Damien Martin

DISPERSION EXPERIMENTS IN CENTRAL LONDON The 2007 Dapple Project

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...

In situ gas chromatographic measurements of halocarbons in an urban environment

Abstract A GC-ECD system has been used to make continuous measurements of nine halocarbons in the urban environment of Bristol, England over the course of about one month. A GC-FID system was deployed in the same location which simultaneously monitored over 30 C2–C8 hydrocarbons. In this paper, the halocarbon time series is presented and compared with the hydrocarbon data set. The influence of local sources is investigated by comparing the fluctuations in halocarbon concentrations with local weather conditions. A complex time series is seen, with no species displaying any clear diurnal cycle. Additionally, large deviations from baseline levels are observed for many of the compounds at different times. Local small-scale industry and landfill sites are postulated as the source of many of these excursions. The geography of Bristol has been found to influence levels of pollution in the city as the surrounding hills trap emissions and prevent their quick dispersion.

Use of Reactive Tracers To Determine Ambient OH Radical Concentrations: Application within the Indoor Environment

The hydroxyl radical (OH) plays a key role in determining indoor air quality. However, its highly reactive nature and low concentration indoors impede direct analysis. This paper describes the techniques used to indirectly quantify indoor OH, including the development of a new method based on the instantaneous release of chemical tracers into the air. This method was used to detect ambient OH in two indoor seminar rooms following tracer detection by gas chromatography-mass spectrometry (GCMS). The results from these tests add to the small number of experiments that have measured indoor OH which are discussed with regard to future directions within air quality research.

Determination of gas-phase ozonolysis rate coefficients of a number of sesquiterpenes at elevated temperatures using the relative rate method

The rates of ozonolysis of four sesquiterpenes, β-caryophyllene, α-humulene, isolongifolene and α-cedrene, are determined in the gas phase at an elevated temperature of 366 ± 3 K and a pressure of ~780 Torr using the EXTreme RAnge chamber (EXTRA). The experimentally obtained rate coefficients agree with extrapolated room temperature rate coefficients for isolongifolene and α-cedrene but not for β-caryophyllene and α-humulene, which were found to be three orders of magnitude slower than this in the literature. These new measurements support the hypothesis that operating under ambient conditions, kinetic measurements of condensable species can be influenced adversely by heterogeneous processes and should therefore be treated with caution.

CityFlux perfluorocarbon tracer experiments

CityFlux perfluorocarbon tracer experiments F. K. Petersson, D. Martin, I. R. White, S. J. Henshaw, G. Nickless, I. Longley, C. J. Percival, M. Gallagher, and D. E. Shallcross School of Chemistry, University of Bristol, Bristol, UK SEAS, University of Manchester, Manchester, UK now at: Ionicon Analytik Gesellschaft m.b.H., Innsbruck, Austria now at: National Institute of Water and Atmospheric Research, New Zealand Received: 30 September 2009 – Accepted: 3 December 2009 – Published: 5 January 2010 Correspondence to: D. E. Shallcross (d.e.shallcross@bristol.ac.uk) Published by Copernicus Publications on behalf of the European Geosciences Union.

Urban pollutant transport and infiltration into buildings using perfluorocarbon tracers

People spend the majority of their time indoors and therefore the quality of indoor air is worthy of investigation; indoor air quality is affected by indoor sources of pollutants and from pollutants entering buildings from outdoors. In this study, unique perfluorocarbon tracers were released in five experiments at a 100 m and ~2 km distance from a large university building in Manchester, UK and tracer was also released inside the building to measure the amount of outdoor material penetrating into buildings and the flow of material within the building itself. Air samples of the tracer were taken in several rooms within the building, and a CO2 tracer was used within the building to estimate air-exchange rates. Air-exchange rates were found to vary between 0.57 and 10.90 per hour. Indoor perfluorocarbon tracer concentrations were paired to outdoor tracer concentrations, and in-out ratios were found to vary between 0.01 and 3.6. The largest room with the lowest air-exchange rate exhibited elevated tracer concentrations for over 60 min after the release had finished, but generally had the lowest concentrations, the room with the highest ventilation rates had the highest concentration over 30 min, but the peak decayed more rapidly. Tracer concentrations indoors compared to outdoors imply that pollutants remain within buildings after they have cleared outside, which must be considered when evaluating human exposure to outdoor pollutants.

Assessment of the effects of changing meteorology on future isoprene and isoprene SOA using a regional climate model

In this study we assess the future ambient levels of isoprene and isoprene SOA for the years 2006, 2030, 2050 and 2100 using a regional climate model. The model is initiliased and boundary values are given by the output of a global model (ECHAM5-HAM–MPIOM-HAMMOC. A key focus point of this study is the variation in particular matter loading with changing meteorology due to climate change.

Future aerosol concentrations in Europe: Effects of changing meteorology and emissions

The ambient particulate matter concentrations are assessed using annual simulations for model validation period 2006, and for future time-slice years 2030, 2050 and 2100 under RCP scenario 6.0. Meteorological initial and boundary conditions are procured from ECHAM5-HAMMOC global simulations. The contribution of natural and anthropogenic processes to aerosol concentrations are assessed with particular emphasis on accumulation mode sea salt, organic enrichment thereof and future levels of secondary organic aerosol from isoprene.

Modelling marine aerosol precursor vapours & impact on aerosol population

Regional climate model REMOTE is employed to assess the impact of two new sources of marine aerosol precursor vapours (DMS and volatile organo-iodine vapours) on the aerosol population. Microphysical model M7 is applied within REMOTE to simulate gas to particle conversion processes. Results indicate new ultra-fine particle production of the order of 103 particles cm−3 in the North East Atlantic, predominantly due to the nucleation of iodinecontaining vapours. The consideration of DMS vapours in the model leads to an increase in sulphur gases (factor of 1.5-2) which is of sufficient magnitude to enhance the growth of accumulation mode particles over the model domain, the resulting effect on the radiative properties of the atmosphere of potential global significance.

Assessment of the effect of trans-boundary air pollution on aerosol concentrations in Ireland

In this work a regional model is deployed in order to determine the effect of trans boundary species on speciated aerosol concentrations over Ireland. A Regional Climate model is deployed and simulations are run for January and August 2006 in order to quantify the magnitude of this pollution transport and its contribution to ambient concentrations.