1Pollution – Chapters 21 and 22• Substance causing alteration of a natural chemical process in an ecosystem.• Anthropogenic vs. Natural– Point source– Non Point SourcePollution• Biodegradable– Natural chemicals that break down or are used by species (eg. nutrients)– Ecosystems can often recover if source is contained• Non biodegradable– Don’t break down, often acumulate in tissue (egDDT, PCBs)Effects of Pollutants• Aesthetic– “trashed” ecosystems not pretty– Over fertilized system –lost biodiversity, algal blooms• Health– Air, drinking water• Altered ecosystem function– Act as disturbance– Increase/decrease productivity– Change in biodiversityWhy pollute? • Pollution has negative impacts on ecosystems.• Pollution is created in the act of increase industrial or economic output• Need to balance the two.• Cost/benefit question• Mitigation2Why pollute? • Tragedy of the commons– Conflict between the public good and availability of a shared resource.– Example – Pasture used by multiple sheep herders. Herders want to maximize profits, add sheep. Each sheep added benefits one owner, while degrading the pasture for the rest.– Actions of self interested parties do not serve the public good.– Other examples:• Fisheries• PollutionAristotle "that which is common to the greatest number has the least care bestowed upon it.”Pollution regulation• Solution is for the government to represent the public good, regulate use of common resources.• Government Regulations– Clean Air Acts (1963, 1967, 1970, 1977, 1990)• Fuel efficiency, smog emissions, power plant emissions– Clean Water Acts (1972, 1977)• Mandated that public waters had to meet criteria to make them suitable for public use (swimming, fishing, drinking)Example Non biodegradable toxin• Polychlorinated biphenyl (PCB)– Class of chemicals that includes dioxin– Marketed by Monsanto under the trade name Aroclor from 1930-1977– Found to be highly toxic – rashes, liver, thyroid and stomach cancer, immune deficiency, reduced reproductive capacity– Hormone mimic- blamed in part for decline in male sperm counts– Banned in all open applications (adhesives, paints, fabrics)– Only allowed in contained applications (capacitors)– General Electric discharged 1.3 million pounds into the Hudson River in the 1970’s, fish are still not edible.– Removal is difficult…Non biodegradable pollutants• Pollutants that organisms can’t deal with physiologically, accumulate in tissues• Bioamplify – larger concentrations accumulate in upper trophic levels• Regulating ambient levels of toxins based on toxicity levels not adequate.3Bioamplification of Non biodegradable Pollutants• Bald Eagle and Peregrine Falcon– Top predators– DDT accumulation resulted in thin egg shells– reduced to 500 pairsPhytoremediation• Some non-biodegradable toxins accumulate in biological tissues• Phytoremediation - Use plants to accumulate and remove or neutralize pollutants.Most Pollutants End Up in WaterPollution in aquatic ecosystems• Aquatic ecosystem productivity– Non-biodegradable pollutants accumulate in sediments– Organic pollutants (nutrients) alter productivity• Oligotrophic• Eutrophic4Eutrophication• Adding nutrients to an aquatic system will lead to eutrophication.• Lakes are closed systems, eutrophicationfaster.• Flowing rivers typically slower to show effects.Mechanism for eutrophication damage• Biological Oxygen Demand (BOD) – total ecosystem respiration rate.• If BOD > oxygen available, system will go anoxic• Organic input – needs to be decomposed• Nutrient input – algae bloom (high night time BOD)Other non-chemical pollutants• Hot water from power plant cooling ponds (thermal pollution)– Raise productivity and BOD– Alter system temperature– Lower oxygen content of waterAtmospheric Pollution - Acid Rain• Emissions combine with atmospheric water to form acidic precipitation.• Result – low pH precipitation, lowering of pH in aquatic ecosystemsSO2(g)+ H2O  SO2·H2OSO2·H2O  H++HSO3-HSO3- H++SO32-5Lowering of Environmental pH• Greatest effects in northeast, high industrial emissions• Not all taxa equally impacted• Successfully mitigated for the most part.Pesticides• Pest – species that occurs in an area where it is not wanted• Pesticides and crop yields –another cost/benefit question– Mechanisms• Neurotoxins• Sterilants• Contact poisons• Systemic poisons– Specificity – pesticides target desirable species.• LD50– lethal dose for 50% of population• Evolved resistance Rachel Carson• Author of “Silent Spring”– Pesticides are non-specific– Chemicals bio-amplify in food webs– Farmers are not adequately educated– Contaminants were directly linked to bird and fish kills, showing up in groundwater• Chemical companies tried to suppress publicationBioengineering and Pesticides• Roundup producing gene placed in some crops• Danger of horizontal gene transfer ?6Biotic Control• Assume top-down control – novel predator will be able to control pest population– Predation on non-pests?– Replacing native predators?Biotic Control and Introduced Species• Non-native or exotic species• Replace native species, alter ecosystem function• Advocated by R. Carson• Arguably one of the biggest environmental problems we have today. Good invaders often outcompete native species.Air Pollution - ozone• Ozone in the upper atmosphere = good• Ozone on the surface = bad“Hole” in the ozone layer• Observation: Steady decline in ozone concentration above Antarctica, roughly 4% per decade since the late 1970s. Not really a “hole”.• Cause: photodissociationof chlorofluorocarbon (CFC, “freons”) compounds• Free Cl O3 → O27“Hole” in the ozone layer• Mitigation: Montreal Protocol (1983) signed by 43 countries, phased out use of all CFC. Eg. Freon use ended in 1995.• Result: CFC concentrations significantly reduced, rate of ozone loss declined, projected full recovery by 2050• No relation to climate changeBad Ozone• Combustion emissions: NO2→ NO + O• 3 O → O3• O3is highly reactive• NOx+ H2O → H2NO3→ H+ + HNO3-– Acidic fog/precipitation– Highly reactive free O3• Worst cities have– dense population– high traffic– Warm– Dry– low windEndangered Species Act (ESA)• Passed by Congress in 1973• Forbids government agency,