Post on 28-Mar-2015
PHOTOCHEMICAL PHOTOCHEMICAL SMOG DISCOVEREDSMOG DISCOVERED
TRANSFORMATIONTRANSFORMATION
The 20th century has been characterised by a transition from urban air dominated primary pollutants to one where secondary pollutants are very important.
Vanishing streetcars
LOS ANGELES LOS ANGELES EARLY 1940sEARLY 1940s
Who Framed Roger Rabbit?
Air pollution so bad baseball games not visible
Japanese gas attacks Southern California Gas
Company’s artificial rubber plant - butadiene
LOS ANGELES LOS ANGELES EARLY 1940sEARLY 1940s
Eye irritation
A 1943 smog
Butadiene plant
http://www.aqmd.gov/news1/Archives/History/marchcov.html
Smog appears, but actually not in Chandler till 1953
LOS ANGELES LOS ANGELES in FICTIONin FICTION
Raymond Chandler’s Philip Marlowe
LOS ANGELES mid 1940sLOS ANGELES mid 1940s
Post war: smog problem still serious LA administration suggests it will take a few
months to solve Tucker invited from St Louis – he’d been
successful in solving Pittsburgh’s problems The automobile not really a problem – no
sulfur in petrol
1950’ SMOG 1950’ SMOG and LIFEand LIFE
February 12 1951
LIFE articleLIFE 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:http://www.arb.ca.gov/html/brochure/history.htm
A RADICAL IDEAA RADICAL IDEA
Arie J Haagen-Smit – biochemist concerned with crop damage
Smelling the air – like an organic chemistry lab
“action of sunlight and automotive vapours”
DOMINANCE of the AUTOMOBILEDOMINANCE of the AUTOMOBILE
Haagen-Smit opposed by auto manufacturers Initiated study at Stanford Research Institute The now classical understanding derives:
P.A. Leighton, Photochemistry of Air Pollution (1961)
and more fully Heicklen, Westberg and Cohen (1969/71)
NONOXX PSUEDO-EQUILIBRIUM PSUEDO-EQUILIBRIUM
0
20
40
60
80
100
120
600 900 1200 1500 1800
hours
con
cen
trat
ion
NO2NOO3NO + O3 NO2 + O2 (R1)
NO2 + hν NO + O (R2)
O + O2 O3
NO + O3 NO2 + O2 + hv
“action of sunlight and automotive vapours”
NONOXX PHOTOSTATIONARY STATE PHOTOSTATIONARY STATE“EQUILIBRIUM”“EQUILIBRIUM”
R1= - k NO O3
k=0.38ppm-1s-1
R2 = -k h NO2 = -JNO2 NO2
JNO2 photolysis rate, s-1
JNO2 NO2 = k NO O3
JNO2NO2/k NO O3 = 1 = p
MODEL MODEL VSVS
REALITYREALITY
0
20
40
60
80
100
120
600 900 1200 1500 1800
hours
con
cen
trat
ion
NO2NOO3
0
20
40
60
80
100
120
140
160
180
400 800 1200 1600 2000
hours
NO2
NO
O3
HC
RCHO
MODEL MODEL VS VS
REALITYREALITY
O3 + NO NO2 + O2
NONOXX PSUEDO-EQUILIBRIUM PSUEDO-EQUILIBRIUM
x
…the nature of X forms a major part of what controls smog formation
“action of sunlight and automotive vapours”
hv
ROLE OF “AUTOMOTIVE VAPOURS”ROLE OF “AUTOMOTIVE VAPOURS”
CH4 + OH CH3 + H2O
CH3 + O2 CH3O2
CH3O2 + NO CH3O + NO2
CH3O + O2 HCHO + HO2
HO2 + NO OH + NO2
CH4 + 2O2 + 2NO HCHO + 2NO2 + H2O
THE RADICAL IDEATHE RADICAL IDEA
In a submission to Industrial and Engineering Chemistry: Haagen-Smit refers to both ozone and peroxides
Significance not quite clear?
0
20
40
60
80
100
120
140
160
180
400 800 1200 1600 2000
hours
NO2
NO
O3
HC
RCHO
OVERALL CHEMISTRYOVERALL CHEMISTRY
CH3CH3 + 2O2 + 2NO CH3CHO + 2NO2+ H2O ethane (alkane) acetaldehyde
O3 + NO NO2 + hv
RO2
“action of sunlight and automotive vapours”
ACETALDEHYDEACETALDEHYDE
CH3CHO + OH CH3CO + H2O
CH3CO + O2 CH3COO2
CH3COO2 + NO CH3CO2 + NO2
CH3CO2 CH3 + CO2
CH3COO2 + NO2 CH3COO2NO2
Breaking and re-entry
Formation ofPeroxyacetylnitrate (PAN)
EYES, POLLUTION and EYES, POLLUTION and OptrexOptrex
“Treat your eyes to some TLC, dusty, smoky atmospheres city air pollution drying atmosphere of air conditioning”
Ad in London underground
Peroxyacetylnitrate
Particle deposition on eyes
0
400
800
1200
1600
1960 1970 1980 1990 2000
Year
Ho
urs
>100
pp
b
Ozone at Crestline California
A LONG AND DIFFICULT PROBLEMA LONG AND DIFFICULT PROBLEM
GOING BEYOND LA!GOING BEYOND LA! Liquid fuels Mobile sources Multiple polluters
NOT SO MUCH IS AIR POLLUTION GETTING NOT SO MUCH IS AIR POLLUTION GETTING WORSEWORSE
…ITS CHANGING!…ITS CHANGING!
WOOD SMOKE VOCs, O3
COAL SMOKE DIESEL SMOKE
LEAD H2SSMELLs
TIME