1. Water Pollution

2. Case Study: The Gulf of Mexico’s Annual Dead Zone
Spring and summer – huge inputs of nutrients from the Mississippi River basin
Depletion of dissolved oxygen in the Gulf of Mexico’s bottom layer of water
Contains little marine life
Disrupts nitrogen cycle
Figure 20.1 Water containing sediments, dissolved nitrate fertilizers, and other pollutants drains from the Mississippi River basin (top) into the Mississippi River and from there into the northern Gulf of Mexico (bottom). The boxed area at the bottom of the map shows the dead zone with the red area having the lowest oxygen level.

3. What Are the Causes and Effects of Water Pollution?
Water pollution causes illness and death in humans and other species, and disrupts ecosystems
Sources:
Primarily agricultural activities, industrial facilities, and mining
Growth of both the human population and our rate of resource use makes it increasingly worse

4. Water Pollution Comes from Point and Nonpoint Sources
Change in water quality that can harm organisms or make water unfit for human uses
Point sources
Located at specific places
Easy to identify, monitor, and
regulate
Figure 20-2: This is a point source of water pollution in Gargas, France

5. Water Pollution Comes from Point and Nonpoint Sources (cont’d.)
Broad, diffuse areas
Difficult to identify and control
Expensive to clean up
Figure 20-3: Nonpoint sediment from farmland runoff flows into streams and sometimes changes their courses or dams them up. As measured by weight, it is the largest source of water pollution.

6. Water Pollution Comes from Point and Nonpoint Sources (cont’d.)
Leading causes of water pollution
Agriculture activities
Sediment eroded from the lands
Fertilizers and pesticides
Industrial facilities
Inorganic and organic chemicals
Mining
Erosion and toxic chemicals

7. Major Water Pollutants Have Harmful Effects
Infectious disease organisms
Contaminated drinking water
An estimated 1.6 million people die every year, mostly under the age of five

8. What Are the Major Water Pollution Problems in Streams and Lakes?
Streams and rivers around the world are extensively polluted
However, they can cleanse themselves of many pollutants if we do not overload them or reduce their flows
Adding excessive nutrients to lakes from human activities can disrupt their ecosystems, and prevention of such pollution is more effective and less costly than cleaning it up

9. Streams Can Cleanse Themselves, If We Do Not Overload Them
Dilution
Biodegradation of wastes by bacteria takes time
Oxygen sag curve
Breakdown of biodegradable wastes by bacteria depletes oxygen
Animated Figure 20-6: Natural capital. A stream can dilute and decay degradable, oxygen-demanding wastes, and it can also dilute heated water. This figure shows the oxygen sag curve (blue) and the curve of oxygen demand (red). Streams recover from oxygen-demanding wastes and from the injection of heated water if they are given enough time and are not overloaded

10. Stream Pollution in More-Developed Countries
1970s – water pollution control laws
Successful water clean-up stories
Ohio Cuyahoga River, U.S.
Thames River, Great Britain
Contamination of toxic inorganic and organic chemicals by industries and mines

11. Stream Pollution in Less-Developed Countries
Half of the world’s 500 major rivers are polluted
Untreated sewage
Industrial waste
Water often used for human activities
Figure 20-7: Natural capital degradation. This portion of China’s Yangtze River near the Three Gorges dam is heavily polluted with chemicals, sediment, and trash.

12. Too Little Mixing and Low Water Flow Makes Lakes Vulnerable to Water Pollution
Less effective at diluting pollutants than streams
Stratified layers
Little vertical mixing
Little of no water flow
Can take up to 100 years to change the water in a lake
Biological magnification of pollutants

13. Cultural Eutrophication Is Too Much of a Good Thing
Natural enrichment of a shallow lake, estuary, or slow-moving stream
Caused by runoff into lake that contains nitrates and phosphates
Oligotrophic lake
Low nutrients; clear water

14. Cultural Eutrophication Is Too Much of a Good Thing
Nitrates and phosphates from human sources
Farms, feedlots, streets, parking lots
Fertilized lawns, mining sites, sewage plants
During hot weather or droughts
Algal blooms
Increased bacteria; anaerobic bacteria
More nutrients
Figure 20-8: In 2010, severe cultural eutrophication affected Chaohu Lake near Hefei City in China’s Anhui Province.

