Results 1 - 10 of 711
Results 1 - 10 of 711. Search took: 0.024 seconds
|Sort by: date | relevance|
[en] Studies focused on pollutants deposition on vegetation surfaces or aerodynamics of vegetation space conflict in whether vegetation planting can effectively reduce airborne particulate matter (PM) pollution. To achieve a more comprehensive understanding of the conflict, we conducted experiments during 2013 and 2014 in Beijing, China to evaluate the importance of vegetation species, planting configurations and wind in influencing PM concentration at urban and street scales. Results showed that wind field prevailed over the purification function by vegetation at urban scale. All six examined planting configurations reduced total suspended particle along horizontal but not vertical direction. Shrubs and trees–grass configurations performed most effectively for horizontal PM2.5 reduction, but adversely for vertical attenuation. Trapping capacity of PMs was species-specific, but species selection criteria could hardly be generalized for practical use. Therefore, design of planting configuration is practically more effective than tree species selection in attenuating the ambient PM concentrations in urban settings. - Highlights: • Study of the relationship between vegetation and PM pollution is presented. • Type of vegetation is secondary to wind field effect in influencing urban-scale PM pollution. • Planting spaces aiding ventilation are crucial in roadside PM pollution control. • Species differences are obvious but difficult to apply in practice. - Wind field triumphs surface deposition by vegetation in attenuating PM pollution, indicating consideration of ventilation as the criteria for spatial planting configuration and species selection.
[en] Response of several particulate monitoring instruments to aerosols which might be encountered during monitoring of an in situ oil spill burn, was examined. The aerosols included road dust, salt and particulates from the combustion of heptane, diesel fuel and crude oil. Total suspended particulates, 10 micron and 2.5 micron sampling heads were used with each instrument. Two optical cell instruments reported similar concentrations as reported by gravimetric instruments in the case of burning heptane, diesel fuel and crude oil. For salt and road dust aerosols, two optical cells reported much lower values than those measured by gravimetric instruments. The differences were attributed to salt and road dust aerosols having different size distributions. These differences, however, can be minimized by careful calibration. Results indicate that with careful calibration any of the instruments tested can be used as a monitoring tool to help response teams to assess whether in situ burning is leading to an increase in airborne particulates above an acceptable level. 8 refs., 7 tabs., 24 figs
[en] Meteorological parameters wind speed, temperature, humidity and stability play a very important role in the transport and dispersion of particulate matter affecting the concentration of Total Suspended Particulate Matter (TSPM). These parameters vary from place to place, month to month and also during day and night. In addition coastal atmospheric conditions widely vary compared to inland site due to land sea interface. This paper presents the results of correlation between various meteorological parameters and TSPM at Kalpakkam (12° 33inch N, 80°11inch E) on the east coast, about 75 km south of Chennai, India
[en] Highlights: • The PaSR-based soot model proposed by the authors’ group has been further improved. • The present model is physically more sound. • The improved model has been implemented into the in-house version of the FireFOAM code. • New formulas have been proposed to compute characteristic time for soot formation and oxidation. • The predictions have achieved improved agreement with the experimental measurements. - Abstract: The extension of the laminar smoke point based approach to turbulent combustion using the partially stirred reactor (PaSR) concept proposed by Chen et al. (2014) has been further improved to overcome the limitation in the formulations of Chen et al. (2014) which assumed infinitely fast soot oxidation chemistry and constant soot formation characteristic time. In the PaSR approach, each computational cell is split into two zones: the reacting zone and the non-reacting zone. Soot formation and oxidation are assumed to take place at finite rates in the reacting zone and computed from the corresponding laminar rates and the mass fractions for soot formation and oxidation, which are evaluated in each computational cell from the characteristic time scales for turbulent mixing, soot formation and oxidation. Since soot would be produced in not only the fine structures but also surrounding fluids in the Eddy-Dissipation-Concept (EDC) model, the average field parameters between the fine structure and surrounding fluid are employed instead of those Favre-averaged values in Chen et al.’s soot formation model. The newly extended model has been implemented in FireFOAM, a large eddy simulation (LES) based solver for fire simulation based on the open source CFD code OpenFOAM®. Numerical simulations of a 30 cm diameter heptane and toluene pool fires tested by Klassen and Gore (1992) were performed for validation. The predicted soot volume fraction and temperature have achieved improved agreement with the experimental measurements in comparison with that of Chen et al. (2014), demonstrating the potential of the improved PaSR-based soot model for fire applications.
