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Nitrogen in the Environment

David Gay1 & Bob Hall2

1 NADP Program Office, dgay@uiuc.edu, 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?

N14

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-Nitrogen is considered a ‘limiting nutrient’

-plant growth

-animal growth (in bodies and waste)

-78% of the Atmosphere

Nitrogen is Essential and Everywhere

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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. Nitrogen (fertilizer) added2. High growth rates3. Population crashes4. Decomposition consumes oxygen5. Low oxygen 6. 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)

• “Acid Rain, snow and fog”

NO2 + OH∙ + M ↔ HNO3 + M

HNO3 + H2O ↔ H+ + NO3-

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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 nitrogenNitratesammonia

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So………

Where does Nitrogen Pollution Come From?

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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

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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 Nitrogento 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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• 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

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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

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

29Source: 2nd International Nitrogen Conference

Nitrogen Use and Emission is UP UP UP

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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

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

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Nitrate Deposition Trends

3-year running average1985 – 2008

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Animation

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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%

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Ammonium Deposition Trends

3-year running average1985 – 2008

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Animation

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Nitrogen in the Environment

David Gay1 & Bob Hall2

1 NADP Program Office, dgay@uiuc.edu, http://nadp.sws.uiuc.edu, (217) 244-0462

2 U.S. Environmental Protection Agency, Region 9, San Francisco, CA