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Lecture 16

11:375:101 Lecture Notes - Lecture 16: Oil Spill, Harmful Algal Bloom, Industrial Waste


Department
Environmental Sciences
Course Code
11:375:101
Professor
Craig Phelps
Lecture
16

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Water Pollution
Chapter 20: Water Pollution
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
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
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, andregulate
Nonpoint sources
Broad, diffuse areas
Difficult to identify and control
Expensive to clean up
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
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
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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
Stream Pollution in More-Developed Countries
1970s - water pollution control laws
Successful water clean-up stories
Ohio Cuyahoga River, US
Contamination of toxic inorganic and organic chemicals by industries and
mines
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
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 or no water flow
Can take up to 100 years to change the water in a lake
Biological magnification of pollutants
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
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
Prevent or reduce cultural eutrophication
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