Envr 890 Organic Aerosols: Lecture 2. What questions do we have to start asking if we are to build a kinetics model to predict aerosol formation from isoprene reactions?

kamens@unc.eduhttp://www.unc.edu/~kamens

Objective

• To describe a predictive technique for the formation of aerosols from biogenic hydrocarbons based on fundamental principals and apply it to isoprene

• Have the ability to embrace a range of different atmospheric chemical and physical conditions which bring about aerosol formation.

Chemical System

-pinene

+ NOx+ sunlight + ozone----> aerosols

Overview

• This reaction system produces low vapor pressure reaction products that distribute between gas and particle phases.

Gas Particle Partitioning

particle

gas phase products

COOHO

cis-pinonicacid

• Equilibrium partitioning between the gas and particle phases is assumed for all products.

• Kinetically this is represented as forward and backward reactions.

• Kp = kon/koff

Kpart TSP

gasp

[ ] /

[ ]

KR T

p M wpLo

7 5 0 1

1 0 9

. fom

The equilibrium constant Kp can be calculated from

[gas] + [surface] [particle]

Overview

• Gas and particle phase reactions were linked in one mechanism and a chemical kinetics solver was used to simulate the reaction over time

• Model simulations were compared with aerosol concentrations obtained by reacting -pinene with either O3 or NOx in

sunlight in an outdoor chamber.

-pinene-O3 experiments in the UNC 190m3

outdoor chamber

1. added O3 O3

O3

O3

O3

-pine

O3

O3

2. added -pinene-pine

-pine

-pinene-O3 experiments in the UNC 190m3

outdoor chamber

1. added O3 O3

O3

O3

O3

-pine

O3

O33. immediate burst of particles

2. added -pinene-pine

-pine

Products

• pinald -

• pinacid -

• diacid -

• oxy-pinald -

• oxy-acid-

pinonaldehyde

CHOO

CHO

O

nor-pinonaldehyde

Pinic acid

HOOC

COOH

HOOC COO

C8 diacid

O CHO

OHO COOH

OH

Pinonic acid

O COOH

COOH

O

Norpinonic acid

CHOOO

CH3

OO

O

Criegee2

Criegee1OO O

-pinene

O3

COOHCOOH

pinic acid

+ otherproducts

O

pinonic acid

CHOO

COOH

+ CO, HO2, OH

COOHO

norpinonaldehyde

norpinonic acid

Mechanism

• Now you need to know about the reactions of alkenes with O3

• C=C +O3

• See pages Pitts and Pitts, 2000, pages 179-206

1st the reaction of O3 with an alkene generates an aldehyde +a high energy bi-radical called a Criegee bi-radical

2nd a certain fraction of these “hot” Criegee’s stabilize and the rest decomposes. (see page 198 of Pitts and Pitts, Table 6.10)

3rd “Hot” Criegee’s R-(H)C.-00. decompose to OH, CO and an R. group

How do we chemically represent his reaction scheme?

propylene +O3 two Criegee’s

C-C=C +O3 H2C.OO.* + CH3C.HOO.*

+ what two aldehydes?

For the propylene +O3 reaction (page 198

Pitts and Pitts)

CH3C.HOO.* 0.15 Stabilized Criegee

0.54 (CH3. + CO +OH.)

CH3. + CO2+ H.

HCO +CH3O 0.17

0.14 (CH4 + CO2)

apine + O3 0.4*crieg1 + 0.6*crieg2 min-1 or ppm-1min-1

1.492 e-732/T

More highly substituted Criegee’s are more stable

How do we chemically represent this for the -pinene system?

crieg1 = 0.47*pinacid + 0.13*stabcrieg1 1x106

+ 0.8*OH + 0.3*HO2 + 0.37*pinald + 0.01*oxypinald + 0.03*O. + 0.19*CO

What would we do for isoprene (see Kamens et al, IJKS, 1982?

OH attack on -pinene

CHO

O

OH

HOOOHOO CHO

OH

+ OH

O2

OOOH

-pinene

pinonaldehyde

Each Reaction can be represented as a differential equation

-pinene + ozone --> pinald

d[-pinene]/dt = -krate1 [-pinene][O3]

d[pinald]/dt = -krate2[pinal][OH]

Particle formation-self nucleation

Particle formation-self nucleation

Criegee’s can react with aldehydes and carboxylic groups to form secondary ozonides and anhydrides.

O=C

C=O

CH3

+C

C=O.

