Chemical and source characterisation of size-segregated urban air particulate matter

Recent epidemiological studies have shown a consistent association of the mass concentration of urban air thoracic (PM10) and fine (PM2.5) particles with mortality and morbidity among cardiorespiratory patients. However, the chemical characteristics of different particulate size ranges and the biological mechanisms responsible for these adverse health effects are not well known. The principal aims of this thesis were to validate a high volume cascade impactor (HVCI) for the collection of particulate matter for physicochemical and toxicological studies, and to make an in-depth chemical and source characterisation of samples collected during different pollution situations. The particulate samples were collected with the HVCI, virtual impactors and a Berner low pressure impactor in six European cities: Helsinki, Duisburg, Prague, Amsterdam, Barcelona and Athens. The samples were analysed for particle mass, common ions, total and water-soluble elements as well as elemental and organic carbon. Laboratory calibration and field comparisons indicated that the HVCI can provide a unique large capacity, high efficiency sampling of size-segregated aerosol particles. The cutoff sizes of the recommended HVCI configuration were 2.4, 0.9 and 0.2 μm. The HVCI mass concentrations were in a good agreement with the reference methods, but the chemical composition of especially the fine particulate samples showed some differences. This implies that the chemical characterization of the exposure variable in toxicological studies needs to be done from the same HVCI samples as used in cell and animal studies. The data from parallel, low volume reference samplers provide valuable additional information for chemical mass closure and source assessment. The major components of PM2.5 in the virtual impactor samples were carbonaceous compounds, secondary inorganic ions and sea salt, whereas those of coarse particles (PM2.5-10) were soil-derived compounds, carbonaceous compounds, sea salt and nitrate. The major and minor components together accounted for 77-106% and 77-96% of the gravimetrically-measured masses of fine and coarse particles, respectively. Relatively large differences between sampling campaigns were observed in the organic carbon content of the PM2.5 samples as well as the mineral composition of the PM2.5-10 samples. A source assessment based on chemical tracers suggested clear differences in the dominant sources (e.g. traffic, residential heating with solid fuels, metal industry plants, regional or long-range transport) between the sampling campaigns. In summary, the field campaigns exhibited different profiles with regard to particulate sources, size distribution and chemical composition, thus, providing a highly useful setup for toxicological studies on the size-segregated HVCI samples.

A quantum chemical investigation of the metal centres in cytochrome c oxidase

Quantum effects are often of key importance for the function of biological systems at molecular level. Cellular respiration, where energy is extracted from the reduction of molecular oxygen to water, is no exception. In this work, the end station of the electron transport chain in mitochondria, cytochrome c oxidase, is investigated using quantum chemical methodology. Cytochrome c oxidase contains two haems, haem a and haem a3. Haem a3, with its copper companion, CuB, is involved in the final reduction of oxygen into water. This binuclear centre receives the necessary electrons from haem a. Haem a, in turn, receives its electrons from a copper ion pair in the vicinity, called CuA. Density functional theory (DFT) has been used to clarify the charge and spin distributions of haem a, as well as changes in these during redox activity. Upon reduction, the added electron is shown to be evenly distributed over the entire haem structure, important for the accommodation of the prosthetic group within the protein. At the same time, the spin distribution of the open-shell oxidised state is more localised to the central iron. The exact spin density distribution has been disputed in the literature, however, different experiments indicating different distributions of the unpaired electron. The apparent contradiction is shown to be due to the false assumption of a unit amount of unpaired electron density; in fact, the oxidised state has about 1.3 unpaired electrons. The validity of the DFT results have been corroborated by wave function based coupled cluster calculations. Point charges, for use in classical force field based simulations, have been parameterised for the four metal centres, using a newly developed methodology. In the procedure, the subsystem for which point charges are to be obtained, is surrounded by an outer region, with the purpose of stabilising the inner region, both electronically and structurally. Finally, the possibility of vibrational promotion of the electron transfer step between haem a and a3 has been investigated. Calculating the full vibrational spectra, at DFT level, of a combined model of the two haems, revealed several normal modes that do shift electron density between the haems. The magnitude of the shift was found to be moderate, at most. The proposed mechanism could have an assisting role in the electron transfer, which still seems to be dominated by electron tunnelling.

