The Secondary Products by Ozone-initiated Reaction with

Terpenes Emitted from Natural Paint

Sang-Guen Jung1),2)

, Rheo B. Lamorena1)

, Woojin Lee1),*

, Gwi-Nam Bae1),

Kil-Choo Moon1) and Shin-Do Kim

2)

1)Air Resources Research Center, Korea Institute of Science and Technology, Seoul, Korea

2)Department of Environmental Engineering , University of Seoul, Seoul, Korea

Abstract

The use of natural paint for the application to walls and furnishings is now increasing

to improve indoor air quality, thereby the natural paint could be a significant source of

biogenic volatile organic compounds (BVOCs) in indoor environments. Recent studies have

shown that gas-phase reactions between terpenes and ozone can generate sub-micron size

particles and toxic volatile organic compounds such as aldehydes and ketones. In this

research, we have studied the formation of particles and secondary organic compounds

during the reaction of ozone with terpenes emitted from commercial natural paint. The paint

applied onto stainless steel was dried and oxidized in a Teflon chamber. Two monoterpenes

(- and -pinenes) were identified by FTIR and GC/MS. Several tests were performed to

evaluate the effects of ozone concentration on particle formation. Increased ozone levels

significantly affect the increase of particle number concentration (monitored with SMPS),

which results in the increase of particle counts ranging from 8,000 to 70,000 particles/cm3.

Gas-phase products such as formaldehyde, acetaldehyde, acetone + acrolein, and

propionaldehyde were identified during the terpene/ozone reactions by HPLC. These

compounds are potential hazardous chemical compounds having harmful health effects to

animals and plants. The results obtained from this study provide an insight on the adverse

effect of eco-friendly natural product on indoor air quality (IAQ).

Key words: Natural paint, Terpenes, Ozonolysis, Particle formation, Secondary organic

compounds

* Corresponding author. Tel.: +82-2-958-5816

E-mail: woojin@kist.re.kr

1. Introduction

Most work activities by humankind of the day are conducted in confined work spaces,

therefore the presence of VOCs in indoor environments has been a growing concern in recent

years. A number of building construction and interior design materials have been identified as

significant sources of indoor pollutants (Sack and Steele, 1992). These materials emit a

variety of VOCs which react with strong atmospheric oxidizing agents such as ozone and OH

radicals forming harmful secondary organic chemicals and aerosols. Such materials have been

used for simple household cleaners and fragrant products for ceiling/wall paints and

decorative furnishings (Liu et al., 2004). Of these, paints and carpets are the prevalent

sources of indoor organic compounds (Weschler et al., 1992; Reiss et al., 1995). Studies

have shown that these materials emit VOCs and react with oxidants to generate aldehydes,

ketones, and even low-molecular weight carboxylic acids (Fjallstrom et al., 2002; Morrison

and Nazaroff, 2002). Chemical paints made from various volatile compounds have been used

as common indoor surface coatings. Alkyd paints typically contain more than 30% of aliphatic

and aromatic hydrocarbons such as octane and xylene (Fortmann et al., 1999). These interior

coatings are now being replaced by natural paints. The raw ingredient materials of natural

paints are plant and essential oils, resins, and plant pigments. Water-based coatings use

water as the primary solvent, however it still contains around 20% of organic solvent for

stabilizing, dispersing and emulsifying the paint. A particular group of VOCs attracting an

intensive interest now are the biogenic terpenes (-pinene, -pinene, and d-limonene) emitted

from the natural paint. The presence of unsaturated bonds in the chemical structure makes

them susceptible for the reaction with ozone and other atmospheric oxidants.

Typical indoor ozone concentration is in the range of 50 - 120 ppb. It is significant

enough to trigger the oxidation reactions with VOCs (Wainman et al., 2000; Weschler, 2000).