CH3

oo.

C

C=O

CH3

C

C=O

CH3

O

oo

• Estimating rates that gas phase products enter and leave the particle

• The equilibrium between the gas and particle phases is:

• Kp = kon/koff

• The equilibrium constant Kp can be calculated from

• [gas] + [surface] [particle]

KR T

p M wpLo

7 5 0 1

1 0 9

. fom

Kp = kon/koff

A general Flux expression for evaporation from a liquid surface is

is the energy barrier for single molecule to evaporate from the surface (Joules)

koff = k evap

in koff = e -Ea/RT is: kbT/h

From koff and Kp the rate coefficient kon can now be calculated

jk T

h k Tk

evapevapb

b

exp

Overall Mechanism

• linked gas and particle phase rate expressions

diacidgas + pinacidpart --> pinacidpart + diacidpart 68

diacidpart diacidgas

3.73x1014 e-10285/T

Diacid is generated in the gas phase. How do we get it on and off the particle phase??

Where do the rate coefficients come from??

KR T

p M wpLo

7 5 0 1

1 0 9

. fom

• Kp = kon/koff

koff = e -Ea/RT

We need vapor pressure (poL ) to calculate Kp

for koff , we need kbT/h for and an

activation energy, Ea

To calculate vapor pressures see Chapter 4 of (Schwarzenbach et al, Environmental Organic Chemistry, 2003)

)]()([TT

ln.TT

.R

S*pln bbvapT

iLb 80181

if we substitute Svap Tb= 88J mol-1 K-1 and R =8.31 Jmol-1 K-1

)]()( ln.ln *

T

T

T

Tp bb

iL 58119

This means we need Tb or boiling point

Boiling points can be estimated based on chemical structure (Joback, 1984)

Tb= 198 + Tb  

T (oK)

-CH3 = 23.58 K-Cl = 38.13-NH2 = 73.23

C=O = 76.75CbenzH- = 26.73

C-OH = 93  Joback obs

(K) (K)acetonitrile 347 355acetone 322 329benzene 358 353amino benzene 435 457benzoic acid 532 522toluene 386 384pentane 314 309methyl amine 295 267trichlorethylene 361 360phenanthrene 598 613 

Stein, S.E., Brown, R.L. Estimating Normal boiling Points from Group Contributions, J.Chem. Inf Comput. Sci, 34, 581-587, 1994

Chamber Data

• First look at experiments with different temperatures and gas phase concentrations of -pinene and ozone

A high concentration warm experiment

• 0.82 ppmV -pinene + 0.60 ppm O3

• Temp = ~295K

• %RH = ~61%

0

0.2

0.4

0.6

0.8

1

pp

mV

9 9.2 9.4 9.6 9.8 10 Time in hours

Gas Phase -pinene and O3 data and model

-pinene

A

MODEL

Particle concentration. Warm high concentration experiment

0

1

2

3

4

5

9 10 11 12 13 time in hours

A

model

Observed

Reacted -pinene

mg

/m3

Other Conditons

0.82 ppmv -pinene + 0.60 ppm O3(295K)

0.60 ppmv -pinene + 0.65 ppm O3 (284K)

0.35 ppmv -pinene + 0.25 ppm O3 (295K)

0.88 ppmv -pinene + 0.47 ppm O3(269K)

Lower concentration experiments

0.20 ppm -pinene + 0.11 ppm O3

TSP data vs model

0

20

40

60

80

100

120

140

160

180

200

21 21.5 22 22.5 23 23.5 24time in hours

ug/m

3

filter mass model TSP

model

data

How do we start to build an Isoprene + O3 mechanism??

The initail attack of O3 on an olefin (alkene) generates two possible Criegee high energy bi-radicals and two possible aldehydes.

A general rule is that the more highly substituted carbon will form a higher fraction of Criegee’s

C=C-C=CH

HCH3

H

HH

+ O3 MACR + H2C.OO.

CI1.OO. + HCHO

MVK + H2C.OO. CI2.OO. + HCHO

What would we do for isoprene (see Kamens et al, IJKS, 1982?

