EUTROPHICATION

Syllabus statements: 5.4.1-5.4.3

ChapterVideoLabs:

SYLLABUS STATEMENTS 5.4.1: Outline the process of

eutrophication 5.4.2: Evaluate the main impacts of

eutrophication 5.4.3: describe and evaluate pollution

management strategies with respect to eutrophication

VOCABULARY Biological oxygen demand Eutrophication Positive feedback

EUTROPHICATION IS The natural or artificial enhancement of

a body of water, particularly with respect to nitrates and phosphates, that results in depletion of the oxygen content of the water

It is accelerated by human activities that add detergents, sewage or agricultural fertilizers to bodies of water

Satellite imagery of the Caspian Sea showing increased turbidity (cloudiness) in the north and east eutrophication

PROCESS OVERVIEW1. Increase in nitrates and phosphates2. Rapid growth of algae3. Accumulation of dead organic material4. High rate of decomposition5. Decrease in oxygen

ENHANCING NATURAL EFFECT In natural conditions plant

communities uptake nutrients and clays in soils trap them

Human alterations remove this storage and increase inputs as well

Sewage effluent – nutrients from waste plus detergents (phosphates)

Agriculture – animal waste & inorganic fertilizer runoff

http://www.appropedia.org/Image:Eutroph_dia.gif

FEEDBACK MECHANISM Positive feedback involved More nutrients mean more plants More dead plants means more organics

means more nutrients More plants…

Until death and decomposition outweighs everything else…

EUTROPHICATION IMPACTS Death of Aerobic organisms Increased turbidity Loss of macrophytes Reduction in the length of food chains Loss of biodiversity

DEAD ZONE FORMATION Worldwide problem in coastal waters (146

areas) In Gulf of Mexico – mouth of Mississippi – area

the size of Massachusetts gets so O depleted (hypoxic) that every aerobic organism that can’t flee dies

Varies in size but growing Nearshore waters are important fisheries

(Gulf one is 18% of US catch) and nursery grounds

They are in jeopardy

RECALL POLLUTION MANAGEMENT Human pollutants produce long term and

far reaching effects Strategies for reducing impacts can be

directed at three different levels in the process1. Altering the human activity2. Reducing the quantity of pollutant released at

the point of emission3. Cleaning up the pollutant and restoring the

ecosystem after pollution occurs

ALTERING THE ACTIVITY THAT POLLUTES Phosphate free

detergents in the home

Reduced residential use of lawn fertilizers

Move agriculture away from inorganic broad scale fertilizers to specifically applied organic fertilizers and manures

Soil conservation

REGULATING AND REDUCING EMISSIONS Sewage treatment modifications

Traditionally remove solids and purify but leave nutrients in effluent

Advanced (more $$$) but removes nutrients for agricultural application

Treatment marshes on farms Use natural wetland capabilities for farm

waste treatment

Raw sewagefrom sewers

Bar screenGritchamber Settling tank Aeration tank Settling tank

Chlorinedisinfection tank

Sludge

Sludge digester

Activated sludgeAir pump

(kills bacteria)

To river, lake,or ocean

Sludge drying bedDisposed of in landfill orocean or applied to cropland,pasture, or rangeland

Primary Secondary

Effluent fromsecondarytreatment

Alumflocculation

plus sedimentsActivated

carbon

Desalination(electrodialysis

or reverse osmosis)Nitrateremoval

Specializedcompoundremoval

(DDT, etc.)

98% ofsuspended solids

90% ofphosphates

98% ofdissolvedorganics

Most ofdissolved salts

Recycled to landfor irrigation

and fertilization

To rivers, lakes,streams, oceans,

reservoirs, or industries

CLEAN UP AND RESTORATION Mud can be pumped out of eutrophic

lakes Plants can be reintroduced to restart

natural nutrient cycling Once that takes hold reintroduce fish

Discharge of untreatedmunicipal sewage

(nitrates and phosphates)Nitrogen compounds

produced by carsand factories

Discharge of treatedmunicipal sewage

(primary and secondarytreatment:

nitrates and phosphates)

Discharge of detergents

( phosphates)

Manure runofffrom feedlots

(nitrates,phosphates,ammonia)

Dissolving of nitrogen oxides

(from internal combustionengines and furnaces)

Runoff and erosion(from cultivation,

mining, construction,and poor land use)

Runoff from streets,lawns, and construction

lots (nitrates andphosphates)

Lake ecosystemnutrient overload and breakdown of chemical cycling

Natural runoff(nitrates andphosphates

Natural runoff(nitrates andphosphates

Inorganic fertilizer runoff(nitrates and phosphates)

REMEMBER THERE ARE MANY FACTORS TO STOP