| 1. |
- Boman, Johan, 1955, et al.
(författare)
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Mass, black carbon and elemental composition of PM2.5 at an industrial site in Kingston, Jamaica
- 2015
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Ingår i: Nuclear Instruments and Methods in Physics Reseach B. - : Elsevier BV. - 0168-583X. ; 363, s. 131-134
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Tidskriftsartikel (refereegranskat)abstract
- An estimated three million premature deaths yearly can be attributed to ambient particulate pollution, a majority of them in low and middle income countries. The rapid increase in the vehicle fleet in urban areas the Caribbean countries have experienced contributes to the bad urban air quality. In this study aerosol particles with an aerodynamic diameter smaller than, or equal to, 2.5 µm (PM2.5) were collected over 24 hours at a site along Spanish Town Road, one of the main commuter roads in Kingston, Jamaica. The study was aimed at determining the mass, black carbon and elemental composition of PM2.5 in Kingston. Although lead in the gasoline was phased out in the year 2000, up to 5000 ppm of sulfur is still allowed in the diesel, leading to an extensive secondary particle formation. PM2.5 samples were collected using a Mini-vol sampler between 12 December 2013 and 21 March 2014 and analyzed for trace elements using the Particle-Induced X-ray Emission (PIXE) facility at Lund University, Sweden. Concentrations of Si, S, Cl, K, Ca, Ti, V, Cr, Fe, Ni, Cu, Zn, Br and Pb were determined. Elemental concentrations showed a high temporal variation and the average PM2.5 concentration (44 µg m-3) is higher than the air quality standards that apply in the European Union (25 µg m-3) and in the USA (12 µg m-3). From this we can conclude that the air quality in the area is severely influenced by PM2.5 pollution and that there is a need to develop plans for improving the air quality in Kingston city.
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| 2. |
- Boman, Johan, 1955, et al.
(författare)
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PM2.5 at a semi-rural site near Beijing, China
- 2023
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Ingår i: X-Ray Spectrometry. - 0049-8246. ; 52:6, s. 447-56
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Tidskriftsartikel (refereegranskat)abstract
- Breathing clean air is a human right still not accessible to everyone. In most of the world, the air is polluted, which affects both the environment and human health. To investigate the air pollution situation in a semi-rural part of northern China, particles with a diameter below 2.5 & mu;m (PM2.5) were collected in Changping, 40 km northwest of Beijing in May and June 2016. The particles were analyzed for mass, trace elements, and black carbon (BC). The mean PM2.5 mass was 49 & mu;g/m(3), ranging from 3.1 to 266 & mu;g/m(3). S, Cl, K, Ca, Ti, V, Mn, Fe, Ni, Cu, Zn, As, and Pb were determined by Energy Dispersive X-Ray Fluorescence (EDXRF). They constituted 4% of the PM2.5 mass, with BC adding another 3%. Enrichment factor evaluation identified S, Ni, Cu, Zn, As, and Pb as the main anthropogenic contributors to environmental impact. A pollution load index (PLI) of 0.03 showed that the site could not be considered as polluted by the trace elements in PM2.5. Positive matrix factorization (PMF) was used for source apportionment of the PM2.5 content. The PMF analysis reveals that a mixture of mineral dust, fossil fuel combustion, industries, and salts were the main sources of air pollution. The non-carcinogenic and carcinogenic health risks were assessed, and both show a small health risk in the short study period. Following the development of PM2.5 concentrations over time in this part of China shows a decreasing trend of PM2.5 pollution, which is promising for the future.
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| 3. |
- Gaita, Samuel Mwaniki, 1976
(författare)
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Air quality assessment and pollution measurements in a typical Sub-Sahara African city: Nairobi, Kenya
- 2016
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Exposure to air pollution is detrimental to human health and is reported to cause about 7 million premature deaths in 2012 according to the World Health Organization. In sub-Sahara Africa (SSA) cities, air quality issue is complex due to challenges resulting from the rapid growth of urban population, poor infrastructure development and an exponential increase in number of vehicles. The problem is compounded by lack of continuous monitoring of air pollution in most SSA cities. In this work, sources of particulate matter (PM) were identified as traffic, mineral dust, industrial, combustion, biomass burning, secondary aerosol and aged sea salt using positive matrix factorization analysis. Traffic and mineral dust factors were found to contribute about 74% of PM2.5 mass (aerodynamic particle diameter less than 2.5 µm). Analysis of size-segregated PM showed the crustal elements (Si and Fe) dominated in all the measured PM size fractions. K, Cu, Zn and Pb displayed a bimodal mass-size distribution pattern emphasizing the multiplicity of their sources. Statistics from size-segregated data was utilized in calculating the deposition fractions of PM in human respiratory system. The head airways region had the highest percentage for both coarse (87%) and fine particles (84%) compared to the tracheobronchial and pulmonary regions. Given the high average PM2.5 concentration (98 µg m-3) measured in the main street of Nairobi city, the urban population is regularly exposed to elevated pollutants concentrations with potentially health risks implications. The information resulting from this study provides a foundation for policy formulation and mitigation strategies with regard to air pollution and quality in SSA cities.
