Ben Marner, Air Quality Consultants

1. Modelling Development-
related Changes in
Concentrations and
Deposition to Habitats
Ben Marner

2. Overview
• How we Model Development-related Changes
• Some Issues with Common Practice
➢ Background or baseline
➢ Traffic-related NH3
➢ Averaging out temporal variation
➢ Model domain size
• Potential Solutions

3. Emissions from New Development
Scheme-generated Concentration
Scheme-generated Deposition Flux
With-scheme Total
Critical Levels / Loads
Process Overview
Deposition
Velocity
Dispersion
Model
Without-scheme Baseline
In Combination
De-Minimis
Wealden vs Lewes
Eu vs German Gov.
Screening
Appropriate Assessment
HRA
SNAP

4. Background vs Baseline
Adding PC to Background
Adding PC to BaselineBaseline
Mapped
background NOx
= 15 mg/m3

5. Don’t Forget Traffic-NH3
Roadside NH3 Monitoring
Map orientation and relative transect positions altered for anonymity
Road

6. Traffic-NH3 Concentrations
* Combining 2 year’s measurements with AQTAG 06 annual average deposition velocities
Vs Deposition

7. Future Trends in Traffic-NH3 ?
3-way
Catalyst
SCR
Lots of NH3
from a few
vehicles - or
small amounts
from lots of
vehicles?

8. NO2 Does Not Deposit at a
Constant Rate
* Deposition Velocity Calculated as per Smith et al, 2000
AverageHourly/AverageAnnual
AverageMonthly/AverageAnnual

9. Hour-by-Hour NO2 Deposition
• Not quite hot off the press:
• Fowler, D., 1980. Wet and dry
deposition of sulphur and nitrogen
compounds from the atmosphere.. In:
Hutchinson, T.C.; Havas, M., (eds.) ,
Effects of acid precipitation on
terrestrial ecosystems.
• Smith, R. I.; Fowler, D.; Sutton, M.
A.; Flechard, C.; Coyle, M., 2000,
Regional estimation of pollutant gas
dry deposition in the UK: model
description, sensitivity analyses and
outputs. Atmospheric Environment,
34, 3757-3777
• Barrowcliffe R., Hall D.J. and
Spanton A.M., 2003. Development
of a methodology for appropriate
assessment for air pollution impacts
on European sites. Environment
Agency.
• DUMG 2010: David Hall, Angela
Spanton and Colin Powlesland.
Modelling Near Field Ciritical Loads
from Generating Stations

10. How Far to Model for Roads?
“Only properties and Designated Sites within 200 m of roads
affected by the project need be considered” (DMRB Guidance)
1-200m from Road 200m – 2km from Road
For habitats assessments,
often interested in small
changes in remote
locations
2 – 10km from Road

11. Local Plans can Affect Lots of
Roads
Receptor 20m from a Road,
with and without the Local
Plan
NOx treated as inert, with no removal either by
chemical reaction or deposition
1% of Critical Level

12. ➢ Depletion of NOx + Formation of other N Species
➢ Local Plan + Other
Traffic Growth
➢ Receptor >2km from
Roads
➢ Increase of 0.8
mg/m3 (3% of Critical
Level)
Local Plans ‘In Combination’
NOx treated as inert, with no removal either by
chemical reaction or deposition
➢ Dispersion across Authority Boundaries

13. Possible Solutions (?)
Issue Solution
Background/Baseline • Consider existing local sources
Traffic-related NH3 • COPERT – Don’t use! a
• TNO
• Remote Sensing
• Ambient Measurements
Temporal Variation • Could we add to Dispersion Models?
Domainsize
• EA guidance for point sources
• Small traffic-schemes 200m?
• Big schemes and Local Plans - go large!
Chemistry (+ wet
deposition) • National Model?
• AERIUS? b
In Combination
(cross-boundary)
a TNO Report R11005 - NH3 emissions factors for road transport
b www.aerius.nl
Effort
proportional
to risk

14. Head Office
23 Coldharbour Road, Bristol BS6 7JT
Tel: 0117 974 1086
London Office
119 Marylebone Road, London NW1 5PU
Tel: 020 3873 4780
BenMarner@aqconsultants.co.uk