Repozitorij Univerze v Novi Gorici

Iskanje po repozitoriju
A+ | A- | Pomoč | SLO | ENG

Iskalni niz: išči po
išči po
išči po
išči po
* po starem in bolonjskem študiju

Opcije:
  Ponastavi


1 - 10 / 12
Na začetekNa prejšnjo stran12Na naslednjo stranNa konec
1.
A study of pollutant concentration variability in an urban street under low wind speeds
Adrian Dobre, Graham Nickless, Iain R White, Catheryn S Price, Damien Martin, Dudley E Shallcross, 2008, izvirni znanstveni članek

Opis: The short time‐scale variability in pollutant concentrations in an urban street under very low wind speed conditions and short source–receptor distance has been investigated using the inert tracer sulfur hexafluoride (SF6) as a continuous point‐source (release times ≥ 5 min), and fast detection using separation by gas chromatography coupled with a μ‐electron capture detector (ECD). The results are complex but can be broadly interpreted in terms of horizontal wind speed and direction coherence. Comparisons with a simple dispersion model suggest that observed time‐averaged maximum concentrations approach predicted values, whilst instantaneous maximum concentrations vary greatly and would therefore be difficult to predict.
Najdeno v: osebi
Ključne besede: dispersion, tracer, intermittency
Objavljeno: 17.07.2019; Ogledov: 193; Prenosov: 10
.pdf Polno besedilo (289,67 KB)

2.
Methyl halide emission estimates from domestic biomass burning in Africa
M Iqbal Mead, M Anwar H Khan, Iain R White, Graham Nicless, Dudley E Shallcross, 2008, izvirni znanstveni članek

Opis: Inventories of methyl halide emissions from domestic burning of biomass in Africa, from 1950 to the present day and projected to 2030, have been constructed. By combining emission factors from Andreae and Merlet [2001. Emission of trace gases and aerosols from biomass burning. Global Biogeochemical Cycles 15, 955-966], the biomass burning estimates from Yevich and Logan [2003. An assessment of biofuel use and burning of agricultural waste in the developing world. Global Biogeochemical Cycles 17(4), 1095, doi:10.1029/2002GB001952] and the population data from the UN population division, the emission of methyl halides from domestic biomass usage in Africa has been estimated. Data from this study suggest that methyl halide emissions from domestic biomass burning have increased by a factor of 4-5 from 1950 to 2005 and based on the expected population growth could double over the next 25 years. This estimated change has a non-negligible impact on the atmospheric budgets of methyl halides.
Najdeno v: osebi
Ključne besede: Africa, Biofuel, Domestic biomass burning, Emission factor, Methyl halide
Objavljeno: 17.07.2019; Ogledov: 201; Prenosov: 0
.pdf Polno besedilo (781,64 KB)

3.
Stable carbon isotope analysis of selected halocarbons at parts per trillion concentration in an urban location
M Iqbal Mead, M Anwar H Khan, Ian D Bull, Iain R White, Graham Nickless, Dudley E Shallcross, 2008, izvirni znanstveni članek

Opis: ∂13C values of a suite of halocarbons have been determined in an urban background site in Bristol, UK. A novel mobile preconcentration system, based on the use of multi-adsorbent sample tubes, has been developed for trapping relatively large-volume air samples in potentially remote areas. An Adsorption Desorption System-Gas Chromatography-Electron Capture Detector was used to measure the mixing ratios of the selected halocarbon species, while a Gas ChromatographyCombustionIsotope Ratio Mass Spectrometer was used to determine ∂13C values. For the species with strong local sources, the variation of isotope ratios has been observed over the experimental period. Some of the results reported in the present study differ from previously reported values and reasons for this are discussed. The reporting of different ∂13C values for selected halocarbons from different areas in the present study suggests that ∂13C values may be used to determine the relative magnitudes of anthropogenic and biogenic sources.
Najdeno v: osebi
Ključne besede: Adsorption Desorption System (ADS), Automated Thermal Desorber (ATD), Electron Capture Detector (ECD), Gas Chromatography (GC), Isotope Ratio Mass Spectrometry (IRMS)
Objavljeno: 18.07.2019; Ogledov: 183; Prenosov: 0
.pdf Polno besedilo (227,35 KB)

