6 PM10 Projections for roadside monitoring sites

The receptor modelling methods have been extended to calculate projections for 1997 of roadside PM₁₀ concentrations for comparison with the NAQS objective and EU limit values. We have used daily measurements of PM₁₀ at the roadside along with rural sulphate values and measurements of NOx at the roadside and at a nearby urban background monitoring site. A regression analysis has been carried out to find the coefficients A, B and R:

1. = A.Background NOx + B.Sulphate + R.Roadside enhancement of NOx + C
   

Where the Roadside enhancement of NOx is defined as the measured daily mean NOx concentration at the roadside site with a background daily mean NOx concentration from a nearby background site subtracted:

roadside enhancement concentration = roadside concentration - background concentration

The regression coefficients and correlation coefficients obtained from this analysis are listed in Table 6.1.

Table 6.1 Coefficients of regression analysis of roadside sites (NOx expressed as ppb)

	Sulphate	Background NOx	Roadside NOx	Intercept	r2
London A3	2.74	0.177	0.0423	6.43	0.74
Bury Roadside	2.64	0.138	0.0662	6.90	0.71
Camden Roadside	2.33	0.120	0.0696	11.2	0.77
Haringey Roadside	2.53	0.125	0.0776	7.90	0.80
Glasgow Kerbside	3.11	0.0689	0.1234	6.92	0.79
London Hillingdon	2.42	0.135	0.0748	5.60	0.78
Marylebone Road	3.26	0.122	0.0901	6.12	0.79
Sutton Roadside	2.40	0.110	0.0961	7.04	0.74

We have then calculated projections for 2004 and 2005 and 2009 using the business as usual scenario. We have assumed that the roadside enhancement of PM₁₀ consists of 50% fine exhaust emissions and 50% coarse resuspended dust. This is consistent with a comparison of the roadside enhancements of PM₁₀, PM2.5 and NOx at Marylebone Road carried out by APEG (APEG 1998). Figure 6.1 shows that the slope of the regression line between the roadside enhancement of particle concentration and the roadside enhancement of NOx for PM₁₀ is twice the slope for PM2.5. The exhaust emissions are asumed to reduce in line with projected urban traffic emissions and the coarse resuspended dust is assumed to remain at 1997 levels.

The resulting projections are shown in Table 6.2. All sites are projected to exceed the NAQS objective in 2005 and the EU Stage 2 2009 98th percentile. Four of the sites are projected to exceed the EU 24-hour limit value in 2004, with three other sites having concentrations close to 50 mgm-3. At Marylebone Road the projected annual mean in 2004 is higher than the annual limit value of 40 mgm-3.

Table 6.2. PM₁₀ projections for Roadside sites based on 1997 monitoring data (mgm-3).

NAQS	London A3 Roadside	Bury Roadside	Camden Roadside	Haringey Roadside	Glasgow Kerbside	London Hillingdon	Marylebone Road	Sutton Roadside
1997 annual mean	28	30	32	26	31	25	39	24
1997 99th percentile	68	79	91	87	81	85	99	78
1997 Days>=50	7	14	32	19	19	15	26	16
Est. An. Mean 2004	24	25	28	23	26	22	32	21
Est. An. Mean 2005	23	25	28	22	26	21	32	21
Est. An. Mean 2009	21	23	26	21	24	19	29	19
99th perc. 2005	58	66	73	70	71	70	76	60
99th perc. 2009	53	61	68	64	68	65	68	58
2005 Days>=50	1	6	17	9	10	7	14	7
2009 Days>=50	0	5	13	7	3	6	10	3
EU
1997 annual mean	36	39	42	34	40	33	51	31
1997 90th percentile	57	61	62	55	61	54	76	49
1997 98th percentile	70	80	96	81	81	77	103	74
1997 Days>=50	25	47	83	51	74	50	66	34
Est. An. Mean 2004	31	33	36	30	34	29	42	27
Est. An. Mean 2009	27	30	34	27	31	25	38	25
2004 90th percentile	48	51	54	47	52	45	65	43
2009 90th percentile	60	46	50	43	48	41	59	38
2004 98th percentile	43	69	80	66	69	65	81	65
2009 98th percentile	55	62	73	62	64	61	72	58
2004 Days>=50	12	27	46	25	36	20	37	22
2009 Days>=50	6	18	36	22	20	14	20	15