ADMS 3.3 Modelling

Summary of Model Features ADMS

ADMS 3.3

• CERC – “New Generation” Model – Detailed description of atmosphere based on boundary layer properties • Features – Point, area, line, volume and jet sources – Multiple sources and pollutants – Buildings and Topography – Plume rise – Single condition or statistical meteorology – Odours, radioactivity, plume visibility – Deposition (Wet and Dry) – Statistics, long and short term, percentiles ADMS

Factors Influencing Dispersion

– Meteorology • Wind Speed and direction • Atmospheric stability (Monin–Obukhov Length and Boundary Layer Height) – Release point and • Elevation • Velocity • Temperature • Ground roughness conditions – Buildings • If > 1/3 stack height – Topography • If steeper than 1:10 slope ADMS

Meteorology

• Older Models – Passive dispersion model • Pasquill-Gifford Stability Classes (A – G) • Wind speed, direction • ADMS – Boundary Layer Model • Boundary layer height • Monin – Obukhov length • Wind speed, direction ADMS

Meteorological Parameters

• Boundary Layer Height – Height at which surface effects influence dispersion – ADMS calculates boundary layer properties for different heights based on meteorology • Monin-Obukhov Length – Measure of height at which mechanical turbulence is more significant than convection or stratification – ADMS calculates M-O length based on meteorology and ground roughness ADMS

Meteorology Options

• Specific Data • Wind speed, wind direction, date, time, latitude, boundary layer height, cloud cover • Met Office Data • Statistical data (10 years) – 2200 lines of data (medium run times) • Hourly sequential data (1 – 5 years) – Can be used to identify specific conditions for known dates and times – 8760 lines of data per year (long run times) – Use to compare releases against environmental standards (preferred option by EA) ADMS

Meteorology Effects

• Typical atmospheric conditions within the UK.

• Pasquill - Gifford Stability Classes as modelled in ADMS • No exact correlation between boundary layer parameters

Stability Class A

B C

D

E

F

G

Wind Speed (m/s) 1

2 5

5

3

2

1

Boundary Layer Height (m) 1300

900 850

800

400

100

100

Monin – Obukhov Length (m) -2

-10 -100

∞

100

20

5

Conditions Convective - Hot Still Day

Convective Convective

Neutral - Normal UK Day

Stable

Stable - Still Night

Stable ADMS

Example of A – G Conditions

•

Stack Release

– SO 2 ,150 g/s – 50 m stack – 5 m diameter, – 20 m/s velocity – 15°C ADMS

A – G conditions

Centre Line Ground Level Concentrations ADMS

A1 Conditions Contour Plot

Convective - Hot Still Day SO2 Concentration (ug/m3)

1000 -200 -400 -600 -800 800 600 400 200 0 -1000 0 200 400 600 800 1000 Metres 1200 1400 1600 1800 2000 600 500 400 300 200 100 ADMS

D5 Conditions Contour Plot

Neutral - Normal UK Day SO2 Concentration (ug/m3)

1000 -200 -400 -600 -800 800 600 400 200 0 -1000 0 200 400 600 800 1000 Metres 1200 1400 1600 1800 2000 160 140 120 100 80 60 40 20 ADMS

F2 Conditions Contour Plot

Stable - Still Night S02 Concentration (ug/m3)

1000 -200 -400 -600 -800 800 600 400 200 0 -1000 0 200 400 600 800 1000 Metres 1200 1400 1600 1800 2000 10 9 8 5 4 7 6 3 ADMS

Buildings

• Can have significant effects – Entrain pollutants into leeward cavity of building – Increased concentrations close to building – Decreased concentrations further away – Only relevant if >1/3 stack height – ADMS allows 10 buildings ADMS

Building Effects – Tall Stack

•

Tall Stack

– Release of NOx from a

50 m stack

(3 m diameter, 5 m/s velocity, 30 °C, 1 g/s NOx) – Unstable weather conditions – Stack is at the centre point of the building – Building is 30 m high, 30 m wide, 67 m long ADMS

Tall Stack – No Building

NOx Concentration (ug/m3)

400 300 200 100 0 -100 -200 -300 -400 0 100 200 300 400 500 Metres 600 700 800 900 1000 12 11 10 9 3 2 5 4 8 7 6 ADMS

Tall Stack – With Building

NOx Concentration (ug/m3)

400 300 200 100 0 -100 -200 -300 -400 0 100 200 300 400 500 Metres 600 700 800 900 1000 10 4 2 6 5 9 8 7 ADMS

Building Effects – Short Stack

•

Short Stack

– Release of NOx from a

35 m stack

(3 m diameter, 5 m/s velocity, 30 °C, 1 g/s NOx) – Unstable weather conditions – Stack is at the centre point of the building – Building is 30 m high, 30 m wide, 67 m long ADMS

Short Stack - Without Building

NOx Concentration (ug/m3)

400 300 200 100 0 -100 -200 -300 -400 0 100 200 300 400 500 Metres 600 700 800 900 1000 24 23 22 21 5 4 3 2 9 8 7 6 20 19 18 17 16 15 14 13 12 11 10 ADMS

