environmental science unit 5 – water pollution (ste 7th ed. chapter 9)
TRANSCRIPT
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Environmental Science
Unit 5 – Water Pollution(STE 7th ed. Chapter 9)
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Natural WatersThe Blue Marble
71 % liquid water
0.001 %water vapor
The Blue Marble is a famous photograph of the Earth taken on 7 December 1972 by the crew of the Apollo 17 spacecraft at a distance of about 29,000 km or about 18,000 miles. It is one of the most widely distributed photographic images in existence. The image is one of the few to show a fully lit Earth, as the astronauts had the Sun behind them when they took the image. To the astronauts, Earth had the appearance of a child's glass marble (hence the name).
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Where are we going?
1. Water: Importance and availability, shortages
2. Water Management / Conservation
3. Water Pollution, Water Quality Today
4. Pollution Control and Legislation
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1. Water Resources
Water Facts
– H2O
– Essential for life
– Moderates Climate
– Used in agriculture, industry, transportation
– Removes and dilutes pollution
– One of our most vital resources
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Representations of Water
Region of partial negative charge
Regions of partial positive charge
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• Water shrinks on melting (ice floats on water)
• Unusually high melting point
• Unusually high boiling point
• Unusually high surface tension
• Unusually high viscosity
• Unusually high heat of vaporization
• Unusually high specific heat capacity
• And more…
Unique Properties
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H-Bonding
• A hydrogen bond is an electrostatic attraction between an atom bearing a partial positive charge in one molecule and an atom bearing a partial negative charge in a neighboring molecule
• The H atom must be bonded to an O, N, or F atom
• Hydrogen bonds typically are only about one-tenth as strong as the covalent bonds that connect atoms together within molecules
H–bonds are intermolecular bondsCovalent bonds are intramolecular bonds
Polarized bonds allow hydrogen bonding to occur
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Natural WatersIce shrinks on melting as 15% H-bonds are lost
A certain mass of ice occupies more space than the same mass of water
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SourcesWhere Does Potable (fit for consumption) Drinking Water Come From?
Surface water: from lakes, rivers, reservoirs (< 0.01 % of total)Ground water: pumped from wells drilled into underground aquifers (0.3 %)
Less than one third of salt-free water is liquid
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Residence Times
CompartmentVolume
(x103 km3)%
Residence Time(Vol / flow)
Ocean 1.3 x 106 97.5 3,000-30,000 yr
Groundwater
(fresh)10,530 0.76 Days - 103 yr
Lakes (fresh)
91 0.007 1 - 500 yr
Atmosphere 12.9 0.001 1 wk
Rivers/streams 2.12 0.0002 1-4 wk
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Hydrologic Cycle
• watershed: region from which water drains into a water body
• Hydrologic Cycle
– precipitation: movement from atmosphere to surface as rain, sleet, hail, & snow
– runoff: movement along surface
– infiltration: movement from surface to groundwater
– evapotranspiration: (evaporation + transpiration): movement from surface to atmosphere
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Purification
Evaporation and transpiration
Evaporation
Stream
InfiltrationWater table
Unconfined aquifer
Confined aquifer
Lake
Well requiring a pump
Flowingartesian well
Runoff
Precipitation
ConfinedRecharge Area
Aquifer
Less permeable materialsuch as clay Confirming permeable rock layer
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Groundwater
• water infiltrates to water table
• aquifer: porous, water–saturated layers of soil or rock through which groundwater flows
• unconfined aquifers: zone of infiltration above (unsaturated) & water table below (saturated)
• confined aquifers: bounded above & below by less permeable rock
• groundwater moves from recharge area through aquifer & out to discharge area (well, spring, lake, geyser, stream, or ocean)
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Rivers, Lakes, Wetlands
Rivers:Nile, Amazon, Orinoco, Congo, Yangtze, Mississippi
Lakes:Contain 100 x water than rivers and streamsBaikal in Siberia, Gt. Lakes, G. Rift lakes of Africa
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Lakes
The 15 largest lakes in the world (insert is outline of Great Britain) all drawn to same scale. The numbers indicate the rank in area, while the figures in brackets denote surface area in square kilometers (after Ruttner, 1963; in Burgess and Morris, 1987; updated to 1996 by ESIG/NCAR).