[en] In recent years, Pakistan has experienced severe and persistent air pollution associated with urbanization and industrialization and it has substantial effects on ecosystem and air quality. In urban and periurban areas, maximum TSP concentration was observed at Satiana Road (987 μgm-3) and Chak 215 RB (1123 μgm-3). Similarly, maximum PM10 concentration was recorded at Gutte Wala (782 μgm-3) and Chak 215 RB (893 μgm-3), while maximum PM2.5 concentration was observed at Madina Food Mill (621 μgm-3) and Chak 215 RB (654 μgm-3). The statistical results suggest that there is significant difference between urban and peri-urban areas. Majority of size segregated pollutants including TSP, PM10 and PM2.5 were found with higher values than the United States Environmental Protection agency (US-EPA), National Ambient air Quality Standards (NAAQS), world health organization (WHO) and National Environmental Quality standards for Pakistan (NEQS-Pak) limits for both urban and peri-urban areas, only 4%, 8% and 4% for TSP, PM10 and PM2.5 in urban and TSP (40%) PM10 (60%) and PM2.5 (44%) in peri urban samples were found under prescribed guidelines. Furthermore, we have also compared metropolitan size segregated pollutant (PM10) with other Pakistan and Asian metropolitan cities’ and purposed strategy to control it. (author)
[en] It has been desired to eliminate or collect the contamination particles of radioisotope in each sort of species or shape and size non-invasively. The shape and size of particle can be determined from the shape and distribution of diffraction pattern of particle in the parallel laser beam, the species of particle can be discriminated by the fluorescence from resonance of laser beam, or by the laser Raman scattering, and the particle suspended in the air or falling down in a vacuum can be levitated against the gravity and trapped by the radiation force and the trapping force of the focussed laser beam in the atmosphere or in a vacuum. For the purpose of the non-invasive manipulation of contamination particles, the laser manipulation technique, image processing technique with Multiplexed Matched Spatial Filter and the determination technique of laser Raman scattering or fluorescence from resonance of laser light were combined in the experiments. The shape, size and species of particles trapped in the focal plane of focused Ar laser beam can be determined simultaneously and instantaneously from the shape and intensity distributions of diffraction patterns of the particles in the irradiation of parallel coherent beam of He-Ne laser, and fluorescence from the resonance of YAG laser beam with variable wave length. In this research, a new technique is proposed to manipulate non-invasively the contamination particles determined with the shape, size and species in the atmosphere or in a vacuum, by laser beam. (author)
[en] An environmental impact study was carried out for a 3000 tpd cement plant to be located in Attock district. The plant will employ electrostatic precipitators to keep dust emissions belong 50 mg/Nm/sup 3/. Field survey was conducted to study the environmental condition of the area. pollutant dispersion modelling was used to assess So/sub 2/, Nox and Total Suspended Particulates (TSP) concentrations. The impacts of project on physical and human environment were considered and necessary mitigation measures recommended. (author)
[en] The information available suggests that the concentration of total suspended particulate matter in major urban areas are reaching unprecended levels(>230μg/m3). From the first documented study on total suspended particulate matter in 1977, a review of the various studies both in Nairobi and Mombasa is made with a view to bring to light, the assessment of air pollution in Kenya. (author)0
[en] This chapter focused on the types of contaminants that can be addressed using nuclear and related analytical techniques. Data evaluation and interpretation in certain application will also be briefly discussed. A brief description on life sciences particularly the importance of trace elements to human life is added with special emphasis on dietary intake of essential and toxic elements by man. (Author)
[en] This document comprises the Operational Test Report for the 241-AZ-101 Suspended Solids Profiler. This document presents the results of Operational Testing of the 241-AZ-101 Suspended Solids Profiler (SSP). Testing of the SSP was performed in accordance with OTP-260-005, ''SUSPENDED SOLIDS PROFILER OPERATIONAL TEST PROCEDURE''. The objective of the testing was to verify that all equipment and components functioned as designed, following construction completion and turnover to operations