Short Stack - With Building

NOx Concentration (ug/m3)

400 300 200 100 0 -100 -200 -300 -400 0 100 200 300 400 500 Metres 600 700 800 900 1000 24 23 22 21 5 4 3 2 9 8 7 6 20 19 18 17 16 15 14 13 12 11 10 ADMS

Topography

• Can effect dispersion – Changes plume trajectory – May increase or decrease concentrations – Include if terrain exceeds 1:10 (maximum 1:3) – Terrain data available from Ordnance Survey ADMS

Topography Example

– Release of NOx from a 65 m stack – 5 m diameter – 5.25 m3/s flowrate – 69°C, – 1 kg/s NOx – Neutral weather conditions • 10 m/s wind • Boundary layer 1000 m – Simple hill 2.6 km to the East and 1 km South of the release ADMS

Without Hill

NOx Concentration (ug/m3)

1000 0 -1000 -2000 4000 3000 2000 -2000 -1000 0 1000 Metres 2000 3000 4000 1600 1500 1400 1300 1200 1100 1000 900 800 700 600 500 400 300 200 ADMS

With Hill

NOx Concentration (ug/m3)

1000 0 -1000 -2000 4000 3000 2000 -2000 -1000 0 1000 Metres 2000 3000 4000 1600 1500 1400 1300 1200 1100 1000 900 800 700 600 500 400 300 200 ADMS

3D Hill

ADMS

Statistical Meteorology

• 10 years statistical data • 1 – 5 years hourly sequential data • Can calculate – Annual averages – Percentiles (worst case conditions) – No of exceedences/year – Areas affected • Direct comparison with UK Legislation (NAQS, PPC) ADMS

Statistical Results

Long Term SO2 Concentration

376000 375800 375600 375400 375200 375000 374800 374600 374400 374200 442000 442200 442400 442600 442800 443000 Metres 443200 443400 443600 443800 1.1

1 0.9

0.8

0.7

0.6

1.6

1.5

1.4

1.3

1.2

ADMS

Statistical + Topography

Reproduced from Ordnance Survey® Panorama Digital Data, by permission of Ordnance Survey® on behalf of the Controller of Her Majesty’s Stationary Office. © Copyright 1990. All rights reserved. Licence No. 100040193 ADMS

Digital Maps

• Available from Ordnance Survey • 1:50000 or 1:10000 • Can overlay release contours onto maps ADMS

Reproduced from Ordnance Survey® 1:10K Raster Data, by permission of Ordnance Survey® on behalf of the Controller of Her Majesty’s Stationary Office. © Copyright 1990. All rights reserved. Licence No. 100040193

Digital Map Example

ADMS

Digital Map + Topography + Concentrations Reproduced from Ordnance Survey® Panorama Digital Data and1:10K Raster Data, by permission of Ordnance Survey® on behalf of the Controller of Her Majesty’s Stationary Office. © Copyright 1990. All rights reserved. Licence No. 100040193 ADMS

Odours

• Model as Odour Units –

ou

: Number of times the mixture must be diluted at STP to reach detection limit of 1 ou.

–

ou E

: The mass of pollutant that when evaporated into 1m 3 of gas at STP is 1 ou.

– Information on detection limit is required.

• ADMS – Input and output in terms of ou or ou E .

ADMS

Odour Example

• Release from landfill site – Odours in ou E – Two area sources, one line source • Landfill 1: 100 m x 100 m, 10 ou E /m 2 /s • Landfill 2: 100 m x 100 m, 5 ou E /m 2 /s • Line 1: 200 m, 2 ou E /m/s – Flat terrain, no buildings – Neutral conditions • 10 m/s wind • Boundary layer 1000 m – Short term hourly average concentration ADMS

Odour Example - Sources

Landfill Site

600 400 200 LANDFILL1 0 LINE1 -200 LANDFILL2 -400 -600 0 Output grid Area/line/volume source 200 400 600 800 1000 1200 1400 ADMS

Odour Example - Results

Landfill Odour Release (ouE)

600 400 200 0 -200 -400 40 35 30 25 20 15 10 5 1 75 70 65 60 55 50 45 100 95 90 85 80 -600 0 200 400 600 Metres 800 1000 1200 1400 ADMS

Time Varying Releases

• Release rates often vary with production • Time varying releases – Hourly sequential meteorological data – Details of release for each hour of met data • flow, temperature, concentration, velocity • Results can differ considerably when compared to average releases ADMS

Fluctuations

• Meteorology usually stable over 1 hour • Turbulence causes short duration fluctuations • • Interest in lower times for exposure – Odours – NAQS (SO 2 , 15 minute mean) ADMS turbulence calculations – Percentiles – Probability distribution function – Toxic response ADMS

Other Features

• Variable surface roughness • Treatment of land sea internal boundary layer • Puffs • NOx Chemistry • Radioactive decay • Plume visibility (condensed plume) ADMS