Nutrient Loading from Point
and Non-Point Sources on
Surface Waters
by Adam Lanning
Why are Nutrients a Concern?
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Nutrients refer to nitrogen and phosphorous.
Excessive levels in waters causes
eutrophication.
Eutrophication leads to diminished aquatic
life.
This limits availability for drinking water due
to buildup of nitrates.
Unsightly, odorous, nuisance for recreation.
Objectives of Paper
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Gain a thorough understanding of the impact
of nutrient enrichment on surface waters.
Learn the current status of U.S. surface
waters.
Learn the sources and proportion of nutrient
discharges to surface waters?
Examine the feasibility of nutrient regulation.
Effects of Nutrient Enrichment
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Enrichment means nutrient inputs beyond the
‘naturally occuring levels’.
Nutrients are ‘naturally occurring’ and
necessary for aquatic plant growth.
Elevated levels unnatural and lead to toxic
conditions.
Effects of Nutrient Enrichment
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Under normal conditions, a water body is
able to buffer nutrients.
Sediment will adsorb excessive inputs to
some degree.
Aquatic plants will cycle, absorbing during
growth and releasing during the decay
process.
Effects of Nutrient Enrichment
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When a water body is unable to adsorb input
levels, excess levels will migrate
downstream.
Eventually downstream levels will build up
and unwanted growth will occur.
Excess growth is primarily the buildup of algal
mass.
Effects of Nutrient Enrichment
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Excessive growths of algae will cause wide
fluctuations in dissolved oxygen
(photosynthesis).
High levels during periods of light.
Low levels of D.O. during periods of low light.
Extended periods of low light can cause D.O.
depletion.
Effects of Nutrient Enrichment
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As a watershed drains to the coastal areas,
nutrient enrichment occurs.
This leads to the same dissolved oxygen
depletion.
Hypoxic zones will form as a result of
decaying algal growths.
Most forms of life will suffer the hypoxic
conditions.
Trophic State
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Trophic state refers to the ‘age’ of a water
body.
Can also be thought of as the amount of
biological activity occurring at any given time.
Younger water means less activity.
The older the water, the more activity that is
occurring within the ecosystem.
Eutrophication
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Nutrient enrichment leads to eutrophication.
Characterized by excessive levels of
nutrients.
Excessive levels of biological activity.
Characterized by algal blooms.
Algae dies and decomposes.
Decomposition process uses oxygen.
Conceptual Model
Clean Water Act
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Enacted in 1972.
Meant to improve water quality of public
waters.
Focused on point source discharges
(municipal and industrial).
Minimal regulation on nutrients.
Focused primarily on the more acutely toxic
parameters (NH3-N, BOD, TSS).
Current Trophic State of Waters
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USGS studied 250 waters over 19 years
across the United States.
Monitored the trophic state of these waters.
As defined by the USEPA.
25% of locations improved.
70% remained the same.
5% worsened.
Current Trophic State of Waters
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These numbers indicate that CWA did slow
eutrophication.
But, limited success on improving the trophic
state.
This was due to the multitude of nutrient
sources.
CWA has limited authority over non point
sources.
Sources of Nutrient Inputs
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Non-Point sources include:
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Agricultural
Urban runoff
Atmospheric deposition.
Point Sources include:
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Wastewater discharges
Industrial discharges.
Agricultural Inputs (Non-Point)
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Fertilizer Application
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Fertilizer application deposits N and P on the soil.
During rain events, excess will run off via erosion
or infiltration.
Unregulated application rates allows for this to
occur.
Agricultural Inputs (Non-Point)
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Fertilizer Application
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Field run off is sporadic and difficult to track.
P adheres to soil particles and can be eroded to
waterways.
N is dissolved and will easily move through the
underlying geology.
Agricultural Inputs (Non-Point)
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Manure containment and disposal
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Majority of the cattle in the U.S. are raised on feed
lots.
Feed lots produce large amounts of manure on
small areas of land.
Manure is high in P and N and must be disposed
of.
Agricultural Inputs (Non-Point)
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Manure can be spread back on the farm
fields as a fertilizer.
Lack of regulation allows for over-application.
This results in nutrient enrichment of the soil.
Excess nutrients will eventually run off to the
waterways.
Urban Runoff (Non-Point)
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Urban runoff includes:
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Construction site runoff
Lawn fertilizer runoff
Septic tank discharges
Pet wastes
Atmospheric Deposition (Non-Point)
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Fixed nitrogen is deposited back on the
surface waters and lands.
Originates from:
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Combusted fossil fuels
Agricultural plant fixation
Wastewater and Industrial Discharge
(Point Source)
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Wastewater discharge is a known contributor
of nutrients to surface waters.
Discharges are easy to monitor as the
effluent is typically constant.
Little regulation exists on N and P.
These nutrients originate primarily from
phosphate detergents and industrial
processes.
Nutrient Contributions
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Contributions to the Gulf of Mexico were
estimated using current modeling software by
the USGS.
Total nutrient (N and P) load rates:
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Point Sources contribute <30%
Non-Point Sources contribute ~70%
Some Solutions to Nutrient Runoff
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Non-point sources typically require some
buffer vegetation to stop P laden soil from
eroding to surface waters.
Natural wetlands can be used to accomplish
this.
Grass strips along waterways are also
effective in filtering the water.
Grass Buffering Strip
Some Solutions to Nutrient Runoff
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Target fertilizer applications to meet the crop
needs will minimize runoff.
Land applying manure can be done in the
same manner, meet the crops nutrient needs.
No-till practices will leave the soil less
erodible.
No-till practice also uses less fuel and
manpower, a benefit to the farmer.
Point Source Regulation
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Regulating wastewater dischargers will
require massive infrastructure upgrades.
It would be a very costly endeavor to upgrade
plants to achieve USEPA proposed limits (.5
mg/L P and 3.0 mg/L N)
Illinois alone would cost ~5.3 billion dollars in
capital costs.
~500 million dollars/year annually to operate
the upgraded facilities.
Summary
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Regulation to achieve low levels of nutrients
will require a focus on all inputs.
A ‘holistic’ approach to reducing inputs would
provide the most benefit.
Wetlands, buffer strips, target fertilization,
and no-till practices would all benefit the
farmer as well as the surface waters.
Wastewater dischargers should be regulated
in conjunction with the ag community.