the exposed cooling medium were determined by ICP-OES after dissolution. Of the three examined candidate structural materials (pure nickel, nickel-based alloy A071EV and nickel-coated iron) pure nickel exhibits the best resistance.

Photo-induced flow-injection determination of nitrate in water

A sensitive flow-injection method for the chemiluminescent determination of ultra-low concentration of nitrate in water is presented. Nitrate is on-line photolytically converted to peroxynitrite by absorption of UV light inside of 60 mm long quartz capillary (i.d. 530 µm, o.d. 720 µm). Peroxynitrite is subsequently determined by the chemiluminescent reaction with luminol. The detection limit of nitrate is 7 × 10−10 M (S/N = 3). The linear range of the method is 2 × 10−9–1 × 10−5 M nitrate. The interference of nitrite is eliminated by its conversion to nitrogen after mixing of sample with a solution of sulfamidic acid. Other common anions do not interfere. The interference of cations is eliminated by passing the sample through a cation-exchange column. The FIA procedure allows analysing of 15 samples per hour. The method was applied to the determination of nitrate in various real water samples. The results are in good agreement with a reference ion chromatographic method.

Tungsten carbide precursors as an example for influence of a binder on the particle formation in the nanosecond laser ablation of powdered materials

A study of LA-ICP-MS analysis of pressed powdered tungsten carbide precursors was performed to show the advantages and problems of nanosecond laser ablation of matrix-unified samples. Five samples with different compositions were pressed into pellets both with silver powder as a binder serving to keep the matrix unified, and without any binder. The laser ablation was performed by nanosecond Nd:YAG laser working at 213 nm. The particle formation during ablation of both sets of pellets was studied using an optical aerosol spectrometer allowing the measurement of particle concentration in two size ranges (10-250 nm and 0.25-17 microm) and particle size distribution in the range of 0.25-17 microm. Additionally, the structure of the laser-generated particles was studied after their collection on a filter using a scanning electron microscope (SEM) and the particle chemical composition was determined by an energy dispersive X-ray spectroscope (EDS). The matrix effect was proved to be reduced using the same silver powdered binder for pellet preparation in the case of the laser ablation of powdered materials. The LA-ICP-MS signal dependence on the element content present in the material showed an improved correlation for Co, Ti, Ta and Nb of the matrix-unified samples compared to the non-matrix-unified pellets. In the case of W, the ICP-MS signal of matrix-unified pellets was influenced by the changes in the particle formation.