The modification of global atmospheric The modification of global atmospheric Nitrogen cycling by human activitiesNitrogen cycling by human activities

David FowlerDavid Fowler

Centre for Ecology and HydrologyEdinburgh UK

BackgroundBackground — The N cycleGlobal N emissions

Oxidised NitrogenOxidised Nitrogen — emissionatmospheric chemistry - O3 productiondeposition of NOycompensation pointsdeposition footprintseffects

Reduced NitrogenReduced Nitrogen — emissionatmospheric chemistrydeposition of Nnon-linearity in S deposition and the role of NH3compensation pointseffects

The Global Nitrogen CycleThe Global Nitrogen Cycle

Biomass burningBiomass burningVehiclesVehicles

IndustryIndustryAgricultureAgriculture

Sources of fixed Sources of fixed Nitrogen to the Nitrogen to the AtmosphereAtmosphere

Relative Importance ofRelative Importance of NOyNOy andand NHxNHx

local scale 1 - 20 km2

regional scale 105 km2

continental scale > 106

km2

AtmosphereAtmosphere--Surface Exchange of Fixed Surface Exchange of Fixed TOTAL (ANTHROPOGENIC) N N TgTg N yN y--11

fossil fuelcombustionfossil fuel

combustionbiomassburning

biomassburning

soils andagriculturesoils and

agricultureLAND OCEAN

12(10) 46(30)10(2) 13(7)

NOx

20(20)

NH3 NO N2O

wet and dry deposition

66 29

8

NH3

N2O

2(2)

TERRESTRIAL EMISSIONSTERRESTRIAL EMISSIONS

NOx 55 Tg N y-1 70% anthropogenic

NH3 46 Tg N y-1 66% anthropogenic

Anthropogenic modification of the atmosphericAnthropogenic modification of the atmosphericcycle of fixed nitrogen in substantial.cycle of fixed nitrogen in substantial.

TOTAL 111 Tg

42 Tg (48%) NATURAL

69 Tg (62%) ANTHROPOGENIC

InputsNatural

BNF 15Human

Fertilizer 22C-BNF 4Fossil Fuel 6Import 10

Total 67

OutputsRiverine 8Atmospheric 5Exports 15Total 28

Europe: Inputs, Outputs and Issues

Points and IssuesLargest source is fertilizer productionLargest sink is Nr exportN policies driven by pollution of groundwater

and North Sea, N deposition causingsoil/water acidification and eutrophication

INI Preliminary Assessment, 2004

InputsNatural

BNF 12Human

Fertilizer 18C-BNF 6Fossil Fuel 7Import 5

Total 49

OutputsRiverine 7Atmospheric 4Exports 8Total 19

N. America: Inputs, Outputs and Issues

Points and IssuesLargest source is fertilizer productionLargest sink is Nr exportN policies driven by impacts on atmosphere, surface waters

And coastal ecosystems

INI Preliminary Assessment, 2004

InputsNatural

BNF 21Human

Fertilizer 40C-BNF 14Fossil Fuel 6Import 14

Total 95

OutputsRiverine 17Atmospheric 10Exports 5Total 32

Asia: Inputs, Outputs and Issues

Points and IssuesLargest source is fertilizer productionLargest sink is riverine~Half of global Nr creation by peopleUneven distribution throughout AsiaSignificant disruption of coastal systems

Galloway et al., 2004 INI Preliminary Assessment, 2004

0

1000

2000

3000

4000

5000

6000

7000

1850 1900 1950 2000Year

Wor

ldpo

pula

tion

and

Agric

ultu

ral s

urfa

ce

0

10

20

30

40

50

60

70

80

90

Ferti

lizer

s an

d N

Ox

World population milionsAgric. surface milions haFertilizer TgrNOx emissions

N- cycle : 100 Tg Natural fixation140 Tg Anthropogenic fixation:

85 Tg Artificial Fertiliser

20 Tg Other Industry35 Tg Combustion

Carl Bosch (1874-1940)

Fritz Haber(1868-1934)

1860 1993

500020001000750500250100

50255

Galloway et al., 2004

mg N m-2 yr-1

Atmospheric Deposition:Past and Present

Changes in global NOy deposition from 1860-1990

(Stevenson et al. 2003)

GOME tropospheric NO2 :

University of Bremen

EMISSIONS EMISSIONS OF OF

OXIDISED NITROGENOXIDISED NITROGEN

Time

1860

1870

1880

1890

1900

1910

1920

1930

1940

1950

1960

1970

1980

Tg N

0

5

10

15

20

25Global Emissions of NOx from CombustionGlobal Emissions of NOx from Combustion

18

19

20

21

22

23

24

25

26

1980

1985

1986

1987

1988

1989

1990

1991

1992

1993

1994

1995

Em

issi

ons

of N

Ox

(kt y

-1)

European Emissions of NOxEuropean Emissions of NOx

0123456789

1980

1985

1986

1987

1988

1989

1990

1991

1992

1993

1994

1995

Emis

sion

s of

NH

3 (kt

y-1

)European Emissions of NHEuropean Emissions of NH33

ATMOSPHERE

CANOPY

SOIL

NO + O3 NO2 + O2

SOIL WATER

TEMPERATURE SOIL N

O3 NO2

EMISSION

DEPOSITION

DEPOSITION

NO

ATMOSPHERE

SOILNO

N2O NO

N2O

NO3 N2NH4

N mineralisation

N fertilizeranimal manureN deposition

NITRIFICATION DENITRIFICATION

6 7 8 9 10 11 12

-3

-2

-1

0

1

2

3

-4.53 + 1.91 * log soil NO3 + 0.274 * soil temp.

