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

4.7 Summary
PM2.5 emissions and receptor modelling
98. The major sources of primary emissions of PM2.5 are combustion in the energy
industries, road transport (both exhaust and non-exhaust emissions), off-road
transport, residential combustion and small-scale waste burning.
99. Total PM2.5 emissions for the UK are predicted to decrease significantly by 2020,
with an especially large contribution from reductions in road traffic exhaust.
100. The main traffic sources of PM2.5 are exhaust emissions from diesel cars, light
goods vehicles and heavy goods vehicles, together with tyre wear, brake wear
and road surface abrasion. A broadly similar picture prevails across the European
Union.
101. There are significant uncertainties attached to some of these emissions
estimates, particularly to the emissions of PM2.5 from non-exhaust traffic
sources.
102. With reductions in exhaust emissions of PM, non-exhaust components of
traffic emissions will become much more important, emphasising the need to
introduce measures to control emissions from these non-exhaust traffic sources.
103. Emissions of precursor gases for secondary PM2.5 components have also been
considered. UK total emissions of NOx have been declining since 1999 and are
set to decline further by 2020. There is some uncertainty in inventories for road
transport emissions for NOx; evidence suggests that vehicle emission directives
have not been effective in reducing “real world” NOx emissions from modern
diesel vehicles manufactured to meet Euro III-V standards. While future road
transport emissions are expected to fall, the rate of reduction may not be as
fast as previous inventory projections have indicated. UK emissions of sulphur
dioxide and non-methane volatile organic compounds have also been declining
and are expected to continue to do so. For ammonia, emissions have fallen
only slightly since 1990 and are not predicted to fall significantly between 2010
and 2020. EU emissions of NOx have not fallen as rapidly as in the UK but are
projected to decline rapidly by 2020 and significant reductions in emissions of
both sulphur dioxide and non-methane volatile organic compounds from the
EU-27 are predicted. On the other hand, emissions of ammonia from the EU-27
are predicted to increase in the coming years.
104. Emissions from shipping are not well quantified. Emissions of NOx and SO2
from shipping in Europe are predicted to increase or only slightly fall in the next
decade, although SO2 emissions in Sulphur Emission Control Areas around the
UK coast are expected to fall significantly. Without further abatement, emissions
from shipping will become a more dominant source of PM2.5 precursor
emissions in Europe.
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