environmental science unit 5 – water pollution (ste 7th ed. chapter 9)

Environmental Science

Unit 5 – Water Pollution(STE 7th ed. Chapter 9)

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).

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

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

Representations of Water

Region of partial negative charge

Regions of partial positive charge

• 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

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

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

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

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

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

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

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)

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

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

Wetlands

• Wetlands

– Bogs, swamps, meadows, marshes

– Vegetation stabilize soil holds back runoff

– Allows time for perculation

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

Water Availability and Uses

• Water is a renewable resource

• Renewel takes time

• Western States have insufficient to meet demand

Distribution is Uneven:Water Area per Capita

0.5% population

20 % water

20 %

7 %water

Uses of Water

World• 70% irrigation

(agriculture)• 20 % Industry• 10% residences

World Resources 1998-99

http://www.bdix.net/sdnbd_org/world_env_day/2003/water_year/consumption.html

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

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

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

Access to Water

Access to Water

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)

Freshwater Shortages

• Many parts of the world are experiencing:

– Rivers running dry

– Lakes and seas shrinking

– Falling water tables from overpumped aquifers

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

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.

Dam installed between N and S.

Bottled WaterBottle Backlash

ABC 2007

Bottled WaterWho Needs It?

BBC 2008

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

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

Groundwater

Areas of greatest aquifer depletion from groundwater overdraft in the continental U.S.

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

Dams, Canals and Reservoirs

• Fundamental basis of civilizations• 90 % built in last 100 yrs• Hydroelectricity

• People benefit, ecosystems suffer

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

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)

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

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

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

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/

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?

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

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

ConservationWater Conservation

CNN 2001

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.

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%

Question

Do you think that pollution is worse now than it was in the past?

3. Water Pollution

• Physical, biological, or chemical change in water quality that adversely affects living organisms or makes water unsuitable for desired uses

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

Point and Non-point Sources

Smol, 2002

Pollutants

Health Problems• Infectious agents• Inorganic chemicals • Organic chemicals• Radioactivity

Ecosystem Disruption• Sediment• Plant nutrients• Oxygen demanding wastes• Thermal pollution

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

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

Thermal Pollution

• As temperature of water rises, gases are removed

• DO concentration decreases

Pollutant ClassificationsVary Country to Country

Inorganic OrganicRadioactive

Metals Metalloids Non-metals

Toxic Non-Toxic

TransitionMetals

HeavyMetals

Chemical type:

Make connections

Pollutant ClassificationsVary Country to Country

Inorganic OrganicRadioactive

Metals Metalloids Non-metals

Toxic Non-Toxic

TransitionMetals

HeavyMetals

Chemical type

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

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

Biological Magnification

• concentrations increase at increasing levels in the food chain

• POP’s– PCBs

(polychlorinated biphenyls)

– DDT

• Metals– Mercury

– Cadmium

– Arsenic

Question

What is the difference between bioaccumulation and biomagnification?

PollutionLake Pollution

CNN 2003

Pollution of Streams & Rivers

flowing water can recover rapidly by dilution & decay

‘Oxygen Sag Curve’

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.

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

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

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

Newspaper Coverage

‘One of the worst chemical spills ever…’

Anonymous

• 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

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

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

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

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;

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

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.

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

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

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

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

Question

What are the sources of nitrogen to Chesapeake Bay?

Sewage Treatment

trap greases & large solids & discharge the

remaining wastes over

drainage field

Primary Treatment

Involves screens & settling tanks to remove solids from sewage

Secondary Treatment

uses biological processes to break down biodegradable, oxygen–demanding wastes

Advanced Treatment

Uses one or more processes to remove specific pollutants

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.