Ron Hamilton

Characterisation of selected speciated organic compounds associated with particulate matter in London

Total suspended particulate matter (TSP) was collected and analysed at two sites in central and north London during 1995/6 for particulate-associated total organic carbon (TOC), particulate elemental carbon (PEC), 16 polycyclic aromatic hydrocarbons (PAHs) and 23 n-alkanes. The analysis revealed slightly higher concentrations of all of these substances at the central London location and generally low correlations between variables. Overall, PEC was measured as 1–13% of TSP, whilst TOC was measured as 7–45% of TSP. Seasonal differences in concentrations were identified at both sites, with higher concentrations of combustion related compounds occurring in winter and autumn. The dominant PAH compounds were found to be the higher molecular weight compounds, namely BghiP, BaA and Chrys. n-alkane compound distributions between C10 and C34 showed that the highest concentrations of compounds were between C21 and C29. Three methods were used to identify specific sources of particulate-associated organic compounds. Ratios of PAHs indicated a dominant petroleum source at both sites, with a higher diesel component at the central London site. Carbon preference index (CPI) values of 1.03 and 1.28 for the central and north London sites, respectively, indicated a stronger anthropogenic (vehicular) influence at the central London location. Using principal component analysis (PCA), key principal components (PCs) were extracted from each data set. These PCs collectively accounted for 76.4 and 78.1% of the total variations within the north and central London data sets, respectively, although differentiation of sources proved difficult because the organic compounds monitored may not be statistically independent.

Characterisation of Particulate Matter Sampled during a Study of Children's Personal Exposure to Airborne Particulate Matter in a UK Urban Environment

The personal exposure of children aged 9 – 11 years to particulate matter (PM10 and PM2.5) was carried out between January and September 1997 in the London Borough of Barnet. Personal sampling along with home, garden and classroom microenvironmental monitoring was completed for all ten children. Each child was monitored for five days during winter, spring and summer. All children completed daily time activity diaries to provide information on any potential activities that could influence their exposure to particulate matter. Each evening a household activity questionnaire was also completed by the parents. Personal Environmental Monitors were used to sample personal exposure to PM10 and PM2.5. Harvard Impactors were used for the microenvironmental sampling of both size fractions. The childrens mean personal exposure concentrations for PM10 during winter, spring and summer were 72, 54 and 35 µg/m3 respectively and for PM2.5 22, 17 and 18 µg/m3 respectively. In order to determine the potential sources of particulate matter, analysis of the Teflon filters has been undertaken. The physical characteristics of the particles have been identified using Scanning Electron Microscopy. The relationships between personal exposure concentrations and the different microenvironments will be discussed.

Water nucleation on aerosol particles containing both soluble and insoluble substances

A theory of heterogeneous water nucleation on aerosol particles consisting of soluble and insoluble substances has been developed. The case of partially wettable spherical insoluble core is considered. The theory links interfacial free energies of the surfaces, size of an insoluble core and chemical characteristics of the soluble substances with the ability of the aerosols to form water droplets. It is shown that water nucleation on such aerosols is strongly influenced by insoluble substances. The theory is compared with Kohlers theory and major differences in equilibrium pressure of water vapour and nucleation rate were found. These differences are explained by the influence of the insoluble substances on the free energy of embryo formation.

A comparison of carbonyl compound concentrations at urban roadside and indoor sites

Measurements of formaldehyde, acetaldehyde, hexanal, crotonaldehyde, acrolein, propanal, benzaldehyde and iso-valeraldehyde concentrations were made at two locations (four sites) in London, UK. One location was in Ealing, West London, while the other was in Wood Green, North London. At each location, a residential and commercial roadside site was identified and monitored. The measurements were made using a derivatisation technique in which sample air was pumped through an acidified solution of 2,4-dinitrophenylhydrazine, producing hydrazones which were separated and quantified using High Performance Liquid Chromatography (HPLC). Quantitative determinations were made for 26 and 47 samples at the Ealing and Wood Green locations respectively during 1991 and 1992. The average concentrations determined at the Ealing location for formaldehyde, acetaldehyde, hexanal and crotonaldehyde (taking into account concentrations below the detection limits) were 15.0, 2.5, 1.5 and 1.2 ppb, respectively (residential site), and for the commercial site the corresponding values were 19.2, 1.6, 1.2 and 0.5 ppb. Similarly, at the residential site in Wood Green, the average concentrations for formaldehyde, acetaldehyde, hexanal and crotonaldehyde were 3.4, 1.9, 0.5 and 0.5 ppb, respectively, while at the commercial site the average concentrations for formaldehyde, acetaldehyde and hexanal were 7.4, 2.3 and 0.6 ppb. Acrolein, propanal, benzaldehyde and iso-valeraldehyde were not detected at either survey location. At the residential location in Wood Green, sufficient samples were collected to allow the data to be statistically divided into morning and afternoon collection periods, and the data show that the aldehyde concentrations were generally slightly higher in the afternoon. The observed concentrations reported here are compared with previously reported measurements in the UK and with indoor measurements taken at the Bounds Green Campus of Middlesex University. The advantages and limitations of the method employed are also discussed and compared with a solid-phase extraction technique.

