freshwater pollution

1. Freshwater PollutionFreshwater Pollution

2. POLLUTION OF FRESHWATERPOLLUTION OF FRESHWATER
STREAMSSTREAMS
 Flowing streams can recover from moderateFlowing streams can recover from moderate
levels of degradable water pollutants – if notlevels of degradable water pollutants – if not
overloaded and flows not reducedoverloaded and flows not reduced

Via dilution and biodegradationVia dilution and biodegradation

In a flowing stream, decomposition by bacteriaIn a flowing stream, decomposition by bacteria
depletes DO and creates anddepletes DO and creates and oxygen sag curveoxygen sag curve

This reduces or eliminates populations ofThis reduces or eliminates populations of
organisms with high oxygen requirementsorganisms with high oxygen requirements

3. Water Pollution Problems in StreamsWater Pollution Problems in Streams
 Oxygen sag curveOxygen sag curve showing dilution and decay ofshowing dilution and decay of
degradable, oxygen-demanding wastes and heat indegradable, oxygen-demanding wastes and heat in
a streama stream
 Biochemical (biological) oxygen demandBiochemical (biological) oxygen demand –– BODBOD
– the amount of dissolved oxygen needed to break– the amount of dissolved oxygen needed to break
down organic materialdown organic material

4. Water Pollution Problems in StreamsWater Pollution Problems in Streams
 Oxygen sag curveOxygen sag curve showing dilution and decay ofshowing dilution and decay of
degradable, oxygen-demanding wastes and heat indegradable, oxygen-demanding wastes and heat in
a streama stream

5. POLLUTION OF FRESHWATERPOLLUTION OF FRESHWATER
STREAMSSTREAMS
 Most more-developed countries have sharplyMost more-developed countries have sharply
reduced point-source pollution (in U.S.reduced point-source pollution (in U.S.
thanks to the Clean Water Act)thanks to the Clean Water Act)
 But accidental or deliberate release of toxicBut accidental or deliberate release of toxic
chemicals, untreated sewage and pollutionchemicals, untreated sewage and pollution
from nonpoint sources are still a problemfrom nonpoint sources are still a problem
 Result in fish kills and drinking waterResult in fish kills and drinking water
contaminationcontamination

6. POLLUTION OF FRESHWATERPOLLUTION OF FRESHWATER
STREAMSSTREAMS
 Ex: Cuyahoga River, ClevelandEx: Cuyahoga River, Cleveland

1959 and 1969 caught fire1959 and 1969 caught fire

Prompted officials to enact lawsPrompted officials to enact laws

Much cleaner todayMuch cleaner today

7. Global Outlook: Stream Pollution inGlobal Outlook: Stream Pollution in
Less-Developed CountriesLess-Developed Countries
 Stream pollution fromStream pollution from
discharges of untreateddischarges of untreated
sewage and industrialsewage and industrial
wastes is a major problemwastes is a major problem
in less-developed countriesin less-developed countries
 Water in many of centralWater in many of central
China's rivers are greenishChina's rivers are greenish
black from uncontrolledblack from uncontrolled
pollution by thousands ofpollution by thousands of
factoriesfactories
Tangtze River near
Three Gorges Dam

8. Case Study: India’s Ganges River:Case Study: India’s Ganges River:
Religion, Poverty and HealthReligion, Poverty and Health
 Daily, more than 1Daily, more than 1
million Hindus inmillion Hindus in
India bathe in, drinkIndia bathe in, drink
from or carry outfrom or carry out
religious ceremoniesreligious ceremonies
in the highly pollutedin the highly polluted
Ganges RiverGanges River

9. Case Study: India’s Ganges River:Case Study: India’s Ganges River:
Religion, Poverty, and HealthReligion, Poverty, and Health
 Religious beliefs, cultural traditions, povertyReligious beliefs, cultural traditions, poverty
and a large population (> 500 million inand a large population (> 500 million in
watershed) interact – severe pollution ofwatershed) interact – severe pollution of
Ganges RiverGanges River

