PM mapping in Scotland, 2007

Andrew Kent

What are we presenting today?

1) Context to the work

2) Modelling process

3) Model results

4) Future work possibilities

Background

2004• Modelled concentrations for multiple pollutants for Scotland• Scotland met data (RAF Leuchars) and Scotland calibration used• Model performance no improvement on UK model• Too few sites for robust calibration and verification

2005• Remodelling undertaken in hope that more sites would help• Concluded that still more sites desireable

2006• No new modelling undertaken but assessed Scottish monitoring against UK

model output• Performance good

What did we do this year?

Modelled PM only

Take advantage of new Scottish monitoring campaign – genuine gravimetric PM for direct comparison with legislation

Outputs• PM10 and PM2.5 1x1 km background map• Modelled concentrations for major road links

Checked calibration performance

Assessed outputs against objectives relevant to Scottish Government

Scottish monitoring

Scottish Government funded expansion of monitoring campaign in 2007

Used Partisol analysers for daily gravimetric concentration

PM10

•10 sites

PM2.5

•8 sites

Used to calibrate model

Modelling process

Generalised description presented here• Full details in annual report on UK AQ Archive:http://www.airquality.co.uk/archive/reports/cat09/0807231621_dd12006mapsrep_v2.pdf

Particulate matter• Complex pollutant• Poorly understood• Many components, each with a degree of uncertainty!

Contributions to the annual mean model• Point sources – big and small point sources• Area sources – the largest contribution• Long-range transport primary – TRACK model output• Sea salt – the only ‘natural’ component in the model• SOA – output from HARM model• SIA – nitrate, sulphate, ammonium

Point sources

Big points Small points

Area sources

Dispersed emissions calibrated against monitoring data

1x1km sector specific emission grids

Emission footprint - Dispersion model output

Invert matrix for dispersion kernel

Dispersed using a kernel approach

Area source calibration

PM10 calibration PM2.5 calibration

y = 2 . 2 8 3 8 x

R 2 = 0 . 1 0 6 2

- 4

- 2

0

2

4

6

8

1 0

- 0 . 5 0 0 . 5 1 1 . 5 2 2 . 5 3

u n c a l i b r a t e d a r e a s o u r c e c o n t r i b u t i o n t o a n n u a l m e a n P M 1 0 ( µ g m - 3 , g r a v i m e t r i c )

Meas

ured

PM

10 - p

oint s

ourc

es - s

econ

dary

comp

onen

ts - lo

ng ra

nge

trans

port

prim

ary -

sea s

alt co

mpon

ent (

µg m

-3, g

ravim

etric)

A l l s i t e s

L in e a r ( A l l s i t e s )

y = 3 . 7 6 1 4 x

R 2 = 0 . 6 7 0 8

- 1

0

1

2

3

4

5

6

0 0 .3 0 .6 0 .9 1 .2 1 .5 1 .8

u n c a l i b r a t e d a r e a s o u r c e c o n t r i b u t i o n t o a n n u a l m e a n P M 2 .5 ( µ g m - 3 , g r a v i m e t r i c )

Meas

ured

PM

2.5

- poin

t sou

rces

- sec

onda

ry co

mpon

ents

- long

rang

e

trans

port

prim

ary -

sea s

alt co

mpon

ent (

µg m

-3, g

ravim

etric)

A l l s i t e s

L in e a r ( A l l s i t e s )

Slope of about 6!

VCM corrected TEOM data

Area type kernels

Formerly used 2 dispersion kernels

• Road traffic kernel• Non-road traffic kernel

Multiple calibrations for different land cover

• Large conurbations• Elsewhere

Now use• multiple kernels for different area

types• single calibration• Better describe dispersion over

different terrain• Less reliance on empirical

relationship

Additional contributions

Long range transport primary • TRACK model• Lagrangian statistical model• 10x10km grid

Secondary organic aerosol• HARM/ELMO model (Lancaster University)• Lagrangian model – changing compositions of air parcels en route to designated receptor

sites

Secondary inorganic aerosol• 28 rural sites measuring sulphate, nitrate and ammonium• Interpolating using Krigging on a 5x5km grid• Split between fine and coarse fractions

