Transcript Metrology for Pollution Monitoring

Metrology for Pollution Monitoring
Pier Giorgio SPAZZINI
INRIM
PG Spazzini – EMPIR Call 2016 meeting
What’s this about?
• Air pollution, despite actions
taken in the last decades, is
still a growing concern in
environmental policies
• It comes in various flavours:
– Particulate pollution (e.g. PM10;
presently attention is being
focused on lower sizes)
– Chemical pollution (e.g. PAHs)
– Biological pollution (bacteria
etc.)
PG Spazzini – EMPIR Call 2016 meeting
What to do?
• Actions can cover a wide
range:
– immediate (e.g. traffic stops)
– Longer term (e.g. more stringent
norms)
– Planning for the future (e.g. 2020-20 vision)
PG Spazzini – EMPIR Call 2016 meeting
And, how?
• All kind of action, regardless of its span,
requires hard and reliable data for:
– Decision on action
– Decision on level of action
– Monitoring of results
– Analysis of effectiveness
PG Spazzini – EMPIR Call 2016 meeting
So, what do we use?
• All data about pollution are based on the
concepts of concentration, i.e. «how much
pollutant (whatever it is) do we have in a
given quantity of air»?
• The quantity of air is expressed as a
volume: particles (or micrograms of PAH,
or bacteria) per cubic meter
PG Spazzini – EMPIR Call 2016 meeting
So, what do we use?
• Of course, measurements are necessarily
made on a statistical basis, i.e. some
portion of air will be taken and analyzed
and will be considered to be
representative of the situation where the
measurement was performed
• Instruments for the measurement of
pollutant concentration are known as «air
samplers»
PG Spazzini – EMPIR Call 2016 meeting
How do we compute concentration?
• The definition of concentration, as given
above, leads to the following formulation:
•
𝐶=
𝑃
𝑉
• Where P is the quantity of pollutant and V
is the volume of air that was analyzed
• And of course the uncertainty on C will be:
•
𝑢2 (𝐶)
𝐶2
=
𝑢2 (𝑃)
𝑃2
+
𝑢2 (𝑉)
𝑉2
PG Spazzini – EMPIR Call 2016 meeting
How do we compute concentration?
• The latter equation shows that the
(relative) uncertainty on the air volume
and the one on the quantity of pollutant
have the same influence on the
uncertainty on the concentration
• BOTH quantities will therefore need to be
determined with comparable uncertainty
in order to have an uncertainty on the
concentration of the same order
PG Spazzini – EMPIR Call 2016 meeting
How do we compute concentration?
• In addition, the differences in the flow
might also indirectly influence the
measurement of the quantity P
– Aerodynamic forces on particulates can change if the
air velocity changes strongly (change of impact
probability
– Impact velocity of bacteria can kill part of them if it is
too high – and unexpected
– Etc.
PG Spazzini – EMPIR Call 2016 meeting
What do we need?
• On the air volume side, we need that our
instrument provides an estimate of the
flown air with a reasonable uncertainty
• Instruments presently on the market are
not calibrated and often not even verified
• Their simple construction provides little
guarantee regarding the uniformity of
measurement in a batch
PG Spazzini – EMPIR Call 2016 meeting
What do we need?
• Also, the influences on the measurement
of ambient conditions are poorly known
• In conclusion, an assessment and
improvement of the measurement of air
quantity aimed at air pollution monitoring
would lead to an improvement of the
environmental policies
PG Spazzini – EMPIR Call 2016 meeting