The concentration of indoor ozone varies depending on ventilation rates, seasonal variations,

and presence of sources (e.g., cleaning equipments, laser printers, fax machines and

photocopiers) (Wolkoff, 1999). Fig.1 shows a general mechanism of ozone attacking on the

double C=C bond yields an energy rich ozonide, and is then decomposed to two difunctional

products, carbonyl and an excited carbonyl oxide biradical. This highly excited biradical, which

is also referred to as the “criegee intermediate (CI)”, forms organic transformation products

via various pathways (Fick et al., 2002). Terpenes are further classified by the location or

number of double carbon-carbon bonds. The fate of these terpenes by ozone attack lies on

these characteristics. An exocyclic structure, i.e., -pinene, will form a criegee intermediate

and nopinone, a ketone, and formaldehyde. For an endocyclic structure, -pinene will form two

criegee intermediates with an aldehydic end. Another byproduct of ozone-alkene reactions is

the OH radical which could catalyze further reactions and generate different organic products

and a source for the formation of particles (Atkinson, 2003). The resulting products are semi-

volatile or low-volatile enough to condense and form fine particles or aerosols. Several

experiments have been conducted to prove this phenomenon. Pinonic acid and pinic acid were

found in aerosol samples due to ozonolysis of , -pinene (Jenkin et al., 2000; Koch et al.,

2000).

A study conducted by Weschler and Shields (1999) has shown that ozone causes

certain reactions with several indoor contaminants generating condensed-phase products,

which lead to the yield of sub-micron size particles. A mouse bioassay conducted by Wilkins

et al. (2003) showed a respiratory irritation effect caused by terpene/ozone reaction system.

The formation of gaseous and condensed phase indoor products may have an adverse effect

on the health of building occupants under poor-ventilation system (Wolkoff et al., 2000). The

employees working in offices have reported various respiratory illnesses since 1980s, which

are now known as the “sick building syndrome”. USEPA has described this syndrome as

“situations in which building occupants experience acute health and comfort effects that

appear to be linked to time spent in a building, but no specific illness or cause can be

identified” (EPA, 1991). Other health effects such as dizziness, skin irritations, and

sensitivity to odors have been also reported.

Experimental works of other researchers have been focused on high concentrations of

monoterpenes or only considered pure monoterpene chemicals in their chamber systems that

lead to overestimation of results with ozonolysis reactions. Moreover, the research on

variation of ozone concentrations on particle formations has not been considered on emission

studies. Therefore in this study, we have investigated the formation of particles and gas

phase products by the reaction of ozone with biogenic terpenes (, -pinene) emitted from

natural paint. We have also demonstrated the effect of ozone concentrations on particle

formation under the same experimental condition (i.e., same quantity of paint).

Fig. 1. Reaction mechanism between unsaturated hydrocarbon compounds and ozone.

2. Experimental

2.1 Chamber design

Teflon film chamber was used to investigate terpene/ozone reactions. The volume of

the chamber is 1 m3 (1 m x 1 m x1 m). Fig. 2 shows a schematic diagram of the chamber.

The chamber includes two inlet ports for air supply and ozone injection, while three outlet

ports were allotted for gas and particle sampling. Stainless steel and PTFE tubings were used

for on-line sampling to minimize adsorption of target organic and products. A sample

specimen holder was used so that the test surface of the specimen can be exposed to the

chamber atmosphere (Fig. 2). The test specimen holder was installed at the bottom of

chamber for testing. Natural paint was applied onto 300 300 5 mm stainless steel plate

with paintbrush. We have used less amount of paint than that recommended by manufacturer.

The chamber was cleaned with high concentration of ozone and flushed with clean air to

remove impurities sorbed on the chamber surface before the start of experiment (Kelly,

1982). A clean air system was used for the experiment, which is composed of an oilless

compressor, a membrane dryer, and particle filter to remove moisture and particles in the air.

Charcoal, purafil, and HEPA filter were also used for the control of organics and removal of

particulate matter.

Fig. 2. Schematic diagrams of chamber and specimen holder.

