7. Clean Water Act (1972)
• Addresses point-source pollution.
• Set benchmarks, deadlines, and penalties for
non-compliance.
• Not perfect but is at least an attempt to
address the problem.
– We are FARbetter off today.
9. Agricultural Pollutants
• The latest EPA National Water Quality
Inventory indicates that agriculture is the
leading contributor to water quality
impairments, accounting for 60 percent of
contamination in rivers and lakes.
• Why?
– Most agricultural pollution is considered non-
point source and therefore not subject to the
Clean Water Act.
– The way agriculture is practiced has changed
greatly in the last 50 years.
• Rise of Factory Farming.
10.
11.
12.
13.
14.
15.
16.
17. Changing Market Conditions
• In the 1970's the top 5 meat packing companies
processed about 25% of the market.
– Today the Top 4 (Tyson, Cargill, Swift, and National
Beef) process more than 80% of the meat we eat.
• In the 1970s, there were thousands of
independent slaughterhouses nationwide
producing the majority of beef sold.
– Today, we have only 13.
• Vertical Integration: When a company assumes
control of multiple stages in the production
process.
18.
19. What to Do With the Poo?
• On a small diversified farm manure is
used as fertilizer for crops.
– Small enough amounts of manure that it
can be broken down naturally to provide
the plants with nutrients.
• Large-scale commercial livestock and
poultry operations produce an estimated
500 million tons of manure each year.
– More than three times the sewage
produced by the entire U.S. human
population.
– Funneled into waste lagoons which often
leak.
• Becomes highly concentrated.
– 75 X More Concentrated than raw human
sewage.
• Then sprayed on fields at levels far byond
what can be absorbed.
– Runoff!
25. Quick Review: Elements vs. Compounds
• Elements: Smallest division of matter. You
can’t break matter down into any smaller
chemically different pieces.
– All material on earth is made up of 92 naturally
occurring elements.
• Compounds: Two or more different elements
bond together to form compounds.
– These compounds often have very different
chemical and physical properties than their
component elements.
30. Nitrogen
• When it comes to nutrient
pollution the element we
are most concerned with
is Nitrogen.
• Elemental nitrogen is a
colorless, odorless, tastele
ss, and mostly inert (non-
reactive) gas.
• Makes up 78.09% of
Earth’s atmosphere.
31. Nitrogen
• Nitrogen itself is a fairly
abundant element here
on earth.
• However, the vast
majority of that
nitrogen is in the form
of N2 an inert gas.
• N2 gas cannot be used
by plants directly.
32. Nitrogen Compounds
• Plants can only make use of
Nitrogen when it is in
chemical compounds such as
NH3 (Ammonia) and NO3
(Nitrate).
• These compounds are fairly
rare in nature.
• For this reason Nitrogen is
often a limiting nutrient in
ecosystems.
– Gets used up quickly (and
replenished slowly).
– When you run out plants stop
growing.
33.
34. Nitrogen and Traditional
Agriculture
• The issue of nutrient (Nitrogen) depletion
has plagued Agriculture for centuries.
– There is a limited amount of useable Nitrogen
in the soil and it replenishes slowly.
– Each planting season removes Nitrogen from
the soil and it is carried away with the crop.
• For many years farmers dealt with this
problem in 3 main ways.
– Move: Find new nutrient rich land to farm.
– Fertilize: Spread animal waste (manure) that
is high in Nitrogen.
– Crop Rotation: Alternate between planting a
crop that uses lots of nutrients, like corn, and
legumes (soy beans) that replenish nitrogen.
• Soy Beans have sacs of Nitrogen fixing bacteria
that convert atmospheric nitrogen into useable
compounds.
35. The Birth of Nitrogen Fertilizers
• During WW2 German chemists
Fritz Haber and Carl Bosch, in
an attempt to make
explosives, developed a
process to synthetically create
Nitrates and Ammonia.
• This technology revolutionized
how agriculture was practiced -
these synthetic nitrogen
compounds could be used as
fertilizer.
• “The Green Revolution”
36. Too Much Nitrogen
• With the availability of cheap
Nitrogen fertilizers many farmers
switched over.
– These are often over-applied in an
attempt to generate the highest
possible yield.
– Also creates an issue of excess manure.
• It is estimated that nitrogen fertilizers
(both artificial and manure) are
grossly over-applied.
– Only 30-50 Percent of the Nitrogen
fertilizer applied by US farmers is used
by the target crop plants.
– The rest enters the environment as
nutrient pollution.
– More is not necessarily better! Use
fertilizer more efficiently.
38. Eutrophication
• Remember: In most aquatic systems Nitrogen
acts as a Limiting Nutrient.
– The ecosystem can only support a certain number
of plant (algae) species.
– You can only have as many plants as there is
nitrogen to support them.
• When nitrogen-rich runoff from factory-scale
livestock operations and farm fields enters a
body of water it greatly alters the nutrient
balance.
– Greatly increases the amount of nitrogen.
39. Eutrophication
• Eutrophication:
Process in which a
body of water
receives excess
nutrients stimulating
excessive plant
growth.
– Nitrogen is no longer
the limiting nutrient.
– Algae Blooms.
41. Think back to Biology?
• What is photosynthesis?
– Occurs in plants.
– Converts Sunlight (energy), Carbon Dioxide, and
Nutrients into Complex Organic Molecules and
Oxygen.
• What is cellular respiration?
– Occurs in animals.
– Breaks down Complex Organic Molecules and
Oxygen into Energy and Carbon Dioxide
42.
43. Hypoxia
• Eutrophication produces lots of organic material.
When this material decomposes it uses up
Oxygen and produces Carbon Dioxide.
• Hypoxia: Water that has very low, or no dissolved
oxygen.
– Incapable of supporting life.
– Result of decaying organic material.
– Generally happens in deep water, at night, or during
droughts.
• Causes fish kills and can lead to dead zones.
– Dead zone in Gulf of Mexico is 8,500 square miles.
44.
45.
46.
47. Deadzones
• Deadzone in Gulf of
Mexico is 8,500 square
miles.
• Hypoxic Zones occur
worldwide.
• Map
• Major threat to the
fishing industry.