log

NO

flux

( µ

g N

m-2

h-1

)

2 5 10

+ 20

-20

0

+ veEMISSION

- veDEPOSITION

ambient NOconcentration,

ppb

COMPENSATION POINT RANGE

NO

Flu

x ng

m-2

s-1

Compensation Point for Compensation Point for NO Emission from SoilNO Emission from Soil

NO2NO

NO3

HNO3

N2O5

O3

O3

bifunctionalorganicnitrates alkenes

M

NO2

RHH2O/surface

HONOnitrateaerosol

fossil fuelcombustion

wet and dry deposition

GROUND

NO2

NO

RONO2

RO2NO2

HONO

NO3

HNO3

HO2NO2

OH

RO2

RO2

O3 HO2

M

M

O3

HO2

nitrateaerosol

wet and dry depositionfossil fuel

combustion

sunlight

OH

sunlight

sunlightNOH2O / surface

GROUND

AIR FLOW

typically 300 - 1000min the UK

hill profile

SEEDERCLOUD

OROGRAPHIC(FEEDER) CLOUD

scavenging offeeder cloud

aerosols activated into cloud droplets

at cloud base

EMISSIONSDRY

DEPOSITION

WET + CLOUDDEPOSITION

40 110

780INPUT EXPORT

69060

From non-UK/Europe

EMISSION 780DEPOSITION 150

UK Oxidised N, 1992 UK Oxidised N, 1992 -- 94 kt N94 kt N

REDUCED REDUCED NITROGENNITROGEN

NH3 emissions kT

EU-15Power generationIndustry Domestic Transport Agriculture Industrial processes

NEC emission ceiling

0

500

1000

1500

2000

2500

3000

3500

2000 2005 2010 2015 2020

Emissions in Europe

Reductions

Reduced Nitrogen – 24%Oxidised Nitrogen – 19%

Oxidised Sulphur – 67%

Excess of critical loads for eutrophication

Percentage of ecosystems area with nitrogen deposition above critical loads, using grid-average deposition. Average of calculations for 1997, 1999, 2000 & 2003 meteorologies

2000 2010 2020

NH3

NH3

DRYDEPOSITION

HNO3

H2SO4

NH4+

aerosol

WETDEPOSITION

atmosphericlifetime

1 - 3 hours

lifetime1 - 3 days

gas to particle conversion

precipitationscavenging

y = 0.0135x2 - 0.2312x + 0.1514 R2= 0.9992

y = -0.16x + 0.1029 R2= 0.982

-1.5-1.3-1.1

-0.9-0.7-0.5-0.3-0.1

0.10.30.5

0 1 2 3 4 5 6 7 8

inlet concentration, µg m-3co

ncen

trat

ion

diffe

renc

e, µ

g m

-3

Compensation Points and NHCompensation Points and NH33

Leaf temperature (ºC)10 15 20 25 30 35 40

-4

-3

-2

-1

0

1

2

3

4

Emission

Absorption

NH

3ex

chan

ge, n

mol

m-2

s-1

EMISSIONSDRY

DEPOSITION

WET + CLOUDDEPOSITION

110 120

260INPUT EXPORT

6030

EMISSION 260DEPOSITION 230

From non-UK/Europe

UK Reduced NUK Reduced N

EMISSIONSDRY

DEPOSITION

WET + CLOUDDEPOSITION

40 110

780INPUT EXPORT

69060

From non-UK/Europe

EMISSION 780DEPOSITION 150

1992 1992 -- 94 kt N94 kt NUK Oxidised NUK Oxidised N

NO2-N6.4

NH3-N5.8 NHx-N

5.6

NOy-N4.60 ? 1.8

European Nitrogen Emissions and Deposition (Mt yEuropean Nitrogen Emissions and Deposition (Mt y--11))

EFFECTSEFFECTS

EmissionEmission PollutantPollutant TargetTargetNOx O3, PAN human health, crops

photochemical smog materialsradiative forcing (+'ve)

NOx, NH3 deposited acidity terrestrial freshwater ecologymaterials

NOx, NH3 aerosols climateradiative forcing (-'ve)human health

NOx, NH3 deposited Nitrogen eutrophicationterrestrial and

freshwatercarbon sequestration

Environmental IssueEnvironmental Issue

Excess of critical loads for eutrophication

Percentage of ecosystems area with nitrogen deposition above critical loads, using grid-average deposition. Average of calculations for 1997, 1999, 2000 & 2003 meteorologies

2000 2010 2020

Scale issue

European emissions,deposition and

critical load exceedances

National targets and policyEcosystem protection

NOyNHx

Deposition footprint

Of reduced and oxidized

Nitrogen emissions from the UK

(zone in which 65%

of emission occurs)

Reduced nitrogen - summary• Reduced N mainly as NH3 is primarily an

agricultural pollutant• A short atmospheric lifetime as NH3 leads to

large spatial variability in concentration and deposition

• Reduced N dominates the N deposition budget in N Europe, and for semi-natural vegetation

• Effects of deposited N on species composition are mainly due to reduced N

Global nitrogen - summary• The global cycle of fixed N is dominated (70%)

by emissions of oxidized and reduced N from human activities.

• Oxidized N, as NOx is an ozone precursor gas and contributes to eutrophication, greenhouse gas emission and is a majo constituent of aerosols.

• Reduced N as NHx is the main contributor to eutrophication, contributes to greenhouse gas emissions and is a major component of aerosols over Europe.