The effect of climate change on the Nitrogen cycle

DAVID FOWLER

CENTRE FOR ECOLOGY AND HYDROLOGY EDINBURGH

OUTLINE AND MOTIVATION

• Nitrogen fixation, natural and anthropogenic…quantifying each

• A global budget for ~2010

• Uncertainties in the budget terms

• Where is all the N we have fixed?

• How will the global N budget change through the 21st Century?

• Effects of Nr on human health, climate and ecosystems

Natural cycling of Nitrogen

degradation

(animals &

microorganisms)

synthesis

(microorganisms,

plants & animals)

amino acids &

other organic

compounds

(Rhizobium &

some other

bacteria)

(anaerobic

bacteria)

nitrification

(Nitrobacter & other

soil bacteria)

nitrification

(Nitrosomonas &

other soil bacteria)

NO2-

nitrite

nitrogen

fixation denitrification

nitrate NH4+ ammonium N2

reduction

(plants & some

anaerobic

bacteria)

NO3-

more oxidized more reduced

4 25-11-2015

Ammonia synthesis

Fritz Haber Carl Bosch

5 25-11-2015

Industrial production of NH3

NITROGEN FIXATION THOUGH COMBUSTION

Nr for food and from energy between 1900 - 2000

half of the global population depends on fertilizers for their food

8

NITROGEN SOURCES AND FORMS

FORMSEXCESS

N2

Manure

Fertilizer

industry

Combustion

Sources

Nitrate

Nitrate

Ammonium-

NH4

Chemical/physical interactions

REPRESENTATIONS OF THE NITROGEN CYCLE

There are two main reasons for the quantitative detail and inclusion of the main fluxes and cycling :

1. Understand the underlying processes

2. Quantify the links between effects and sources, which provides the evidence for remedial action

NITROGEN FIXATION N2 TO NR (Tg-N) 2010

OCEAN

BNF – Biological Nitrogen Fixation

Lightning Combustion BNF Fertilizer Production BNF

40 10%

33 30%

140 50%

5 50%

120 50%

Annual fixation Nr 458 TgN y-1 Anthropogenic 193 TgN y-1 ~50%

Agricultural BNF

120 10%

NITROGEN: PROCESSING

O

O 3

O 3

NO 2

NO OH

RH R

-H

NO 2

NO

HO 2

RO 2 RO

O 2

O 2 O 2

O 2

sunlight

sunlight

NO NO2

NH4NO3 aerosol HNO3

O3 …….

Atmospheric Chemistry

atmospheric transport

Burial

140

60

Dry & Wet Deposition

20

NH4+ microbes NO3 Dead Soil

Organic Matter

Plant N

Soil/Plants Crops Livestock Forest GPP

240

Leaching and transport to ocean

80

NH3

40

Burial

t0.5 lifetime NOy NHx

< 1 month

t0.5 lifetime < 10 years

NO

40

Denitrification

N2

N2O

Denitrification

N2

N2O

TO WHAT EXTENT ARE THE GLOBAL MODELS OF N VALIDATED

SCIAMACHY TROPOSPHERIC NO2

• Burrows et al 2012 biomass burning pollution

IASI satellite remote sensing (Van Damme et al. 2015)

Faculty of Earth and Life Sciences

Average ammonia concentrations 2008-2013 (Van Damme et al. 2015)

15

2009 2010 2011 2008

NH3

mg/m²

NITROGEN: FATE

140

NH4+ microbes NO3 Dead Soil

Organic Matter

Plant N

280 Tg-N

Leaching and transport to ocean

80

Terrestrial

• Most Nr returns rapidly to the

atmosphere as N2

• Nr is accumulated in specific

terrestrial and oceanic reservoirs

Denitrification

N2

N2O

Denitrification

N2

N2O

120 Tg-N ~200 Tg-N ?

Burial • Forests • Soils • Peatlands • Aquifers

Burial

Effects of reactive nitrogen

% of ecosystems area with grid

average N deposition > eutrophication

(for 2000)

Critical load exceedance

for N effects on ecosystems

Predicted effects across Europe

% of ecosystems area with grid

average N deposition > eutrophication

(for 2000)

Critical load exceedance

for N effects on ecosystems Loss in life expectancy

attributable to PM2.5

Loss in average life expectancy

in months due to identified

anthropogenic PM2.5 (for 2000)

Predicted effects across Europe

The spatial scale of assessment strongly influences outcomes

SCALE ISSUES

ATMOSPHERIC NITROGEN DEPOSITION: GLOBAL, REGIONAL, LOCAL (Nr mg-N m-2) Dentener et al 2006

