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

2.5.4 What about measurements of chemical components of PM2.5?
81. Measurements of specific components of PM2.5 used within this report can
have lower uncertainties than the mass concentration itself, especially if they
are non-volatile, as they are independent of water content. However, specific
instruments such as the MARGA at Auchencorth Moss have had ongoing
operational problems making the data less reliable. Moreover, care must be
taken when comparing method-dependent quantities such as black carbon,
elemental carbon and organic carbon. In some cases, specific components of
PM10 have been used in this report where PM2.5 data are not available, and the
inclusion of the coarse size fraction needs to be taken into consideration.
2.6 Recommendations
Measuring PM2.5 and its components
82. Measurements of PM2.5 in the UK depend heavily on the FDMS
instrument, which has a relatively short track record in monitoring
networks. AQEG recommends that issues including long-term reliability,
dryer performance and the handling of semi-volatile components
are further investigated with the aim of better understanding the
measurement results and of improving data capture and measurement
uncertainty.
83. At present the measurement of PM2.5 remains a challenge, with
current measurements falling below the requirements of the Air Quality
Directive. AQEG recommends a focused working group is assembled
to address the achievement of Directive requirements using current
methods.
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