4.
Year-long measurements of C1-C3 halocarbons at an urban site and their relationship with meteorological parameters
Dudley E Shallcross, Brian G R Greally, Alison C Rivett, Damien Martin, Alan Knights, Graham Nickless, Ben Golledge, Iain R White, M Iqbal Mead, M Anwar K Khan, 2009, izvirni znanstveni članek

Opis: The mixing ratios of 11 C1–C3 halocarbons have been measured using a GC–twin‐linked ECD system over the period from October 2004 to December 2005 at an urban site in Bristol, UK. Time series and seasonal variations of the halocarbons were analysed over the period to determine biogenic and anthropogenic sources and sinks. Correlations between the target halocarbons were also observed, suggesting common sources within the area. Wind rose plots for all halocarbons have been used to assist in the determination of halocarbons sources. Halocarbon concentrations are highest at low‐wind speeds and decrease as wind speed increases, a few species (CCl4 and CH3Cl most notably) rise at very high‐wind speeds suggesting release from the Bristol Channel.
Najdeno v: osebi
Ključne besede: adsorption–desorption system, anthropogenic halocarbons, biogenic halocarbons, electron capture detector, gas chromatography, methyl bromide
Objavljeno: 18.07.2019; Ogledov: 168; Prenosov: 0
.pdf Polno besedilo (897,06 KB)

5.
A feasibility study of the use of reactive tracers to determine outdoor daytime OH radical concentrations within the urban environment
Iain R White, Damien Martin, K Fredrik Petersson, Stephen J Henshaw, Graham Nickless, Guy C Lloyd-Jones, Kevin C Clemitshaw, Dudley E Shallcross, 2014, izvirni znanstveni članek

Opis: Using a specifically designed chemical tracer to indirectly measure local atmospheric hydroxyl radical (OH) concentrations is a very appealing concept. Such a tracer will provide information on the amount of OH a tracer encounters, as it moves through the urban environment and provide a stringent test of models. However, to date an outdoor experiment such as this has not been conducted. This article discusses the reasons why this is so and examines the feasibility of using tracers to measure integrated urban OH levels over short (≤1km) distances.
Najdeno v: osebi
Ključne besede: reactive tracers, OH radicals, NO3 radicals, oxidising rate, dispersion, urban
Objavljeno: 18.07.2019; Ogledov: 179; Prenosov: 0
.pdf Polno besedilo (748,36 KB)

6.
Atmospheric chemistry and physics in the atmosphere of a developed megacity (London): An overview of the REPARTEE experiment and its conclusions
Gavin J Phillips, Carole Helfter, Chiara F Di Marco, Eiko Nemitz, Fay Davies, Janet F Barlow, Tyrone Dunbar, Iain R White, Dudley E Shallcross, Stephen J Henshaw, K Fredrik Peterson, Brian Davison, Damien Martin, Ben Langford, C Nicholas Hewitt, Stephen M Ball, Justin M Langridge, A K Benton, Roderick L Jones, Paul I Williams, John Whitehead, Martin W Gallagher, Claire Martin, James R Dorsey, Hugh Coe, James D Allan, William J Bloss, Alistair J Thorpe, David C S Beddows, Manuel DallOsto, Roy M Harrison, Steven Smith, 2012, pregledni znanstveni članek

