ivan kourtchev, iustinian bejan, john r.sodeau and … · ivan kourtchev, iustinian bejan, john...

Ivan Kourtchev, Iustinian Bejan, John R.Sodeau and John C.Wenger

Department of Chemistry and Environmental Research Institute

University College Cork, Ireland

Sesquiterpenes are a class of terpenes that consist of three isoprene units and

have the molecular formula C15H24

o Emitted by a large variety of plants (e.g., Scots pine, birch, oak.. )

o Very reactive towards O3, OH• and NO3•

o Short lived compounds

o No agreement on the contribution of sesquiterpenes to the global budget of

BVOCs

β-caryophyllene longifolene aromadendrene α-humulene α-cedreneα-copaene

o A number of laboratory studies have been performed on a series of

sesquiterpenes with cyclic structures (e.g., β-caryophellene, α-humulene,..)

o No information concerning the atmospheric reactivity of farnesene, an

acyclic compound emitted from a wide range of plants (Duhl et al., 2008,

Biogeosciences) and detected in various branch enclosure studies (e.g.,

Goldstein et al., 2004 Geophys. Res. Lett., Helmig et al., 2007 ES&T)

(E)-β –Farnesene C15H24

α-Farnesene C15H24

+ O3, OH• & NO3•

Radicals

Oxygenated

organics

or

SOA

x x x x

x x

x

x

α-farneseneChesmos

α-farneseneSigma

(E)-β-farneseneLGC

(E)-β-farneseneSigma

o To identify gas and particle phase products from farnesene/O3

reactions;

o To determine aerosol yields under various conditions (e.g., RH,

effect of scavenger & aerosol seed).

(E)-β -farnesene

o FEP foil;

o Volume of 3.91 m3;

o Four fans;

o In situ FTIR spectroscopy using

a path length of 229.6 m;

o SMPS (TSI Model 3080; CPC

3010 & DMA 3081).

• Five channel annular denuder

• Coated with XAD-4 resin

• Flow: 15 L/min

Denuder tube

(gas collection)

Filter pack

(particle collection)

Air flow

O-(2,3,4,5,6-pentafluorobenzyl)

hydroxylamine (PFBHA)

Agilent 6890 GC coupled to

Agilent 5975 quadrupole MS

PFBHA derivatization

PFBHA oxime

Varian 3800 GC coupled to

Ion trap-MS Varian Saturn 2000

BSTFA derivatization

After 30 min

After 60 min

After 90 min

PF

BH

A

a

b

c

d

e

a

b

c

d

e

a

b

c

d

e

PF

BH

AP

FB

HA

(a)

(b)

(c)

(d)

(e)

acetone

4-methyl-8-methyldeca-4,9-dienal

6-methylhept-5-en-2-one

4-methylenehex-5-enal

4-oxopentanal

T.I.

S

S

All species except tentatively identified 4-methyl-8-methyldeca-4,9-dienal have been

detected in ambient samples by various groups.

m/z=181

Kourtchev et al., 2009 AE

Kourtchev et al., 2009, Atmos. Environ.

43, 3182-3190

kO3=4.01x10-16 cm3 molecule-1 s-1

(E)-β-farnesene

DB1 DB2DB4

DB3

kDB1 ≈ kDB2 >>>kB3 ≈ kDB4

40x

EPI SuiteTM software (US EPA, 2007)

Also observed in the gas phase!!!

All species have been detected in ambient samples by various groups.

][exp

aerosolgasC

particleC

Kp

Kp = (1.68 ± 1.22) x 10-3 m3 µg-1 Kp = (1.98 ± 1.34) x 10-2 m3 µg-1

Kp = 1.3 x 10-4 m3 µg-1 (Hellen et al., ES&T, 2008)

Kp = 1.77 x 10-4 m3 µg-1 (Healy et al., ACP, 2008) Kp = 2.53 x 10-2 m3 µg-1 (Kavouras et al, 2002)

Odum et al., 1996 (ES&T)

Initial concentration

C(E)-β-farnesene = 80 ppb - 1.1ppm

CO3 = 240 ppb - 3.3 ppm

Conditions

Dry experiment (RH<0.1%)

Dry experiment + scavenger (CO)

RH=50% + scavenger (CO)

RH=50% + scavenger (CO)+ (NH4)2SO4 seed

RH 0-80% + scavenger (CO)

Different scavengers (FTIR limitations)

Instantaneous particle formation!

Limitation of SMPS ( resolution 3 min)!

Farnesene decay was monitored using in situ FTIR

Aerosol growth monitored with SMPS

Par

ticle

dia

met

er D

p (n

m)

Particle formation from the ozonolysis of (E)-β-farnesene

0

250

500

750

1000

0 2000 4000 6000 8000

ΔM

0 (

µg

m-3

)

ΔHC (µg m-3)

690 ppb (E)-β-farnesene + scavenger+ (NH4)2SO4 seed

Ng et al., 2006, ES&T

i iom

iomi

MK

KMY

0,

,

01

Dry without scavenger

SOA yield ~43% at

conc. 80 ppb to1.1 ppm

RH(0.03%) + scav. RH(50%)+scav. RH(50%)+scav.+seed

α K α K α K

0.19 0.0049 0.1687 0.0064 0.1787 0.0034

One compound model

0

0.01

0.02

0.03

0.04

0.05

0.06

0 10 20 30 40 50 60 70 80

Yie

ld

RH, %

150 ppb (E)-β-farnesene

CO & without seed

o (E)-β–farnesene has a lifetime ~1 hour with respect to reaction withozone - react close to its source and have an impact at local level;

o (E)-β–farnesene/O3 is another possible source of the ubiquitouscarbonyls (acetone, 4-oxopentanal and 6-methylhept-5-en-2-one) andacids (4-oxopentanoic acid and succinic acid);

o High Kp values for 4-oxopentanal and 4-oxopentanoic acids confirmtheir significance in SOA formation;

o SOA yields varied from 0.05-43% depending on the conditions (conc.,RH, presence of OH scavenger);

o Presence of OH scavenger decreases aerosol yield indicating Criegeeintermediates produce OH and that OH/(E)-β–farnesene reactionsproduces SOA;

o RH decreases SOA yield dramatically at low conc. but has minimaleffect at high conc. of (E)-β–farnesene;

o The presence of neutral aerosol seed does not have a significantinfluence on the SOA yield

Photooxidation of (E)-β–farnesene (gas and particulate phase organic

composition, SOA yields)

Thank you for your attention