There are 4 general product channels by which high energy Criegee’s (Criegee intermediates) decompose:

1. Stabilized Criegee biradicals

2. an Ester Channel

3. O-atom elimination

4. Hydroperoxide channel

The hydroperoxide channel is a source of dark OH

Homework 3: For MVK write a set of Chemical equations to show it’s decomposition

MVK + O3

H2C=C - C-CH3

H O (MVK)MVK + O3 MGLY+ H2C.OO.*

.OOC.C(H)-C(=O)-CH3 +HCHO

let’s assign splitting ratios

2. MVK + O3 0.4 MGLY+ 0.4 H2C.OO.*

0.6 CI2*+0.6 HCHO

MVK + O3

MVK + O3 0.4 MGLY+ 0.4 H2C.OO.*

0.6 CI2 * +0.6 HCHO

how does H2C.OO. decompose??

(look at page 197 of Pitts and Pitts,2000)

H2C.OO.* 0.37 Stabcrieg1 +0.12 HCO+

0.12 OH. +0.38 CO+ 0.38 H2O

Stabilized Criegee’s usually react with water

Stabcrieg + H2O Aldehyde +H2O2

H2C.OO.* + H2O H2C=O + H2O2

Stabcrieg + Aldehyde secondary ozonide

How do we add rate constants??

Adding Rate constants

MVK + O3 MGLY+ H2C.OO.

.OOC.C(H)-C(=O)-CH3 +HCHO

6X10-3 ppm-1 min-1

H2C.00. + H2O H2C=O + H2O2

5.4x10-2 ppm-1 min-1

look in Pitts and Pitts to convert

ppm-1 min-1 to cm3molecule-1sec-1

Does OH attack Isoprene, MACR,MVK,MGLY and HCHO???

isoprene + OH products

MACR+ OH products

MVK + OH products

MGLY +OH products

H2C=O +OH products

NO3+alkenes products

radical +radicals stable products

aldehydes photolyze

Light model for -pinene + NOx

• -pinene + OH Noizoire et al.

• -pinene + NO3 Martinez et al., Wangberg et al.

• -pinene(OH)-OO + NOx--> products Aschmann et al.

• pinonaldehyde +OH or NO3 Calogirou et al.

• pinonaldehyde photolysis Hallquist et al

• acyl peroxy + NO2 --> PAN analogues Noizoire et al.

• partition nitrate products

pinonaldehyde

OH

OO

O2

+

(a)(b)

(c)

(d)

(e)

pinonaldehyde

acetone

O

OO.

NO2NO

O

O.

pinald-oo

OH

pinonic acid

O

pinO2

OO.

NO2

NO

organic nitrate

+HO2

+NO2

pinald-PAN

=o

=o

=o

=o

=o

=o

=o

OO.

O2

=o

OO=C8=O

C8-oo.

O2

NO2NO

O

+ h

+

+CO+HO2=o

OO.

NO2NO

=o

=o+HO2

+ h

NO2NO

=o

OO.

C8-oo. (C8O2)

+CO+HO2

NO2

NO

(f)

(g)

CO2+

pinO2H2O+

+HO2

O2

OO

H3C-OO.

+oxygenated products

+NO2

+H3C-OONO2PAN

(stab-oxy)

+HO2

norpinonaldehyde

OOH

O=o+

pin-ooH

+OH

O

OO.

=o

NO2

NO

+CO2

norpinaldPAN

+NO2

+HO2

norpinonic acid+norpin-ooH

O

OONO2

=o

+O2

ONO2

=o

+

=o

ONO2

+

organic nitrate

Pinonaldehyde chemistry

Pinald +h = 0.65pinO2 + 1.35 CO + HO2 + 0.35*C8O2`

# hpinald

pinO2 + NO= .765pinald + .85 HO2 + 0.1*acetone +0.2C2O3 + .865NO2 # 6056 exp 180/T

C8O2 + NO = NO2 {+ C8-dicarb } # 6056 exp 180/T pinald + OH = . 8 pinald-oo + 0.1C3O2 + 0.1C8O2 + 0.1 acetone +0.3XO2 # 134417, pinald + NO3 = 0.95*pinald-oo +0.03*pinO2

+0.02*C8O2 + 0.07*CO +NO2 # 79

pinald-oo + NO = pinO2 +CO2 +NO 2 # 7915 exp250/T

pinald-oo + NO 2 = pinald-PAN #3885exp380/T

pinald-PAN = pinald-oo + NO2 # 1.067e11 exp-8864/T pinald-oo + pinald-oo = 2*pinO2 # 2551

pinald-oo + HO2 = Pinacid

# 677 @1040

kphototyis = ( I)

