Presentation on theme: "PHOTOCHEMICAL SMOG DISCOVERED. TRANSFORMATION l The 20 th century has been characterised by a transition from urban air dominated primary pollutants to."— Presentation transcript:
PHOTOCHEMICAL SMOG DISCOVERED
TRANSFORMATION l The 20 th century has been characterised by a transition from urban air dominated primary pollutants to one where secondary pollutants are very important.
l Vanishing streetcars LOS ANGELES EARLY 1940s Who Framed Roger Rabbit?
l Air pollution so bad baseball games not visible l Japanese gas attacks l Southern California Gas Companys artificial rubber plant - butadiene LOS ANGELES EARLY 1940s Eye irritation A 1943 smog Butadiene plant
l Smog appears, but actually not in Chandler till 1953 LOS ANGELES in FICTION Raymond Chandlers Philip Marlowe
LOS ANGELES mid 1940s l Post war: smog problem still serious l LA administration suggests it will take a few months to solve l Tucker invited from St Louis – hed been successful in solving Pittsburghs problems l The automobile not really a problem – no sulfur in petrol
1950 SMOG and LIFE February
LIFE article Now industrialisation has caught up with Los Angeles to the extent that it has its own special brand of smog – less grim, but more eye- burning chemicals… Good esrly video at:
A RADICAL IDEA l Arie J Haagen-Smit – biochemist concerned with crop damage l Smelling the air – like an organic chemistry lab l action of sunlight and automotive vapours
DOMINANCE of the AUTOMOBILE l Haagen-Smit opposed by auto manufacturers l Initiated study at Stanford Research Institute l The now classical understanding derives: P.A. Leighton, Photochemistry of Air Pollution (1961) and more fully Heicklen, Westberg and Cohen (1969/71)
NO X PSUEDO-EQUILIBRIUM NO + O 3 NO 2 + O 2 (R1) NO 2 + hν NO + O (R2) O + O 2 O 3 NO + O 3 NO 2 + O 2 + hv l action of sunlight and automotive vapours
NO X PHOTOSTATIONARY STATE EQUILIBRIUM l R1= - k NO O 3 k=0.38ppm -1 s -1 l R2 = -k h NO 2 = -J NO2 NO 2 l J NO2 photolysis rate, s -1 l J NO2 NO 2 = k NO O 3 l J NO2 NO 2 /k NO O 3 = 1 = p
MODEL VS REALITY
O 3 + NO NO 2 + O 2 NO X PSUEDO-EQUILIBRIUM x …the nature of X forms a major part of what controls smog formation l action of sunlight and automotive vapours hv
ROLE OF AUTOMOTIVE VAPOURS CH 4 + OH CH 3 + H 2 O CH 3 + O 2 CH 3 O 2 CH 3 O 2 + NO CH 3 O + NO 2 CH 3 O + O 2 HCHO + HO 2 HO 2 + NO OH + NO 2 CH 4 + 2O 2 + 2NO HCHO + 2NO 2 + H 2 O
THE RADICAL IDEA l In a submission to Industrial and Engineering Chemistry: Haagen-Smit refers to both ozone and peroxides l Significance not quite clear?
OVERALL CHEMISTRY CH 3 CH 3 + 2O 2 + 2NO CH 3 CHO + 2NO 2 + H 2 O ethane (alkane)acetaldehyde O 3 + NO NO 2 + hv RO 2 l action of sunlight and automotive vapours
ACETALDEHYDE CH 3 CHO + OH CH 3 CO + H 2 O CH 3 CO + O 2 CH 3 COO 2 CH 3 COO 2 + NO CH 3 CO 2 + NO 2 CH 3 CO 2 CH 3 + CO 2 CH 3 COO 2 + NO 2 CH 3 COO 2 NO 2 Breaking and re-entry Formation of Peroxyacetylnitrate (PAN)
EYES, POLLUTION and Optrex Treat your eyes to some TLC, l dusty, smoky atmospheres l city air pollution drying atmosphere of air conditioning Ad in London underground Peroxyacetylnitrate Particle deposition on eyes
Ozone at Crestline California A LONG AND DIFFICULT PROBLEM
GOING BEYOND LA! l Liquid fuels l Mobile sources l Multiple polluters
NOT SO MUCH IS AIR POLLUTION GETTING WORSE …ITS CHANGING! WOOD SMOKEVOCs, O3 COAL SMOKE DIESEL SMOKE LEADH2SSMELLs TIME