Largest by volume, 20% Earth’s freshwater
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Wetlands
• Wetlands
– Bogs, swamps, meadows, marshes
– Vegetation stabilize soil holds back runoff
– Allows time for perculation
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Question
What changes might occur in the hydrologic cycle if our climate were to warm or cool significantly?
- Changes in the availability of water resources
- Increased precipitation in areas, drought in others
- Possible feedbacks to the global climate system
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Water Availability and Uses
• Water is a renewable resource
• Renewel takes time
• Western States have insufficient to meet demand
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Distribution is Uneven:Water Area per Capita
0.5% population
20 % water
20 %
7 %water
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Uses of Water
World• 70% irrigation
(agriculture)• 20 % Industry• 10% residences
World Resources 1998-99
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http://www.bdix.net/sdnbd_org/world_env_day/2003/water_year/consumption.html
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Some Requirements
• 2000 gallons / kg beef • 100,000 gallons / car• 3,000 gallons / kg Al
1 gallon = 3.8 L
50 times more water to produce a calorie from beef as
it does from potatoes
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Freshwater Shortages
• Clean drinking water– Sanitation– Prevents disease– Essential for health
• Polluted water greatest environmental threat• U.N estimates 1.5 billion lack access to safe drinking water• 5 million deaths each year
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SourcesThe number of people living in countries facing severe or chronic water shortages is projected to increase more than fourfold over the next 25 years. This will be from an estimated 505 million people today to between 2.4 and 3.2 billion people by 2025.
Engelman et al., 2000
< 1000 m3 per person per year
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Access to Water
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Access to Water
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Uneven distribution of water
Region Total Renewable Water Resources
(km3 yr-1)
Total Water Withdrawals
(m3 yr-1)
Per Capita (m3 person-1)
Average % of Renewable Resources
Average % Used by Agriculture
Average % Used by Industry
World 43,249 3,414,000 650 - 71 20
Asia 11,321 1,516,247 1,028 29 79 10
Europe 6,590 367,449 503 9 25 48
Middle East/N. Africa
518 303,977 754 423 80 5
N. America 4,850 512,440 1,720 14 27 58
Subject to contamination
Using water at a rate faster than it can be supplied (>100 due to use of sea water)
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Freshwater Shortages
• Many parts of the world are experiencing:
– Rivers running dry
– Lakes and seas shrinking
– Falling water tables from overpumped aquifers
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Aral Sea
• Once world's 4th largest freshwater lake
• Shrinking & getting saltier since 1960
• River water diverted for crops• Increased pollutants
– pesticides, – fertilizers, – Weapons etc
http://veimages.gsfc.nasa.gov//11040/a002117.mpg
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Consequences and Restoration
• South Aral Sea - Beyond repair– Desertification– Vast salt plain– Dust storms– 20 of 24 native fish extinct
• North (little) Aral Sea – Salvagable
• Eastern half may evaporate before west
As the agricultural land becomes contaminated by the salt, the farmers try to combat it by flushing the soil with huge volumes of water. What water makes its way back to the Sea is increasingly saline and polluted by pesticides and fertilizer.
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Dam installed between N and S.
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Bottled WaterBottle Backlash
ABC 2007
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Bottled WaterWho Needs It?
BBC 2008
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2. Water Management
• Cities are outbidding farmers for water supplies from rivers and aquifers
• Countries are importing grain as a way to reduce their water use
• More crops are being used to produce biofuels
• Our water options are:
– get more water from aquifers and rivers,
– desalinate ocean water,
– waste less water
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Groundwater
Pros• Renewable resource (unless
over used)• Available year round• Exists everywhere• No evaporation loss• Cheap to extract
Use• Half of all Americans• 95 % rural population
Cons• May get depleted• Subsidence• Reduced stream flow• Easily polluted• Salt water intrusion• Costly if contaminated
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Groundwater
Areas of greatest aquifer depletion from groundwater overdraft in the continental U.S.
