Transcript Nitrogen_DGay.ppt

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
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Nitrogen is Good…..
right?
N
14
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Nitrogen is Essential and Everywhere
-plant growth
-Nitrogen is considered a
‘limiting nutrient’
-animal growth
(in bodies and waste)
-78% of the Atmosphere
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But Nitrogen is also a Pollutant
-Adverse effects on health and the environment
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Topics To Discuss
• How & Why is N a pollutant?
• Where does Nitrogen Pollution come from?
•Other impacts?
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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
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Add Nitrogen to lake or Ocean…
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Eutrophication
is the term used to describe these responses to nutrient
(N) over-enrichment
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Eutrophication can lead to Hypoxia
Hypoxia = ‘low oxygen’
HOW?
1.
2.
3.
4.
5.
6.
Nitrogen (fertilizer) added
High growth rates
Population crashes
Decomposition consumes oxygen
Low oxygen
Fish kills, dead zones
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Dead Zones
Red = high N fertilizers
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Add Nitrogen to the Atmosphere?
• All nitrogen is ultimately oxidized (N2?)
• Result HNO3 (Nitric Acid)
NO2 + OH∙ + M ↔ HNO3 + M
HNO3 + H2O ↔ H+ + NO3-
• “Acid Rain, snow and fog”
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Results of Acid Precipitation
Mt. Mitchell, North Carolina
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You also get Smog…..
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Nitrogen to Groundwater?
Organic nitrogen
Nitrates
ammonia
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So………
Where does Nitrogen Pollution Come From?
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Nitrogen comes in Lots of Forms
Chemical
Compound Formula
Reactivity
Mobility
Nitrogen gas
N2
Not very
Very
Ammonia
(gas)
NH3
Very
Nitrate
NO3
Moderately
Very
Fertilizer, combustion,
explosives
Organic N
lots
depends
depends
Example: Urea
Moderately
Misc.
Product of HB, Fert
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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
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Nitrogen Cycle
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Sources of Nitrogen
to the Atmosphere
Burning
(oxidized nitrogen, particularly)
Animals
(ammonia)
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Hog Production in USA
(1 dot= 10,000 Hogs and Pigs)
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Cows and Pigs and Chickens and
Sheep and Goats and etc. etc. etc.
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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%
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Sources to the Atmosphere:
NH3
• 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
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Natural Sources
• Lightning
• Soil bacteria
• Algae
• Uncultivated legumes
Total = 140 mil. M.tons
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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
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The Fate of Reactive Nitrogen
Only 4% of the reative N produced in the Haber-Bosch process
and used for animal production enters the human mouth.
N Fertilizer
N Fertilizer
Applied
Produced
100
94
-6
-47
N
in Crop
N
In Feed
47
31
-16
N
in Store
N
Consumed
7
-24
4
-3
The rest ( 96%) escapes into air, soil, surface water (rivers, streams)
and groundwater (aquifers) and cascades towards the oceans
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Galloway JN and
Cowling2002
EB. 2002
Galloway
Nitrogen Use and Emission is UP UP UP
Source: 2nd International Nitrogen Conference
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Deposition Is Also Increasing
(N into Ecosystems)
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Inorganic Nitrogen Wet Deposition, 2007
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Nitrogen Deposition Past and Present
mg N/m2/yr
5000
2000
1000
750
500
250
100
50
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5
1860
1993
-Change in Northern Hemisphere – Fossil fuels (industrial revolution), and ag
-Change in Southern Hemisphere – Slash and burn
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Galloway and Cowling, 2002; Galloway et al., 2002b
Nitrate Deposition
Trends
3-year running average
1985 – 2008
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Animation
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Nitrate Trend in Precipitation
1985-2009
INCREASING
Trend
DECREASING
Trend
Number of
Sites
Number
Significant
Number of Sites
Number
Significant
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9
122
92
Trends
Emissions
-37%
Concentration
-22%
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Ammonium
Deposition Trends
3-year running average
1985 – 2008
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Animation
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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
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