2.2 Experimental procedure

Fig. 3 shows an experimental schedule. We have conducted an experiment to check

chamber leakage before every run. 10 mL of natural paint was applied onto the stainless steel

specimen and was air-dried for 8 hours (A, B). A sample specimen holder was installed

inside chamber (C). Chamber was flushed with purified air several times (D). The sample

specimen was allowed to emit for 24 hours (E). Ozone was injected in chamber and

secondary products were measured by SMPS, FTIR, and HPLC (F). Ozone was supplied by

an ozone generator (Advanced Pollutant Instrument, Model 401). The required ozone

concentration varied from 100 to 1000 ppb. All experiments were conducted under the room

temperature (26.5 ± 1.5 ℃) and relative humidity (29 ± 1%). After testing, the sample

specimen was cleaned by wiping the surface with an alkaline detergent, followed by thorough

rinsing with tap water, cleaning with methanol, rinsing with deionized water, and drying at

220 ℃ during 2 hours.

Fig. 3. Experimental schedule.

2.3 Analysis

We have qualitatively measured the components of natural paint (i.e., biogenic

hydrocarbons) emitted in the 5 L bag using a gas chromatograph/mass spectrometer (GC/MS,

Varian-Saturn 2000) equipped with a 60 m DB-1 column (J&W). Contents of the bag were

pre-concentrated by the injection into a sample preparation trap (SPT) before desorption at

170 ℃. Mass spectra and retention time of unknown chemical compounds were compared to

National Institute of Standards and Technology (NIST) and Saturn Search databases. , -

pinene concentration were analyzed by Fourier Transform Infrared Spectroscopy (FTIR,

MIDAC-I-2000) during the main experiment. The spectra were obtained by co-adding 64

scans recorded at 0.5 ㎝-1

instrumental resolution in the range from 650 to 3700 ㎝-1

.

Ozone concentration was measured by a U.V. photometric ozone analyzer (Thermo

Environmental Instrument, Model 49), which was calibrated with ozone calibrator (API, Model

401) before each run. The U.V photometer determined ozone concentration by measuring the

attenuation of light due to ozone in the absorption cell at a wavelength of 254 nm. The

concentration ranges used were 0-1000 ppb. The response time is less than 20 seconds and

noise is less than ±1 ppb. The air in chamber was sampled by passing a particulate filter at a

rate of 2 L/min. The concentration of ozone was monitored and recorded by an on-line

computing system at every 1 minute.

Aldehyde and ketone samples were collected using Sep-Pak C18 cartridges coated

with 2,4-dinitrophenylhydrazine (DNPH). We have sampled carbonyl compounds by

connecting the downstream end of the cartridge to air sampling pump (Sensidyne, GILAIR-5).

An ozone scrubber was connected at the tip of the cartridge to remove ozone. The sampling

pump was calibrated before and after sampling for constant flow rate. It was suitable for

sampling because of its low noise level. The sampling flow rate was 300 mL/min and the

sampling duration was 20 min. After sampling, each cartridge was resealed with Teflon tape,

wrapped in aluminum foil, and stored in refrigerator at 4 ± 0.5℃. The cartridge was eluted

with 5 mL of acetonitrile (J. T. Baker, USA) and analyzed by high performance liquid

chromatograph/ultra violet detector (HPLC/UV, Waters 600s)(ASTM D 5197, 1997; EPA

TO-11A, 1999).

A scanning mobility particle sizer (SMPS) was used to investigate the nucleation of

particles and to identify the effects of ozone concentration and paint quantity on the

formation of particles. The SMPS consists of an electrostatic classifier (TSI 3080) with a

nano differential mobility analyzer (NDMA, TSI 3085) and an ultra-fine condensation particle

counter (CPC, TSI 3025) as a detector. The SMPS system was operated at a sample flow of

0.3 L/min and the sheath flow inside the NDMA was set at 3.0 L/min. The system was

scanned with time resolution of 5 min (240 s up-scan and 30 s down-scan) and used 0.0457

㎝ impactor nozzle. The particle size was monitored in the range of 4.4 - 168 nm in this

study.

Table 1. Conditions of HPLC analysis.

