Title of Example

Example

Further to the requirements of a stage four review and assessment, local authorities are required to identify “hotspots” or problem areas within the Air Quality Management Area and to conduct further monitoring to verify the scale of the problem and the relative required improvement in air quality.

In Bristol it was decided that further monitoring would be introduced in certain areas, and more detailed modelling would also be conducted. The map of hotspots shown below was derived from the initial modelling output for the whole city for annual mean NO₂. Locations within these hotspots were predicted to experience the highest concentrations of NO₂ in the city.

A “hotspot” is interpreted to mean a location at which the relevant exposure criteria is realised, and where higher than average concentrations of an National Air Quality Standards (NAQS) pollutant are likely to be measured or are predicted by a validated model for the relevant target year.

Figure SEQ Figure \* ARABIC 1 Hotspots modelled for stage four review

Figure SEQ Figure \* ARABIC 2 Diffusion tube surveys instigated at hotspots prior to stage four review

Figure SEQ Figure \* ARABIC 3 Diffusion tube monitoring and the extent of the AQMA at the Parson Street hotspot

Parson Street hotspot, shown above, is a good example of a pollution hotspot in Bristol. High traffic flows, a residential area with houses close to the roadside, vulnerable receptors (school) and enclosed “canyon” type streets combine to highlight this area as a potential pollution “hotspot”.

Pollution in the Parson Street area is relatively high, due to high traffic flows and congested traffic. It has been decreasing over the years, though the rate of decrease will slow and possibly reverse over the next few years without remedial action. The Parson Street gyratory has been extensively monitored and modelled as part of the City Council’s statutory duties under local air quality management. It is currently within an Air Quality Management Area (AQMA) which was declared in 2001 due to likely exceedences of the governments air quality objectives.

The Parson Street Gyratory System is a traffic light controlled one – way system linking the busy arterial route the A38 (Bedminster Down Road), Hartcliffe Way, Winterstoke Road, West Street and Bedminster Road. Traffic flows on the A38 and Winterstoke Road are particularly high and congestion on the gyratory is considerable, especially in peak hours.

The high traffic flows and congestion in this area had led officers in the Environmental Quality Team to suspect that this area constituted a “hot spot” of poor air quality following the initial “Stage 1” review and assessment of air quality during 1998. In order to research this further, two continuous atmospheric monitors were purchased and monitoring was started in February 1999. The two monitors measure carbon monoxide (CO) and oxides of nitrogen (NOx). The pollutant most likely to lead to health problems due to high concentrations is one oxide of nitrogen, nitrogen dioxide (NO₂). This is the pollutant on which this report will focus.

In addition to these continuous monitors, located in the grounds of Parson Street Primary School, near the pavement of Bedminster Road, a number of NO₂ diffusion tubes were placed on lampposts on the roads linking the one way system. This survey was instigated following the “Stage 3” review and assessment of air quality in Bristol that was published in November 2000. The placement of diffusion tubes was also driven by the forthcoming requirements of the stage four review and assessment.

The most stringent objective for the concentration of nitrogen dioxide set by government in the National Air Quality Strategy in an annual mean of 40µgm^-3. The Parson Street gyratory was included in the Air Quality Management Area declared in 2001 on the basis that it would not meet this objective by 2005 without remedial action.

Figure SEQ Figure \* ARABIC 4 Results of detailed dispersion modelling for stage four review at the Parson Street hotspot

Last Updated

13th January 2005