Local and regional sources of C(2)-C (8) hydrocarbon concentrations at a sub-urban motorway site (M4) in Ireland.

Approximately 8 months of C(2)-C(8) online-sampling of hydrocarbons was carried out in the vicinity of a sub-urban Motorway in Ireland. A comprehensive description of air quality monitoring adjacent to the M4 at Leixlip in Ireland is presented where the primary objective was to ascertain the local and regional C(2)-C(8) hydrocarbon emissions in the vicinity of a sub-urban Motorway (M4). Nineteen HC compounds were monitored where different analysis techniques were employed in an attempt to isolate the Motorway source effect. Included in these were analyses into various hydrocarbon ratios, including 1,3 butadiene/propene, m + p xylene/ethylbenzene and ethene/acetylene. In addition, the local source effect was quantitatively assessed using COPERTIII and CALINE4 modelling, and the regional effects and source contributions were analysed using 2-D back trajectory analysis. Our results show that conditions associated with high regional contributions are associated with conditions also conducive to high local contributions, particularly evident at the M4 site due to the road orientation, as air masses from continental Europe and the UK are likely to be associated with near parallel, slow moving local winds relative to the M4, yielding higher local contributions.

Exposure to hydrocarbon concentrations while commuting or exercising in Dublin.

In Ireland, several studies have monitored the air pollution due to traffic in both urban and rural environments. However, few studies have attempted to quantify the relative exposure to traffic derived HC pollutants between different modes of commuter transport. In this study, the difference in pollution exposure between bus and cycling commuters on a route in Dublin was compared by sampling for five vehicle related hydrocarbons: benzene, 1,3-butadiene, acetylene, ethane and ethylene. Samples were collected during both morning and afternoon rush hour periods using a fixed speed pump to gain representative concentrations across the whole journey. Journey times were also measured, as were typical breathing rates in order to calculate the overall dose of pollutant inhaled on the journey. Results clearly picked up significantly higher pollutant concentrations in the bus compared to cycling and also revealed elevated concentrations on the congested side of the road compared to the side moving against the traffic. However, when respiration rates and travel times were taken into account to reveal the mass of pollutants inhaled over the course of a journey, the pattern was reversed, showing slightly enhanced levels of hydrocarbons for the cyclist compared to the bus passenger. In addition, the concentrations of these compounds (excluding ethane), were ascertained at playing pitches in the vicinity of a heavily trafficked suburban motorway and in Dublin city centre. Although the concentrations were relatively low at all sites, when breathing rates were taken into consideration, the average inhaled weights of pollutants were, on occasion, higher than those average values observed for both bus and bicycle commuters.

C2-C6 background hydrocarbon concentrations monitored at a roof top and green park site, in Dublin City centre.

A 5 week monitoring campaign was carried out in Dublin City centre, to establish which site gave a more accurate background city centre estimation: a roof-top or green field site. This background represented a conservative estimate of HC exposure in Dublin City centre, useful for quantifying health effects related to this form of pollution and also for establishing a local background relative to the four surrounding main roads when the wind direction is travelling towards each road with the background receptor upwind. Over the entire monitoring campaign, the lowest concentrations and relative standard deviations were observed at the green field site, regardless of time of day or meteorological effects.