Air quality expert group - Fine particulate matter (PM2.5) in ... - Defra

PM2.5 in the UK
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105. Receptor modelling methods depend upon measured airborne concentrations
to infer the contributions of different source categories to concentrations in the
atmosphere. Both chemical mass balance and multivariate statistical methods
are applicable and results for the UK are available from a chemical mass balance
model. The results have been compared with those of the PCM model and
highlight significant differences in relation to industrial/commercial/residential
emissions of primary particles and the model predictions for secondary organic
aerosol particles. The receptor modelling results highlight the weaknesses in
current knowledge of a number of sources, including wood smoke and cooking
aerosol, and also suggest that NAEI emission factors for gas combustion may
be rather high. Use of carbon-14 as a tracer allows a distinction to be drawn
between carbon derived from contemporary sources, such as wood burning or
emissions from vegetation, and that derived from fossil fuel sources. Analysis
of carbon-14 in airborne particulate matter collected in Birmingham indicates a
major contribution to secondary organic carbon from biogenic precursors.
106. Formulation of abatement strategies is made difficult by inadequacies in
knowledge about the contribution of certain sources and weaknesses in
understanding precursor–secondary particle relationships for the major
secondary components.
107. Enhancement of emissions inventories is essential if numerical models of
atmospheric PM2.5 are to be improved. Areas of particular importance are
emissions of wood smoke, cooking aerosol, abrasion particles from traffic
and the PM2.5 precursor gas ammonia. Both the emissions and atmospheric
chemistry of biogenic VOCs are also in urgent need of further research.
108. A critical assessment of emission inventories and their ability to provide the
data required for modelling PM2.5 concentrations and its component parts
has been carried out. Inventories have traditionally been constructed for
reporting to international bodies following prescribed methods and procedures,
but these can fall short of the requirements of air quality modellers. AQEG
recommends developing inventories that provide a quantification of
the spatial and temporal variability in emissions of primary PM2.5 and
its precursors from all contributing sources including those not covered
in national inventories or provide the means for calculating them in air
quality models. This should include spatially-gridded inventories with high
resolution temporal profiles for different source sectors. This requires a better
understanding and means of quantifying emissions from key sources. Several
areas are identified for further research to achieve this goal, and which would
help underpin the development of more complete and reliable inventories for
modellers to use. The key areas are:
• non-exhaust vehicle emissions including tyre and brake wear, road abrasion
and road dust resuspension;
• fugitive dust emissions from construction, demolition, quarrying, mineral
handling, and industrial and agricultural processes, and methods for
quantifying them nationally and locally;
• PM2.5 emissions from domestic and commercial cooking;