15. Cultural Eutrophication Is Too Much of a Good Thing
Prevent or reduce cultural eutrophication
Remove nitrates and phosphates
Diversion of lake water
Clean up lakes
Remove excess weeds
Use herbicides and algaecides
Pump in air

16. Revisiting The Gulf of Mexico: An Extreme Case of Cultural Eutrophication
Nitrates discharged from the Mississippi have nearly tripled since 1950
Nitrogen cycle disrupted
Blue-green algae blooms
Flood-control along the Mississippi
Flow faster; increase sediment pollution
Fish kills

17. Case Study: Pollution in the Great Lakes
1960s – many areas with cultural eutrophication
1972 – Canada and the United States Great Lakes pollution control program
Decreased algal blooms
Increased dissolved oxygen
Increased fishing catches
Better sewage treatment plants

18. Case Study: Pollution in the Great Lakes
Pollution control program
Fewer industrial wastes
Bans on phosphate-containing household products
Problems still exist
Raw sewage and biological pollution
Nonpoint runoff of pesticides and fertilizers
Atmospheric deposition of pesticides and Hg

19. Case Study: Pollution in the Great Lakes
Continuing problems
Urban sprawl and runoff
Biological pollution
Zebra mussels
Atmospheric deposition of pollutants
Figure 20-11: The five Great Lakes of North America make up the world’s largest freshwater system. Dozens of major cities in the United States and Canada are located on their shores, and water pollution in the lakes is a growing problem.

20. What Are the Major Pollution Problems Affecting Groundwater?
Chemicals used in agriculture, industry, transportation, and homes can spill and leak into groundwater and make it undrinkable
There are both simple ways and complex ways to purify groundwater used as a source of drinking water, but protecting it through pollution prevention is the least expensive and most effective strategy

21. Groundwater Cannot Cleanse Itself Very Well
Source of drinking water for about half of the U.S. population
Common pollutants
Fertilizers and pesticides
Gasoline
Organic solvents
Fracking
Pollutants dispersed in a widening plume
Figure 20-12: Natural capital degradation. Principal sources of groundwater contamination in the United States (Concept 20-3A). Another source in coastal areas is saltwater intrusion from excessive groundwater withdrawal. (Figure is not drawn to scale.)

22. Groundwater Cannot Cleanse Itself Very Well
Slower chemical reactions in groundwater due to:
Slow flow – contaminants not diluted
Less dissolved oxygen
Fewer decomposing bacteria
Low temperatures

23. Groundwater Pollution Is a Serious Hidden Threat in Some Areas
China – 90% of urban aquifers are contaminated or overexploited
U.S. – FDA reports of toxins found in many aquifers
Nitrate ions
Can turn into cancer causing chemicals
Slowly degrading wastes
Non-degradable wastes

24. Case Study: Arsenic in Drinking Water
Rocks rich in arsenic can contaminate wells
Long-term exposure can lead to:
Skin, lung, bladder cancer
Treatment
Nanoparticles of rust

25. There Are Many Ways to Purify Drinking Water
Reservoirs and purification plants
Process sewer water to drinking water
Expose clear plastic containers to sunlight (UV)
The LifeStraw
PUR – chlorine and iron sulfate powder

26. Case Study: Is Bottled Water a Good Option?
Bottled water can be useful but expensive
The U.S. has some of the world’s cleanest drinking water
Bottled water less regulated than tap water
Use of bottled water can create environmental problems

27. Using Laws to Protect Drinking Water Quality
1974 – U.S. Safe Drinking Water Act
Sets maximum contaminant levels for any pollutants that affect human health
Health scientists
Strengthen the law
Water-polluting companies
Weaken the law

28. What Are the Major Water Pollution Problems Affecting Oceans?
Most ocean pollution originates on land and includes:
Oil and other toxic chemicals
Solid waste, which threaten fish and wildlife and disrupt marine ecosystems
Key to protecting the oceans
Reduce the flow of pollution from land and air and from streams emptying into ocean waters

29. Ocean Pollution Is a Growing and Poorly Understood Problem
Municipal sewage from less-developed countries are often dumped into oceans without treatment
Deeper ocean waters
Dilution
Dispersion
Degradation

30. Ocean Pollution Is a Growing and Poorly Understood Problem
U.S. coastal waters
Raw sewage – viruses
Sewage and agricultural runoff: NO3- and PO43-
Harmful algal blooms
Oxygen-depleted zones
Figure 20-15: Natural capital degradation. Residential areas, factories, and farms all contribute to the pollution of coastal waters.

