The modification of global atmospheric Nitrogen cycling by human activities David Fowler Centre for Ecology and Hydrology Edinburgh UK
Background The N cycle Global N emissions Oxidised Nitrogen Reduced Nitrogen emission atmospheric chemistry - O 3 production deposition of NOy compensation points deposition footprints effects emission atmospheric chemistry deposition of N non-linearity in S deposition and the role of NH 3 compensation points effects
The Global Nitrogen Cycle
Biomass burning Vehicles Industry Agriculture Sources of fixed Nitrogen to the Atmosphere
Relative Importance of NOy and NHx local scale 1-20 km 2 regional scale 10 5 km 2 continental scale > 10 6 km 2
Atmosphere-Surface Exchange of Fixed TOTAL (ANTHROPOGENIC) N Tg N y -1 20(20) 12(10) 46(30)10(2) 13(7 ) wet and dry deposition 8 2(2) NOx NH 3 NO N 2 O 66 29 NH N 2 O 3 fossil fuel combustion biomass burning LAND soils and agriculture OCEAN
TERRESTRIAL EMISSIONS NOx 55 Tg N y -1 70% anthropogenic NH 3 46 Tg N y -1 66% anthropogenic
Anthropogenic modification of the atmospheric cycle of fixed nitrogen in substantial. TOTAL 111 Tg 69 Tg (62%) ANTHROPOGENIC 42 Tg (48%) NATURAL
Europe: Inputs, Outputs and Issues Inputs Natural BNF 15 Human Fertilizer 22 C-BNF 4 Fossil Fuel 6 Import 10 Total 67 Outputs Riverine 8 Atmospheric 5 Exports 15 Total 28 Points and Issues Largest source is fertilizer production Largest sink is Nr export N policies driven by pollution of groundwater and North Sea, N deposition causing soil/water acidification and eutrophication INI Preliminary Assessment, 2004
N. America: Inputs, Outputs and Issues Inputs Natural BNF 12 Human Fertilizer 18 C-BNF 6 Fossil Fuel 7 Import 5 Total 49 Outputs Riverine 7 Atmospheric 4 Exports 8 Total 19 Points and Issues Largest source is fertilizer production Largest sink is Nr export N policies driven by impacts on atmosphere, surface waters And coastal ecosystems INI Preliminary Assessment, 2004
Asia: Inputs, Outputs and Issues Inputs Natural BNF 21 Human Fertilizer 40 C-BNF 14 Fossil Fuel 6 Import 14 Total 95 Outputs Riverine 17 Atmospheric 10 Exports 5 Total 32 Points and Issues Largest source is fertilizer production Largest sink is riverine ~Half of global Nr creation by people Uneven distribution throughout Asia Significant disruption of coastal systems Galloway et al., 2004 INI Preliminary Assessment, 2004
7000 90 World population and Agricultural surface 6000 5000 4000 3000 2000 1000 World population milions Agric. surface milions ha Fertilizer Tgr NOx emissions 80 70 60 50 40 30 20 10 Fertilizers and NOx Fritz Haber (1868-1934) 0 1850 1900 1950 2000 Year N- cycle : 100 Tg Natural fixation 140 Tg Anthropogenic fixation: 85 Tg Artificial Fertiliser 20 Tg Other Industry 35 Tg Combustion 0 Carl Bosch (1874-1940)
Atmospheric Deposition: Past and Present mg N m -2 yr -1 5000 2000 1000 750 500 250 100 50 25 5 1860 1993 Galloway et al., 2004
Changes in global NOy deposition from 1860-1990 (Stevenson et al. 2003)
GOME tropospheric NO 2 : University of Bremen
EMISSIONS OF OXIDISED NITROGEN
Global Emissions of NOx from Combustion 25 20 15 Tg N 10 5 1860 1870 1880 1890 1900 1910 1920 1930 1940 1950 1960 1970 0 1980 Time
1980 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 26 25 24 23 22 21 20 19 18 European Emissions of NOx Emissions of NOx (kt y -1 )
1980 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 9 8 7 6 5 4 3 2 1 0 European Emissions of NH 3 Emissions of NH3 (kt y -1 )
DEPOSITION EMISSION O 3 NO 2 ATMOSPHERE CANOPY DEPOSITION NO + O 3 NO 2 + O 2 NO SOIL TEMPERATURE SOIL WATER SOIL N
N 2 O NO ATMOSPHERE SOIL N 2 O N O NH 4 NITRIFICATION N fertilizer N mineralisation animal manure N deposition NO 3 N 2 DENITRIFICATION
3 log NO flux ( µg N m -2 h -1 ) 2 1 0-1 -2-3 6 7 8 9 10 11 12-4.53 + 1.91 * log soil NO 3 + 0.274 * soil temp.
