032 SC.D.2.4.2 as SC.G.2.4.4 Nitrate and Phosphate Pollution
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Transcript of 032 SC.D.2.4.2 as SC.G.2.4.4 Nitrate and Phosphate Pollution
8/8/2019 032 SC.D.2.4.2 as SC.G.2.4.4 Nitrate and Phosphate Pollution
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Nitrogen : Friend or Foe
or
The Promiscuous Lifestyle of Nitrogen
on Planet Earth
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Nitrogen is one of the most important
elements on earth
NWhy?
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-Nitrogen is often considered a
‘limiting nutrient’
-plant growth
- animal growth
-your growth
Nitrogen is essential for BIOLOGICAL PRODUCTIVITY
%
ofbo
dy
weight
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-A little bit of N goes a long way because it is very reactive
(N ‘gets around’….’it cascades through the biosphere’)
-Nitrogen can be too much of a good thing
However…….
-Nitrogen is also a pollutant
-Adverse effects on health and the environment
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Global N Reservoirs
Atmosphere = 4 billion Tg
Turnover Time = 10 million years78% of the atmosphere
Ocean Biomass = 500Tg
Ocean Chemical = 25 millionTg
Terrestrial Biomass = 35 thousand TgTurnover Time = 50y
Ocean Sediments = 100 millionTg
Soils = 95 thousand TgTurnover Time = 2000 years
1 Tg = teragram = 1012 = trillion
(Dissolved atm)
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Global N Reservoirs
Atmosphere = 4 billion Tg
Turnover Time = 10 million years
Ocean Biomass = 500Tg
Ocean Chemical = 25 millionTg
Terrestrial Biomass = 35 thousand TgTurnover Time = 50y
Ocean Sediments = 100 millionTg
Soils = 95 thousand TgTurnover Time = 2000 years
1 Tg = 1012 = trillion
‘Fixed N’
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Increased delivery of reactive N to the environment has
Allowed for increased global food production
Without human-derived N fixation, the current globalPopulation could not be sustained.
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Increased delivery of reactive N to the environment has
Allowed for increased global food production
Without human-derived N fixation, the current globalPopulation could not be sustained.
The problem is that N doesn’t stay where it is supposed to.
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The Fate of Reactive Nitrogen
N Fertilizer
Produced
N Fertilizer
Applied
N
in Crop
N
In Feed
N
in Store
N
Consumed
-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
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Nitrogen Pollution Sources
-Wastewater / Septic – Organic N, nitrate, ammonia
Water quality both surface water and
groundwater
-Agricultural/Livestock – Organic N, ammonia, nitrate
Air and Water quality
-Industry (Powerplants, cars) – Mostly N + O compoundsAir Quality initially
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Human Health
Nitrate toxicity in children (blue baby syndrome)
Nitrogen oxides, smog, respiratory disease
Environment
Acid rain
Adverse responses of aquatic ecosystem(algae blooms, low oxygen, fishkills)
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Pathways of N Cascade
AIR
-Nitrate emissions from combustion sources
Can travel great distances
-Ammonia emissions from livestock sources
Do not usually travel far from source
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Hog Production in USA(1 dot= 10,000 Hogs and Pigs)
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Nitrogen Deposition Past and Present
Galloway and Cowling, 2002; Galloway et al., 2002bGalloway et al. 2002
1860 1993
5000
2000
1000
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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Pathways of N CascadeWater
Surface water
Ground water
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GroundWater
-Groundwater N pollution
Commonly from wastewater
-Can also be from Ag
-Groundwater N pollution
Usually in the form of
Nitrate (very mobile)
Org NAmmonia
nitrate
Unsaturated
zone
(vadose)
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N Loading and Aquatic ecosystem response
• Too much of a good thing
• Increased algal productivity (algae gone wild!)
• Harmful algal blooms
• Formation of nuisance algal mats that get
stuck on your windsurfer
‘Eutrophication’ is the term used to describe
these responses to nutrient
(N) overenrichmentSybil Seitzinger, 2003
Surface water
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Eutrophication can lead to Hypoxia
-Hypoxia = ‘low oxygen’
HOW?
-Algae are growing like crazy. At the same time algae are dyin
like crazy.
-Bacteria are decomposing the algae and consuming oxygen….
Remember Biological Oxygen Demand (BOD)?
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Nitrogen Induced Hypoxia Example:
Gulf of Mexico…..’Dead Zone’
Red = high N
1) Reactive N pours out of the
Mississippi River into the Gulf of Me
2) N fuels algae that sink and get decomposed.
3) Decomposition consumes oxygen = hypoxia
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-Hypoxia (low oxygen) can extend 20% of Gulf Coast
-Responsible for huge economic loss of shellfish
Gray area is hypoxic
‘The Dead Zone’
Gulf of Mexico
F l
o r
i d
a
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Algal loading to the sediments Midwest fertilzer use
History of Gulf of Mexico algal response
Increased fertilzer use in the Midwest = Increased algae
growth in the Gulf of Mexico
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Am I painting a bleak picture? (aka. Review)
-Nitrogen is being ‘fixed’ at unprecedented rates using
The ‘Haber –Bosch’ process.
-Reactive N in the forms of ‘ammonia and nitrate’ are
‘cascading’ through the environment
-Livestock production and fossil fuel burning leads to air
transport of N.
-Agriculture and poor waste management are contributing
To surface water and groundwater N loads.
-All this N is fueling ‘eutrophication’
Is there no stopping it?
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Good places for denitrification
Wetland sediments
DEEP Portions of the Deep Ocean
Your friendly neighborhood
Wastewater treatment plant
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-Natural Denitrification is not currently keeping pace
with human N fixation
-Other strategies are needed to minimize N use and its cascade
N Management
-The global balance between denitrification and N fixation has
changed over geologic time
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THE CHALLENGE
• Human N fixation must increase to support a growing global
population. So how can we minimize the impacts of adding more
reactive nitrogen to the environment?
?