| 1. |
- Winnes, Hulda, 1975, et al.
(author)
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Particle Emissions from Ships: Dependence on Fuel Type
- 2009
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In: Journal of the Air & Waste Management Association. - : Informa UK Limited. - 1047-3289 .- 1096-2247 .- 2162-2906. ; 59:12, s. 1391-1398
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Journal article (peer-reviewed)abstract
- This paper presents the results of field emission measurements that have been carried out on the 4500-kW four-stroke main engine on-board a product tanker. Two fuel qualities-heavy fuel oil (HFO) and marine gas oil (MGO)-have been tested on the same engine for comparable load settings. A fuel switch within the marine sector is approaching and the aim of this study is to draw initial conclusions on the subsequent effects on ship exhaust gas composition and emission factors with a focus on particles. Measurements on exhaust gas concentrations of carbon dioxide (CO2), carbon monoxide (CO), nitrogen oxides (NOx), sulfur dioxide (SO2), total hydrocarbons (HCs), and particulate matter (PM) were conducted. The gases, except SO2, did not show any major differences between the fuels. Specific PM emissions were generally higher for HFO than for MGO; however, for the smallest size-fraction measured containing particles 0.300.40 mu m in diameter, the opposite is observed. This finding emphasizes that to minimize negative health effects of particles from ships, further regulation may be needed to reduce small-sized particles; a fuel shift to low sulfur fuel alone does not seem to accomplish this reduction. The average of this and previously published data from on-board studies on particle emissions from ships results in emissions factors of 0.33 and 1.34 g/kWh for marine distillate oil (MDO) and HFO, respectively. Accounting for 1 standard deviation in each direction from the average values gives a range of 0.18-0.48 g/kWh for MDO and 0.56-2.12 g/kWh for HFO.
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| 2. |
- Krecl, Patricia, et al.
(author)
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Spatiotemporal Variability of Light-Absorbing Carbon Concentration in a Residential Area Impacted by Woodsmoke
- 2010
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In: 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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Journal article (peer-reviewed)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.
(author)
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Road Dust Emissions from Paved Roads Measured Using Different Mobile Systems
- 2010
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In: 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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Journal article (peer-reviewed)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.
(author)
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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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In: 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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Journal article (peer-reviewed)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. |
- Sharma, Prabhakar, 1976-, et al.
(author)
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Gaseous Oxygen Uptake in Porous Media at Different Moisture Contents and Airflow Velocities
- 2009
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In: Journal of the Air & Waste Management Association. - : Informa UK Limited. - 1047-3289 .- 1096-2247 .- 2162-2906. ; 59:6, s. 676-682
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Journal article (peer-reviewed)abstract
- The presence and distribution of water in the pore space isa critical factor for flow and transport of gases throughunsaturated porous media. The water content also affectsthe biological activity necessary for treatment of pollutedgas streams in biofilters. In this research, microbial activityand quantity of inactive volume in a porous mediumas a function of moisture content and gas flow rate wereinvestigated. Yard waste compost was used as a test medium,and oxygen uptake rate measurements were used toquantify microbial activity and effective active compostvolume using batch and column flow-through systems.Compost water contents were varied from air-dry to fieldcapacity and gas flows ranged from 0.2 to 2 L min1. Theresults showed that overall microbial activity and therelative fraction of active compost medium volume increasedwith airflow velocity for all levels of water contentup to a certain flow rate above which the oxygen uptakerate assumed a constant value independent of gas flow.The actual value of the maximum oxygen uptake rate wascontrolled by the water content. The oxygen uptake ratealso increased with increasing water content and reacheda maximum between 42 and 48% volumetric water content,above which it decreased, again likely because offormation of inactive zones in the compost medium.Overall, maximum possible oxygen uptake rate as a functionof gas flow rate across all water contents and gas flowscould be approximated by a linear expression. The relativefraction of active volume also increased with gas flowrate and reached approximately 80% for the highest gasflows used.
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| 6. |
- Andersson, Fräs Annika, et al.
(author)
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Occurrence and abatement of volatile sulfur compounds during biogas production
- 2004
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In: Journal of the Air & Waste Management Association. - 1047-3289. ; 54:7, s. 855-861
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Journal article (peer-reviewed)abstract
- Volatile sulfur compounds (VSCs) in biogas originating from a biogas production plant and from a municipal sewage water treatment plant were identified. Samples were taken at various stages of the biogas-producing process, including upgrading the gas to vehicle-fuel quality. Solid-phase microextraction was used for preconcentration of the VSCs, which were subsequently analyzed using gas chromatography in combination with mass spectrometry. Other volatile organic compounds present also were identified. The most commonly occurring VSCs in the biogas were hydrogen sulfide, carbonyl sulfide, methanethiol, dimethyl sulfide, and dimethyl disulfide, and hydrogen sulfide was not always the most abundant sulfur (S) compound. Besides VSCs, oxygenated organic compounds were commonly present (e.g., ketones, alcohols, and esters). The effect of adding iron chloride to the biogas reactor on the occurrence of VSCs also was investigated. It was found that additions of 500-g/m3 substrate gave an optimal removal of VSCs. Also, the use of a prefermentation step could reduce the amount of VSCs formed in the biogas process. Moreover, in the carbon dioxide scrubber used for upgrading the gas, VSCs were removed efficiently, leaving traces (ppbv levels). The scrubber also removed other organic compounds.
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| 7. |
- Gál, Erika, et al.
(author)
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A fifth- to sixth-century CE lynx (Lynx lynx L., 1758) skeleton from Hungary 2 : Stature and archaeological interpretations
- 2024
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In: International journal of osteoarchaeology. - 1047-482X .- 1099-1212. ; 34:2
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Journal article (peer-reviewed)abstract
- Lynx remains are rare in archaeological assemblages. The skeleton of an adult male accompanied by four dogs was found in a large Migration Period pit at Zamárdi–Kútvölgyi-dűlő II, Hungary. Extant lynx skeletons were used in estimating the shoulder height of this individual. Its stature is comparable to those of the large dogs it was buried with. None of the five skeletons showed skinning marks. Although the physical reconstruction of the lynx was of help in appraising this special pit, the actual nature of the deposit remains in question. Possible interpretations range from the mundane discard of carcasses to the poorly understood ritual burial of carnivores, beginning with the lynx. We reviewed these options within the framework of cultural diversity of Migration Period peoples in west-central Hungary.
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