secondary organic aerosol formation: ozonolysis of terpenes

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Secondary Organic Aerosol Formation: Ozonolysis of Terpenes. George Marston , Yan Ma and Rachel Porter Department of Chemistry . - PowerPoint PPT Presentation

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© University of Reading 2006 www.reading.ac.uk

Secondary Organic Aerosol Formation: Ozonolysis of

Terpenes

George Marston, Yan Ma and Rachel PorterDepartment of Chemistry

Uncertaintues in Ozone Terpene Mechanisms: UC, Davis, 2008

Ronald Reagan

"Trees cause more pollution than automobiles do.” ‘88

"A tree is a tree. How many more do you have to look at?" '66

"The American Petroleum Institute filed suit against the EPA [and] charged that the agency was suppressing a scientific study for fear it might be misinterpreted. The suppressed study reveals that 80 percent of air pollution comes not from chimneys and auto exhaust pipes, but from plants and trees." ‘79

Uncertaintues in Ozone Terpene Mechanisms: UC, Davis, 2008 3

Background• The ozonolysis of alkenes is important for

atmospheric chemistry:

Oxidation of VOCs

Generation of radicals

Generation of oxygenated products Secondary Organic Aerosol (SOA)

Uncertaintues in Ozone Terpene Mechanisms: UC, Davis, 2008 4

SOA Formation• Acid products from the ozonolysis of

terpenes are components of SOA and may lead to particle formation

• Health implications

• SOA can have direct and indirect effects on climate change

Uncertaintues in Ozone Terpene Mechanisms: UC, Davis, 2008 5

Alkene Ozonolysis

+ O3

O O

O

O O

O

+

*POZ

CI

Criegee Intermediate

Uncertaintues in Ozone Terpene Mechanisms: UC, Davis, 2008 6

OH Formation

OO

H

OO

H

O O

+ OH

Uncertaintues in Ozone Terpene Mechanisms: UC, Davis, 2008 7

Terpenes

-pinene -

pinene

3-carene terpinole

ne

Uncertaintues in Ozone Terpene Mechanisms: UC, Davis, 2008 8

-Pinene Ozonolysis Products

Pinonic acid Pinic acid Norpinonic acid

Norpinic acid

Pinalic acid Norpinalic acid OH-pinonic acid

OH-pinalic acid

OH

O

O

OH

O

OH

O

OH

OO

OH

O

HOO

OOH

O

O

OH

O

OH

O

O

OHOH

HOO

O

Uncertaintues in Ozone Terpene Mechanisms: UC, Davis, 2008 9

First step

OO

O

O

O

O

+ O3O

OO

POZ

CI1

CI2

k1

(1 )k1

Uncertaintues in Ozone Terpene Mechanisms: UC, Davis, 2008 10

Aims• To develop mechanisms for acid formation in

terpene ozonolysis • To model results to provide input of rate

constants and branching ratios for the Master Chemical mechanism

To determine which channel (CI) gives rise to which product

To determine branching ratios for decomposition of primary ozonides

To compare product yields from different terpenes

Uncertaintues in Ozone Terpene Mechanisms: UC, Davis, 2008 11

Methodology

O

OO

O

+ O3

CI2

O + O3

O

O O

CI1

Enone

Enal

Uncertaintues in Ozone Terpene Mechanisms: UC, Davis, 2008 12

Experimental

• Static reaction chamber coupled to gas chromatography / mass spectrometry / flame ionisation detection

• Acid products trapped on filters and derivatised to methyl esters (BF3/Methanol)

• Enal and enone synthesised from ozonolysis of a suitable terpene

Uncertaintues in Ozone Terpene Mechanisms: UC, Davis, 2008 13

-Pinene Results

OH

O

OH

O

OH

O

O

0

1

2

3

4

0 20 40 60 80 100Relative Humidity / %

Yiel

d / %

Pinonic acidPinonic acid (acetic acid added)Pinic acidPinic acid (acetic acid added)

Uncertaintues in Ozone Terpene Mechanisms: UC, Davis, 2008 14

Enal Results

OH

O

OH

O

OH

O

O

0

1

2

3

4

5

0 20 40 60 80 100

Relative Humidity / %

Yiel

d / %

Pinonic acidPinonic acid (acetic acid added)Pinic acidPinic acid (acetic acid added)

