Post on 27-Dec-2015
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• point sources (e.g., factories, sewage treatment plants, mines, oil wells, oil tankers);
• nonpoint sources (e.g., acid deposition, substances picked up in runoff, seepage into groundwater);
• nonpoint source water pollution from agriculture is largest source of water pollution in the U.S. (64% of pollutants into streams & 57% of pollutants entering lakes)
Sources of Pollution
• disease–causing agents (500+ identified)
• 3.2 mil die yearly from contaminated water complications
• oxygen demanding wastes
• Plant debris, animal wastes
• fertilizers
• water–soluble inorganic chemicals
• Acids, salts, metals
• organic chemicals
• Pesticides, oil & gasoline, plastics, PCBs
• sediment
• water–soluble radioactive isotopes
• thermal pollution
Types & Sources of Water Pollution
decomposing wastes deplete dissolved oxygen
•dissolved oxygen (DO) indicatorof water quality
Oxygen–Demanding Wastes
• amount of dissolved oxygen needed by aerobic decomposers to break down organic materials in a certain volume over a 5–day incubation period at 20° C
• greater BOD --> more rapidly oxygen depleted
• consequences of high BOD are the same as those for low dissolved oxygen
• Sources of BOD:• leaves and woody debris• dead plants and animals• animal manure• effluents from pulp and paper mills• wastewater treatment plants• feedlots• food-processing plants• failing septic systems• urban stormwater runoff
Biological Oxygen Demand (BOD)
Clean ZoneDecomposition
Zone
Septic ZoneRecovery
Zone
Clean Zone
Normal clean water organisms(trout, perch, bass,
mayfly, stonefly)
Trash fish(carp, gar,leeches)
Fish absent, fungi,sludge worms,bacteria
(anaerobic)
Trash fish(carp, gar,leeches)
Normal clean water organisms(trout, perch, bass,
mayfly, stonefly)
8 ppmDissolved oxygen (ppm)
Biological oxygendemand
8 ppmTypes of
organisms
BOD & DO & Water Quality
"oxygen sag curve"
Flowing water can often recover rapidly by dilution & decay.© Brooks/Cole Publishing Company / ITP
Pollution of Fresh Water
results when human activities accelerate input of nutrients (which?) to a lake
© Brooks/Cole Publishing Company / ITP
Cultural Eutrophication
Lakes and reservoirs pollution persists due to
•Little mixing between layers
•Little flow into & out of
•Turnover can take as long as 100 years
• basin contains >95% of fresh surface water in U.S. & 20% of world
• severe cultural eutrophication since the 1960s
• $20 billion pollution–control program improved water quality since 1972
• ¾ of shoreline still not suitable for swimming
Fig. 12–22© Brooks/Cole Publishing Company / ITP
Great Lakes
Organic chemicals pollution: Cuyahoga River, Cleveland OH
So polluted that it caught on fire in 1868, 1936, 1959, 1969 and burned for several days.
Today: not flammable, water quality is good enough for boating
concentrations increase at increasing levels in the food chain -- PCBs (polychlorinated biphenyls), heavy metals, certain pesticides
© Brooks/Cole Publishing Company / ITP
Biological Magnification
Groundwater
Supplies nearly ½ of drinking water in the US (95% of drinking water in rural areas)
Many pollutants can seep into groundwater (pesticides, fertilizers, gasoline, organic solvents)
Fig. 21-7, p. 501
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
• 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;
• in 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.
© Brooks/Cole Publishing Company / ITP
Ocean Pollution
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
• largest estuary in U.S.
• severely degraded by water pollution from 6 states
• deposition of air pollutants
© Brooks/Cole Publishing Company / ITP
Example: Chesapeake Bay
What is hypoxia? Where else do we see it in the U.S.?