Little sewage is treatedLittle sewage is treated

Hindu believe in cremating dead to free soul –Hindu believe in cremating dead to free soul –
throw ashes in the holy Gangesthrow ashes in the holy Ganges
• Some are too poor to afford the wood to fully cremateSome are too poor to afford the wood to fully cremate
• Decomposing bodies promote disease and depletesDecomposing bodies promote disease and depletes
DODO

10. POLLUTION OFPOLLUTION OF
FRESHWATER LAKESFRESHWATER LAKES
 Dilution of pollutants in lakes is less effectiveDilution of pollutants in lakes is less effective
than in streams:than in streams:

Lakes and reservoirs are often stratified – littleLakes and reservoirs are often stratified – little
mixingmixing

Low flow – runoff and pollutants build upLow flow – runoff and pollutants build up
 Various human activities can overload lakesVarious human activities can overload lakes
with plant nutrients, which decrease DO andwith plant nutrients, which decrease DO and
kill some aquatic specieskill some aquatic species

11. Cultural EutrophicationCultural Eutrophication
 EutrophicationEutrophication – natural nutrient enrichment– natural nutrient enrichment
of a shallow lake, estuary or slow movingof a shallow lake, estuary or slow moving
stream, mostly from runoff of plant nutrientsstream, mostly from runoff of plant nutrients
from the surrounding landfrom the surrounding land

Oligotrophic lakeOligotrophic lake – low in nutrients, clear water– low in nutrients, clear water

Eutrophic lakeEutrophic lake – high nutrients, turbid, algae– high nutrients, turbid, algae
 Cultural eutrophicationCultural eutrophication – human activities– human activities
accelerate the input of plant nutrients (mostlyaccelerate the input of plant nutrients (mostly
nitrate- and phosphate-containing effluents)nitrate- and phosphate-containing effluents)
to a lake or estuaryto a lake or estuary

85% of large lakes near major population centers85% of large lakes near major population centers
in the U.S. have some degree of culturalin the U.S. have some degree of cultural
eutrophicationeutrophication

12. Cultural EutrophicationCultural Eutrophication
 Excess nutrients = algae bloomsExcess nutrients = algae blooms

Phosphorus – limiting nutrient in freshwaterPhosphorus – limiting nutrient in freshwater

Nitrogen – limiting nutrient in marine watersNitrogen – limiting nutrient in marine waters
 Block light and photosynthesisBlock light and photosynthesis
 Die, sink, decomposeDie, sink, decompose
 Use up oxygen – result:Use up oxygen – result:

hypoxiahypoxia (low oxygen)(low oxygen)

anoxiaanoxia (no oxygen)(no oxygen)

fish killsfish kills

14. Cultural EutrophicationCultural Eutrophication
 Excess nutrients – nitrates (limiting in marineExcess nutrients – nitrates (limiting in marine
systems) and phosphates (limiting insystems) and phosphates (limiting in
freshwater systemsfreshwater systems
 Sources: runoff from farm fertilizer, animalSources: runoff from farm fertilizer, animal
feedlots, urban areas, fertilized suburbanfeedlots, urban areas, fertilized suburban
lawns, mines, treated and untreated sewagelawns, mines, treated and untreated sewage
(WTPs and septic systems), atmospheric(WTPs and septic systems), atmospheric
depositiondeposition
-

16. Fig. 3-29, p. 75
Gaseous nitrogen (N2)
in atmosphere
Ammonia, ammonium in soil Nitrogen-rich wastes,
remains in soil
Nitrate in soil
Loss by
leaching
Loss by
leaching
Nitrite in soil
Nitrification
Nitrification
Ammonification
Uptake by autotrophs
Uptake by
autotrophsExcretion, death,
decomposition
Loss by
denitrification
Food webs on land
Fertilizers
Nitrogen fixation

