A transition of atmospheric emissions of particles and gases from on-road heavy-duty trucks

The transition, in extent and characteristics, of atmospheric emissions caused by the modernization of the heavy-duty on-road fleet was studied utilizing roadside measurements. Emissions of particle number (PN), particle mass (PM), black carbon (BC), nitrogen oxides (NOx), carbon monoxide (CO), hydrocarbon (HC), particle size distributions, and particle volatility were measured from 556 individual heavy-duty trucks (HDTs). Substantial reductions in PM, BC, NOx, CO, and to a lesser extent PN were observed from Euro III to Euro VI HDTs by 99 %, 98 %, 93 %, and 57 % for the average emission factors of PM, BC, NOx, and CO, respectively. Despite significant total reductions in NOx emissions, the fraction of NO2 in the NOx emissions increased continuously from Euro IV to Euro VI HDTs. Larger data scattering was evident for PN emissions in comparison to solid particle number (SPN) for Euro VI HDTs, indicating a highly variable fraction of volatile particle components. Particle size distributions of Euro III to enhanced environmentally friendly vehicle (EEV) HDTs were bimodal, whereas those of Euro VI HDTs were nucleation mode dominated. High emitters disproportionately contributed to a large fraction of the total emissions with the highest-emitting 10 % of HDTs in each pollutant category being responsible for 65 % of total PM, 70 % of total PN, and 44 % of total NOx emissions. Euro VI HDTs, which accounted for 53 % of total kilometres driven by Swedish HDTs, were estimated to only contribute to 2 %, 6 %, 12 %, and 47 % of PM, BC, NOx, and PN emissions, respectively. A shift to a fleet dominated by Euro VI HDTs would promote a transition of atmospheric emissions towards low PM, BC, NOx, and CO levels. Nonetheless, reducing PN, SPN, and NO2 emissions from Euro VI HDTs is still important to improve air quality in urban environments

Airborne particulate matter in a Sub-Saharan Africa city: Nairobi, Kenya, and at an Equatorial high altitude site: Mount Kenya

In Sub-Saharan Africa (SSA), air quality is gravely understudied despite the existing influential factors such a rapid urbanization and population growth that negatively affect the environment. Majority of urban areas in SSA face challenges that include lack of social services, poor infrastructure development, exponential increase of second-hand vehicles and extensive use of biomass-based fuel for energy needs. There is a systemic lack of continuous monitoring of air pollution in most SSA cities and hence it is yet to be seen if SSA will meet the set air quality targets of the sustainable development goals (SDGs) by the year 2030. Although the focus of air quality is on the urban areas, there is a need to monitor atmospheric composition at remote areas in SSA in order to build a baseline level and understand the influence of anthropogenic and natural aerosol sources on regional/global scale. This thesis work sought to study physical and chemical properties of airborne particulate matter (PM) in a typical SSA urban area, Nairobi city, and a high altitude site, Mount Kenya. Results from spatial distribution of black carbon (BC) and PM2.5 (particulate matter less than 2.5 aerodynamic diameter) showed that air quality on the road to the city and within the city is deteriorating. Factor analysis of the PM2.5 results showed that pollution sources were traffic, mineral dust, industrial, combustion, biomass burning, secondary aerosol and aged sea salt. Traffic and mineral dust contributed about 74% of the PM2.5 in Nairobi. Exposure to particulate pollutants was expressed in terms of deposition fractions from the size segregated PM data. The head airways region was found to receive the highest dose (about 86%) compared to the tracheobronchial and pulmonary regions. The reported high PM2.5 and BC concentrations measured along the main street of Nairobi city, indicated the urban population is frequently exposed to elevated pollutants concentrations and thus have high risk factor to respiratory illnesses and lung cancer. Aerosol study from Mount Kenya showed air pollutants are transported from the surrounding and far away sources by local and regional meteorology dynamics. The results from this study provides insight into the air quality issues from pollution sources, exposure to the population and dispersal to remote regions

Characterization of Size-Fractionated Particulate Matter and Deposition Fractions in Human Respiratory System in a Typical African City: Nairobi, Kenya

Information from elemental and mass composition of size-fractionated airborne particle matter (PM) provides insightful knowledge about their impact on human health, meteorology and climate. To attain insight into the nature of sizefractionated PM from a typical African city, samples were collected from an urban background site in Nairobi, Kenya, during the months of August and September in 2007. PM samples ranging in size from 0.06 to 16 µm aerodynamic diameter were collected on pre-weighed polycarbonate filters with 0.4 µm pore size using a nine-stage cascade impactor. Particles less than 0.06 µm were collected on a backup filter. A total of 170 samples were collected and analysed for trace elements using the Proton Induced X-Ray Emission (PIXE) technique. The analysis showed that Si, Fe and S dominated in all size ranges and displayed unimodal mass-size distribution whereas K, Cu, Zn and Pb, depicted bimodal mass-size distribution highlighting the multiplicity of their sources. To estimate human exposure to PM, deposition fractions of both the coarse and fine PM in the human respiratory system were calculated. The deposited concentration was found to be highest in the head airways region compared to the tracheobronchial and pulmonary regions

Eu3+ as a luminescent probe for the local structure of trivalent dopant ions in barium zirconate-based proton conductors

The luminescence spectra and decay kinetics of dry and hydrated samples of BaZr0.9Y0.099Eu0.001O2.95 have been measured at room temperature. The spectra of the dry sample evidence two D-5(0) -> F-7(0) bands clearly indicating that Eu3+ (replacing Y3+ in the Zr4+ position of the average cubic perovskite structure) occupies two different local structures, whilst only one Eu3+ site is observed for the hydrated material. From the spectral data, it is possible to identify the nature of these two sites and to propose point group symmetries for the average local geometry around Eu3+. The decay time of the D-5(0) level becomes shorter upon hydration, due to the interaction with high-frequency O-H stretching vibrations, indicating an attractive interaction between protons and dopant atoms. (C) 2013 Elsevier B.V. All rights reserved

Influence of Yttrium Concentration on Local Structure in BaZr1-xYxO3-delta Based Proton Conductors

The evolution of local structure, coordination of protons, and proton conductivity in yttrium-doped barium zirconate, BaZr1-xYxO3-delta (x = 0-0.5), has been investigated using thermal-gravimetric analysis, impedance spectroscopy, and infrared spectroscopy. Low-frequency (50-1000 cm(-1)) infrared absorbance spectra provide evidence of increasing local structural distortions as a function of yttrium concentration as well as subtle differences, mainly linked to the oxygen sublattice, between the dry and hydrated samples. High-frequency (1700-4500 cm(-1)) spectra of the hydrated samples, distinguished by a broad O-H stretch continuum, manifest a varying degree of hydrogen bond interactions between the protons and nearest neighbor oxygens due to the disordered crystal structure with a general weakening in. particular of the strongest hydrogen bonding interactions with increasing dopant levels. It is argued that compositions within the range 0.1