5 Projections based on 1997 monitoring data

5.1 Introduction
There was a substantial increase in the number of automatic PM₁₀ monitoring sites within the DETR national monitoring networks during 1996 and 1997. This has enabled us to calculate projections from a 1997 base year for many more sites than was possible for 1996 and 1995. Projections for urban background and rural sites are discussed in this section and the results are compared with those for the 1996 and 1995 base years. The extension of the receptor modelling methods to roadside and industrial sites is discussed in section 6 and section 7.

5.2 Projections for urban background sites
Projections of PM₁₀ concentrations have been calculated for comparison with both the NAQS objective and the EU Daughter Directive limit values. These projections are based on an analysis of 1997 monitoring data for 30 sites classified as either urban background, urban centre, suburban or rural. We have used daily measurements of PM₁₀ and NOx at each site along with rural sulphate values. A regression analysis then enables us to divide the measured roadside PM₁₀ concentrations into the following components

• primary (based on the site NOx)
  
• secondary (based on rural sulphate)
  
• other (largely background coarse, calculated by difference)
  

The regression coefficients obtained for these 30 sites are listed in Table 5.1. The data for most urban sites fit the model reasonably well, with coefficients close to those calculated using 1995 and 1996 data.

PM₁₀ concentration forecasts were calculated using these coefficients and the business as usual scenario. These projections are listed in Table 5.2 and the results have been compared with NAQS objective and EU limit values:

	NAQS -	2005: 99 th percentile not to exceed 50 mgm-3.
	EU Stage 1 -	2004: 90 th percentile not to exceed 50 mgm-3; with the maximum annual mean of 40 mgm-3.
	EU Stage 2 -	2009: 98 th percentile not to exceed 50 mgm-3; with the maximum annual mean of 20mgm-3.

The results listed in Table 5.2 suggest that most sites would exceed the NAQS 2005 99th percentile objective for the business as usual scenario. All sites should achieve the EU Stage 1 objective for annual mean but not the indicative Stage 2 annual mean limit value. Leeds is the only site predicted to exceed the EU stage 1 2004 90th percentile target. However, many sites - Belfast Centre, London Bexley, London Bloomsbury, Derry, London Hillingdon, Hull Centre, London N. Kensington, Leeds Centre, Sheffield Centre, Southampton Centre, Thurrock and Wolverhampton Centre would exceed the EU 2009 98th percentile.

NAQS 99th percentile and EU Stage 1 90th percentile projections for base years 1995, 1996 and 1997 for background sites are summarised in Table 5.3. The projections based on 1996 data are generally the highest because of the unusual episodes of elevated secondary partcile concentrations in 1996. The 1997 based values are generally similar to the 1995 based values, with the 1997 value often being a bit lower. At a few sites the NAQS objective is achieved for projections based in 1997 data.