| 1. |
- Komakech, Allan, et al.
(författare)
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Characterization of municipal waste in Kampala, Uganda
- 2014
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Ingår i: Journal of the Air and Waste Management Association. - : Taylor & Francis. - 1096-2247 .- 2162-2906. ; 64:3, s. 340-348
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Tidskriftsartikel (refereegranskat)abstract
- In Kampala, Uganda, about 28,000 tons of waste is collected and delivered to a landfill every month. Kampala Capital City Authority (KCCA) records show that this represents approximately 40% of the waste generated in the city. The remaining uncollected waste is normally dumped in unauthorized sites, causing health and environmental problems. However, the organic fraction of domestic waste can provide an opportunity to improve livelihoods and incomes through fertilizer and energy production. This study characterized the municipal waste generated in Kampala and delivered to Kiteezi landfill between July 2011 and June 2012, that is, covering the dry and wet months. On each sampling day, waste was randomly selected from five trucks, sorted and weighed into different physical fractions. Samples of the organic waste from each truck were analyzed for total solids, major nutrients, and energy content. During the wet months, the waste consisted of 88.5% organics, 3.8% soft plastics, 2.8% hard plastics, 2.2% paper, 0.9% glass, 0.7% textiles and leather, 0.2% metals, and 1.0% others. During the dry months, the waste consisted of 94.8% organics, 2.4% soft plastics, 1.0% hard plastics, 0.7% papers, 0.3% glass, 0.3% textile and leather, 0.1% metals, and 0.3% others. The organic waste on average had a moisture content of 71.1% and contained 1.89% nitrogen, 0.27% phosphorus, and 1.95% potassium. The waste had an average gross energy content of 17.3 MJ/kg. It was concluded that the organic waste generated can be a suitable source of some plant nutrients that are useful especially in urban agriculture. Implications: The result of the waste characterization in Kampala was found to be significantly different from that obtained for other Sub-Saharan African (SSA) cities, showing that studies assuming average values for the waste fractions are likely to result in erroneous results. Furthermore, no reduction in organic fraction of the waste was noticed when compared with a study done two decades ago in spite of greatly improved economic status of Kampala city, a finding that is not in agreement with several other similar studies done for other SSA cities.
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| 2. |
- Krecl, Patricia, et al.
(författare)
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Spatiotemporal Variability of Light-Absorbing Carbon Concentration in a Residential Area Impacted by Woodsmoke
- 2010
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Ingår i: Journal of the Air & Waste Management Association. - : Informa UK Limited. - 1047-3289 .- 1096-2247 .- 2162-2906. ; 60:3, s. 356-368
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Tidskriftsartikel (refereegranskat)abstract
- Residential wood combustion (RWC) is responsible for 33% of the total carbon mass emitted in Europe. With the new European targets to increase the use of renewable energy, there is a growing concern that the population exposure to woodsmoke will also increase. This study investigates observed and simulated light-absorbing carbon mass (M-LAC) concentrations in a residential neighborhood (Lycksele, Sweden) where RWC is a major air pollution source during winter. The measurement analysis included descriptive statistics, correlation coefficient, coefficient of divergence, linear regression, concentration roses, diurnal pattern, and weekend versus weekday concentration ratios. Hourly RWC and road traffic contributions to M-LAC were simulated with a Gaussian dispersion model to assess whether the model was able to mimic the observations. Hourly mean and standard deviation concentrations measured at six sites ranged from 0.58 to 0.74 mu g m(-3) and from 0.59 to 0.79 mu g m(-3), respectively. The temporal and spatial variability decreased with increasing averaging time. Low-wind periods with relatively high M-LAC concentrations correlated more strongly than high-wind periods with low concentrations. On average, the model overestimated the observations by 3- to 5-fold and explained less than 10% of the measured hourly variability at all sites. Large residual concentrations were associated with weak winds and relatively high M-LAC loadings. The explanation of the observed variability increased to 31-45% when daily mean concentrations were compared. When the contribution from the boilers within the neighborhood was excluded from the simulations, the model overestimation decreased to 16-71%. When assessing the exposure to light-absorbing carbon particles using this type of model, the authors suggest using a longer averaging period (i.e., daily concentrations) in a larger area with an updated and very detailed emission inventory.
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| 3. |
- Pirjola, Liisa, et al.
