HR: 0830h
AN: A31C-0052    [PDF]
TI: Tracer Dispersion Within an Urban Environment.
AU: * Martin, D
EM: D.Martin@bristol.ac.uk
AF: University of Bristol, School of Chemistry Cantocks Close, Bristol, BS8 1TS United Kingdom
AU: Shallcross, D
EM: d.e.shallcross@bristol.ac.uk
AF: University of Bristol, School of Chemistry Cantocks Close, Bristol, BS8 1TS United Kingdom
AU: Price, C
EM: catheryn.price@bristol.ac.uk
AF: University of Bristol, School of Chemistry Cantocks Close, Bristol, BS8 1TS United Kingdom
AU: Nickless, G
EM: grah.nickless@bristol.ac.uk
AF: University of Bristol, School of Chemistry Cantocks Close, Bristol, BS8 1TS United Kingdom
AU: Simmonds, P
EM: petergsimmonds@aol.com
AF: University of Bristol, School of Chemistry Cantocks Close, Bristol, BS8 1TS United Kingdom
AB: The transport and dispersion of pollutants has extremely important implications for the environment on urban, regional and global scales. At the urban level localised emissions of both biogenic and anthropogenic pollutants can directly impact the health of the inhabitants. The DAPPLE (Dispersion of Air Pollutants and their Penetration into the Local Environment) project is a consortium of six universities, which involves a multidisciplinary approach to characterise relatively small-scale urban atmospheric dispersion including wind tunnel modelling, computer simulations, fieldwork and analysis. This work describes the tracer technology used to characterise atmospheric dispersion as well as preliminary results from the first tracer release experiment in Central London. A steady state finite duration release of both perfluoromethylcyclohexane (PMCH) and Sulfur Hexafluoride (SF6 ) was performed as part of the first DAPPLE campaign. These compounds were released over a fifteen-minute integrated time period with the SF6 release staggered one and a half minutes behind the PMCH. The low background concentrations of PMCH (~ 5 x 10-3 pptv) and SF6 (~5pptv) along with non-depositing and non-reactive characteristics allow for the implementation of near ideal fluid dynamic experiments. Sampling consists of a multiport ladder fitting with solenoid valves onto which a succession of sampling bags is attached. These are electrically actuated in sequential order with an integrated sampling time of three minutes. The samplers are placed at various receptor positions in the DAPPLE zone in predefined positions designed to best validate these model simulated meteorological dispersion processes. Analysis of PMCH is carried out using sample enrichment on carbon based adsorbents, separation by capillary Gas Chromatography and Negative Ion Chemical Ionisation Mass Spectrometry detection (GC-MS-NICI). SF6 concentrations are determined using fixed volume loop injections with Gas Chromatography with an Electron Capture Detector (ECD). Preliminary results from the first field campaign in London are presented. These results compare well with those obtained from an advanced operational dispersion model and simple analytical models run at Cambridge University, UK as well as wind tunnel tracer simulation experiments carried out at the University of Surrey, UK.
DE: 0300 ATMOSPHERIC COMPOSITION AND STRUCTURE
SC: Atmospheric Sciences [A]
MN: 2003 Fall Meeting