31. Case Study: Ocean Garbage Patches: There Is No Away
North Pacific Garbage Patch
Two rotating gyres
On or just beneath the water surface
Tiny plastic pieces harmful to wildlife
No practical way to clean up
Figure 20-17: The North Pacific Garbage Patch is actually two vast, slowly swirling masses of small plastic particles floating just under the water. Four other huge garbage patches have been discovered in the world’s other major oceans.

32. Ocean Pollution from Oil
Crude and refined petroleum
Highly disruptive pollutants
Largest source of ocean oil pollution
Urban and industrial runoff from land
1989 – Exxon Valdez, oil tanker
2010 – BP Deepwater Horizon in the Gulf of Mexico
Figure 20-19: The Deepwater Horizon drilling platform burned and sank in the Gulf of Mexico after exploding on April 20, 2010.

33. Ocean Pollution from Oil
Volatile organic hydrocarbons
Kill many aquatic organisms
Tar-like globs on the ocean’s surface
Coat animals
Heavy oil components sink
Affect the bottom dwellers

34. Ocean Pollution from Oil
Faster recovery in warm water with rapid currents
In cold, calm waters recovery can take decades
Methods of preventing oil spills
Double hulls

35. Case Study: The BP Deepwater Horizon Oil-Rig Spill
Spill from deep-sea oil drilling – 1 mile deep
Released 4.9 million barrels of crude oil
Contaminated vast areas of coastline
Caused by equipment failure and poor decisions
Government developed new standards for offshore drilling procedures

36. How Can We Deal with Water Pollution?
Reducing water pollution requires that we:
Prevent it
Work with nature to treat sewage
Use natural resources far more efficiently

37. Reducing Ocean Water Pollution
Reduce flow of pollution from land
Land-use
Air pollution
Linked to energy and climate policy
Figure 20-21: Methods for preventing excessive pollution of coastal waters and methods for cleaning it up (Concept 20-4B).

38. Reducing Surface Water Pollution from Nonpoint Sources
Agriculture
Reduce erosion
Reduce the amount of fertilizers
Plant buffer zones of vegetation
Use organic farming techniques
Use pesticides prudently
Institute tougher pollution regulations for livestock operations

39. Case Study: The U.S. Experience with Reducing Point-Source Pollution
1972 – Clean Water Act
1987 – Water Quality Act
Experimenting with a discharge trading policy that uses market forces

40. Sewage Treatment Reduces Water Pollution
How do septic tank systems work?
Wastewater or sewage treatment plants
Primary sewage treatment
Physical process
Secondary sewage treatment
Biological process with bacteria
Tertiary or advance sewage treatment
Special filtering processes
Bleaching, chlorination
Figure 20-23: Solutions. Septic tank systems are often used for disposal of domestic sewage and wastewater in rural and suburban areas.
Figure 20-24: Solutions: Primary and secondary sewage treatment systems help to reduce water pollution.

41. Sewage Treatment Reduces Water Pollution
Many cities violate federal standards for sewage treatment plants
Federal law requires primary and secondary treatment
Exemptions from secondary treatment
There are health risks of swimming in water with blended sewage wastes

42. We Can Improve Conventional Sewage Treatment
Remove toxic wastes before water goes to the municipal sewage treatment plants
Reduce or eliminate use and waste of toxic chemicals
Use composting toilet systems
Wetland-based sewage treatment systems
Work with nature

43. There Are Sustainable Ways to Reduce and Prevent Water Pollution
Developed countries
Bottom-up political pressure to pass laws
Developing countries
Little has been done to reduce water pollution
China
Small sewage treatment plants
How can we avoid producing water pollutants in the first place?