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
synthesis
reduction
(microorganisms,
plants & animals)
(plants & some
anaerobic
bacteria)
NO3-
(anaerobic
bacteria)
more oxidized
(animals &
microorganisms)
NH4+ ammonium
N2
(Rhizobium &
some other
bacteria)
nitrification
(Nitrobacter & other
soil bacteria)
degradation
nitrogen
fixation
denitrification
nitrate
amino acids &
other organic
compounds
NO2
-
nitrite
nitrification
(Nitrosomonas &
other soil bacteria)
more reduced
Ammonia synthesis
Carl Bosch
4
25-11-2015
Fritz Haber
Industrial production of NH3
5
25-11-2015
NITROGEN FIXATION THOUGH COMBUSTION
Nr for food and from energy between 1900 - 2000
half of the global population depends on fertilizers for their food
NITROGEN SOURCES AND FORMS
FORMSEXCESS
Nitrate
Manure
AmmoniumNitrate
NH4
N2
Fertilizer
industry
Combustion
Sources
8
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
BNF Lightning
Fertilizer Agricultural
Combustion Production
BNF
BNF
40  10%
5  50%
120  10% 33  30%
120  50%
140  50%
Annual fixation Nr 458 TgN y-1
Anthropogenic 193 TgN y-1
~50%
OCEAN
BNF – Biological Nitrogen Fixation
NITROGEN: PROCESSING
O
NO
3 O2 2
sunlight
OH NO
RH
O2
RO2
HO2
O2
NO RO
R-HO
Atmospheric
Chemistry
t0.5 lifetime
NOy
< 1 month
NHx
sunlight
O
NO2 O2
3
NO 
NH4NO3 aerosol
NO2 HNO3
O3 …….
Denitrification
N2
atmospheric
transport
N2O
NO
40
NH3
40
Soil/Plants
240
Plant N
Dead Soil
Organic
Matter
t0.5 lifetime
< 10 years
Denitrification
Dry & Wet
Deposition
microbes NH4+ NO3
N2
N2O
20
60
Crops
Livestock
Forest
GPP
Burial
140
80
Leaching and transport to ocean Burial
TO WHAT EXTENT ARE THE GLOBAL MODELS OF N VALIDATED
SCIAMACHY TROPOSPHERIC NO2
pollution
biomass burning
• Burrows et al 2012
IASI satellite remote sensing (Van Damme et al. 2015)
Average ammonia concentrations 2008-2013
(Van Damme et al. 2015)
NH3
mg/m²
2008
15
2009
2010
2011
Faculty of Earth and Life Sciences
NITROGEN: FATE
Denitrification
N2
Denitrification
N2
• Most Nr returns rapidly to the
atmosphere as N2
• Nr is accumulated in specific
terrestrial and oceanic reservoirs
N2O
120 Tg-N
N2O
~200 Tg-N ?
Terrestrial
280 Tg-N
Plant N
Dead Soil
Organic
Matter
140
microbes NH4+ NO3
80
Burial
• Forests
• Soils
• Peatlands
• Aquifers
Leaching and transport to ocean
Burial
Effects of reactive nitrogen
Predicted effects across Europe
Critical load exceedance
for N effects on ecosystems
% of ecosystems area with grid
average N deposition > eutrophication
(for 2000)
Predicted effects across Europe
Critical load exceedance
for N effects on ecosystems
% of ecosystems area with grid
average N deposition > eutrophication
(for 2000)
Loss in life expectancy
attributable to PM2.5
Loss in average life expectancy
in months due to identified
anthropogenic PM2.5 (for 2000)
SCALE ISSUES
The spatial scale of assessment strongly influences
outcomes
ATMOSPHERIC NITROGEN DEPOSITION:
GLOBAL, REGIONAL, LOCAL (Nr mg-N m-2)
Dentener et al 2006
2009
2000
2007
FLUXES AND EFFECTS IN THE FIELD OCCUR AT FINE SCALE
Woodland N sink
~30 kg-N ha-1
Livestock source
~100 kg-N ha-1
Arable N source
~5 kg-N ha-1
Grassland N source
~10 kg-N ha-1
5 km
QUANTIFYING SPATIAL DISTRIBUTIONS
Fraction of total surface area (km 2)
0.25
250 Gg-N
30% at 50 x 50 km
40% at 5 x 5 km
0.2
0.15
0.1
5 x 5 km
50 x 50 km
0.05
0
450 - 500
400 - 450
350 - 400
300 - 350
250- 300
200 - 250
150 - 200
100 - 150
50 - 100
0 - 50
• As the resolution increases, Deposition
the magnitude
of peak values
Gg-N
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
Stomatal
Resistance Compensatio
(RS=1/GS) n Point (χS)
Temperature

Precipitation

Soil moisture

Rel. Humidity (or VPD)

CO2, O3 mixing ratios





?
Atmospheric acids (SO2, HNO3)
Nitrogen supply
Non-Stomatal
Resistance
(RW)
?


Stomatal conductance (Gs):
Gs  Gs,max  f T  f VPD  f ψ
(EMEP model, 2003)
1.0
f T (dimensionless)
0.9
fT
0.8
0.7
0.6
0.5
0.4
Temperate/boreal coniferous forests
Temperate/boreal deciduous forests
Mediterranean needleleaf forests
Mediterranean broadleaf forests
Seminatural/Moorland
Temperate crops/Grassland
0.3
0.2
0.1
0.0
0
5
10
15
20
25
30
35
40
1.0
1.0
0.9
0.9
f SWP (dimensionless)
f VPD (dimensionless)
Temperature (°C)
0.8
fVPD
0.7
0.6
0.5
0.4
Temperate/boreal coniferous forests
Temperate/boreal deciduous forests
Mediterranean needleleaf forests
Mediterranean broadleaf forests
Seminatural/Moorland
Temperate crops/Grassland
0.3
0.2
0.1
Temperate/boreal coniferous forests
Temperate/boreal deciduous forests
Mediterranean needleleaf forests
Mediterranean broadleaf forests
Temperate crops/Grassland
Seminatural/Moorland
0.8
0.7
0.6
0.5
fSWP
0.4
0.3
0.2
0.1
0.0
0.0
0
0.5
1
1.5
2
VPD (kPa)
2.5
3
3.5
-3
-2.5
-2
-1.5
SWP (MPa)
-1
-0.5
0
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)
Gradient in equilibrium
dissociation constant
Ke [NH3]x[HNO3]
[HNO3]
NH4NO3
[NH3]
Temperature
gradient
Gradient in actual
[NH3]x[HNO3]
HNO3
Driver for
evaporation
NH3
Changes in N fixation in the 21st century
NITROGEN EFFECTS
Climate change
GHG interactions
Nitrate
Ecosystems
and
biodiversity
Manure
AmmoniumNitrate
NH4
N2
Fertilizer
industry
Human and
animal
health
Combustion
Sources
36
Materials
and
cultural
heritage
Chemical/physical interactions
25-11-2015
Effects
Predicted effects across Europe
Critical load exceedance
for N effects on ecosystems
% of ecosystems area with grid
average N deposition > eutrophication
(for 2000)
Loss in life expectancy
attributable to PM2.5
Loss in average life expectancy
in months due to identified
anthropogenic PM2.5 (for 2000)
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