O

Uncertaintues in Ozone Terpene Mechanisms: UC, Davis, 2008 15

Enone Results• Only Pinonic Acid and Norpinonic

Acid are observed

OH

O

O

OH

OO

O

Uncertaintues in Ozone Terpene Mechanisms: UC, Davis, 2008 16

Enone Results

OH

OO

Norpinonic acid

0

0.05

0.1

0.15

0.2

0 20 40 60 80 100

Relative Humidity / %

Yiel

d / %

from the enone

from ?-pinene

O

Uncertaintues in Ozone Terpene Mechanisms: UC, Davis, 2008 17

Branching Ratio

OO

O

O

O

O

CI1

CI2

O + O3

O

O O

CI1

H2COO

Uncertaintues in Ozone Terpene Mechanisms: UC, Davis, 2008 18

Pinonic Acid FormationPinonic acid

0

1

2

3

4

5

0 20 40 60 80 100

Relative Humidity / %

Yiel

d / %

from the enonefrom the enalfrom α-pineneenone + enal OH

O

O

Uncertaintues in Ozone Terpene Mechanisms: UC, Davis, 2008 19

-Pinene Summary

O

O

OO

O

CI1 CI2

O

+ O3 + O3

50 % 50%

OO

OH

OHO

OOH

O

OH

O

O

OOH

O

OOHOH

O

OHO

norpinic acid

pinalic acid

norpinalic acid OH-pinalic acid

pinonic acid

pinic acid OH

O

O

OH-pinonic acidOH

OH

OHO

O

norpinonic acid

+H20

Uncertaintues in Ozone Terpene Mechanisms: UC, Davis, 2008 20

3-Carene Yields

y = 1.2435xR2 = 0.8898

0

0.5

1

1.5

2

2.5

3

3.5

0 0.5 1 1.5 2 2.5 33-carene product yield / %

-p

inen

e pr

oduc

t yie

ld /

%

0

0.1

0.2

0.3

0 0.1 0.2 0.3

O

OH

O

Uncertaintues in Ozone Terpene Mechanisms: UC, Davis, 2008 21

3-Carene, Enone and Enal

3-carene

Enal

Enone

OH

O

O

Uncertaintues in Ozone Terpene Mechanisms: UC, Davis, 2008 22

3-Carene and Enone

Nor-3-caronic acid

0

0.05

0.1

0 20 40 60 80 100

Relative humidity / %

Yiel

d / %

O

OH

O

O

Uncertaintues in Ozone Terpene Mechanisms: UC, Davis, 2008 23

3-Caronic Acid MechanismO

O

O

OOH

O

O

O

OH

3-Caronic acid

CI2

O

O

OO

OH

+ O2

Isom.

+ RO2or HO2

O

O

OO

O

O

CI1 stab.+ H2O

ester channel

O

O OH

OH

Uncertaintues in Ozone Terpene Mechanisms: UC, Davis, 2008 24

3-Carene Summary

OO

O

O

O

O

OH

OO

O

O

OH

OH

O

O

OH

OH

OH

OO

HOO

OH

O

O

O

OH

O

HO

OHO

+ O3

CI1 CI2

+ O3

3-caronic acid

OH

O

O

3-norcaronic acid

OH OH

32%

3-OH-caronic acid3-caralic acid3-caric acid

3-norcaralic acid 3-OH-caralic acid3-norcaric acid

decomp. decomp.

68%

OHdecomp.stab.

+ H2Oisom.

Uncertaintues in Ozone Terpene Mechanisms: UC, Davis, 2008 25

-pinene

Uncertaintues in Ozone Terpene Mechanisms: UC, Davis, 2008 26

MechanismO

O

O

O

OO

O

-OH

+O2

OO

+O2-OH

O

OO

+RO2

O

O

-pinene

-pinene

+RO2

-H2COOO

O

O

+O2

Uncertaintues in Ozone Terpene Mechanisms: UC, Davis, 2008 27

Pinalic-4-acidO

O

O

O

O

O

O2

O

O

OH

O

O

O

O

O2

O

O

OH

+

O

O

OH

92 % 8 %

Pinalic-3-acid Pinalic-4-acid

Uncertaintues in Ozone Terpene Mechanisms: UC, Davis, 2008 28

Terpinolene

OH

OO

OHO

O

OO

OO

OOO

O

O

O

93 % 7 %+

Terpinolalic Acid (a) Terpinolalic Acid (b)

Uncertaintues in Ozone Terpene Mechanisms: UC, Davis, 2008 29

Hydroperoxide Formation

OH

OO

OO

O

OOH

OOH

+ O3

OH

O

O

terpinolalic acid (a)

terpinolalic acid (c)

80 %

20 %

Uncertaintues in Ozone Terpene Mechanisms: UC, Davis, 2008 30

Hydroperoxide Formation

OO

OO

favoured over ?O

OH

OHO

O2

M ?Formation of hydroperoxide directly from quenching of nascent Criegee Intermediates?

Uncertaintues in Ozone Terpene Mechanisms: UC, Davis, 2008 31

Summary

Ring opening in -pinene and terpinolene

Intramolecular reactions

Hydroperoxide formation

O

O

OH

OO

O

O

O Isomerisation

+O2

• Improvements in mechanisms• Uncertainties:

• Some quantitative data, but more needed

OO

O

OOH

OIsom.

Uncertaintues in Ozone Terpene Mechanisms: UC, Davis, 2008 32

Acknowledgements

• Natural Environment Research Council• University of Reading

• Dr Yan Ma• Dr David Johnson• Rachel Porter

• Dr Andy Russell• Dr David Chappell• Tim Wilcox• Thomas Luciani

Uncertaintues in Ozone Terpene Mechanisms: UC, Davis, 2008 33

Uncertaintues in Ozone Terpene Mechanisms: UC, Davis, 2008 34

Mechanisms

O

OOEsterChannel

OH

OO OH

OH

O

OO

O

O

CI1

+ M+ H2O H2O

Pinonic acid

Uncertaintues in Ozone Terpene Mechanisms: UC, Davis, 2008 35

Mechanisms

OO

OO

OH

O

OO

O

O

OH

CI2

O

O

OOPinonic acid

OH

+ O2

Isom.

+ RO2

or HO2

Uncertaintues in Ozone Terpene Mechanisms: UC, Davis, 2008 36

MechanismsO

OO

O

1

.O

O

O

O

OH

O

OO

Isom.RO2

O

OH

O

+ O2

2 3

5

OH

O

pinic acid OH

O

OH

O

OO

Isom. +O2

+ RO2or HO2

+ RO2

O

OH

O

O

CO2+ O2

OH

OO

+ RO2

+ O2

O

O

8

9

10

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