Network for the support of European Policies on Air Pollution

The assessment of European control measures and the effects of

non-linearities

Non-linearities

Definition• What goes up comes down, the atmospheric mass

balance for the emitted reactive pollutants is closed.• However, the distance scale for the processes of

transport, transformation and deposition are large, and differ between the different pollutants (some emitted nitrogen escapes from the European domain, and surface ozone concentrations over Europe are dominated by the advected flux into Europe from the North Atlantic).

• In this project, we have identified non-linearities in source-receptor relationships at regional scales in sulphur and nitrogen compounds in air or deposition.

• Apparent non-linearities………where for example unknown sources contribute to the deposition

• Real non-linearities occur when the processes regulating the lifetime of pollutants change with time (oxidation, deposition)

Three examples

1. Shipping and the sulphur budget

2. Changes in dry deposition with time due to changes in SO2 / NH3

3. Oxidized nitrogen budgets

Trends in sulphur deposition throughout the UK 1986-2001

Group 1* : nss-SO42- = -3.25 y + 6542

Group 2* : nss-SO42- = -1.06 y + 2159

Group 3* : nss-SO42- = -0.21 y + 459

Group 4 : nss-SO42- = -0.11 y + 237

* Statistically significant, P < 0.01

Shipping!

Vessel traffic densities for year 2000 based on the sum of reported distributions from AMVER data (AMVER, 2001)

• Some areas of the UK show large reductions in acid deposition while other areas (eg Wales and Western Scotland), including some very heavily affected areas have changed little.

• Work continues on the influence of shipping emissions on S and N deposition (Univ Oslo)

% reduction from 87-01 in total non-marine Sulphur

2. Has the SO2 dry deposition velocity changed ?

• Concentrations are declining faster than expected by models

• Current LRT models treat deposition velocity as simply coupled to meteorology and vegetation

• LIFE project provides important clues• Is there evidence of regional variations in surface

resistance and deposition velocity?

KhsKha KhhonoKhc

Kn1 Ks1Kc1Ka

NH3,aq CO2,aq HNO2,aq

NH3 CO2 HNO2 SO2

SO2,aq

CO32- SO3

2- SO42-

NH4+ HCO3

- NO2- HSO3

- HSO4-

Ks2Kc2 Ks3

KwH2O H++OH-

d

Rd

AQUEOUS

GASEOUS

Kha

s(NH3)

Rs

Rcut

Fcut

Rb

Ra{z-d}

{z-d}

{z0’}=c

{z0}

WET DRY

HNO3

HCl

Cl-

NO3- H2O2

O3

APOPLAST

Ft

Fd

FsK+Mg2+

Na+ Ca2

+

K+Mg2+

Na+ Ca2

+

KaNH3,aqNH4

+

KwH2O H++OH-

The surface reactions are regulated by

SO2/NH3 interactions in

suface water films

EMEP 2003 : Total deposition of oxidized S, 2000

mg S m-2 yr-1

0

20

40

60

80

100

120

140

160

180

200

Speulder Forest Melpitz Auchencorth

Rc (

sm-1)

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

NH

4/S

O4

RcSO2

RcNH3

NH4/SO4

Dry deposition rates of SO2 are regulated by chemical processes

in water films on terrestrial surfaces.

NH3 is the most important of the pollutants which regulate canopy

resistance to SO2 deposition.

Long term rates of SO2 deposition have increased with time as

NH3/SO2 ratios have increased.

Non-linearity is introduced into source-receptor matrices by

changes in SO2 emission in the presence of significant NH3

concentrations.

Dynamic chemical models are able to reproduce the measured

fluxes and resistances of SO2 and NH3 but are not currently

applied in Long-Range Transport models.

EMEP model predicts slower trend in ambient

SO2 than observed

Sulphur in the UK 1987-2001

Non-linearities in the oxidized nitrogen budgets

NOx emissions

Most of the change in emission has already taken place (2005: 50% since late 80’s, only <10% in the next 15 years)

UK Emission deposition and export of atmospheric N 1900-2000 Emission Deposition Export

Oxidized N Emission

Reduced N Emission

Total Emission

Oxidized N Deposition

Reduced N Deposition

Total Deposition

Oxidized N Export

Reduced N Export

Total Export

1900 3121 1683 480 665 1637 229 246 5 250

1910 3181 1283 446 675 1257 192 251 4 255

1920 3271 1523 480 695 1487 217 258 4 262

1930 3271 1513 479 695 1477 216 258 4 262

1940 3451 1623 508 735 1587 231 272 4 277

1950 4841 1743 658 1025 1697 271 382 5 387

1960 6591 1813 840 1395 1767 315 520 5 525

1970 7311 1903 920 1545 1857 339 577 5 582

1980 7871 2283 1015 1946 2227 416 593 6 599

1990 6652 2413 906 1966 2348 430 470 7 476

2000 4602 2634 723 1916 2119 402 270 52 321

Total10 50014 18026 68040 11475 17484 28959 38539 542 39081

Cause 1

From 1990 to 2010 land-based NOx will decrease from 13.4 to 6.6 MtWhile NOx from shipping will increase from 2.8 to 4.6 Mt. So, by 2010, 70%

of NOx will originate from shipping (in EU)

Cause 2

NO2 emissions declined ~50%More O3 at nightNO2 NO3 HNO3

Ecosystem Type 1995-1997 2010

Acid grassland 27 19

Heathland 56 42

Coniferous woodland 88 79

Deciduous woodland 96 92

All ecosystems 40 32

Exceedances of critical loads of ecosystems for eutrophication by nitrogen

in the UK (%)

Detecting the signal of Nitrogen deposition in semi-natural vegetation

• 400 1kmx1km survey plots throughout the UK• Species composition and cover 1978, 1980,

2000• N deposition (Reduced and Oxidized) 5km• Clear signal linking loss of biodiversity to N

deposition.

Conclusions

• Non-linearities exist and are a cause of regional variation in response to emission changes

• Detailed examination of the excellent long term data for air and precipitation composition is a vital step

• Models are the tools to summarize our knowledge, for integration, assessment and exploration of the interactions…but they lag behind our understanding of processes