By adding pinonaldehyde to the chamber in clear sunlight in the presence of an OH scavenger and measuring its rate of decay

can be fit to the decay data assuming

a shape with wave length similar to other aldehydes

Pinonaldehyde quantum yields in natural sunlight

Pinonaldehyde quantum yields in sunlight

0

0.2

0.4

0.6

0.8

1

280 310 340 370Wavelenght /nm

quan

tum

yie

ld

CH2=O

CH3CH2CH2=O

OO

pinonaldehyde

CH3CH2=O

0

0.4

0.8

1.2

280 300 320 340

Normalized to one

pinonaldehyde

0.97 ppm -pinene + 0. 48ppm NOx;

October Sunlight

O3

NO

NO2

NO2

-pinene data vs. model

model

data

-pinene

Gas phase pinonaldehye

model

data

OO

=o

=o

pinonaldehyde

norpinonaldehyde

Particle phase pinonic acid

model

pinonic acid data

norpinonic acid

OH

pinonic acid

O=o

Measured particle mass vs. model

model

products

Particle phase

filter data

mg

/m3

0.95 ppm -pinene + 0. 44ppm NOx

O3

NO

NO2

NO2

model

data

Measured particle mass vs. model

reacted -pinene

data

model

Gas phase pinonaldehye

OO

particle phase pinonaldehye

model

data

OO

d-limonene + O3

(Sirakarn Leungsakul, ES&T 2004)

8.00 9.00 10.00 11.00 12.00 13.00 14.00 15.00 16.000

500000

1000000

1500000

2000000

2500000

3000000

3500000

4000000

4500000

5000000

5500000

T ime-->

AbundanceT IC: 3S1F1FD.D

keto-limononaldehyde

limononaldehyde

7OH-limononaldehyde

7OH-keto-limononaldehyde

keto-limononic acid

7OH-keto-limononic acid

7OH-limononic acid

Major particle phase productsMajor particle phase products

+ O3O

O

OOO

OOO

OO

OO

O

+ CH2-OO

O

OH

O

OO

O

O

O

O

O

O

HO

CH3-OH +

+ H2O

+ OH

O

OO

O

O

+ H2O

O

O

+ H2O

0.15

0.500.35

0.65

0.200.25

0.20

0.10

0.68

0.85

0.32

0.30

keto-limonene

limononaldehyde

limonalic acid

keto-limald

7OH-limononaldehyde

Crieg1*

Crieg2* Stab-Crieg2

Stab-Crieg1

OH

+ H2O

limononic acid0.37

0.63

d-limonene

O3

Filter data and Model

d-limonene + Od-limonene + O33

(Sirakarn Leungsakul, 2004)

aero

sol

(mg

/m3)

v

p

pm

V

.00

.02

.04

.06

.08

.10

18 19 20 21 22 23 24 1:00

LDT (hour)

(p

pm

)

0.00

30

60

90

120

150

aero

sol (

g/m

3 )

OO33

Filter

d-limonene + O3

(Sirakarn Leungsakul, 2004)(Sirakarn Leungsakul, 2004)

Model

-pinene + O3

(Mohammed Jaoui, 2003)

-pinene + O3

CH3

OH OHCH2.

NO NO2

+O2

CH3

H

OH

H .

*

O2

+ toluene

O=CHCH3

OH

+ HO2

+ H2O

CH3

O

o-cresolbenzaldehyde

CH3

H

OH

H

CH3

O

O

.CH3

H

OH

H

.O

NO

NO2

+O2

rearrangement

oxygen bridge

OH

H

O .

H

H

O

H

OH

H

O

H

+O2

CH3H+

methylglyoxalbutenedial

+ HO2

ring cleavageradical

Aerosol concentration from -pinene-NOx-sunlight

0

2000

4000

6000

8000

10000

0.01 0.1 1

particle diameter (m)

par

ticl

e co

nc.

(# /

cm)

5:19am(background)

initial

6.5 hours later

3 hours later

Experiments that explore heterogeneous carbonyl reactions (Myoseon Jang et al., Science, 2002)

• Nebulizes NH4(SO4)2 acid coated aerosols into Teflon bags

• Reacts aldehydes on the surface of the acid coated particles (~2% H2SO4 by weight)

• Diesel exhaust is 1-5% sulfuric acid

nebulizer

(NH4)2SO4

Solution

aldehydesalcoholsglyoxal

aldehydesalcoholsglyoxal

(NH4)2SO4+H2SO4

Solution

500 liter Teflon bag

•The aldehyde phenomenon can be explained as follows:

• Aldehyde functional groups can further react in the aerosol phase through heterogeneous reactions via hydration, polymerization, and hemiacetal/acetal formation with alcohols.