Preparation of Industrially Important Hydroxy Acids and Diacids from 2,2-Disubstituted Propane-1,3-Diols and Linear Primary Diols by Green Chemistry Methods

Environmentally benign and economical methods for the preparation of industrially important hydroxy acids and diacids were developed. The carboxylic acids, used in polyesters, alkyd resins, and polyamides, were obtained by the oxidation of the corresponding alcohols with hydrogen peroxide or air catalyzed by sodium tungstate or supported noble metals. These oxidations were carried out using water as a solvent. The alcohols are also a useful alternative to the conventional reactants, hydroxyaldehydes and cycloalkanes. The oxidation of 2,2-disubstituted propane-1,3-diols with hydrogen peroxide catalyzed by sodium tungstate afforded 2,2-disubstituted 3-hydroxypropanoic acids and 1,1-disubstituted ethane-1,2-diols as products. A computational study of the Baeyer-Villiger rearrangement of the intermediate 2,2-disubstituted 3-hydroxypropanals gave in-depth data of the mechanism of the reaction. Linear primary diols having chain length of at least six carbons were easily oxidized with hydrogen peroxide to linear dicarboxylic acids catalyzed by sodium tungstate. The Pt/C catalyzed air oxidation of 2,2-disubstituted propane-1,3-diols and linear primary diols afforded the highest yield of the corresponding hydroxy acids, while the Pt, Bi/C catalyzed oxidation of the diols afforded the highest yield of the corresponding diacids. The mechanism of the promoted oxidation was best described by the ensemble effect, and by the formation of a complex of the hydroxy and the carboxy groups of the hydroxy acids with bismuth atoms. The Pt, Bi/C catalyzed air oxidation of 2-substituted 2-hydroxymethylpropane-1,3-diols gave 2-substituted malonic acids by the decarboxylation of the corresponding triacids. Activated carbon was the best support and bismuth the most efficient promoter in the air oxidation of 2,2-dialkylpropane-1,3-diols to diacids. In oxidations carried out in organic solvents barium sulfate could be a valuable alternative to activated carbon as a non-flammable support. In the Pt/C catalyzed air oxidation of 2,2-disubstituted propane-1,3-diols to 2,2-disubstituted 3-hydroxypropanoic acids the small size of the 2-substituents enhanced the rate of the oxidation. When the potential of platinum of the catalyst was not controlled, the highest yield of the diacids in the Pt, Bi/C catalyzed air oxidation of 2,2-dialkylpropane-1,3-diols was obtained in the regime of mass transfer. The most favorable pH of the reaction mixture of the promoted oxidation was 10. The reaction temperature of 40°C prevented the decarboxylation of the diacids.

A simple method of estimating the detonation velocity from chemical composition of organic explosives

A simple yet fairly accurate method of calculating the ideal detonation velocity of an organic explosive from a knowledge of the chemical composition alone is proposed. The method is based on the concept that the energetics of a stoichiometrically balanced fuel-oxidizer system is a function of the total oxidizing or reducing valences of the composition. A combination of the valences in the form of Image , where R and P are, respectively, the reducing and oxidizing valences and MW is the molecular weight, has been found to be linearly related to the detonation velocity of the expolosive. The predicting capacity of the method has been found to be superior to other methods in the literature.

Critical review on the stability of illicit drugs in sewers and wastewater samples

Wastewater-based epidemiology (WBE) applies advanced analytical methods to quantify drug residues in wastewater with the aim to estimate illicit drug use at the population level. Transformation processes during transport in sewers (chemical and biological reactors) and storage of wastewater samples before analysis are expected to change concentrations of different drugs to varying degrees. Ignoring transformation for drugs with low to medium stability will lead to an unknown degree of systematic under- or overestimation of drug use, which should be avoided. This review aims to summarize the current knowledge related to the stability of commonly investigated drugs and, furthermore, suggest a more effective approach to future experiments. From over 100 WBE studies, around 50 mentioned the importance of stability and 24 included tests in wastewater. Most focused on in-sample stability (i.e., sample preparation, preservation and storage) and some extrapolated to in-sewer stability (i.e., during transport in real sewers). While consistent results were reported for rather stable compounds (e.g., MDMA and methamphetamine), a varying range of stability under different or similar conditions was observed for other compounds (e.g., cocaine, amphetamine and morphine). Wastewater composition can vary considerably over time, and different conditions prevail in different sewer systems. In summary, this indicates that more systematic studies are needed to: i) cover the range of possible conditions in sewers and ii) compare results more objectively. To facilitate the latter, we propose a set of parameters that should be reported for in-sewer stability experiments. Finally, a best practice of sample collection, preservation, and preparation before analysis is suggested in order to minimize transformation during these steps.

