1. No category

Representativeness of monitoring stations
for air pollutants
Munich March 20 2015
Jan Duyzer
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EU AQ directive : purpose of networks
Identify exceedances of limit values
Assess exposure
Other areas where the general public is exposed
Other purposes (not discussed)
How to address all these issues in one network?
How to obtain comparable results across Europe?
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Study
Model calculations for four cities
Use the results of model calculations to assess exposure
Evaluate quality of networks using the above results
Investigate hot spots (checks on actual situation)
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Representativeness
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Barcelona Berlin
London Stuttgart
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Macro-siting
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Comparison of four cities
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How do the highest concentrations in cities compare?
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Macro-siting street stations
Concentrations measured in street stations (hot spots) represent only
a small fraction of the exposure
Concentrations measured at hot spot street stations cannot be
compared across cities (representing different exposure levels). The
difference in concentrations is very large in the range of the highest
concentrations
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Exposure from urban background sites
Background sites easily represent large fractions of the population
(90%)
Exposure can be assessed quite well based upon urban background
sites (Location is not difficult)
Compare population weighted concentration with concentration
calculated at background sites
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Micro-siting
Urban background: no obstacles or sources nearby
Street stations
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The effect of street type and congestion on the contribution of a road to the
concentration observed at certain distances from the middle of first lane .
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Micro-siting (general)
Background no obstacles or sources
Street (hot spot) stations more difficult
Parameters:
the distance to road, the type of street (width of the road, buildings
on one or two sides, height of the buildings), traffic flow (free flow or
congestion) and meteorological conditions wind speed.
Range
5-30 µg/m3
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Conclusions micro-siting
Parameters that cannot be influenced
Wind speed
Wind direction
Parameters that can be influenced by choosing the site:
Emission, distance to road, street type
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Conclusions: hot spots
Micro-siting
Difficult due to large influence of many parameters
Macro-siting
Selection of location is very important for the result (large range)
Conclusion: Comparison across cities is difficult (if not impossible)
Very few people are exposed to these concentrations
The fraction of people exposed to hotspot concentrations varies across
cities
Time activity patterns
Conclusion: hotspot stations are not useful for exposure
assessment.
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End of presentation
Thank you for your attention