Water Pollution: Causes, Effects, and Solutions

1. 20 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

3. Missouri River Mississippi River Basin Ohio River Mississippi River Fig. 20-1a, p. 544

4. Mississippi River GULF OF MEXICO Fig. 20-1b, p. 544

5. 20-1 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

6. Water Pollution Comes from Point and Nonpoint Sources • Water pollution • 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

7. Water Pollution Comes from Point and Nonpoint Sources (cont’d.) • Nonpoint sources • Broad, diffuse areas • Difficult to identify and control • Expensive to clean up

8. 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

9. Fig. 20-2, p. 545

10. Fig. 20-3, p. 546

11. 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

12. Table 20-1, p. 547

13. 20-2 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

14. 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

15. Point source Normal clean water organisms (Trout, perch, bass, mayfly, stonefly) Pollution-tolerant fishes (carp, gar) Fish absent, fungi, sludge worms, bacteria (anaerobic) Pollution-tolerant fishes (carp, gar) Normal clean water organisms (Trout, perch, bass, mayfly, stonefly) 8 ppm Types of organisms 8 ppm Dissolved oxygen (ppm) Biochemical oxygen demand Clean Zone Recovery Zone Septic Zone Decomposition Zone Clean Zone Fig. 20-6, p. 549

16. 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

17. 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

18. Fig. 20-7, p. 550

19. 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

20. Cultural Eutrophication Is Too Much of a Good Thing • Eutrophication • 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

21. Cultural Eutrophication Is Too Much of a Good Thing (cont’d.) • Cultural eutrophication • 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

22. Cultural Eutrophication Is Too Much of a Good Thing (cont’d.) • 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

23. Fig. 20-8, p. 551

24. 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

25. 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

26. Case Study: Pollution in the Great Lakes (cont’d.) • Pollution control program (cont’d.) • 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

27. Case Study: Pollution in the Great Lakes (cont’d.) • Continuing problems • Urban sprawl and runoff • Biological pollution • Zebra mussels • Atmospheric deposition of pollutants

28. Fig. 20-11, p. 553

29. 20-3 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

30. Ground Water 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

31. Ground Water Cannot Cleanse Itself Very Well (cont’d.) • Slower chemical reactions in groundwater due to: • Slow flow – contaminants not diluted • Less dissolved oxygen • Fewer decomposing bacteria • Low temperatures

32. Polluted air Hazardous waste injection well Pesticides and fertilizers Coal strip mine runoff Deicing road salt Buried gasoline and solvent tanks Cesspool, septic tank Pumping well Gasoline station Water pumping well Waste lagoon Sewer Landfill Leakage from faulty casing Accidental spills Discharge Freshwater aquifer Freshwater aquifer Freshwater aquifer Groundwater flow Fig. 20-12, p. 554

33. 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

34. 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

35. 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

38. 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

39. 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

40. 20-4 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

41. 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

42. Ocean Pollution Is a Growing and Poorly Understood Problem (cont’d.) • U.S. coastal waters • Raw sewage – viruses • Sewage and agricultural runoff: NO3- and PO43- • Harmful algal blooms • Oxygen-depleted zones

43. Industry Nitrogen oxides from autos and smokestacks, toxic chemicals, and heavy metals in effluents flow into bays and estuaries. Cities Toxic metals and oil from streets and parking lots pollute waters; sewage adds nitrogen and phosphorus. Urban sprawl Bacteria and viruses from sewers and septic tanks contaminate shellfish beds and close beaches; runoff of fertilizer from lawns adds nitrogen and phosphorus. Construction sites Sediments are washed into waterways, choking fish and plants, clouding waters, and blocking sunlight. Farms Runoff of pesticides, manure, and fertilizers adds toxins and excess nitrogen and phosphorus. Closed shellfish beds Red tides Excess nitrogen causes explosive growth of toxic microscopic algae, poisoning fish and marine mammals. Closed beach Oxygen-depleted zone Toxic sediments Chemicals and toxic metals contaminate shellfish beds, kill spawning fish, and accumulate in the tissues of bottom feeders. Oxygen-depleted zone Sedimentation and algae overgrowth reduce sunlight, kill beneficial sea grasses, use up oxygen, and degrade habitat. Healthy zone Clear, oxygen-rich waters promote growth of plankton and sea grasses, and support fish. Fig. 20-15, p. 559

44. 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

45. Canada Alaska Russia United States China Japan Hawaii PACIFIC OCEAN Fig. 20-17, p. 560

46. 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

47. Ocean Pollution from Oil (cont’d.) • 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

48. Ocean Pollution from Oil (cont’d.) • Faster recovery in warm water with rapid currents • In cold, calm waters recovery can take decades • Methods of preventing oil spills • Double hulls

49. Fig. 20-19, p. 561

50. 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