2000

2007

2009

FLUXES AND EFFECTS IN THE FIELD OCCUR AT FINE SCALE

Arable N source ~5 kg-N ha-1

Livestock source ~100 kg-N ha-1

Woodland N sink ~30 kg-N ha-1

Grassland N source ~10 kg-N ha-1

5 km

0

0.05

0.1

0.15

0.2

0.25

0 -

50

50 -

100

100 -

150

150 -

200

200 -

250

250-

300

300 -

350

350 -

400

400 -

450

450 -

500

Fra

cti

on

of to

tal su

rface a

rea (

km

2)

Deposition Gg-N

5 x 5 km

50 x 50 km

QUANTIFYING SPATIAL DISTRIBUTIONS

250 Gg-N

30% at 50 x 50 km 40% at 5 x 5 km

• As the resolution increases, the magnitude of peak values increases and the exceedance of thresholds increases

• With developments in understanding and increases in computing power, exceedances of thresholds increase

2000 TO 2100 TRENDS

Two important issues: 1. Estimates of projected

emissions of NOx ,NH3, and N2O

2. Influence of climate and land-use change on the N cycle (emissions).

NOX EMISSIONS (VAN VUUREN et al 2011)

N2O EMISSIONS 1950-2100 (VAN VUUREN et al 2011)

VAN VUUREN et al 2011

• Effects of global change during the 21st century on the

nitrogen cycle

•

• David Fowler1 , Claudia E Steadman1,2 , David Stevenson2

, Mhairi Coyle1 , Robert M Rees3 , Ute M. Skiba1 , Mark A.

Sutton1 J. Neil Cape1 , Tony Dore1 , Massimo Vieno1,2 ,

David Simpson4 , Sönke Zaehle5 , Benjamin Stocker6 ,

Matteo Rinaldi7 , Christina Facchini7 , CR Flechard8 , Eiko

Nemitz1 , Marsailidh Twigg1 , Jan Willem Erisman9 and Jim

Galloway

• Atmospheric Chemistry and Physics Discussion 2014

GLOBAL CHANGE DRIVERS OF NH3 EXCHANGE

Stomatal Resistance (RS=1/GS)

Stomatal Compensation Point (χS)

Non-Stomatal Resistance

(RW)

Temperature

Precipitation

Soil moisture

Rel. Humidity (or VPD)

CO2, O3 mixing ratios ? ?

Atmospheric acids (SO2, HNO3)

Nitrogen supply

Stomatal conductance (Gs):

ψVPDTmaxs,s fffGG (EMEP model, 2003)

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

0 5 10 15 20 25 30 35 40

Temperature (°C)

fT (

dim

ensi

on

less

)

Temperate/boreal coniferous forests

Temperate/boreal deciduous forests

Mediterranean needleleaf forests

Mediterranean broadleaf forests

Seminatural/Moorland

Temperate crops/Grassland

fT

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

-3 -2.5 -2 -1.5 -1 -0.5 0

SWP (MPa)

fS

WP (

dim

ensi

on

less

)

Temperate/boreal coniferous forests

Temperate/boreal deciduous forests

Mediterranean needleleaf forests

Mediterranean broadleaf forests

Temperate crops/Grassland

Seminatural/Moorland

fSWP

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

0 0.5 1 1.5 2 2.5 3 3.5

VPD (kPa)

fV

PD (

dim

ensi

on

less

)

Temperate/boreal coniferous forests

Temperate/boreal deciduous forests

Mediterranean needleleaf forests

Mediterranean broadleaf forests

Seminatural/Moorland

Temperate crops/Grassland

fVPD

Leaf surface chemical processing and stomatal exchange

Ammonia exchange and surface temperature

Flechard and Fowler,

QJRMS, 1998

MECHANISM LEADING TO FAST NITRATE & AMMONIUM

DEPOSITION

NH4NO3(S, AQ) NH3(G) + HNO3(G); KE = FN(T, RH)

Temperature gradient

Gradient in equilibrium dissociation constant Ke [NH3]x[HNO3]

[HNO3] [NH3]

Driver for evaporation

Gradient in actual [NH3]x[HNO3]

NH4NO3

HNO3 NH3

Changes in N fixation in the 21st century

36 25-11-2015

NITROGEN EFFECTS

N2

Manure

Fertilizer

industry

Combustion

Sources

Nitrate

Nitrate

Ammonium-

NH4

Chemical/physical interactions

Materials

and

cultural

heritage

Human and

animal

health

Climate change

GHG interactions

Ecosystems

and

biodiversity

Effects

% of ecosystems area with grid

average N deposition > eutrophication

(for 2000)

Critical load exceedance

for N effects on ecosystems Loss in life expectancy

attributable to PM2.5

Loss in average life expectancy

in months due to identified

anthropogenic PM2.5 (for 2000)

Predicted effects across Europe

conclusions

• The main effects of changes in climate during

the 21st century on the nitrogen cycle are to

increase emission fluxes, especially of

ammonia

• These changes will erode benefits of measures

to reduce emissions, which to date are modest

for ammonia.

Thank you