3. Results and Discussion

3.1 Chemical compounds emitted from natural paint

The major chemical components of natural paint were identified using a 5 L Teflon

bag. A 10 mL of paint was applied on a 100 x 90 mm2 stainless steel specimen. After 4

hours of drying, the specimen was placed and sealed in the bag. Hydrocarbons were emitted

in the bag for 24 hours. Fig. 4 shows the qualitative analysis of chemical compounds emitted

from natural paint and Table 2 shows their response. , -pinenes, which were peaks 4 and

6, respectively, show very significant responses among the chemical compounds emitted in

Table 2. Other dominant peaks were observed at points 1, 2, 3, 5, 7 and 8 but they were not

identified at this time. We have shown their corresponding molecular weights and formulas in

Table 3. The 6 dominant peaks are possible VOCs based on the NIST and Saturn Search

libraries. Peak 5 and peak 8 have the same molecular weights and similar retention times

compared to those of monoterpenes. Although , -pinenes were only identified from the

natural paint emission, the results indicate that natural paint may contain other reactive

monoterpenes. The concentration of -pinene was monitored by FTIR.

Fig. 4. A GC/MS chromatogram of gas-phase sample emitted from natural paint.

Table 2. Relative abundance of chemical compounds emitted from natural paint.

Table 3. Properties of peaks based on NIST and Saturn databases.

3.2 Variation of ozone concentration

A mass balance equation was considered to calculate the variation of ozone

concentration in chamber. The volume of chamber was kept constant at 1000 L and 1000 ppb

of ozone was continuously injected in chamber. The equation describing a theoretical ozone

concentration in chamber was represented by equation (1).

(1)

where, V = volume in chamber (L)

C0 = injected ozone concentration (ppb)

Q1 = inlet flow (L/min)

Q2 = outlet flow (L/min)

In this equation, inlet flow (Q1) is equal to outlet flow (Q2). If V, C0 remain constant, then

(2)

(3)

Given at t1 =0, C1 =0, then at time, t, theoretical ozone concentration in chamber is

(4)

where, Ct = ozone concentration at time, t (ppb)

Theoretical ozone concentration at time t was calculated using Eq. (4). A theoretical

ozone concentration curve was plotted in Fig. 5 when ozone injection flow is 3.5 L/min. It was

similar to blank ozone concentration (i.e., analyzed without sample specimen). A theoretical

ozone concentration was adjusted to blank ozone concentration for a comparison purpose.

Blank ozone concentration curve deviated slightly from the theoretical ozone curve, which

could be due to the incomplete mixing of ozone in the chamber. This usually results in wrong

measurement of ozone concentration. We observed the difference between the ozone

concentrations with and without a sample specimen in Fig. 6. The difference may be due

mainly to the reaction with hydrocarbons emitted from the specimen.

Fig. 5. Comparison of ozone concentration (theoretical vs. experimental, initial ozone

concentration = 1000 ppb).

Fig. 6. Comparison of theoretical ozone to real ozone concentrations.

3.3 Particle formation

Terpene/ozone reactions are known to occur the formation of particles. The

possible pathways for the particle formation are a thermodynamic equilibrium distribution

between the gas-phase and particle-phase leading to gas-particle partitioning of semi-

volatile organic products (SVOC) and a self-nucleation with the subsequent condensation of

new particles (Odum et al. 1996; Koch et al. 2000). The sources of formation of these

particles may be mainly from oxidation products with low vapor pressures (e.g., dicarboxylic

acids) formed from both pathways. Ozone was introduced into the chamber and the particle

formations were observed in this work, which is consistent with the findings of Rohr et al.

(2003) and Sarwar et al. (2003). We have observed an increase and subsequent decrease

in particle concentrations. This may be due to the increase of particle diameter. As shown in

Fig. 7, -pinene concentration decreases as ozone concentration increases. This result

indicates that -pinene reacts with ozone and its degradation could be one of the sources for

particle formation in the chamber.

