The use of receptor modelling and emission inventory data to explain the downward trend in UK PM10 concentrations

Statistically significant downward trends in measured UK annual mean PM10 concentrations have been observed at eight out of the nine urban background monitoring sites between the start of monitoring in 1992 or 1993 and 2000. Site-specific projections of the individual components of measured PM10 concentrations have been derived for the period 1992–2000 at three monitoring sites from receptor modelling results for 1999 monitoring data. Measured annual average PM10 concentrations declined to between 71% and 66% of the 1992 values during this period at the sites studied. The largest contributions to the decline in total PM10 are from secondary particles at London Bloomsbury (40%, 3.4 μg m−3, tapered element oscillating microbalance (TEOM)), stationary sources at Belfast Centre (53%, 4.6 μg m−3, TEOM) and roadside traffic emissions at Bury Roadside (49%, 5.0 μg m−3, TEOM). The good agreement between the projected total PM10 concentrations and measured values for the years 1992–2000 indicate that the combination of the receptor model and the site-specific projections provide a suitably robust method for predicting future PM10 concentrations and the quantification of the impact of possible future policy measures to reduce PM10 concentrations. The good agreement between the projections and measured concentration also provides a useful verification of the trends in emissions inventory estimates for the 1990s. Projections of estimated PM10 concentrations have also been calculated for the London Bloomsbury site for the period from 1970 to 1991. Annual mean concentrations are predicted to have been in the range from 30 to 35 μg m−3, TEOM from 1977 to 1991 but much higher at values between 39 and 46 μg m−3, TEOM in the early 1970s.