AP Environmental Science Review Chapter 19: Water Pollution Miller’s Living in the Environment.
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Transcript of AP Environmental Science Review Chapter 19: Water Pollution Miller’s Living in the Environment.
AP Environmental Science Review
Chapter 19: Water PollutionMiller’s Living in the Environment
WATER POLLUTION: SOURCES, TYPES, AND EFFECTS
• Water pollution is any chemical, biological, or physical change in water quality that has a harmful effect on living organisms or makes water unsuitable for desired uses.– Point source: specific location (drain pipes, ditches,
sewer lines).– Nonpoint source: cannot be traced to a single site of
discharge (atmospheric deposition, agricultural / industrial / residential runoff)
Major Water Pollutants and Their Effects
Major Water Pollutants and Their Effects
• Water quality and dissolved oxygen (DO) content in parts per million (ppm) at 20°C.– Only a few fish species can survive in water less than
4ppm at 20°C.
POLLUTION OF FRESHWATER STREAMS
• Most developed countries have sharply reduced point-source pollution but toxic chemicals and pollution from nonpoint sources are still a problem.
• Stream pollution from discharges of untreated sewage and industrial wastes is a major problem in developing countries.
Cultural Eutrophication
• Eutrophication: the natural nutrient enrichment of a shallow lake, estuary or slow moving stream, mostly from runoff of plant nutrients from the surrounding land.
• Cultural eutrophication: human activities accelerate the input of plant nutrients (mostly nitrate- and phosphate-containing effluents) to a lake.– 85% of large lakes near major population centers
in the U.S. have some degree of cultural eutrophication.
Coal strip mine runoff
Polluted air
Deicing road salt
Pesticidesand fertilizers
Hazardous waste
injection well
Pumping well
Gasoline station
Water pumping well
LandfillSewer
Buried gasoline and solvent tanks
Cesspool, septic tank
Groundwater flow
Confined aquifer
Confined freshwater aquifer
Unconfined freshwater aquifer
Accidentalspills
Waste lagoonLeakage from faulty casing
Discharge
POLLUTION OF GROUNDWATER
• It can take hundreds to thousand of years for contaminated groundwater to cleanse itself of degradable wastes.– Nondegradable wastes (toxic lead, arsenic,
flouride) are there permanently.– Slowly degradable wastes (such as DDT) are there
for decades.
Aquifer
Water well
Migrating vapor phase
Contaminant plume moveswith the groundwater
Free gasolinedissolves ingroundwater(dissolved phase)
Groundwaterflow
Watertable
Gasolineleakage plume(liquid phase)
Leakingtank
Bedrock
Solutions
Groundwater Pollution
CleanupPrevention
Find substitutes for toxic chemicals
Install monitoring wells near landfills and underground tanks
Require leak detectors on underground tanks
Ban hazardous waste disposal in landfills and injection wells
Store harmful liquids in aboveground tanks with leak detection and collection systems
Pump to surface, clean, and return to aquifer (very expensive)
Pump nanoparticles of inorganic compounds to remove pollutants (may be the cheapest, easiest, and most effective method but is still being developed)
Keep toxic chemicals out of the environment
Inject microorganisms to clean up contamination (less expensive but still costly)
Fig. 21-10, p. 505
Healthy zoneClear, oxygen-richwaters promote growthof plankton and sea grasses,and support fish.
Oxygen-depleted zoneSedimentation and algaeovergrowth reduce sunlight,kill beneficial sea grasses, useup oxygen, and degrade habitat.
Red tidesExcess nitrogen causesexplosive growth of toxicmicroscopic algae,poisoning fish andmarine mammals.
FarmsRunoff of pesticides, manure, and fertilizers adds toxins and excess nitrogen and phosphorus.
Toxic sedimentsChemicals and toxic metals contaminate shellfish beds, kill spawning fish, andaccumulate in the tissues of bottom feeders.
Construction sitesSediments are washed intowaterways, choking fish and plants, clouding waters, and blocking sunlight.
Urban sprawlBacteria and viruses fromsewers and septic tanks contaminate shellfish beds
Oxygen-depletedzone
Closedbeach
CitiesToxic metals and oil from streets and parking lots pollute waters;
IndustryNitrogen oxidesfrom autos andsmokestacks,toxic chemicals,and heavy metals in effluents flow into bays and estuaries.
Closedshellfish beds
OCEAN POLLUTION
• Harmful algal blooms (HAB) are caused by explosive growth of harmful algae from sewage and agricultural runoff.
OCEAN OIL POLLUTION
• Most ocean oil pollution comes from human activities on land.– Studies have shown it takes about 3 years for many
forms of marine life to recover from large amounts of crude oil (oil directly from ground).
– Recovery from exposure to refined oil (fuel oil, gasoline, etc…) can take 10-20 years for marine life to recover.
Reduce input of toxic pollutants
SolutionsCoastal Water Pollution
Prevention Cleanup
Use wetlands, solar-aquatic, or other methods to treat sewage
Require at least secondary treatment of coastal sewage
Sprinkle nanoparticles over an oil or sewage spill to dissolve the oil or sewage without creating harmful by-products(still under development)
Improve oil-spill cleanup capabilities
Recycle used oil
Regulate coastal development
Protect sensitive areas from development, oil drilling, and oil shipping
Ban ocean dumping of sludge and hazardous dredged material
Ban dumping of wastes and sewage by maritime and cruise ships in coastal waters
Separate sewage and storm lines
Require double hulls for oil tankers
Reducing Water Pollution through Sewage Treatment
• Raw sewage reaching a municipal sewage treatment plant typically undergoes:– Primary sewage treatment: a physical process that
uses screens and a grit tank to remove large floating objects and allows settling.
– Secondary sewage treatment: a biological process in which aerobic bacteria remove as much as 90% of dissolved and biodegradable, oxygen demanding organic wastes.
Reducing Water Pollution through Sewage Treatment
• Primary and Secondary sewage treatment.
• Prevent groundwater contamination
Solutions
Water Pollution
• Reduce birth rates
• Reduce poverty
• Reduce air pollution
• Practice four R's of resource use (refuse, reduce, recycle, reuse)
• Work with nature to treat sewage
• Find substitutes for toxic pollutants
• Reuse treated wastewater for irrigation
• Reduce nonpoint runoff