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| 4. |
- Gaita, Samuel Mwaniki, 1976
(författare)
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Airborne particulate matter in a Sub-Saharan Africa city: Nairobi, Kenya, and at an Equatorial high altitude site: Mount Kenya
- 2017
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- 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.
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| 5. |
- Gaita, Samuel Mwaniki, 1976, et al.
(författare)
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Characterization of Size-Fractionated Particulate Matter and Deposition Fractions in Human Respiratory System in a Typical African City: Nairobi, Kenya
- 2016
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Ingår i: Aerosol and Air Quality Research. - : Taiwan Association for Aerosol Research. - 2071-1409 .- 1680-8584. ; 16:10, s. 2378-2385
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Tidskriftsartikel (refereegranskat)abstract
- Information from elemental and mass composition of size-fractionated airborne particle matter (PM) provides insightfulknowledge about their impact on human health, meteorology and climate. To attain insight into the nature of sizefractionatedPM 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 aerodynamicdiameter 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 traceelements using the Proton Induced X-Ray Emission (PIXE) technique. The analysis showed that Si, Fe and S dominated inall size ranges and displayed unimodal mass-size distribution whereas K, Cu, Zn and Pb, depicted bimodal mass-sizedistribution highlighting the multiplicity of their sources. To estimate human exposure to PM, deposition fractions of boththe coarse and fine PM in the human respiratory system were calculated. The deposited concentration was found to behighest in the head airways region compared to the tracheobronchial and pulmonary regions.
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| 6. |
- Gaita, Samuel Mwaniki, 1976, et al.
(författare)
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Source apportionment and seasonal variation of PM2.5 in a Sub-Sahara African city : Nairobi, Kenya
- 2014
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Ingår i: Atmospheric Chemistry And Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 14:18, s. 9977-9991
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Tidskriftsartikel (refereegranskat)abstract
- Sources of airborne particulate matter and their seasonal variation in urban areas in Sub-Saharan Africa are poorly understood due to lack of long-term measurement data. In view of this, filter samples of airborne particulate matter (particle diameter ≤2.5 μm, PM2.5) were collected between May 2008 and April 2010 at two sites (urban background site and suburban site) within the Nairobi metropolitan area. A total of 780 samples were collected and analyzed for particulate mass, black carbon (BC) and 13 trace elements.The average PM2.5 concentration at the urban background site was 21±9.5 μg m−3, whereas the concentration at the suburban site was 13±7.3 μg m−3. The daily PM2.5 concentrations exceeded 25 μg m−3 (the World Health Organization 24 h guideline value) on 29% of the days at the urban background site and 7% of the days at the suburban site. At both sites, BC, Fe, S and Cl accounted for approximately 80% of all detected elements. Positive matrix factorization analysis identified five source factors that contribute to PM2.5 in Nairobi, namely traffic, mineral dust, industry, combustion and a mixed factor (composed of biomass burning, secondary aerosol and aged sea salt).Mineral dust and traffic factors were related to approximately 74% of PM2.5. The identified source factors exhibited seasonal variation, apart from the traffic factor, which was prominently consistent throughout the sampling period. Weekly variations were observed in all factors, with weekdays having higher concentrations than weekends. The results provide information that can be exploited for policy formulation and mitigation strategies to control air pollution in Sub-Saharan African cities.
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| 7. |
- Haro-Gonzalez, P., et al.
(författare)
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Eu3+ as a luminescent probe for the local structure of trivalent dopant ions in barium zirconate-based proton conductors
- 2013
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Ingår i: Solid State Ionics. - : Elsevier BV. - 0167-2738. ; 247, s. 94-97
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 8. |
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| 9. |
- Mburu, Caroline W., et al.
(författare)
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Influence of Yttrium Concentration on Local Structure in BaZr(1-x)Y(x)O(3-δ) Based Proton Conductors
- 2017
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Ingår i: Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 121:30, s. 16174-16181
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Tidskriftsartikel (refereegranskat)abstract
- © 2017 American Chemical Society. The evolution of local structure, coordination of protons, and proton conductivity in yttrium-doped barium zirconate, BaZr 1-x Y x O 3-δ (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 0.15 ≤ x ≤ 0.3 possess a favorable level of local structural distortions to facilitate high proton conductivity, and this, coupled with a significant proton concentration, may be a factor in explaining the high proton conductivity these phases display.
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| 10. |
- Mburu, C. W., et al.
(författare)
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Influence of Yttrium Concentration on Local Structure in BaZr1-xYxO3-delta Based Proton Conductors
- 2017
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Ingår i: Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 121:30, s. 16174-16181
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Tidskriftsartikel (refereegranskat)abstract
- 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 0.15
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