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Ogallawa Aquifer
• World’s largest aquifer
• 90% withdrawn for irrigation; supplies 30% of irrigation water
• supports $32 billion agriculture
• most areas water withdrawn much faster than recharge
Once held more water than all other sources on Earth
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Dams, Canals and Reservoirs
• Fundamental basis of civilizations• 90 % built in last 100 yrs• Hydroelectricity
• People benefit, ecosystems suffer
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Provides water for year-round irrigation of cropland
Flooded land destroys forests or cropland and displaces people
Large losses of water through evaporation
Provides water for drinking Downstream
cropland and estuaries are deprived of nutrient-rich silt
Reservoir is useful for recreation and fishing
Risk of failure and devastating downstream flooding
Can produce cheap electricity (hydropower)
Downstream flooding is reduced
Migration and spawning of some fish are disrupted
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Case Study: The Colorado BasinAn Overtapped Resource
• Colorado River • So many withdrawals that it
often does not reach the ocean
– Largest reservoirs in US
– Water is mostly used in desert area of the U.S.
– Provides electricity from hydroelectric plants for 30 million people (1/10th of the U.S. population)
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Case Study: The Colorado BasinAn Overtapped Resource
• Lake Powell, is the second largest reservoir in the U.S.
• It hosts one of the hydroelectric plants located on the Colorado River
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Case Study: The Colorado BasinAn Overtapped Resource
• Hoover Dam– Colorado river would
periodically overflow
– Built for flood control
– Water for LA
Lake Mead – largest man-made reservoir in US
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CA Water Project
The Problem• most rainfall in northern
California• most population growth &
agriculture in southern California
The Solution• water transferred via dams,
pumps, & aqueducts
The Controversy• southern California wants more
water for growth• much of water wasted by
inefficient irrigation• north needs water for fisheries
& flushing pollutants out of San Francisco Bay
North BayAqueductNorth BayAqueduct
South BayAqueductSouth BayAqueduct
California AqueductCalifornia Aqueduct
CALIFORNIANEVADA UTAH
MEXICO
Central ArizonaProject
Colorado RiverAqueduct
Los AngelesAqueduct
Shasta Lake
Sacramento
Fresno
Phoenix
Tucson
ARIZONA
ColoradoRiver
SacramentoRiverSacramentoRiver
San FranciscoSan Francisco
Los AngelesLos Angeles
San DiegoSan Diego
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Consequences of LA Aqueduct
San Fernando Valley• Irrigated
Owens Lake• Desertified• Largest source of PM
pollution in US• Mitigated using flooding +
vegetation
http://geochange.er.usgs.gov/sw/impacts/geology/owens/
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Other Methods
• Desalinization: expensive and produces large amounts of salty wastewater
– Distillation: heating saltwater until it evaporates
– Reverse osmosis: uses high pressure to force saltwater through a membrane filter
• Cloud seeding
• Towing icebergs?
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Water Conservation
• We waste about two-thirds of the water we use, but we could cut this waste to 15%.
– 65-70% of the water people use throughout the world is lost through evaporation, leaks, and other losses
– Water is underpriced through government subsidies
– The lack of government subsidies for improving the efficiency of water use contributes to water waste
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Water Conservation
• Wetland conservation– Clear steady flow, vegetation
reduces flow– Reduces erosion
• Irrigation efficiency– drip irrigation, central–pivot,
computer monitoring• Recycling
– use of gray water• Repair leaky pipes• Water conservation
– Low flush toilets, faucets, & shower heads
• Xeriscaping
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ConservationWater Conservation
CNN 2001
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Center pivotCenter pivot
Drip irrigationDrip irrigation
Gravity flowGravity flow
(efficiency 60% and 80% with surge valves)
Above- or below-ground pipes or tubes deliver water to individual plant roots.
Water usually comes from an aqueduct system or a nearby river.
(efficiency 90–95%)
(efficiency 80%–95%)
Water usually pumped from underground and sprayed from mobile boom with sprinklers.
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Raising the Price of WaterA Key to Water Conservation
• We can reduce water use and waste by raising the price of water– When Boulder, Colorado introduced water meters, water use per
person dropped by 40%.– A 10% increase in water prices cuts domestic water use by 3-7%
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Question
Do you think that pollution is worse now than it was in the past?
