Announcements. Pollution week continues. Thinking about pollution. Why are polar bears so contaminated?

Transcription

1 Announcements Grades for exam 2 have been posted March 7 th - Last day to submit LEAD summary to TA, extra credit videos due next Tuesday (no late videos will be accepted) Next Thursday, Environmental Film Festival Monday, March 14 th at 8 AM Final Exam Study guide has been posted Pollution week continues Why are polar bears so contaminated? Thinking about pollution Source Fate Effect Control Benzene hexachloride in polar bears vs. latitude (Norstrom et al. 1988) 1

2 Behavior of organic contaminants in water More polar (charged) compounds remain dissolved in water Smaller volatile compounds move toward the atmosphere Volatility depends on temperature Biologically active molecules accumulate in the food chain Water Air Water Living things Bioaccumulation and biomagnification in the Arctic Figures from greenpeace.org Atmospheric pollution Topics for today Geometry of the atmosphere Types of air pollution SO 2 and acid rain Smog: NO x, ozone, and volatile organic compounds Mercury deposition CFCs and the ozone hole Trends in air pollution and public policy Objective for today Understand the sources fates and effects of major air pollutants in the US Atmosphere s layers Temperature profile 2

3 Pollutant Common air pollutants Major Sources Pollutant Common air pollutants Human health and environmental effects Suspended particulate matter Fossil fuel combustion, burning (SPM) Volatile organic compounds Fossil fuel combustion, refining (VOC) Carbon monoxide (CO) Incomplete combustion Nitrogen oxides (NO x ) Combustion (coal and oil) Sulfur oxides (SO x ) Combustion (mostly coal) Heavy metals Combustion (fossil fuel, solid waste) Ozone Photochemical product of NO x and VOC Toxic and radioactive gasses Natural, or industrial discharge Suspended particulate matter Asthma and emphysema. Caries toxins into lungs. Impairs visibility Volatile organic compounds Carcinogenic, harmful to crops, bioaccumulation, smog, ozone Carbon monoxide (CO) Impairs oxygen delivery in blood. dizziness, unconsciousness or death Nitrogen oxides (NOx) Precursor to ozone, acid rain, photochemical smog, eutrophication Sulfur oxides (SOx) Acid rain. Impairs visibility Heavy metals Can be toxic to the nervous system, organs, body function Ozone Lung, membrane, heart problems, Crop damage, property damage Toxic and radioactive gasses Cancer, toxic Sources of air pollutants SO x primarily from coal-burning power plants NO x primarily from vehicle exhaust VOCs from vehicle exhaust and fuel industry Nearly all forms of combustion produce (SPM) CO comes mostly from vehicle exhaust Figure from Wright and Nebel (2002) Fate of air pollutants Transport and dispersion Wind, atmospheric conditions Volatility (ability to stay airborne) Formation of secondary pollutants Primary pollutants released directly Secondary pollutants formed from chemical reactions of 1 o pollutants in atmosphere Photochemical reactions 3

4 Distribution of SPM Coal-burning power plants 50 largest utilities are located in the Midwest Photochemical reactions convert 1 o pollutants to 2 o pollutants Figure from Wright and Nebel (2002) Photochemistry I - ozone Ozone creation (ground level) NO 2 + light NO + O* O* + O 2 O 3 (Ozone generated) NO + O 3 NO 2 + O 2 little O 3 generated Nitric oxide + VOCs NO + VOC peroxyacetyl nitrates (O 3 is not consumed) net O 3 generated Ground-level ozone is a health hazard Ozone + NO x = photochemical smog Photochemistry II acid rain Formation of hydroxyl radical (upper troposphere) O 3 + UV light O 2 + O* O* + H 2 O 2 OH (hydroxyl radical) Important reactions with hydroxyl radical OH + NO 2 + catalyst (SPM) 2HNO 3 (nitric acid produced) 2OH + SO 2 + catalyst (SPM) H 2 SO 4 (sulfuric acid produced) 4

5 Fate of nitric and sulfuric acids ph = -log([h + ]) Fish are adversely affected by acidity ANC: Acid neutralizing capacity ph: -log([h + ]) Effects of acid rain Daibutsu Great Buddha of Kamakura, cast in 1252 A.D. Over 40 feet tall, 121 tons Serious corrosion from Korean and Chinese industries and coal-fired power plants New Hampshire stream data (Clean Air Act 1970) Inverse relationship ph still low! Years of acid rain reduced buffering capacity of streams ph and SO 2 Hubbard Brook LTER program: lternet.edu 5

6 NO x and coastal eutrophication Nitrogen availability limits productivity in coastal waters Adding more NO x raises algal production Water clarity drops Algae sink to seafloor and are consumed by bacteria Bottom-water dissolved oxygen drops creating dead zones Global distribution of dead zones Number of dead zones has doubled each decade since the 1960s From Diaz and Rosenberg, Science 2008 Hg 0 emitted by coal combustion Bioaccumulation of CH 3 Hg Hg 0 Hg in freshwater fish 6

7 Hg in canned tuna Global change policy that all support: Ozone depletion and CFCs Buy cheap tuna and eat < one tuna sandwich per week. Sept. 2006: 11 million square miles Data from: Atmosphere s layers Temperature profile The ozone problem O 3 in the stratosphere absorbs UV radiation CFCs and other compounds destroys O 3 in the stratosphere UV radiation has consequently increased at the earth s surface Rates of skin cancer, cataracts, and other medical problems have increased 7

8 CFCs: What are they and why make them? Ozone destruction animation Chlorofluorocarbon (CFC): chlorine, fluorine, and carbon compound Methane CFC-11 H F H C H Cl C Cl H Cl UV light Example: CFC-11 (CCl3F) Trichlorofluoromethane CFCs stable, non-toxic in troposphere Exchange heat refrigerants and propellants Broken down in stratosphere by UV light Animation from: More animations at: http ://ozonewatch.gsfc.nasa.gov/multimedia/index.html Illustration of the chlorine cycle Troposheric vs. Stratospheric O 3 Tropospheric ozone Stratospheric ozone Bad Good Formation NO 2 + light + VOCs - UV light Problem Reactive molecule - Loss of O 3 in causes health problems stratosphere leads to increased UV 8

9 Ozone and UV radiation Relationship between ozone and UV index in New Zealand Source: Science (1999) 285: Ozone and sunburn Erythema: Redness and swelling caused by UV exposure (sunburn) Erythema dose (microwatts cm -2 ) strongly correlated with ozone Data from: Ozone and CFC policy Trends in air pollutant emissions 1987: Montreal protocol adopted by 140 nations - Scale back CFC production 50% by Amendments complete phase out by 1996 Problem: long residence times Why was it so easy to phase out CFCs? Chlorofluorocarbon production Source: 9

10 Concentration (ppm) Trends in average air pollutant concentrations in United States 10 9 CO Concentration (µg m -3 ) Lead Air pollution in China Concentration (ppm) NO SO Concentration (ppm) Source: Clean air policy Clean air act: 1970 Results: Dramatic reductions in emissions, elimination of leaded gasoline, reduction of SO 2 emissions, etc. Montreal protocol: 1987 Results: CFCs phased out, slow change initiated Kyoto protocol: 1997 Results: 135 nations agreed to reduce GHGs UN Climate Change Conference (Paris) Results: 195 nations agreed to reduce GHGs? Changes in atmospheric CO 2 concentration Current: ~403 ppm >25% increase since 1958, ~40% since