TRL Ltd is monitoring the environmental effects of the Gloucester Safer City project. As part of this work, a city-wide network of monitoring sites has been set up to determine concentrations of nitrogen dioxide, PM10 and benzene in Gloucester. The network comprises 10 kerbside sites and a background site. This document reports on the first two years (1997 and 1998) of the air quality monitoring in Gloucester. In both years benzene concentrations at all of the sites were below the Air Quality Standard of 16.25 micrograms/cu m (5ppb). Over the monitoring period, the mean concentrations fell at the kerbside locations by 24% and at the background by 53%, which reflects the general decline in hydrocarbon emissions from traffic in Gloucester. For nitrogen dioxide, concentrations at the kerbside were close to or greater than the Air Quality Standard of 40 microgram/cu m. On average concentrations fell by 9% at the kerbside, which again reflects a decline in the emissions of oxides of nitrogen from traffic in Gloucester. However over the same period, nitrogen dioxide concentrations increased at the background site by 7%. Air quality monitoring is to continue until the end of 2001 largely as described in this report, except for additional sampling of kerbside PM10 and carbon monoxide. (A)
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