•Aldehyde reactions can be radically accelerated by acid catalysts such as particle sulfuric acid

H

OH

OH

H

H

OH

H OH

OH

H

H

O OH

H

H

OH H

O O

H

H

OH H

OH

H

H

O OH

H

H

OH-H+

+

+-H+

Polyimerization

H H

OH

H H

OH

H H

O

H H

OHH

+

Acid catalyzing step

H H

OH

+

H O

OH

H

HH

H OH

OH

H+ H2 O

-H+Hydration

H H

OH+

Hemiacetal and acetal formation

H O

OH

H

RH

H OR

OHH

H OR

OHH

H OR

OH2+

H

+ ROH-H+

H+ -H2O

H H

OH

H H

OR

hemiacetal

+H O

OR

H

RH

H OR

ORH

H H

ORROH

-H+

acetal

Aerosol yields from aldehydes

0.0

1.0

2.0

3.0

4.0

glyoxal hexanal octanal decanal

Aer

oso

l Yie

lds

(%)

non-acid seedacid seed

*Yield data and method from Jang et al. 2001

Acid seed experiments with O3 + organics

Nebulizer

Ozone Ozone

(NH4)2SO4

Solution

(NH4)2SO4+H2SO4

Solution

Volatilized organics

Volatilized organics

OzoneOzone

Yields from Teflon bag experiments

0.000

0.100

0.200

0.300

0.400

0.500

% y

ield

non acid seed

acid seed

isoprene isoprene/ decanol

-pinene acrolein acrolein/ decanol

Aldehyde acid catalyzed heterogeneous reactions

• Acid catalyzing step

• Hydration

• Polymerization

H

O

H

OH

H

OH

O

OH

H

H

H

OH

OHH

H

OH

+ H2O

H

OH

OH

OHH

O

OHH

H

OH

+

Etc...

H+

Particle Phase reactions

particleC=OO

polymers

Gas phase reactions

C=OO

cis-pinonaldhyde

Particle Phase reactions

particle

C=OO

cis-pinonaldhyde

C=OO

polymers

Gas phase reactions

Particle Phase reactions

C=OO

polymers

Gas phase reactions

C=OO

cis-pinonaldhyde

MS Analysis of Filter Samples from the reaction of acid seed particles with a-pinene + O3

ESI-QTOF mass spectrum of SOA from reaction of -pinene + O3 + acid seed aerosol (Tolocka et. al., 2004)

200 300 400 500 600 700 800 900 1000

m/z

337.

18 351.

18

361.

21

377.

2

393.

2

407.

2

423.

2

439.

2

453.

21 489.

32

300 320 340 360 380 400 420 440 460 480 500

321.

21

m/z

17

7.0

7

19

1.1

2 20

7.1

1

22

5.1

12

33

.14

24

5.1

2

25

5.1

82

61

.11

28

9.1

8

30

1.1

8

31

3.2

3

32

7.1

6

34

1.2

35

9.2

36

0.2

150 200 250 300 350

Inte

nsity,

A.U

.

m/z

O

OH

O

H2C

O

177

207

341

261289

91

77

.07

19

1.1

2 20

7.1

1

22

5.1

12

33

.14

24

5.1

2

25

5.1

82

61

.11

28

9.1

8

30

1.1

8

31

3.2

3

32

7.1

6

34

1.2

35

9.2

36

0.2

150 200 250 300 350

Inte

nsity,

A.U

.

m/z

O

OH

O

H2C

O

177

207

341

261289

9

M Na+ (ESI-QTOF Tolocka et al, 2003)

Particle phase pinonaldehyde dimers from -pinene +O3 on acid particles

Similar results were obtain by Hartmut Herrmann’s group (Atmos Envir, 2004)

• Kalberer and Baltensperger et al. (Science, 2004) identified polymers as the main constituents of SOA formed from the photo-oxidation of 1,3,5-trimethylbezene. These account for about 50% of the aerosol mass after 30 hours of aging.

LDI-TOFMS Spectrum of SOA from Photo-oxidation of 1,3,5-

Trimethylbezene

Time Evolution of Polymer in SOA Measured by LDI-MS

Where do we go from here for isoprene??

1. Learn what products it makes that go into the particle phase

2. Begin to describe the chemistry

3. Start to collect papers on isoprene and SOA