Social awareness of air quality information

In the UK, air quality information is made available through a range of media. However, limited attention has been paid to ensuring that the information is provided to the public in a format that is understandable and relevant to their needs. This research has begun the task of determining the nature and extent of public air quality requirements by performing a social survey (using a postal questionnaire) to provide a basic snapshot of the publics views and by determining the views of information providers and interested professionals. The paper identifies the main shortcomings in current public air quality information provision. The social survey and workshop results demonstrate that current information provision and dissemination does not match public requirements; the depth and breadth of local information needs to be enhanced. Local authorities need to improve their co-ordination and collaboration, the role of the mass-media needs to be considered carefully, air quality needs to be better described and its implications for individuals spelled out and certain public groups need special consideration. In addition, local authorities need more guidance on communicating air quality, possibly through a best practice guide. Further research is required to identify the best descriptors for air quality, to improve the effectiveness of public advice during episodes of poor air quality and to use public air quality information to effect behavioral changes.

Dose–response functions for the soiling of heritage materials due to air pollution exposure

A set of materials (Portland limestone, white painted steel, white plastic and polycarbonate filter material) was exposed at locations in London, Athens and Krakow. Regular measurements of reflectance were taken over a period of twelve months. Co-located measurements of PM(10) concentrations were available. Based on these results, the relationship between soiling (measured as loss of reflectance) and ambient PM(10) concentrations was quantified leading to the development of dose-response functions for the soiling of materials. The results for limestone revealed too much scatter for a prediction to be made. Implications for air quality management and for the conservation of cultural heritage buildings are considered, including public acceptability and economic factors.

Airborne particulate-associated polyaromatic hydrocarbons, n-alkanes, elemental and organic carbon in three European cities

Total suspended particulate (TSP) samples were collected weekly over a period of one year at four European sites during 1995/6. Two sites were in London-a Central London site (CL, St Pauls Cathedral) and a suburban North London site (NL, Bounds Green); the other two sites were in Porto, Portugal and Vienna, Austria. TSP was collected using a low volume sampler. Organic carbon (OC) and elemental carbon (EC) concentrations were measured using a thermal-optical carbon analyser. Parallel samplers collected TSP for subsequent GC-MS analysis of thirty-nine combustion-associated organic compounds; 16 polyaromatic hydrocarbons (PAHs) and 23 n-alkanes. OC and EC correlate well at all sites (r2 = 0.39-0.65), although the London inter-site correlations were low, suggesting that local sources of OC and EC have a significant influence on local concentrations. Concentrations do not vary widely across the four urban sites, despite the significant differences in urban characteristics. Seasonal patterns of OC:EC ratios were similar at the London and Vienna sites, with highest ratios in autumn and winter, and annual mean OC:EC ratios were identical at these sites. The Carbon Preference Index (CPI) indicated vehicle emissions to have a stronger influence over particulate concentrations at the Vienna and central London sites; there was a stronger biogenic signature in north London and Porto. In addition, two PAH compounds (pyrene and fluoranthene) previously associated with diesel exhaust, were correlated with OC and EC concentrations at the London and Vienna sites.

Using GIS and Dispersion Modelling Tools to Assess the Effect of the Environment on Health

A feasibility study in progress to integrate health and air quality information is presented. The methods of using integrated GIS and air quality dispersion modelling tools to assess the effect of the environment on health are discussed. The main aim is to model human personal exposure to air pollutants and compare the predictions to respiratory health data for asthmatics in a health telematics project. The MEDICATE project develops and tests the feasibility of using a health telematic system for asthmatics. Key to this is the determination of the real-time health (lung function) response to the ambient environment. For this, air quality information is related to respiratory measurements by modelling personal exposure through a GIS. The methods of integrating environmental modelling and assessment tools (GIS) in this case are examined. ESRI’s ArcView is used to locate and compile environmental information about the patients’ locations and lifestyles in the study areas (London and Barcelona). A dispersion modelling extension to ArcView, ADMS Urban, is used to interrogate the spatial environmental databases (e.g. emission inventories) to model air pollution concentrations. Patients’ personal exposure is modelled by time-weighted estimates of their exposure to ambient air quality at each defined location. Lung function data can be compared on a time-wise basis with these air quality indicators to see if there is a relationship on an hourly, daily or lagged-day basis. The aim of this paper is to propose a methodology and discuss the integration and practicalities of using air quality assessment tools (inventories, dispersion modelling and a GIS) in assessing the impacts of the environment on human health.

Remote sensing of carbon monoxide vehicle emissions

The University of Denvers remote sensor for automobile exhaust emissions has been used to obtain valid model year (defined here as the year of first registration) and emissions data from roadside locations in Middlesbrough and London. Mean carbon monoxide emissions have been plotted against model year to determine if there is a relationship between mean pollutant emissions and the age of the vehicle. The results initially showed a large degree of scatter and no inference, concerning age and emissions, could be made. This can be largely attributed to the older vehicles in the fleet. Older vehicles were then omitted from an additional investigation providing a much stronger relationship with R2 values of 0.88 being calculated for London and 0.77 for Middlesbrough. Analyses of model year fleet emissions were also undertaken. It was demonstrated that old vehicles do not contribute significantly to fleet emissions. Pre-1983 registered vehicles contributed only 9% of total fleet emissions in Middlesbrough and only 21% of total fleet emissions in London. It was also shown that the vast majority of fleet emissions come from a small number of highly polluting new vehicles (quintile 5). Quintile 5 for model year 1989 represented 140 vehicles (2% of the measured fleet) which contributed to 10.6% of fleet emissions at the Middlesbrough site.

Sulphur and nitrogen particulate pollutant deposition on to building surfaces

Abstract Results are presented for the fluxes of sulphur and nitrogen to the surfaces of three historic buildings in the UK. The relative importance of wet and dry deposition are considered and it is shown that dry deposition was the dominant input mechanism at these sites. The gaseous form contributed most of the flux and the contribution from particulate-associated matter was small. Gas-particle relationships for sulphur are examined in detail.