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Unformatted text preview: 3/3/2008 Biogeochemical cycles
A general model for cycling of materials in global ecological systems
Consumers Producers Detritivores Nutrients available to producers Abiotic reservoir Geologic processes Biogeochemical Cycles are made up of: Reservoirs and Processes Biotic Abiotic
=without life The Water (Hydrological) Cycle Mineral Cycles (e.g., phosphorus) The Nitrogen Cycle Human Impacts on Biogeochemical Cycles 1. Air Pollution/Acid Rain 1 3/3/2008 The burning of fossil fuels releases sulfur (e.g., SO2) and nitrogen (e.g., NO) oxides that react with water in the atmosphere to produce sulfuric and nitric acids Rainfall acidity compared to natural rainfall pH of rainfall normal 5.65 Remember: Change of 1 pH unit=10X in acidity So...what's the problem? Acid deposition (dry and wet) alters environment conditions (pH): Soil chemistry changes Plant growth is reduced and susceptibility to stresses (drought, disease) is increased Lakes, rivers, and streams become acidified Marble, limestone, and other minerals are dissolved Decreased pH dissolves metals (e.g., zinc, copper, lead) makes them more toxic So what? Dead trees - forest decline and reduced biodiversity Dead fish - sterile lakes and reduced biodiveristy Dissolved statues - lost culture Effects on human health? Black Forest, Germany Sandstone figure over the portal of a castle in Westphalia, Germany 1908 1968 2 3/3/2008 So, what do (should) we do now? Do nothing (the (perceived?) industry and
government approach) Hope that environmental issues become political issues (the activist
approach) Human Impacts on Biogeochemical Cycles 1.Air 1.Air Pollution/Acid Rain 2.The 2.The Ozone Hole Walk the fine line ( (government to balance b l
industry demands and public opinion) Demand reductions in "point-source" "pointpollutants (scrubbers, alternative fuels) Contribute to reductions in "non-point "nonhighsource" pollution (conservation, high-mileage
cars, mass transit) Where is the ozone layer?
So, how do we get this ozone, and why is it a problem if we lose it? So, as ozone forms it absorbs And ozone is short-lived, so it shortbreaks down to oxygen and the cycle repeats itself over... and over...and over...and over... 3 3/3/2008 The Ozone Hole What human products harm the ozone layer? Ozone layer in stratosphere
O2 + UV-B light UVO2 + O O3 Depletion of ozone layer
O2 + UV-B light UVO2 + O O3 UVUV-A light + O3 UVUV-A light + O3 O + O2 Cl ClO Normally a balance of formation and dissociation 350,000 metric tons formed and destroyed daily Mostly from chlorofluorocarbons (freons) Small, volatile molecules Catalyze chain reactions that destroy ozone UV light + F Cl - C - F Cl What's the latest on the Ozone hole? Ozone hole cycle During the polar winter, clouds of ice crystals form CFC reactions on the ice crystal surface release active chemicals As sunlight comes back during polar spring, chlorine reacts with ozone Rapid production of ozone hole during polar spring 2004 2000 2001 4 3/3/2008 What's the latest on the Ozone hole? Concentrations of one type of CFC over time. Notice the steady rise until about 1990 -- three years after the Montreal Protocol established a phase-out program for phaseCFCs.
Image courtesy of the National Oceanic and Atmospheric Administration's Climate Monitoring and Diagnostics Laboratory. Modeled and observed surface UV-B UVlight changes as a function of ozone loss Impacts of ozone loss (=increase in UV radiation) Increase in cancer Eye damage (cataracts) Damage to marine and aquatic life g q such as coral reefs Genetic damage to crops Decline of amphibians (?) Making decisions on environmental clean-up clean(regional and global scale) How do we decide what to? What if we're wrong? Who pays? PROBLEM: Conflicting perspectives You are what you eat... and Other disturbing facts 5 3/3/2008 Contaminants of concern Is our food supply safe? Chemicals that are: Persistent don't degrade Bioaccumulate increase in concentration from water to fish Toxic at low levels Are called PBT chemicals The science Solubility Glucose 1,000 g/L Hydrophilic "water-loving"; dissolves in water How we viewed PBT pesticides in the 1940s
D.D.T. Powerful Insecticide Harmless to Humans applied by TODD Classic PBT chemical: DDT - <1 mg/L Million-f ld less soluble i water than Million-fold l illi l bl in h glucose Lipophilic "fat-loving"; dissolves in fat "fat- National Geographic (1945) How we viewed PBT pesticides in the 1950s Successful (?) history of DDT
1873 DDT was synthesized in the lab of A. von Bayer 1939 Dr. Paul Mller discovered insecticidal properties 1948 Dr. Paul Mller received Nobel Prize for discovery WW II usage of large quantities to control typhus, malaria 19451945-1972 widespread agricultural/commercial usage e.g., in US: (1,350 million lbs/yr) 1972 US EPA ban on DDT 6 3/3/2008 Biomagnification Rachel Carson 1962 "Silent Spring" PBT chemicals undergo biomagnification 13X Highly lipid soluble, persistent compounds Not degraded by bacteria or vertebrate metabolism Organochlorine pesticides (DDT) Xenobiotic (man-made) organic chemicals (PCBs, dioxins) Organometals (tetra ethyl lead, methyl mercury) 4X 10X 1300X What are the sources of these chemicals? Industrial discharges Pulp & paper mills, chemical refineries Incineration Atmospheric Deposition Agriculture Runoff Direct application overspray, drift Natural sources (anthropogenic enrichment) mercury and hydroelectric dams What effects do these chemicals have on humans? Mercury (Hg, metal), Methylmercury (HgCH3, organometal) Brain neurotoxicity Fetus transplacental; milk - transmammarial PCBs (PolyChlorinated Biphenyls) Stored in body fat Fetus - neurodevelopmental effects Possible carcinogen What effects on humans? Great Lakes region Study examined consumption of fish from Great Lakes Lower birth weight infants Delayed learning processes Reduced fine motor skills What effects on humans? Potential Endocrine Disrupting Chemical (EDC) Mimic estrogen in function
Testosterone Other studies show no effects Aboriginal peoples Inuit, native North Americans Muktuk or Arctic bubble gum Consume whale and seal blubber, organ meats (liver and kidney) Reduced human sperm counts 66 Estradiol 113 million sperm/mL semen in 1940 DDT million/mL in 1990 20 million/mL problems with reproduction
PCB 7 3/3/2008 What can I do to minimize risk? Reduce inputs to the environment Individual inputs Water and soil quality standards - industry Fish Consumption Advisories
Lake Erie All Waters (Ashtabula, Cuyahoga, Erie, Lake, Lorain, Lucas, Ottawa, Sandusky Counties) Channel Catfish 16" and over Do Not Eat PCBs Support effective and justifiable regulation and enforcement f Follow consumption advisories Sport fish Shellfish State health department Channel Catfish under 16", Lake Trout 2 Months PCBs Chinook Salmon 19" and over, Coho Salmon, Common Carp, Freshwater Drum, Month PCBs Smallmouth Bass,
Steelhead Trout, Walleye 23" and over, White Bass, Whitefish, White Perch Source: Ohio EPA, Division of Surface Water 8 ...
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- Winter '08