Assessment Methods for Ammonia Hot-Spots

(Working Group 3)

Expert Workshop under the UNECE Convention on Long-range Transboundary Air Pollution

4-6 Dec 2006, Edinburgh, Scotland

Outline

• What is a hot-spot?• How can they be assessed?

• Objectives• Tools

• Modelling• Uncertainties• Research Priorities

• Integrated assessment• Models/Monitoring

• Large ammonia emission source

• Localised either in space

What is a hot-spot?

• Large ammonia emission source

• Localised either in space or time

NH3 emission time series

Vragender area (~3x3km); periode: 2 feb - 30 april 2003

0

100

200

300

400

2 5 8 11 14 17 20 23 26 1 4 7 10 13 16 19 22 25 28 31 3 6 9 12 15 18 21 24 27 30

kg

_N

H3

/da

y

animal housing emissions

manure spreading emissions

How can they be assessed?

Objectives

• Understanding small-scale processes• Assessing impacts of dry deposition• Spatial planning• Assessing effects of local abatement measures• Provide relationships for larger-scale models• Impact on air quality and PM formation

Modelling Tools

• Lagrangian stochastic models• Local-scale Gaussian/Eulerian models• Screening/simple models (e.g. SCAIL)

Uncertainties - Emissions

Diurnal coarse of outdoor emissions Vragender area (3x3km); 27 feb 2003

0

5000

10000

15000

20000

25000

1 3 5 7 9 11 13 15 17 19 21 23

time

g/h

_NH

3

Monthly NH3 emissions Vragender area (3x3km); period: aug. 2002- aug. 2003

0

5000

10000

15000

20000

25000

8 9 10 11 12 1 2 3 4 5 6 7 8

2002 - 2003

g/h

fertilyser emissions

cattle grazing emissions

manure application emissions

animal housing emissions

Process-based ?

• Suitable for source type• Temporally variable

• Diurnal variation• Seasonal variation

• In the correct location• Depends on objectives/accuracy

Uncertainties – Exchange processes

• Better knowledge of compensation point of natural vegetation and crops

• Better knowledge/improvement of surface resistance = f(NH3, surface humidity) for different vegetation

• Effect of deposition on compensation point and surface resistance

• Need for in-canopy transfer/deposition + 2-layer model for simpler application

-20

20

60

100

140

180

0 20 40 60 80 100 120

NH3 Concentration (µg m-3)

Ca

no

py

Re

sis

tan

ce

(s

m-1

)

DAY Rc

y = 0.4568x + 11.099

R2 = 0.62

NIGHT Rc

y = 1.1307x + 4.5938

R2 = 0.91

Uncertainties – Specific to model type

• Lagrangian Stochastic, short-range models:• Compensation point (Cp)• Effect of exposure to NH3 on Rw and Cp• Detailed turbulence field near buildings/forest edges

• Gaussian/Eulerian models:• Compensation point (Cp)• Effect of exposure to NH3 on Rw and Cp• Chemistry (depending on spatial scale)• Accurate locations of sources and receptors

• Screening/simple model: • Source strength, • Applicability to other locations/sources/receptors

Spatial Planning

Receptor buffer zones

Linking to larger-scale modelling

• Regional scale (e.g. EMEP)

• Upscaling local interactions• Estimates of within-grid recapture

• Providing boundary conditions

• Use of local relationships at regional scale

Use of local relationships at regional scale

Assessment Strategies

• Objectives

• Modelling tools

• Monitoring tools

• Integrated approaches (model + monitoring)

Assessment Strategies - Objectives

• Existing or planned source

• Single source and receptor

• Multiple source-receptor (local measures)

• Comparison with thresholds

• Critical levels• Critical loads

• Modelling tools• Simple/Landscape/Lagrangian Stochastic

• Monitoring tools• Low cost e.g. passive samplers

• Comparison with continuous measurement• Sampling period• Sampling locations• Biomonitoring ?

• Methods for deposition measurement

Assessment Strategies - Tools

Assessment Strategies – Integrated approach?

• Objectives (e.g. existing/planned source)

• Combined modelling and monitoring?

• Comparison with critical levels:• Measurements used to verify model predictions

• Comparison with critical loads:• Concentration measurement Deposition estimate• Deposition velocity approach probably too simplistic• Inferential modelling approach is better (and possible)

Working Group Achievements

• Assessed range of objectives

• Prioritised uncertainties (for different model types)

Research priorities

• Concluded that model inter-comparisons would be very useful

• Suggested possible assessment strategies• Depending on objectives (existing/planned source, single/multi-sources and receptors, comparisons with critical levels/loads)