The total particle concentration was measured by CPC and SMPS. The different

levels of ozone were used to identify the effect of ozone concentration on particle number

concentration. The initial particle concentrations were low in the chamber. As shown in Fig. 8

(b), a rapid increase of particle number concentration was observed approximately 5 minutes

after the injection of ozone. The peak concentration (7 x 104 particles/cm

3) was observed

approximately 30 min after ozone mixing. Nucleation time can also be affected by ozone

concentration. The nucleation at high ozone concentration (e.g., 1000 ppb) occurred earlier

than that at lower ozone concentration shifting the initiation of nucleation late. We also

observed significant increase of particle count at high ozone levels. The peak particle

concentrations are similar at ozone concentration of 500 and 1000 ppb in Fig. 9. These

results indicate that hydrocarbons emitted in the chamber were completely consumed by

ozone at 500 ppb and that particle formation at 1000 ppb occurred at under the ozone limit

condition. It is concluded that the concentration of ozone significantly affects the formation of

particles during nucleation period.

Fig. 7. Degradation profile of -pinene with ozone concentration using FTIR.

C0: -pinene concentration before ozone injection.

Ct: -pinene concentration at reaction time.

Fig. 8. Variation of ozone and particle number concentration during the terpene/ozone

reaction in a chamber.

Fig. 9. Variation of maximum particle number concentration during terpene/ozone reaction.

The ozonolysis was found to have a significant effect on the new particle formation at

high ozone concentration (i.e., > 500ppb). This is shown in Fig. 10 (b) (particle number

concentration and total particle mass concentration), 10 (b) (particle size distribution by

monitoring SMPS), and 10 (c) (change in mean particle diameter). Particle mass concentration

was estimated by assuming that the density of particle formed in chamber equals 1 g/㎤.

Weschler and Shields (1999) measured average mass-concentrations (2.5 - 5.5 g/㎥) during

the reaction of ozone and various terpenes in typical indoor environments. Our results are

consistent with these findings obtaining mass concentrations until approximately 6 g/㎥ as

shown in Fig. 10 (a). In Fig. 10 (a), each single line represents a single particle size distribution

measurement obtained at a time resolution of five minutes. The base line displays the results

of blank run performed prior to the ozone addition and represent the formation of particles

without ozone addition. The particle concentrations decreased as particle diameter increased.

This leads to an increase in particle mass concentrations, which implies that the

condensational growth and wall loss of particles occurred during the reaction. We have

observed the initiation of particle formation at approximately 10-20 nm, which is consistent

to the experimental work done by Rohr et al. (2003) and Sarwar et al. (2003). The result

implies that partitioning and/or saturation of the nucleating compounds occurs at the particle

diameter range of 10-20 nm. The peak diameter for the particle size distribution was found

at 70 nm, when 500 ppb ozone was injected at 92 min. The size distribution shifted toward

larger particle diameters during the experiment. We have observed particle formation on a

limited particle size range from 4.4 nm-165 nm. Fig. 10 (c) shows the mean diameter of

particles illustrating that particle growth was being continued until 120 nm. It has been

expected that the size of particle continuously grows until approximately 1 m. In contrast to

our experimental result, other researchers have observed the formation of large particles (<

1 m) (Fan et al., 2003; Sarwar et al., 2003). The characteristics of these condensed

products needs to be characterized.

Fig. 10. Characterization of aerosol formation.

3.4 Secondary organic compounds

The products observed in this study were similar to those reported in literatures. As

shown in Fig. 1, the ozonide rapidly decomposed terpene to carbonyls and criegee biradicals.