17. Fig. 3-31, p. 77
Dissolved
in Ocean
Water
Marine Sediments Rocks
uplifting over
geologic time
settling out weatheringsedimentation
Land
Food
Webs
Dissolved
in Soil Water,
Lakes, Rivers
death,
decomposition
uptake by
autotrophs
agriculture
leaching, runoff
uptake by
autotrophs
excretion
death,
decomposition
mining Fertilizer
weathering
Guano
Marine
Food
Webs

19. Cultural EutrophicationCultural Eutrophication
 Prevention: advanced treatment at WTP toPrevention: advanced treatment at WTP to
remove nutrients, no-phosphate detergents,remove nutrients, no-phosphate detergents,
soil conservation and land use controlsoil conservation and land use control
 Clean up: mechanically remove plants,Clean up: mechanically remove plants,
herbicides, pump airherbicides, pump air
 Prevention is more effective and cheaperPrevention is more effective and cheaper
than cleanupthan cleanup

20. Core Case Study: Dead Zone in GulfCore Case Study: Dead Zone in Gulf
of Mexicoof Mexico
 Nitrates discharged from the Mississippi haveNitrates discharged from the Mississippi have
nearly tripled since 1950nearly tripled since 1950

Nitrogen cycle disruptedNitrogen cycle disrupted

Blue-green algae bloomsBlue-green algae blooms

Hypoxia < 2 ppmHypoxia < 2 ppm
 Flood-control along the MississippiFlood-control along the Mississippi

Flow faster – increases speed of nutrient andFlow faster – increases speed of nutrient and
sediment pollutionsediment pollution
 Fish killsFish kills

21. Case Study: Pollution in the GreatCase Study: Pollution in the Great
LakesLakes
 1960s – many areas with cultural1960s – many areas with cultural
eutrophicationeutrophication
 1972 – Canada and the United States Great1972 – Canada and the United States Great
Lakes pollution control programLakes pollution control program

Decreased algal bloomsDecreased algal blooms

Increased dissolved oxygenIncreased dissolved oxygen

Increased fishing catchesIncreased fishing catches

Better sewage treatment plantsBetter sewage treatment plants

22. Case Study: Pollution in the GreatCase Study: Pollution in the Great
LakesLakes
 Pollution control program (cont’d.)Pollution control program (cont’d.)

Fewer industrial wastesFewer industrial wastes

Bans on phosphate-containing householdBans on phosphate-containing household
productsproducts
 Problems still existProblems still exist

Raw sewage and biological pollutionRaw sewage and biological pollution

Nonpoint runoff of pesticides and fertilizersNonpoint runoff of pesticides and fertilizers

Atmospheric deposition of pesticides and HgAtmospheric deposition of pesticides and Hg

23. Case Study: Pollution in the GreatCase Study: Pollution in the Great
LakesLakes
 Continuing problemsContinuing problems

Urban sprawl and runoffUrban sprawl and runoff

Biological pollutionBiological pollution
• Zebra musselsZebra mussels

Atmospheric deposition of pollutantsAtmospheric deposition of pollutants

24. BiomagnificationBiomagnification
 BioaccumulationBioaccumulation – higher concentration of– higher concentration of
toxic substance in organism than surroundingstoxic substance in organism than surroundings
 BiomagnificationBiomagnification – increase in concentration– increase in concentration
higher in the food webhigher in the food web
 Examples:Examples:

DDT – pesticide, thins eggshells of predator birdsDDT – pesticide, thins eggshells of predator birds

PCBs – polychlorinated biphenyls – in HudsonPCBs – polychlorinated biphenyls – in Hudson
River from GE – in striped bass and bluefishRiver from GE – in striped bass and bluefish

Mercury – from coal-fired power plants – in tuna,Mercury – from coal-fired power plants – in tuna,
swordfish and sharksswordfish and sharks