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

Chapter 4
PM2.5 emissions and receptor modelling
PM2.5 emissions and receptor modelling
4.1 Introduction
1. PM2.5 is present in the atmosphere as a result of direct emissions from a
range of sources (primary PM2.5) and as a result of the chemical and physical
transformation of various precursor gases from a range of sources (secondary
PM2.5). The relationship between emissions and atmospheric concentrations is
therefore complex and a change in emissions does not necessarily lead to the
same relative change in PM2.5 concentrations and exposure.
2. This chapter discusses emissions of PM2.5 and its precursor gases from various
sources and gives projections to 2020. The uncertainties associated with
emissions inventories are also described. Receptor modelling is an approach to
the source apportionment of particles in the atmosphere which uses particle
composition to estimate source contributions to airborne concentrations.
4.2 Emissions and sources of primary PM2.5
4.2.1 Quantifying the emissions of all primary PM2.5 components and
their spatial distribution
3. Direct emissions of PM2.5 in the UK are estimated by the National Atmospheric
Emissions Inventory (NAEI). 1 A time series of the annual rates of emission by
source sector is reported to the United Nations Economic Commission for
Europe (UNECE) Convention on Long-Range Transboundary Air Pollution
(CLRTAP). A consistent time series of UK emissions is updated annually by the
NAEI; the latest version covers the years from 1980-2009 (the 2009 NAEI). The
emissions are reported to comply with CLRTAP by source sector as defined
under the Nomenclature for Reporting (NFR) format. 2
4. Emissions are estimated for anthropogenic sources from combustion and noncombustion
processes. The methodology for estimating emissions is described
in the UK’s Informative Inventory Reports (for example, in Passant et al. (2011))
and was described in detail in AQEG (2005). The methodology generally
involves combining sector-specific emission factors and activity data. The
activity data come from UK statistics on energy consumption, industrial output
or transport. Emission factors are taken from emission inventory guidebooks,
literature sources or national datasets, such as the compilation of emission
factors for road vehicles published by the Department for Transport (DfT)
(Boulter et al., 2009). Exhaust emission factors for road vehicles are affected by
type and size of vehicle, its age and what emission standard it complied with
when manufactured and sold new, what fuel it runs on and the way the vehicle
is driven. Vehicle emission factors are provided as a set of equations relating
emission factors for each detailed vehicle type to average speed and are derived
from measurements of emissions from vehicles driven over different ‘real world’
drive cycles. For some industrial point sources, emissions and activity data
1 See http://naei.defra.gov.uk/index.php.
2 See http://cdr.eionet.europa.eu/gb/un/cols3f2jg/envtvpebw.
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