(författare)
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Road Dust Emissions from Paved Roads Measured Using Different Mobile Systems
- 2010
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Ingår i: Journal of the Air & Waste Management Association. - : Informa UK Limited. - 1047-3289 .- 1096-2247 .- 2162-2906. ; 60:12, s. 1422-1433
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Tidskriftsartikel (refereegranskat)abstract
- Very few real-world measurements of road dust suspension have been performed to date. This study compares two different techniques (referred to as Sniffer and Emma) to measure road dust emissions. The main differences between the systems are the construction of the inlet, different instruments for recording particulate matter (PM) levels, and different loads on the wheel axes (the weight of Sniffer was much higher than that of Emma). Both systems showed substantial small-scale variations of emission levels along the road, likely depending on-road surface conditions. The variations observed correlated quite well, and the discrepancies are likely a result of variations in dust load on the road surface perpendicular to the driving direction that cause variations in the measurements depending on slightly different paths driven by the two vehicles. Both systems showed a substantial influence on the emission levels depending on the type of tire used. The summer tire showed much lower suspension than the winter tires (one nonstudded and one studded). However, the relative importance of the nonstudded versus studded tire was rather different. For the ratio of studded/nonstudded, Emma shows higher values on all road sections compared with Sniffer. Both techniques showed increased emission levels with increasing vehicle speed. When the speed increased from 50 to 80 km hrthe relative concentrations increased by 30-170% depending on the tire type and dust load. However, for road sections that were very dirty, Sniffer showed a much higher relative increase in the emission level with the nonstudded tire. Sniffer's absolute concentrations were mostly higher than Emma's. Possible reasons for the differences are discussed in the paper. Both systems can be used for studying relative road dust emissions and for designing air quality management strategies.
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| 4. |
- Sharma, Prabhakar, 1976-, et al.
(författare)
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Gas dispersion and immobile gas volume in solid and porous particle biofilter materials at low air flow velocities
- 2010
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Ingår i: Journal of the air & waste management association. - : Informa UK Limited. - 1047-3289 .- 1096-2247 .- 2162-2906. ; 60:7, s. 830-837
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Tidskriftsartikel (refereegranskat)abstract
- Gas-phase dispersion in granular biofilter materials with awide range of particle sizes was investigated using atmosphericair and nitrogen as tracer gases. Two types ofmaterials were used: (1) light extended clay aggregates(LECA), consisting of highly porous particles, and (2)gravel, consisting of solid particles. LECA is a commercialmaterial that is used for insulation, as a soil conditioner,and as a carrier material in biofilters for air cleaning. Thesetwo materials were selected to have approximately thesame particle shape. Column gas transport experimentswere conducted for both materials using different meanparticle diameters, different particle size ranges, and differentgas flow velocities. Measured breakthrough curveswere modeled using the advection-dispersion equationmodified for mass transfer between mobile and immobilegas phases. The results showed that gas dispersivity increasedwith increasing mean particle diameter for LECAbut was independent of mean particle diameter for gravel.Gas dispersivity also increased with increasing particlesize range for both media. Dispersivities in LECA weregenerally higher than for gravel. The mobile gas contentin both materials increased with increasing gas flow velocitybut it did not show any strong dependency onmean particle diameter or particle size range. The relativefraction of mobile gas compared with total porosity washighest for gravel and lowest for LECA likely because of itshigh internal porosity.
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| 5. |
- van der Gon, Hugo A. C. Denier, et al.
(författare)
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The Policy Relevance of Wear Emissions from Road Transport, Now and in the FutureAn International Workshop Report and Consensus Statement
- 2013
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Ingår i: Journal of the Air and Waste Management. - : Informa UK Limited. - 1096-2247 .- 2162-2906. ; 63:2, s. 136-149
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Forskningsöversikt (refereegranskat)abstract
- Road transport emissions are a major contributor to ambient particulate matter concentrations and have been associated with adverse health effects. Therefore, these emissions are targeted through increasingly stringent European emission standards. These policies succeed in reducing exhaust emissions, but do not address nonexhaust emissions from brake wear, tire wear, road wear, and suspension in air of road dust. Is this a problem? To what extent do nonexhaust emissions contribute to ambient concentrations of PM10 or PM2.5? In the near future, wear emissions may dominate the remaining traffic-related PM10 emissions in Europe, mostly due to the steep decrease in PM exhaust emissions. This underlines the need to determine the relevance of the wear emissions as a contribution to the existing ambient PM concentrations, and the need to assess the health risks related to wear particles, which has not yet received much attention. During a workshop in 2011, available knowledge was reported and evaluated so as to draw conclusions on the relevance of traffic-related wear emissions for air quality policy development. On the basis of available evidence, which is briefly presented in this paper, it was concluded that nonexhaust emissions and in particular suspension in air of road dust are major contributors to exceedances at street locations of the PM10 air quality standards in various European cities. Furthermore, wear-related PM emissions that contain high concentrations of metals may (despite their limited contribution to the mass of nonexhaust emissions) cause significant health risks for the population, especially those living near intensely trafficked locations. To quantify the existing health risks, targeted research is required on wear emissions, their dispersion in urban areas, population exposure, and its effects on health. Such information will be crucial for environmental policymakers as an input for discussions on the need to develop control strategies. Implications: Road transport particulate matter (PM) emissions are associated with adverse health effects. Stringent policies succeed in reducing the exhaust PM emissions, but do not address nonexhaust emissions from brake wear, tire wear, road wear, and suspension in air of road dust. In the near future the nonexhaust emissions will dominate the road transport PM emissions. Based on the limited available evidence, it is argued that dedicated research is required on nonexhaust emissions and dispersion to urban areas from both an air quality and a public health perspective. The implicated message to regulators and policy makers is that road transport emissions continue to be an issue for health and air quality, despite the encouraging rapid decrease of tailpipe exhaust emissions. Supplemental Materials: Supplemental materials are available for this paper. Go to the publisher's online edition of the Journal of the Air & Waste Management Association.
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