Prof. Dudley Shallcross ACRGTim Harrison Bristol ChemLabS2008

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 inertGas at 25 OC, liquid at – 196 OC

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5

Bacterial scrapheap challenge by Dr. Hazel Mottram

6 Oxygen

O=O bond energy = 496 kJ/mol21% 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

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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?

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11 High temperature combustion

VOCs can be burned in air (combustion) and oxidised in the processCaC2 + 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

ppb

14

NO2 + sunlight O * + NO < ~ 400 nm

O* + O2 O3

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Photochemical smog

15 Photochemical smog in Bristol: 27/07/2001Ozone episode 27th July 2001 Bristol area

0

10

20

30

40

50

60

70

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

and

O3

ppb

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

CO

ppm

NOO3CO

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

25 Impacts of global warming

• Impacts associated with

changes in – Precipitation– Sea level– Extreme weather

1941 2004

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

Observedsimulated 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

19550

Historical emissions

2105

The Stabilization Wedge – Two Scenarios

20552005

14

7

Billion of Tons of Carbon Emitted per

Year

19550

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 %)

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38 Thanks to

Bristol ChemLabS

British Council

Sci Fest Africa 2008

t.g.harrison@bris.ac.ukd.e.shallcross@bris.ac.ukwww.chemlabs.bris.ac.uk/outreach