+ 20 Compensation Point for NO Emission from Soil NO Flux ng m -2 s -1 + ve EMISSION 0 -ve DEPOSITION 2 5 10 ambient NO concentration, ppb -20 COMPENSATION POINT RANGE
bifunctional organic NO NO 3 nitrates alkenes M HONO H 2 O/surface O 3 NO 2 NO 2 RH N 2 O 5 nitrate aerosol fossil fuel combustion O 3 HNO 3 wet and dry deposition GROUND
RONO 2 RO 2 NO 2 sunlight HONO OH NO M RO 2 RO 2 O 3 HO 2 NO sunlight NO 2 sunlight OH O 3 NO 3 nitrate aerosol H 2 O / surface HO 2 M HNO 3 fossil fuel combustion HO 2 NO 2 wet and dry deposition GROUND
SEEDER CLOUD AIR FLOW OROGRAPHIC (FEEDER) CLOUD scavenging of feeder cloud aerosols activated into cloud droplets at cloud base typically 300-1000m in the UK hill profile
UK Oxidised N, 1992-94 kt N INPUT WET + CLOUD EMISSIONS DEPOSITION DRY 780 DEPOSITION EXPORT From non- UK/Europe 60 40 110 690 EMISSION 780 DEPOSITION 150
REDUCED NITROGEN
NH 3 emissions kt 3500 3000 2500 2000 1500 1000 500 EU-15 0 2000 2005 2010 2015 2020 Power generationindustry Domestic Transport Agriculture Industrial processes NEC emission ceiling
Emissions in Europe Reductions Reduced Nitrogen 24% Oxidised Nitrogen 19% Oxidised Sulphur 67%
Excess of critical loads for eutrophication 2000 2010 2020 Percentage of ecosystems area with nitrogen deposition above critical loads, using grid-average deposition. Average of calculations for 1997, 1999, 2000 & 2003 meteorologies
atmospheric lifetime 1-3 hours NH 3 DRY DEPOSITION gas to particle conversion HNO 3 NH 4 H 2 SO 4 + aerosol lifetime 1-3 days precipitation scavenging WET DEPOSITION NH 3
Compensation Points and NH 3 concentration difference, µg m -3 0.5 0.3 0.1-0.1-0.3-0.5-0.7-0.9-1.1-1.3-1.5 inlet concentration, µg m -3 0 1 2 3 4 5 6 7 8 y = -0.16x + 0.1029 R 2 = 0.982 y = 0.0135x 2-0.2312x + 0.1514 R 2 = 0.9992
NH 3 exchange, nmol m -2 s -1 4 3 2 1 0-1 -2 Emission -3 Absorption -4 10 15 20 25 30 35 40 Leaf temperature (ºC)
UK Oxidised N UK Reduced N 1992-94 kt N INPUT WET + CLOUD EMISSIONS DEPOSITION DRY 780 DEPOSITION EXPORT INPUT WET + CLOUD EMISSIONS DEPOSITION 260 DRY DEPOSITION EXPORT From non- UK/Europe 60 40 110 690 From non- UK/Europe 30 110 120 60 EMISSION 780 DEPOSITION 150 EMISSION 260 DEPOSITION 230
European Nitrogen Emissions and Deposition (Mt y -1 ) NO 2 -N 6.4 NO y -N NH 3 -N 4.6 0? 1.8 5.8 NH x -N 5.6
Emission EFFECTS Environmental Issue Pollutant Target NOx O 3, PAN human health, crops photochemical smog materials radiative forcing (+'ve) NOx, NH 3 deposited acidity terrestrial freshwater ecology materials NOx, NH 3 aerosols climate radiative forcing (-'ve) human health NOx, NH 3 deposited Nitrogen eutrophication terrestrial and freshwater carbon sequestration
Excess of critical loads for eutrophication 2000 2010 2020 Percentage of ecosystems area with nitrogen deposition above critical loads, using grid-average deposition. Average of calculations for 1997, 1999, 2000 & 2003 meteorologies
Scale issue European emissions, deposition and critical load exceedances Ecosystem protection National targets and policy
Deposition footprint Of reduced and oxidized Nitrogen emissions from the UK NHx NOy (zone in which 65% of emission occurs)
Reduced nitrogen - summary Reduced N mainly as NH 3 is primarily an agricultural pollutant A short atmospheric lifetime as NH 3 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 NO x is an ozone precursor gas and contributes to eutrophication, greenhouse gas emission and is a majo constituent of aerosols. Reduced N as NH x is the main contributor to eutrophication, contributes to greenhouse gas emissions and is a major component of aerosols over Europe.