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3. Water Pollution
• Physical, biological, or chemical change in water quality that adversely affects living organisms or makes water unsuitable for desired uses
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Sources
• point sources – discrete and identifiablee.g., factories, sewage treatment plants, mines, oil wells, oil tankers
• nonpoint sources – diffuse and hard to identifye.g., acid deposition, substances picked up in runoff, seepage into groundwater
• nonpoint sources:
– Agriculture: largest source of water pollution in the U.S. (64% of pollutants into streams & 57% of pollutants entering lakes)
– Industry: Atmospheric deposition sometimes from many thousands of km away
– Mining
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Point and Non-point Sources
Smol, 2002
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Pollutants
Health Problems• Infectious agents• Inorganic chemicals • Organic chemicals• Radioactivity
Ecosystem Disruption• Sediment• Plant nutrients• Oxygen demanding wastes• Thermal pollution
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Biological Pollution
• Infectious Agents from human waste
– Typhoid, cholera, dysentry, enteritis, polio, hepatitis
• Insect borne diseases
– Malaria, yellow fever
• Fecal Coliform
– ‘coliform bacteria’ basis for water quality testing
– E. Coli, Salmonella, Listeria
– Bacteria (microbe) of colon or intestines
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O2 Demanding Wastes
• All animal life in natural waters is dependent on the presence of dissolved O2 (DO)
• Amount of DO indicates water quality
• O2 consumed by sewage and organic materials
Water in streams and rivers is constantly replenished with oxygen. Stagnant water and deep lakes can have depleted oxygen
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Thermal Pollution
• As temperature of water rises, gases are removed
• DO concentration decreases
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Pollutant ClassificationsVary Country to Country
Inorganic OrganicRadioactive
Metals Metalloids Non-metals
Toxic Non-Toxic
TransitionMetals
HeavyMetals
Chemical type:
Make connections
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Pollutant ClassificationsVary Country to Country
Inorganic OrganicRadioactive
Metals Metalloids Non-metals
Toxic Non-Toxic
TransitionMetals
HeavyMetals
Chemical type
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Inorganic Pollutants
• Heavy metals– Lead, cadmium, mercury
• Soluble salts– Arsenic, selenium, nitrate, sulfate, perchlorate
• Acids and bases– Acid deposition
• e.g. mercury from incinerators and coal burning plants; acid-mine drainage
• Generally warned to not exceed one meal of fish per week
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Organics
• Uses
– Pesticides, plastics, pharmaceuticals, pigments etc.
• Sources
– Household waste, pesticide runoff, bacteria, VOC’s
• Bioaccumulate very rapidly in fat
– e.g. PCB’s, DDT
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Biological Magnification
• concentrations increase at increasing levels in the food chain
• POP’s– PCBs
(polychlorinated biphenyls)
– DDT
• Metals– Mercury
– Cadmium
– Arsenic
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Question
What is the difference between bioaccumulation and biomagnification?
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PollutionLake Pollution
CNN 2003
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Pollution of Streams & Rivers
flowing water can recover rapidly by dilution & decay
‘Oxygen Sag Curve’
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Reducing Point-Source Pollution
• water pollution laws of 1970s greatly increased number & quality of wastewater treatment plants in U.S.
• also improvements in Canada, Japan, & most western European countries;
• large fish kills & contamination of drinking water still occur, especially in developing countries
• lakes, reservoirs & ponds more vulnerable to contamination than streams because of less mixing & aeration.