A retrospective study of vase life determinants for cut Acacia holosericea foliage

Short and variable vase life of cut Acacia holosericea foliage stems limits its commercial potential. Retrospective evaluation of factors affecting the vase life of this cut foliage line was assessed using primary data collected from 30 individual experiments. These data had been collected by four different researchers over 17 months, from late Summer to mid Winter across two consecutive years. Vase life data of cut A. holosericea stems held in deionised water (DIW) was analysed for general vase life variation and to define the most influential factor affecting vase life of the cut stems. Meanwhile, vase life of cut stems exposed to various chemical and physical postharvest treatments was analysed using meta-analysis to evaluate their efficacy in prolonging vase life of the stems. The overall mean vase life (±standard deviation) of cut A. holosericea stems was 6.4 ± 1.2 days (n = 30 trials). Longer vase life of ≥7 days was obtained from cut stems harvested at vegetative and flowering stage, which was between Summer and Autumn. Cut stems harvested at fruiting stage, between Winter and Spring displayed shorter vase life of ≤5.5 days. Mixed model analysis indicated that vase life variation of the cut stems was mostly determined by season (P < 0.001). In averaged, postharvest treatments increased vase life 1.4-fold compared to stems in DIW, with 68.32% had a large positive treatment effect size (d). Among the treatments, nano silver (NS) and copper (Cu2+) were the most beneficial to vase life. Retrospective analysis was found to be beneficial for identifying conditions and targeting practices to maximise the vase life of cut A. holosericea and, potentially for other species.

Assessing refrigerating and freezing effects on the biological/chemical composition of two livestock manures

Assessing storage impacts on manure properties is relevant to research associated with nutrient-use efficiency and greenhouse gas (GHG) emissions. We examined the impact of cold storage on physicochemical properties, biochemical methane-emitting potential (BMP) and the composition of microbial communities of beef feedlot manure and poultry broiler litter. Manures were analysed within 2 days of collection and after 2 and 8 weeks in refrigerated (4 °C) or frozen (–20 °C) storage. Compared with fresh manure, stored manures had statistically significant (p < 0.05) but comparatively minor (<10%) changes in electrical conductivity, chloride and ammonium concentrations. Refrigeration and freezing did not significantly affect (p > 0.05) BMP in both manure types. We did not detect ammonium- or nitrite-oxidising bacterial taxa (AOB, NOB) using fluorescence in situ hybridisation (FISH). Importantly, the viability of microbes was unchanged by storage. We conclude that storage at –20 °C or 4 °C adequately preserves the investigated traits of the studied manures for research aimed at improving nutrient cycling and reducing GHG emissions.

Human health risk of toxic chemical pollutants generated from traffic and land use activities

The research project developed a quantitative approach to assess the risk to human health from heavy metals and polycyclic aromatic hydrocarbons in urban stormwater based on traffic and land use factors. The research outcomes are expected to strengthen the scientifically robust management and reuse of urban stormwater. The innovative methodology developed can be applied to evaluate human health risk in relation to toxic chemical pollutants in urban stormwater runoff and for the development of effective risk mitigation strategies.

Atomic Layer Deposition and Photocatalytic Properties of Titanium Dioxide Thin Films

