air quality modelling
TRANSCRIPT
Air Quality ModellingMark Chapman, Air Quality and Odour Discipline Manager
01483 731378
07976 344 311
Air Quality ModellingMark Chapman, Air Quality and Odour Discipline Manager
01483 731378
07976 344 311
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Air Quality Modelling Overview
• Key Guidance Documents
• Defining the AQ Modelling Domain
• Model Setup
– Input Parameters
– Road Traffic Emissions;
• Model Verification and Adjustment
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Key Guidance Documents
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Defining The AQ Modelling Domain
Brief Reminder: DMRB Screening Criteria (Guidance)
For Local Air Quality ‘Affected roads’ are those that meet any of the following criteria:
• road alignment will change by 5 m or more; or
• daily traffic flows will change by 1,000 AADT or more; or
• Heavy Duty Vehicle (HDV) flows will change by 200 AADT or more; or
• daily average speed will change by 10 km/hr or more; or
• peak hour speed will change by 20 km/hr or more.
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Defining The AQ Modelling Domain
For Regional Emissions ‘Affected roads’ are those that are expected to have :
• a change of more than 10% in AADT; or
• a change of more than 10% to the number of HDV; or
• a change in daily average speed of more than 20 km/hr.
However…
Air Quality Assessments are
Receptor Based not Source Based
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Defining The AQ Modelling Domain
In addition to identifying ‘Affected roads’:
• Receptors within 200m of Affected roads;
– Including future receptors
• Roads (including non-affected) within 200m of these receptors;
• Locations where it is anticipated that EU Limit Values are likely to be exceeded in the Opening Year;
– Air Quality Management Areas (AQMA)
– Monitoring Locations
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Air Quality Modelling – Affected Roads
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Air Quality Modelling - Final Study Area
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Model Setup
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Model Setup – The ‘basics’
Air Quality Concentration = …
Emission
• Factors derived from speeds, fleet composition (LDV/HDV), fleet age (EURO Standard)
X
Activity
• Magnitude of each factor for local network
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Dispersion
• Chemistry - Oxidation reactions, etc.
• Physics – Turbulence, Meteorology, etc.
Better inputs = Better outputs
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Model Setup – Input Parameters
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Model Setup – Input Parameters
Internal to Model:
• Terrain Data
• Meteorological Data
• Surface Roughness (Horizontal Dispersion)
• Monin-Obukhov Length (Vertical Dispersion)
• Road Traffic Emissions Data
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Model Setup – Input Parameters
External Processing:
• Local Monitoring Data
– Model Verification and Adjustment
• Background Concentrations
– National Mapping
– Local Monitoring Data
• NOx to NO2 Empirical Formulae (Basic Chemistry)
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Model Setup – Road Traffic Emissions2010 LDV vs HDV Nox Emissions
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2
4
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5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 105 110 115 120
Speed (kph)
Em
iss
ion
s
LDVs HDVs
Optimum speed for HDVs is 60-70 kph
Optimum speed for LDVs is 45-50 kph
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x20
x14
x10
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Model Setup – Road Traffic Emissions2010 Motorway NOx Emissions
0
500
1000
1500
2000
2500
3000
5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 105 110 115 120
Speed (kph)
Em
iss
ion
Ra
te
LDVs HDVs Cumulative
Optimum speed for LDVs is 45-50 kph
Optimum speed for HDVs is 60-70 kph
Optimum speed for entire motorway fleet is 55-65
kph
Best Resolution Fleet Breakdown
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Model Setup – Road Traffic EmissionsNOx Emissions 2010-2025
0
500
1000
1500
2000
2500
3000
2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 2021 2022 2023 2024 2025
LDVs HDVs Cumulative
45% Reduction in Nox Emissions from 2011 to
2016
72% Reduction in Nox Emissions from 2011 to
2021
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Model Verification and Adjustment
The predicted results from a dispersion model may differ from measured concentrations for a large number of reasons:
• estimates of background concentrations;
• meteorological data uncertainties;
• uncertainties in source activity data such as traffic flows and emissions factors;
• model input parameters such as roughness length, minimum Monin-Obukhov; and
• overall model limitations; and
• uncertainties associated with monitoring data, including locations.
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Model Verification and Adjustment
• checks on:
– traffic data;
– road widths;
– distance between sources and monitoring;
– monitoring data;
– estimates of background concentrations;
• consideration of speed estimates on roads in particular at junctions where speed limits are unlikely to be appropriate;
• consideration of source type, such as roads and street canyons;
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Model Verification and Adjustment
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Model Verification and Adjustment
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Model Verification and Adjustment
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Model Verification and Adjustment
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Model Verification and Adjustment
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Model Verification and Adjustment
Mark ChapmanAir Quality and Odour Discipline [email protected] 01483 731 37807976 344 311