Fe and Ca rich dusts• Emission not included in NAEI so formerly part of residual in model• Distribution based on population and vehicle km travelled

Sea salt• Same method as SIA, using chloride measurements on a 5x5km grid• Split between fine (27%) and coarse (73%) – from Harrison & Yin (2006), APEG (1999)

The background map

Addition of …

•Big point sources

•Small point sources

•Calibrated area sources

•Sea salt

•Long range transport primary

•SOA

•Secondary inorganic aerosol

•Fe and Ca rich dusts

Roadside model

Uses scaled emissions from NAEI attributed to each major urban road link in UK

Roadside increment derived from roadside monitoring sites• measured roadside concentration – modelled background concentration

Calibration using roadside increment against traffic-flow adjusted emissions for each road link

Roadside model and calibration

PM10 calibration PM2.5 calibration

y = 0 .0 0 0 0 0 6 6 7 x

0 .0

1 .0

2 .0

3 .0

4 .0

5 .0

6 .0

7 .0

0 1 0 0 0 0 0 2 0 0 0 0 0 3 0 0 0 0 0 4 0 0 0 0 0 5 0 0 0 0 0 6 0 0 0 0 0 7 0 0 0 0 0 8 0 0 0 0 0

R o a d l in k g r a v im e t r ic P M 1 0 e m is s io n s ( g /k m /y e a r ) a d ju s t e d f o r t r a f f ic f lo w

PM10

road

side i

ncre

men

t (ug

m-3

, gra

vimet

ric)

y = 0 . 0 0 0 0 0 8 2 7 x

0 . 0

0 . 5

1 . 0

1 . 5

2 . 0

2 . 5

3 . 0

3 . 5

4 . 0

0 1 0 0 0 0 0 2 0 0 0 0 0 3 0 0 0 0 0 4 0 0 0 0 0 5 0 0 0 0 0 6 0 0 0 0 0

R o a d l i n k g r a v i m e t r i c P M 2 . 5 e m i s s i o n s ( g / k m / y e a r ) a d j u s t e d f o r t r a f f i c f l o w

PM2.5

road

side i

ncre

ment

(ug

m-3

, gra

vimet

ric)

Calibration checking – background maps

PM2.5 backgroundPM10 background

0

2

4

6

8

1 0

1 2

1 4

1 6

1 8

2 0

0 2 4 6 8 1 0 1 2 1 4 1 6 1 8 2 0

M e a s u r e d P M 1 0 ( µ g m - 3 , g r a v i m e t r i c )

Mode

lled

PM10

(µg

m-3

, gra

vimet

ric)

S c o t la n d - s p e c i f i c m o d e lU K m o d e ly = x y = x + 5 0 %y = x - 5 0 %

0

2

4

6

8

1 0

1 2

0 2 4 6 8 1 0 1 2

M e a s u r e d P M 2 . 5 ( µ g m - 3 , g r a v i m e t r i c )

Mod

elle

d PM

2.5

(µg

m-3

, gra

vim

etric

)

S c o t la n d - s p e c i f ic m o d e lU K m o d e ly = x y = x - 5 0 %y = x + 5 0 %

Calibration checking – road links

PM2.5 roadsidePM10 roadside

0

2

4

6

8

1 0

1 2

1 4

1 6

1 8

2 0

0 2 4 6 8 1 0 1 2 1 4 1 6 1 8 2 0

M e a s u r e d P M 1 0 ( µ g m - 3 , g r a v i m e t r i c )

Mode

lled

PM10

(µg m

-3, g

ravim

etric

)

S c o t la n d - s p e c i f i c m o d e lU K m o d e ly = x y = x - 5 0 %y = x + 5 0 %

0

1

2

3

4

5

6

7

8

9

1 0

0 1 2 3 4 5 6 7 8 9 1 0

M e a s u r e d P M 2 . 5 ( µ g m - 3 , g r a v i m e t r i c )

Mode

lled

PM2.5

(µg

m-3

, gra

vimet

ric)

S c o t la n d - s p e c i f ic m o d e lU K m o d e ly = x y = x - 5 0 %y = x + 5 0 %