Photocatalytic TiO2 thin films can be highly useful in many environments and applications. They can be used as self-cleaning coatings on top of glass, tiles and steel to reduce the amount of fouling on these surfaces. Photocatalytic TiO2 surfaces have antimicrobial properties making them potentially useful in hospitals, bathrooms and many other places where microbes may cause problems. TiO2 photocatalysts can also be used to clean contaminated water and air. Photocatalytic oxidation and reduction reactions proceed on TiO2 surfaces under irradiation of UV light meaning that sunlight and even normal indoor lighting can be utilized. In order to improve the photocatalytic properties of TiO2 materials even further, various modification methods have been explored. Doping with elements such as nitrogen, sulfur and fluorine, and preparation of different kinds of composites are typical approaches that have been employed. Photocatalytic TiO2 nanotubes and other nanostructures are gaining interest as well. Atomic Layer Deposition (ALD) is a chemical gas phase thin film deposition method with strong roots in Finland. This unique modification of the common Chemical Vapor Deposition (CVD) method is based on alternate supply of precursor vapors to the substrate which forces the film growth reactions to proceed only on the surface in a highly controlled manner. ALD gives easy and accurate film thickness control, excellent large area uniformity and unparalleled conformality on complex shaped substrates. These characteristics have recently led to several breakthroughs in microelectronics, nanotechnology and many other areas. In this work, the utilization of ALD to prepare photocatalytic TiO2 thin films was studied in detail. Undoped as well as nitrogen, sulfur and fluorine doped TiO2 thin films were prepared and thoroughly characterized. ALD prepared undoped TiO2 films were shown to exhibit good photocatalytic activities. Of the studied dopants, sulfur and fluorine were identified as much better choices than nitrogen. Nanostructured TiO2 photocatalysts were prepared through template directed deposition on various complex shaped substrates by exploiting the good qualities of ALD. A clear enhancement in the photocatalytic activity was achieved with these nanostructures. Several new ALD processes were also developed in this work. TiO2 processes based on two new titanium precursors, Ti(OMe)4 and TiF4, were shown to exhibit saturative ALD-type of growth when water was used as the other precursor. In addition, TiS2 thin films were prepared for the first time by ALD using TiCl4 and H2S as precursors. Ti1-xNbxOy and Ti1-xTaxOy transparent conducting oxide films were prepared successfully by ALD and post-deposition annealing. Highly unusual, explosive crystallization behaviour occurred in these mixed oxides which resulted in anatase crystals with lateral dimensions over 1000 times the film thickness.

A New Rare-Gas Compound: HXeOXeH

Rare-gas chemistry is of growing interest, and the recent advances include the "insertion" of a Xe atom into OH and water in the rare-gas hydrides HXeO and HXeOH. The insertion of Xe atoms into the H-C bonds of hydrocarbons was also demonstrated for HXeCC, HXeCCH and HXeCCXeH, the last of which was the first rare-gas hydride containing two rare-gas atoms. We describe the preparation and characterization of a new rare-gas compound, HXeOXeH. HXeOXeH was prepared in solid xenon by photolysis of a suitable precursor, for example water, and subsequent mobilization of the photoproducts. The experimental identification was carried out by FTIR spectroscopy, isotopic substitution and by use of various precursors. The photolytical and thermal stability of the new rare-gas hydride was also studied. The experimental work was supported by extensive quantum chemical calculations provided by our co-workers. HXeOXeH forms in a cryogenic xenon matrix from neutral O and H atoms in a two-step diffusion-controlled process involving HXeO as an intermediate [reactions (1) and (2)]. This formation mechanism is unique in that a rare-gas hydride is formed from another rare-gas hydride. H + Xe + O → HXeO (1) HXeO + Xe + H → HXeOXeH (2) Similarly to other rare-gas hydrides, HXeOXeH has a strongly IR-active H-Xe stretching vibration, allowing its spectral detection at 1379.3 cm-1. HXeOXeH is a very high-energy metastable species, yet thermally more stable than many other rare-gas hydrides. The calculated bending barrier of 0.57 eV, is not enough to explain the observed stability, and HXeOXeH might be affected by additional stabilization from the solid xenon environment. Chemical bonding between xenon and environmentally abundant species like water is of particular importance due to the “missing-xenon” problem. The relatively high thermal stability of HXeOXeH compared to other oxygen containing rare-gas compounds is relevant in this respect. Our work also raises the possibility of polymeric (–Xe–O)n networks, similarly to the computationally studied (XeCC)n polymers.

Mass transfer with chemical reaction in a foam bed contactor

On the basis of dodecahedral structure of a foam bed, a model to predict conversion in a foam bed contactor with mass transfer with chemical reaction has been developed. To verify the proposed model, experiments have been carried out in a semi-batch apparatus for the absorption of lean CO2 gas in a foam of sodium hydroxide solution. The proposed model predicts fairly well the experimentally found absorption values.