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Transcript of Air Quality Modelling
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Air Quality ModellingMark Chapman, Air Quality and Odour Discipline Manager
01483 731378
07976 344 311
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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
X
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
0
2
4
6
8
10
12
14
16
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
x16
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
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Mark ChapmanAir Quality and Odour Discipline [email protected] 01483 731 37807976 344 311