prof. dudley shallcross acrg tim harrison bristol chemlabs 2008 a pollutants tale
TRANSCRIPT
Prof. Dudley Shallcross ACRG
Tim Harrison Bristol ChemLabS
2008
A Pollutant’s Tale
2 Talk outlineTalk outline• Comparison of the Earth
with other planets
• Nitrogen and oxygen
• Temperature structure
• Tropospheric pollutants
33 most abundant gases in each planetary atmosphere
Jupiter H2 (93%) He (7%) CH4 (0.3 %)
Saturn H2 (96%) He (3%) CH4 (0.45 %)
Uranus H2 (82%) He (15%) CH4 (2.3 %)
Neptune H2 (80%) He (19%) CH4 (1-2 %)
Venus CO2 (96%) N2 (3.5%) SO2 (0.015 %)
Mars CO2 (95%) N2 (2.7%) Ar (1.6 %)
Earth N2 (78%) O2 (21%) Ar (0.93 %)
4 Nitrogen
NN bond energy = 944 kJ/mol
78% of the atmosphere inert
Gas at 25 OC, liquid at – 196 OC
TGH
5
Bacterial scrapheap challenge by Dr. Hazel Mottram
6 Oxygen
O=O bond energy = 496 kJ/mol
21% of the atmosphere
Gas at 25 OC, liquid at -183 OC
Photosynthesis is the main source of O2 6CO2 + 6H2O + sunlight C6H12O6 + 6O2
2H2O2 2H2O + O2
TGH
7
Life spring by Dr. Adrian Mulholland
8
9 Urban Atmospheric Chemistry10 km
NO, NO2, VOC
VOCs
?
0 kmCompounds of both biogenic and anthropogenic origin
1 km
The Tropopause
The Boundary Layer
10 What happens to VOCs (volatile organic compounds)?
• Plants and trees emit a vast range of organic
material; alkenes, alcohols, carbonyls, acids
• Vehicles emit hydrocarbons and aromatic species
Many of these species are insoluble and are not
rained out, how are they removed?
TGH
11 High temperature combustion
VOCs can be burned in air (combustion) and
oxidised in the process
CaC2 + 2H2O Ca(OH)2 + C2H2
C2H2 + (5/2)O2 2CO2 + H2O
CH3OH + (3/2)O2 CO2 + 2H2O
The atmosphere oxidises VOCs using free radicals
12
O3 + sunlight O * + O2 < ~ 330 nm
O* + H2O OH + OH
OH + R-H R + H2O
VOCs broken down by the OH radical,
generated by sunlight
13 Air measurements in Bristol of NO2
Data from 21st January 2001: Combustion is the main source of NO2 TGH
NO Bristol 20th January 2001
0
50
100
150
200
250
300
350
400
450
0 3 6 9 12 15 18 21 24
Hour
NO
pp
b
14
NO2 + sunlight O * + NO < ~ 400 nm
O* + O2 O3
TGH
Photochemical smog
15 Photochemical smog in Bristol: 27/07/2001
Ozone episode 27th July 2001 Bristol area
0
10
20
30
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60
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80
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23
hour of day
NO
an
d O
3 p
pb
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
CO
pp
m
NO
O3
CO
16 CO2 measurements in Bristol
CO2 has been measured for several years at the top of Old Park Hill.
17 CO2 measurements at Bristol
18 Longer term CO2 measurements
CO2 measurements
have been made at
Mauna Loa for many
many years, and
show that CO2 has
been rising steadily
for some time
19 The enhanced greenhouse effect
20
Secrets in the Ice
• Snow accumulation lays down record
of environmental conditions
• Compacted to ice preserving record
• Drill ice core & date
Secrets in the Ice
21 CO2 levels over the last 1000 years
Gases are extracted from bubbles trapped in ice cores and provide record of past
atmospheric concentrations
22
Frog chorus by Dr. Simon Hall
23 Methane (CH4) and Nitrous Oxide (N2O)
24Increased global temperature
25Impacts of global warming
• Impacts associated with
changes in – Precipitation– Sea level– Extreme weather
19412004
26
Model simulation of recent climate
Natural forcings only(solar, volcanic etc.
variability)
Anthropogenic forcings only(human-induced changes)
The Met Office
27 Simulated global warming 1860-2000:Natural & Man-made factors
Observed
simulated by model
Tem
pera
ture
ris
e
o C
0.0
0.5
1.0
1850 1900 1950 2000
Hadley Centre
28Impacts of Climate on the world: Temperature
29Impacts of Climate on the World: Rainfall
Stabilisation Wedges
20552005
14
7
Billion of Tons of Carbon Emitted per
Year
1955
0
Historical emissions
2105
The Stabilization Wedge – Two Scenarios
20552005
14
7
Billion of Tons of Carbon Emitted per
Year
1955
0
Historical emissions
2105
The Stabilization Wedge – Two Scenarios
14
7
Billion of Tons of Carbon Emitted per
Year
0
Historical emissions
Currently
projected path
Flat path
205520051955 2105
14
7
Billion of Tons of Carbon Emitted per
Year
0
Stabilization Triangle
Currently
projected path
Flat path
Historical emissions
Easier CO2 target
~850 ppm
Tougher CO2 target
~500 ppm
205520051955 2105
14
7
Billion of Tons of Carbon Emitted per
Year
0
Currently
projected path
Flat path
Historical emissions
14 GtC/y
7 GtC/y
Seven “wedges”
205520051955 2105
Current technology options to provide a wedge
• Improve fuel economy• Reduce reliance on cars• More efficient buildings• Improved power plant efficiency• Decarbonisation of Electricity and Fuels• Substitution of Natural gas for coal• Carbon capture and storage• Nuclear fission• Wind electricity• Photovoltaic electricity• Biofuels
373 most abundant gases in each planetary atmosphere
Jupiter H2 (93%) He (7%) CH4 (0.3 %)
Saturn H2 (96%) He (3%) CH4 (0.45 %)
Uranus H2 (82%) He (15%) CH4 (2.3 %)
Neptune H2 (80%) He (19%) CH4 (1-2 %)
Venus CO2 (96%) N2 (3.5%) SO2 (0.015 %)
Mars CO2 (95%) N2 (2.7%) Ar (1.6 %)
Earth N2 (78%) O2 (21%) Ar (0.93 %)
TGH
38 Thanks to
Bristol ChemLabS
British Council
Sci Fest Africa 2008
www.chemlabs.bris.ac.uk/outreach