Opis: The Regents Park and Tower Environmental Experiment (REPARTEE) comprised two campaigns in London in October 2006 and October/November 2007. The experiment design involved measurements at a heavily trafficked roadside site, two urban background sites and an elevated site at 160-190 m above ground on the BT Tower, supplemented in the second campaign by Doppler lidar measurements of atmospheric vertical structure. A wide range of measurements of airborne particle physical metrics and chemical composition were made as well as measurements of a considerable range of gas phase species and the fluxes of both particulate and gas phase substances. Significant findings include (a) demonstration of the evaporation of traffic-generated nanoparticles during both horizontal and vertical atmospheric transport; (b) generation of a large base of information on the fluxes of nanoparticles, accumulation mode particles and specific chemical components of the aerosol and a range of gas phase species, as well as the elucidation of key processes and comparison with emissions inventories; (c) quantification of vertical gradients in selected aerosol and trace gas species which has demonstrated the important role of regional transport in influencing concentrations of sulphate, nitrate and secondary organic compounds within the atmosphere of London; (d) generation of new data on the atmospheric structure and turbulence above London, including the estimation of mixed layer depths; (e) provision of new data on trace gas dispersion in the urban atmosphere through the release of purposeful tracers; (f) the determination of spatial differences in aerosol particle size distributions and their interpretation in terms of sources and physico-chemical transformations; (g) studies of the nocturnal oxidation of nitrogen oxides and of the diurnal behaviour of nitrate aerosol in the urban atmosphere, and (h) new information on the chemical composition and source apportionment of particulate matter size fractions in the atmosphere of London derived both from bulk chemical analysis and aerosol mass spectrometry with two instrument types.
Najdeno v: osebi
Ključne besede: megacity, trace gas, urban atmosphere, atmospheric transport, chemical composition, aerosol
Objavljeno: 18.07.2019; Ogledov: 186; Prenosov: 0
.pdf Polno besedilo (4,66 MB)

7.
Short-range urban dispersion experiments using fixed and moving sources
Stephen E Belcher, Alison S Tomlin, James Tate, Marina K Neophytou, Rex E Britter, Fredrik Petterson, Iain R White, Graham Nickless, Catheryn S Price, Damien Martin, Dudley E. Shallcross, Janet F Barlow, Alan Robins, 2009, izvirni znanstveni članek

Opis: Four perfluorocarbon tracer dispersion experiments were carried out in central London, United Kingdom in 2004. These experiments were supplementary to the dispersion of air pollution and penetration into the local environment (DAPPLE) campaign and consisted of ground level releases, roof level releases and mobile releases; the latter are believed to be the first such experiments to be undertaken. A detailed description of the experiments including release, sampling, analysis and wind observations is given. The characteristics of dispersion from the fixed and mobile sources are discussed and contrasted, in particular, the decay in concentration levels away from the source location and the additional variability that results from the non-uniformity of vehicle speed.
Najdeno v: osebi
Ključne besede: dapple, perfluorocarbon, tracer, mobile source
Objavljeno: 18.07.2019; Ogledov: 169; Prenosov: 0
.pdf Polno besedilo (265,68 KB)

8.
Dispersion experiments in central London: The 2007 DAPPLE project
Curtis R Wood, Samantha J Arnold, Ahmed A Balogun, Janet F Barlow, Stephen E Belcher, Rex E Britter, Hong Cheng, Adrian Dobre, Justin J N Lingard, Damien Martin, Marina K Neophytou, Fredrik K Petersson, Alan G Robins, Dudley E. Shallcross, Robert J Smalley, James E Tate, Alison S Tomlin, Iain R White, 2009, izvirni znanstveni članek

Opis: In the event of a release of toxic gas in the center of London, emergency services personnel would need to determine quickly the extent of the area contaminated. The transport of pollutants by turbulent flow within the complex streets and building architecture of London, United Kingdom, is not straightforward, and we might wonder whether it is at all possible to make a scientifically reasoned decision. Here, we describe recent progress from a major U.K. project, Dispersion of Air Pollution and its Penetration into the Local Environment (DAPPLE; information online at www.dapple.org.uk). In DAPPLE, we focus on the movement of airborne pollutants in cities by developing a greater understanding of atmospheric flow and dispersion within urban street networks. In particular, we carried out full-scale dispersion experiments in central London from 2003 through 2008 to address the extent of the dispersion of tracers following their release at street level. These measurements complemented previous studies because 1) our focus was on dispersion within the first kilometer from the source, when most of the material was expected to remain within the street network rather than being mixed into the boundary layer aloft; 2) measurements were made under a wide variety of meteorological conditions; and 3) central London represents a European, rather than North American, city geometry. Interpretation of the results from the full-scale experiments was supported by extensive numerical and wind tunnel modeling, which allowed more detailed analysis under idealized and controlled conditions. In this article, we review the full-scale DAPPLE methodologies and show early results from the analysis of the 2007 field campaign data.
Najdeno v: osebi
Ključne besede: Air quality, Atmospheric thermodynamics, Dispersions, Experiments
Objavljeno: 18.07.2019; Ogledov: 167; Prenosov: 0
.pdf Polno besedilo (17,86 MB)