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Pollution of Lakes
• Eutrophic = well-nourished
• Increase in nutrients and biological productivity
– Elevated Nitrogen and Phosphorus
– Algal blooms, aquatic plants
– Increase of bacterial populations
– Cloudy, turbid, bad tasting and smelly water
• Accelerates natural ‘aging’ of water bodies
95% US surface fresh water
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Case Study: Lake Onondaga
• Contaminated with raw sewage, salt (sodium and calcium chloride) from soda ash industry
• 1946 mercuric waste discharged from production of chlorine via mercury cell process
http://www.onlakepartners.org
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Case Study: Lake Onondaga
• Placed on Superfund list in 1995
• Most contaminated lake in US
– Nutrients – phosphate, nitrate, ammonia, bacteria, turbidity, salinity, mercury, excess sedimentation
• Metals do not degrade, est. 165,000 lbs of Hg
• Much of which becomes methylated and bioconcentrated
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Newspaper Coverage
‘One of the worst chemical spills ever…’
Anonymous
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• Fire at Sandoz Ltd. released pesticides, solvents and dyes
• Pulse release– 10 days to travel to
North Sea– ½ million fish killed– Disulfoton (pesticide)
Capel et al, 1988
Historical ExampleRhine River, 11-01-86
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Groundwater Pollution
Cannot dilute and disperse like lakes and rivers can
Low DO concentrations and colder temperatures slow degradation of contaminants
Extremely difficult to clean up contaminated groundwater; prevention more effective
Main approach: pump groundwater to surface, purifying water, & returning to aquifer; costs high
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Groundwater Pollution :Prevention
• Reduce sources that feed into the aquifer;• Monitor aquifers near landfills & underground storage tanks• Require leak detection systems & liability insurance for existing & new
underground tanks that store hazardous liquids• Ban or more strictly regulate disposal of hazardous wastes in deep
injection wells & landfills• Store hazardous liquids aboveground with more safeguards
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Ocean Pollution
• Coastal areas most impacted – especially wetlands & estuaries, coral reefs, & mangrove swamps;
• Half of world's population lives within 100 km (60 miles) of oceans & 14 of 15 largest cities coastal
• U.S. about 35% of municipal sewage discharged virtually untreated in marine waters
• Ocean ultimate repository of waste• Dumping of industrial waste directly into ocean off U.S. coasts stopped,
but many countries still dump large quantities of toxic substances
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Oil Spills
• Crude & refined petroleum accidentally & deliberately released into environment;
• Most from normal operation of offshore wells, washing tankers, & leaks of pipeline & storage tanks;
• Tanker & offshore drilling rig accidents can release large amounts in short time;
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Effects of Oil Spills
• volatile organics immediately kill of many aquatic organisms (especially plankton & larvae) & contaminate fish
• floating oil coats birds & marine mammal; destroys natural insulation & buoyancy, & causes deaths
• heavy oil sinks to ocean bottom & washes into estuaries where it contaminates crabs, oysters, mussels, clams, etc
• oil slicks on beaches harm intertidal life & cause economic losses to tourism & fishing industries
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Case Study: Exxon Valdez Oil Spill
• March 24, 1989, tanker in Prince William Sound, Alaska, worst oil spill in U.S. waters;
• coated 1,600 of shoreline, killed wildlife, & caused serious contamination;
• Exxon spent $2.2 billion on direct cleanup + $1 billion fines & damages; another $5 billion being appealed.
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Water Quality Today
• legislation: Clean Water Act (1972, amended 1977) & Water Quality Act (1983) in U.S.;
– main goals: 1) to make U.S. surface waters safe for fishing & swimming by 1983; & 2) to restore chemical, physical & biological integrity of waters;
– progress made, but goals not met
• technology: septic tanks, sewage treatment
• most effective for point pollution sources
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4. Pollution Control and Legislation
• Most effective method is to not produce pollution
– Elimination of lead from gasoline
– Banning of DDT and PCB’s in 1970’s
– Recycling or reclaming materials
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Nonpoint Sources and Land Management
• Requires changing farming practices to reduce runoff from fertilizer, pesticides, & livestock, as well as to reduce soil erosion
– Soil conservation
– Wetland preservation (e.g. Olentangy River Wetland Research Park Project)
• Non–farm use of fertilizers & pesticides (golf course, lawns, & public lands) can be similarly controlled
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Case Study: Chesapeake Bay
• Largest estuary in U.S.
• Severely degraded by water pollution from 6 states
• Also deposition of air pollutants
• Land-use regulations to control runoff
• Ban on phosphate detergents
• Phosphorus discharge dropped 40% since 1980’s
• Nitrogen levels still high
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Question
What are the sources of nitrogen to Chesapeake Bay?
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Sewage Treatment
trap greases & large solids & discharge the
remaining wastes over
drainage field
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Primary Treatment
Involves screens & settling tanks to remove solids from sewage
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Secondary Treatment
uses biological processes to break down biodegradable, oxygen–demanding wastes
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Advanced Treatment
Uses one or more processes to remove specific pollutants
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Water Legislation
• Much of the world's drinking water contaminated & poses serious health threats
• Most drinking water purified by storage in reservoir (suspended matter settles), & treated by sand filters, activated charcoal, & addition of chlorine;
• U.S. Safe Drinking Water Act of 1974 requires EPA to establish national drinking water standards;
• Many using bottled water & home filters; bottled water is often more contaminated than tap water.