U. Dusek

Bio: U. Dusek is an academic researcher. The author has contributed to research in topics: Particulates & Aerosol. The author has an hindex of 1, co-authored 1 publications receiving 20 citations.

Secondary Organic Aerosol - Formation Mechanisms and Source Contributions in Europe

Abstract: Fine particulate matter (PM2.5) as an atmospheric pollutant is strongly related to increased mortality and morbidity. The empirically established link between aerosol concentration and human health compels increased efforts to reduce the atmospheric concentrations of fine particles. Organic material accounts for about 20-60% of the total PM2.5 and contains substances of known toxicity. It has been shown that in some areas secondary organic aerosol (SOA) accounts for 20% of the total organic aerosol throughout the year but can contribute up to 70% in smog episodes. The estimation of the sources and concentrations of organic aerosol is therefore crucial to the proper assessment of related health effects Part of this work attempts a critical review of the literature on SOA. The goal is to describe formation mechanisms, to identify likely precursor gases, and to estimate the SOA contribution to PM2.5. SOA forms by oxidation of volatile organic compounds (VOC). The aerosol yield varies significantly among different VOC species as well as source sectors and the contribution of SOA to the total particulate organic material is dependent on the time of the day and the season. The consequences of these findings for reduction strategies are discussed. The knowledge gained in the literature review is further used to exemplify a possible procedure to assess and compare the aerosol formation potential of some source sectors used in the RAINS model. It is found that traffic and solvent use in the printing industry and paint are important sectors for SOA production.

Blood pressure changes and chemical constituents of particulate air pollution: results from the healthy volunteer natural relocation (HVNR) study.

Abstract: Background: Elevated blood pressure (BP) has been associated with particulate matter (PM) air pollution, but associations with PM chemical constituents are still uncertain. Objectives: We investigated associations of BP with various chemical constituents of fine PM (PM2.5) during 460 repeated visits among a panel of 39 university students. Methods: Resting BP was measured using standardized methods before and after the university students relocated from a suburban campus to an urban campus with different air pollution contents in Beijing, China. Air pollution data were obtained from central monitors close to student residences. We used mixed-effects models to estimate associations of various PM2.5 constituents with systolic BP (SBP), diastolic BP (DBP), and pulse pressure. Results: An interquartile range increase of 51.2 μg/m3 in PM2.5 was associated with a 1.08-mmHg (95% CI: 0.17, 1.99) increase in SBP and a 0.96-mmHg (95% CI: 0.31, 1.61) increase in DBP on the following day. A subset of PM2.5 constituents, including carbonaceous fractions (organic carbon and elemental carbon), ions (chloride and fluoride), and metals/metalloid elements (nickel, zinc, magnesium, lead, and arsenic), were found to have robust positive associations with different BP variables, though robust negative associations of manganese, chromium, and molybdenum with SBP or DBP also were observed. Conclusions: Our results support relationships between specific PM2.5 constituents and BP. These findings have potential implications for the development of pollution abatement strategies that maximize public health benefits.

Chemical constituents of ambient particulate air pollution and biomarkers of inflammation, coagulation and homocysteine in healthy adults: a prospective panel study.

Abstract: Ambient air pollution has been associated with activation of systemic inflammation and hypercoagulability and increased plasma homocysteine, but the chemical constituents behind the association are not well understood. We examined the relations of various chemical constituents of fine particles (PM2.5) and biomarkers of inflammation, coagulation and homocysteine in the context of traffic-related air pollution. A panel of 40 healthy college students underwent biweekly blood collection for 12 times before and after their relocation from a suburban campus to an urban campus with changing air pollution contents in Beijing. Blood samples were measured for circulatory biomarkers of high-sensitivity C reactive protein (hs-CRP), tumor necrosis factor alpha (TNF-α), fibrinogen, plasminogen activator inhibitor type 1 (PAI-1), tissue-type plasminogen activator (t-PA), von Willebrand factor (vWF), soluble platelet selectin (sP-selectin), and total homocysteine (tHcy). Various air pollutants were measured in a central air-monitoring station in each campus and 32 PM2.5 chemical constituents were determined in the laboratory. We used three different mixed-effects models (single-constituent model, constituent-PM2.5 joint model and constituent residual model) controlling for potential confounders to estimate the effects of PM2.5 chemical constituents on circulatory biomarkers. We found consistent positive associations between the following biomarkers and PM2.5 chemical constituents across different models: TNF-α with secondary organic carbon, chloride, zinc, molybdenum and stannum; fibrinogen with magnesium, iron, titanium, cobalt and cadmium; PAI-1 with titanium, cobalt and manganese; t-PA with cadmium and selenium; vWF with aluminum. We also found consistent inverse associations of vWF with nitrate, chloride and sodium, and sP-selectin with manganese. Two positive associations of zinc with TNF-α and of cobalt with fibrinogen, and two inverse associations of nitrate with vWF, and of manganese with sP-selectin, were independent of the other constituents in two-constituent models using constituent residual data. We only found weak air pollution effects on hs-CRP and tHcy. Our results provide clues for the potential roles that PM2.5 chemical constituents may play in the biological mechanisms through which air pollution may influence the cardiovascular system.

Review of Experimental and Computational Studies on Spray, Combustion, Performance, and Emission Characteristics of Biodiesel Fueled Engines

Abstract: Biodiesel has emerged as a suitable alternative to mineral diesel in compression ignition (CI) engines in order to ensure global energy security and to reduce engine out emissions in near future. Biodiesel derived from various feedstocks available worldwide fits well in the current fuel supply arrangement for transport sector. However, biodiesel as an alternative transportation fuel has been extensively investigated because of differences in its important fuel properties compared with baseline mineral diesel. Since fuel properties greatly influence spray development, combustion, and emission formation in internal combustion (IC) engines, a number of experimental and computational studies on biodiesel usage in CI engines have been performed to determine its brake thermal efficiency (BTE), gaseous emissions, durability, etc., by various researchers using variety of engines and feedstocks. In the present paper, a critical review of the effect of biodiesel's fuel properties on engine performance, emissions, and combustion characteristics in existing diesel engines vis-a-vis conventional diesel has been undertaken. In addition, the progress and advances of numerical modeling involving biodiesel are also reviewed to determine the effect of fuel properties on spray evolution and development of reaction mechanisms for biodiesel combustion simulations. Fuel properties are discussed in two categories: physical and chemical properties, which are key parameters affecting spray and combustion processes. Subsequent sections review spray, combustion, emissions, and performance characteristics of biodiesels under various engine operation conditions. In the last section of this review paper, numerical modeling of biodiesel covering recent numerical models and schemes to understand the behavior of biodiesel combustion and pollutants formation is included. This review paper comprehensively summarizes biodiesel fuel's (BDFs) spray, combustion, and emission characteristics using experimental and numerical approaches. Limitations and scope for future studies are discussed in each section.