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



Nitrogen is one of the most important

elements on earth

NWhy?



-Nitrogen is often considered a

‘limiting nutrient’

-plant growth

- animal growth

-your growth

Nitrogen is essential for BIOLOGICAL PRODUCTIVITY

%

ofbo

dy

weight



-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



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)



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’



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.



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.



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



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



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)



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



Hog Production in USA(1 dot= 10,000 Hogs and Pigs)



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



Pathways of N CascadeWater

Surface water

Ground water



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)



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



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)?



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



-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



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



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?



Good places for denitrification

Wetland sediments

DEEP Portions of the Deep Ocean

Your friendly neighborhood

Wastewater treatment plant



-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



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?

?

032 sc.d.2.4.2 as sc.g.2.4.4 nitrate and phosphate pollution

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