Exceedences Assessment

Model outputs interrogated to calculate exceedence statistics for• area and population (from background model)• road links and road length (from roadside model)

Assessed model results against appropriate values

Pollutant Metric Objective Applies

PM10 Annual mean 18 µg m-3 Scotland only

PM10 Annual mean * 22 µg m-3 Scotland only

PM10 Annual mean * 31.5 µg m-3 UK

PM2.5 Annual mean 12 µg m-3 Scotland only

PM2.5 Annual mean 25 µg m-3 UK

Exceedences PM10

No background exceedences

Roadside exceedences• Scotland annual objective – exceeds over 4 zones• Scotland daily mean objective – exceeds over 2 zones• UK daily mean objective – no exceedences

No

. ro

ad

s

Ro

ad

len

gth

(k

m)

No

. ro

ad

s

Ro

ad

len

gth

(k

m)

No

. ro

ad

s

Ro

ad

len

gth

(k

m)

No

. ro

ad

s

Ro

ad

len

gth

(k

m)

Glasgow Urban Area 209 306.5 41 52.7 3 8.1 0 0Edinburgh Urban Area 61 103.2 7 11.1 0 0 0 0Central Scotland 237 375.9 6 6.7 2 1.2 0 0North East Scotland 138 233.5 13 12.1 0 0 0 0Highland 11 34.5 0 0 0 0 0 0Scottish Borders 38 59.9 0 0 0 0 0 0Scotland 694 1113.4 67 82.6 5 9.4 0 0

>31.5 µg m-3Zone/Agglomeration Total >18 µg m-3 >22 µg m-3

Exceedences PM2.5

No background exceedences

Roadside exceedences• Scotland 2010 objective – exceeds at 2 zones• Scotland 2020 target value – no exceedences

No

. ro

ad

s

Ro

ad

le

ng

th (

km

)

No

. ro

ad

s

Ro

ad

le

ng

th (

km

)

No

. ro

ad

s

Ro

ad

le

ng

th (

km

)

Glasgow Urban Area 209 306.5 4 10 0 0Edinburgh Urban Area 61 103.2 0 0 0 0Central Scotland 237 375.9 3 2.6 0 0North East Scotland 138 233.5 0 0 0 0Highland 11 34.5 0 0 0 0Scottish Borders 38 59.9 7 12.6 0 0

Zone/Agglomeration Total >12 µg m-3 >25 µg m-3

y = 2.1217x + 3.6054

R2 = 0.721

0

20

40

60

80

100

120

140

0 5 10 15 20 25 30 35 40 45 50 55

Measured annual mean (µg m-3)

Me

as

ure

d 9

8th

pe

rce

nti

le d

aily

me

an

(µ

g m

-3)

Scotland daily mean objective

y = 1.5553x + 0.7613

R2 = 0.9003

0

10

20

30

40

50

60

70

80

90

0 5 10 15 20 25 30 35 40 45 50

Measured annual mean (µg m-3)

Me

as

ure

d 9

0th

pe

rce

nti

le d

aily

me

an

(µ

g m

-3)

UK daily objective… for comparison

Maps - background

PM10 PM2.5

Maps - roadside

PM10 PM2.5

Background maps - difference

PM10 PM2.5

Like pollutants examined in previous years – a Scotland-specific model provides mixed results

Difference between Scotland-specific and UK models is not very large and is attributable to calibration rather than met variation

Scotland-specific model results in generally lower PM10 than UK model but are higher PM2.5. This is due to the calibration factors

derived from the monitoring data.

Largest differences between models was across urban areas – probably due to greater urban representation in UK model than in Scotland-specific model (predominantly rural calibration)

Conclusions

Will need discussion with and direction from Scottish Government

No PM mapping possible for 2008

Recommend:• Comparison of Scottish monitoring against UK model outputs – Scottish

verification

• Interrogation of UK model outputs for values relevant to Scotland – Scotland AQS values, EU limit values.

• These will provide confidence in UK outputs for Scotland

• Help identify areas of exceedence for further policy focus and action

Future work

?

Questions…

andrew.kent@aeat.co.uk