EOH 468: Air Pollution and Health. Introduction. History of Air Pollution. Dr. Peter Bellin, CIH, Ph.D. Spring 2008

Transcription

1 EOH 468: Air Pollution and Health Dr. Peter Bellin, CIH, Ph.D. Spring 2008 Introduction Syllabus posted on-line. Lecture notes. Texts: recommend they be purchased. Try to do readings, draft answers to questions. History of Air Pollution Ancient times, not a significant problem Burning sea coal in 1300 s Nineteenth century: literature references to polluted air 1892: 1000 die in London 1930: Meuse Valley, Belgium, 50 dead. 1943: Los Angeles incident 1

2 History of Air Pollution 1948: Los Angeles APCD is established 1948: Donora, PA 20 dead, thousands made ill. (Essay by Berton Roueche) 1952: London Killer Fog, over 4000 dead. 1953: Smog in NYC kills between 170 and 260 people. 1963: First US Federal Clean Air Act. London 1952 London

3 London 1952 London 1952 London

4 Donora, PA at noon Thin blanket of air The moon through atmosphere 4

5 Smog in Los Angeles History of Air Pollution Video on the history of air pollution California Air Resources Board video Structure of the Atmosphere EOH 468 Spring 2008 Week 2 5

6 Structure of Atmosphere Evolution of the Atmosphere Current composition Layers of the atmosphere Temperature profile Ozone profile Weather systems Pollution distribution Evolution of the Atmosphere Original atmosphere had no oxygen. Any oxygen created was absorbed by earth (iron, etc.) Carbon dioxide levels were high. Chemical reactions created water 3 H 2 + CO 2 CH 4 + H 2 O H 2 + CO 2 CO + H 2 O Water created oceans, sink for CO 2 Evolution of the Atmosphere Nitrogen was present, but relatively inert, and built up to high concentration. Nitrogen cycle helps maintain balance. Early photosynthesis resulted in more free oxygen (once minerals were oxidized) CO 2 + H 2 O CH 2 O + O 2 By 400 million years ago, current levels of oxygen were reached. By about 400 million years ago, current level of carbon dioxide was reached. 6

7 Composition of Atmosphere Nitrogen Oxygen Argon Water Vapor % % % % Oxygen, 20.9% Other, 2.5% Carbon Dioxide % Neon % Ozone % Helium % Methane % Krypton Hydrogen Xenon Nitrous Oxide % % % % Nitrogen, 78.1% Carbon Monoxide % Ozone (Troposphere) % Layers of the Atmosphere Troposphere Stratosphere Ionosphere eog1010/fall05/chapter_03/chapt er 03 html 7

8 eog1010/fall05/chapter_03/chapt er 03 html 8

9 Ozone Depletion Related to release of chlorofluorocarbons Chlorine catalyzes depletion of ozone Strong effect over Antarctica Related to weather patterns there. Visit here for explanation: Ozone Depletion Chemistry on polar stratospheric clouds HCL + ClONO 2 HNO 3 + Cl 2 ClONO 2 + H 2 O HNO 3 + HOCl HCl + HOCl H 2 O + Cl 2 N 2 O 5 + HCl HNO 3 + ClONO N 2 O 5 + H 2 O 2 HNO 3 The net effect is to build up chlorine and nitric acid. 9

10 Ozone Depletion The nitric acid is not active in reducing chlorine oxide in the atmosphere. Chlorine gas is easily split into chlorine atoms. ClO + ClO + M Cl 2 O 2 + M Cl 2 O 2 + hv Cl + ClO 2 ClO 2 + M Cl + O 2 + M 2 x (Cl + O 3 ) 2 x (ClO + O 2 ) Net: 2 O 3 3 O 2 This occurs at very low temperatures. Ozone Depletion Arctic region also experiences ozone depletion, but this reaction predominates: ClO + BrO Br + Cl + O 2 Cl+ O 3 ClO + O 2 Br + O 3 BrO + O 2 Net: 2 O 3 3 O 2 10

11 Ozone Depletion Ozone Depletion Ozone Depletion 11

12 Temperature Profile Troposphere profile Lapse rate Temperature inversion Mixing cap Troposphere Temperature Profile 12

13 Troposphere Temperature Profile Troposphere Temperature Profile Cyclones and anticyclones Deflection of wind causes air to flow in a roughly circular pattern This circular flow may be clockwise (anticyclonic) or counterclockwise (cyclonic) 13

14 Cyclones and anticyclones On weather maps isobars describe circulation cells of high and low pressure Air flows parallel to isobars in a curved path Associated winds called gradient winds Caused by the combined effects of pressure gradiant force (PGF) and coriolis effect Cyclones and anticyclones In northern hemisphere air flow is counterclockwise in low pressure systems and clockwise in high pressure systems This pattern is just the opposite in the southern hemisphere High and low pressure systems 14

15 Low pressure systems Air flows inward(convergence) and upward and outward(divergence) Have cyclonic flows in the northern hemisphere Represent very unstable air masses Characterized by cloudiness, precipitation, storminess High pressure systems Air flows downward (subsidence) and outward (divergence) Have anticyclonic flows in the northern hemisphere High pressure systems As air subsides it compresses air beneath it causing a warm air layer to form Characterized by clear skies, no precipitation, low wind speeds and stability 15

16 High and low pressure systems Cross-sectional diameters of km Commonly are migratory In temperate latitudes affected by tropical and polar air Move from east to west Have a life span of 1-2 weeks Global air circulation Best described by a three-zone model Air at the equator flows pole-ward and descends at about 30 o N & S latitude flowing along the surface back to the equator Global air circulation Cold air flowing along the surface from the poles toward the equator is warmed and ascends toward poles These flows are Hadley-type 16

17 Three-zone model Three-zone model Air in middle latitudes forms only weak north-south circulation patterns because of the intrusion of tropical and polar air Jet steams form at discontinuities between zones Jet streams Systems of fast moving air in upper troposphere Produced as a result of strong pressure differences at surface that produce strong pressure gradients aloft Polar jet stream forms over middle latitudes associated with polar front 17

18 Jet streams North polar jet stream meanders with movement of polar front In winter may extend as far south as 30 o N In summer average position is 50 o N Because of this migration described as midlatitude jet stream Jet streams Semi-permanent jet stream forms over tropics in winter Slower than polar jet stream Centered at about 25 o N Jet Streams 18

19 Jet Streams Important because they influence surface air flow patterns and weather On acceleration they cause divergence aloft that promotes converge near the surface and cyclonic motion Supply energy to storm systems and direct their path Also cause convergence aloft which intensifies high pressure systems Weather Systems Weather dynamics affects air pollution Jet Streams tstream.html# Pollution Distribution Intensity of air pollution varies Interior areas in LA basin in.swf Air Now site (current conditions) 19

20 Pollution Distribution Pollution Distribution Pollution Distribution 20

21 Pollution Distribution Pollution Distribution Pollution Distribution 21

22 Pollution Distribution 22