1
Nitrogen in the Environment
David Gay1 & Bob Hall2
1 NADP Program Office, [email protected], http://nadp.sws.uiuc.edu, (217) 244-0462
2 U.S. Environmental Protection Agency, Region 9, San Francisco, CA
3
-Nitrogen is considered a ‘limiting nutrient’
-plant growth
-animal growth (in bodies and waste)
-78% of the Atmosphere
Nitrogen is Essential and Everywhere
5
Topics To Discuss• How & Why is N a pollutant?• Where does Nitrogen Pollution come from?•Other impacts?
6
How and Why is Nitrogen a Pollutant?
• Nitrogen is limited
• Adding N is adding “fertilizer”
• Makes things grow (algal blooms, red tide, etc.)
• These live thinks die, and consume oxygen
• O2 breathing life then die
9
Eutrophication can lead to Hypoxia
Hypoxia = ‘low oxygen’
HOW?
1. Nitrogen (fertilizer) added2. High growth rates3. Population crashes4. Decomposition consumes oxygen5. Low oxygen 6. Fish kills, dead zones
11
Add Nitrogen to the Atmosphere?
• All nitrogen is ultimately oxidized (N2?)
• Result HNO3 (Nitric Acid)
• “Acid Rain, snow and fog”
NO2 + OH∙ + M ↔ HNO3 + M
HNO3 + H2O ↔ H+ + NO3-
17
Nitrogen comes in Lots of Forms
Nitrogen gas
Compound Reactivity Mobility Misc.ChemicalFormula
N2 Not very Very
Nitrate NO3 Moderately Very
Organic N lots depends depends
Fertilizer, combustion, explosives
Example: Urea
Ammonia (gas)
NH3 Very ModeratelyProduct of HB, Fert
18
Nitrogen is Moving Around the Environment
• Denitrification in Soil– Bacteria change NO3 in the soil to atmospheric N2.
• Volatilization from Soil– urea fertilizers and manures on the soil surface converts to
atmospheric NH3.
• Runoff over Soil– Carries the N fertilizers and manure into rivers and
streams; water quality concerns.
• Leaching from Soil– Carries NO3s down past where plants can use, into
groundwater
24
Sources to the Atmosphere: NOx
• Fossil fuel combustion: 40-58%• Soils: 13-20%• Lightning: 8-17%• Biomass burning: 12-17%• Photo-chemical oxidation: 5-8%• Aircraft: 1%• Transport through stratosphere: 0.2-
0.3%
25
• Agricultural: 49-63%CAFO
• Fertilizer: 11-12%• Oceanic emissions: 10-13%• Soil emissions: 10-13%• Biomass burning: 4-7%• Human excrement: 5-8%• Coal combustion and automobiles:3-4%Holland et al., 2005. Ecological Applications 15(1): 2005, pp 38-57
Sources to the Atmosphere: NH3
27
Fertilizers
• Soil bacteria fix atmospheric nitrogen – N2 gas to reactive forms in the soil)
• Haber Process (fertilizer production) is the same thing; – artificial nitrogen fixation
28
The Fate of Reactive Nitrogen
N Fertilizer Produced
N Fertilizer Applied
N in Crop
N In Feed
Nin Store
NConsumed
-6 -47 -3
100 44794 731
-24-16
Only 4% of the reative N produced in the Haber-Bosch process and used for animal production enters the human mouth.
Galloway JN and Cowling EB. 2002Galloway 2002
The rest ( 96%) escapes into air, soil, surface water (rivers, streams)and groundwater (aquifers) and cascades towards the oceans
32
Nitrogen Deposition Past and Present
Galloway and Cowling, 2002; Galloway et al., 2002b
1860 1993
500020001000 750 500 250 100 50 25 5
mg N/m2/yr
-Change in Northern Hemisphere – Fossil fuels (industrial revolution), and ag
-Change in Southern Hemisphere – Slash and burn
35
INCREASING
Trend
DECREASING
TrendNumber of
SitesNumber
SignificantNumber of Sites Number
Significant
29 9 122 92
Nitrate Trend in Precipitation1985-2009
Trends Emissions Concentration
-37% -22%
38
Nitrogen in the Environment
David Gay1 & Bob Hall2
1 NADP Program Office, [email protected], http://nadp.sws.uiuc.edu, (217) 244-0462
2 U.S. Environmental Protection Agency, Region 9, San Francisco, CA