9.
CityFlux perfluorocarbon tracer experiments
Fredrik K Petersson, Damien Martin, Iain R White, Stephen J Henshaw, Graham Nickless, Ian Longley, Carl J Percival, Martin Gallagher, Dudley E. Shallcross, 2010, izvirni znanstveni članek

Opis: In June 2006, two perfluorocarbon tracer experiments were conducted in central Manchester UK as part of the CityFlux campaign. The main aim was to investigate vertical dispersion in an urban area during convective conditions, but dispersion mechanisms within the street network were also studied. Paired receptors were used in most cases where one receptor was located at ground level and one at roof level. One receptor was located on the roof of Portland Tower which is an 80m high building in central Manchester. Source receptor distances in the two experiments varied between 120 and 600 m. The results reveal that maximum concentration was sometimes found at roof level rather than at ground level implying the effectiveness of convective forces on dispersion. The degree of vertical dispersion was found to be dependent on source receptor distance as well as on building height in proximity to the release site. Evidence of flow channelling in a street canyon was also found. Both a Gaussian profile and a street network model were applied and the results show that the urban topography may lead to highly effective flow channelling which therefore may be a very important dispersion mechanism should the right meteorological conditions prevail. The experimental results from this campaign have also been compared with a simple urban dispersion model that was developed during the DAPPLE framework and show good agreement with this. The results presented here are some of the first published regarding vertical dispersion. More tracer experiments are needed in order to further characterise vertical concentration profiles and their dependence on, for instance, atmospheric stability. The impact of urban topography on pollutant dispersion is important to focus on in future tracer experiments in order to improve performance of models as well as for our understanding of the relationship between air quality and public health.
Najdeno v: osebi
Ključne besede: air quality, atmospheric chemistry, concentration (composition), convective system, dispersion, public health, street canyon, tracer, urban area
Objavljeno: 18.07.2019; Ogledov: 181; Prenosov: 0
.pdf Polno besedilo (1,07 MB)

10.
Urban tracer dispersion experiments during the second DAPPLE field campaign in London 2004
Damien Martin, Catheryn S Price, Iain R White, Graham Nickless, K Fredrik Petersson, Rex E Britter, Alan G Robins, Stephen E Belcher, Janet F Barlow, Marie Neophytou, Samantha J Arnold, Alan S Tomlin, Robert J Smalley, Dudley E. Shallcross, 2010, izvirni znanstveni članek

Opis: As part of the DAPPLE programme two large scale urban tracer experiments using multiple simultaneous releases of cyclic perfluoroalkanes from fixed location point sources was performed. The receptor concentrations along with relevant meteorological parameters measured are compared with a three screening dispersion models in order to best predict the decay of pollution sources with respect to distance. It is shown here that the simple dispersion models tested here can provide a reasonable upper bound estimate of the maximum concentrations measured with an empirical model derived from field observations and wind tunnel studies providing the best estimate. An indoor receptor was also used to assess indoor concentrations and their pertinence to commonly used evacuation procedures.
Najdeno v: osebi
Ključne besede: Dapple, dispersion
Objavljeno: 18.07.2019; Ogledov: 165; Prenosov: 0
.pdf Polno besedilo (1,69 MB)

Iskanje izvedeno v 0 sek.
Na vrh