Criegee biradicals further reacts to form carbonyls, hydroxyl carbonyls, dicarbonyls,

carboxylic acids, and oxocarboxylic acids. Formaldehyde, one of the major carbonyl

products generated from these reactions, was observed during the reaction and other

aldehydes, such as acetaldehyde, propionaldehyde, glyoxal, and methyl glyoxal, were also

observed as minor components (Grosjean et al. 1992; Fan et al. 2003). Fig. 11 shows the

formation of aldehydes and ketones during the reaction of terpenes with ozone. The

identified products from the terpene/ozone reactions were formaldehyde, acetaldehyde,

acetone+acrolein, and propionaldehyde. The concentrations of these compounds increased

after the injection of ozone and decreased after 5 hours. No increase of acetone was

observed but the concentration of formaldehyde rapidly increased. The decrease of the

compounds may be caused by OH yields. OH radicals have been observed as one of by-

products in terpene/ozone reactions. OH radicals are believed to form from CIs via the

hydroperoxide channel, which is one of the reaction channels of CIs. CIs will isomerize to

form a hydroperoxide followed by dissociation to OH radicals and alkyl radical. The products

formed, such as aldehydes and ketones, during the terpene/ozone reactions could be

simultaneously degraded by OH radicals (Weschler and Shield, 1996). These secondary

reactions shows that more compounds could form apart from ozonolysis reactions. OH radical

scavengers (i.e, 2-butanol, cyclohexane) have been used to inhibit product/OH reactions during

the terpene/ozone reactions (Reiss et al., 1995; Aschmann et al., 2002).

Fig. 11. Secondary organic compounds formed by ozone/terpene reaction.

4. Summary

The experimental study has been conducted to identify the effect of ozone and

hydrocarbons emitted from natural paint on the formation of indoor particles. We have

observed that significant amounts of monoterpenes are emitted from natural paint and that

monoterpenes and VOCs at low concentrations are still significant enough to init iate particle

formations in indoor environments. The formation of particles and secondary organic products

were identified and quantified during the reactions of terpenes emitted from natural paint with

ozone. Peak particle number concentrations ranges from 8,000 to 70,000 particle/cm3

at

different ozone concentrations. Mean particle diameters shifted from 5 nm to 120 nm. Particle

condensation was observed as particle number concentration decreased during the particle

growth. It is concluded that the formation of additional products (i.e., formaldehyde,

acetaldehyde, and propionaldehyde) can form from natural paint in the presence of atmospheric

oxidants. The presence of these particles and potentially irritating organic compounds on

indoor environments are very harmful to human health. The results obtained from this research

could be used as basic knowledge for the future evaluation of consumer products for the

potential formation of particles and secondary organic products during the reaction with

atmospheric indoor oxidants. Further studies on the characterization of the condensed-phase

products are needed to identify the chemical nature of the particles formed. Further

experiments on the presence of OH radical scavengers are also needed to validate the

secondary reactions of the aldehydes and ketones with OH radicals.

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천연 페인트로부터 방출되는 털핀류와 오존 반응에

의한 이차 오염물질 생성

정상근1),2)

, Rheo B. Lamorena1), 이우진

1),*, 배귀남

1), 문길주

1), 김신도

2)

1)한국과학기술연구원 대기자원연구센터,

2)서울시립대학교 환경공학과

초 록

실내 공기질 향상을 위해 천연 페인트가 벽, 가구 등의 실내공간에 많이 사용되고 있다. 그런데 천

연페인트는 실내에서 털핀(자연적 휘발성 유기화합물)의 중요한 배출원으로 작용할 수 있다. 최근

연구에 의하면 털핀과 오존의 가스상 반응에 의해 미세입자, 알데히드류, 케톤 같은 유해한 휘발성

유기화합물들이 생성된다는 보고가 있었다. 이번 연구에서는 천연 페인트에서 방출되는 털핀과 오

존의 반응에 의한 미세 입자와 이차 유기화합물 생성에 대해서 조사하였다. 시편에 페인트를 칠하

여 실내에서 건조시킨 후 테플론 챔버 내에서 오존과 반응 시켰다. , -파이닌은 GC-MS와

FTIR을 사용하여 정성하였다. 입자생성에 대한 오존의 영향을 조사하기 위해 여러가지 실험이 수

행 되었다. 오존 농도가 100 ppb에서 1000 ppb로 증가할 때 입자 수농도는 8,000에서 70,000

particles/㎤까지 증가하였다. 포름알데하이드, 아세트알데하이드, 아세톤+아크로레인, 프로피온알

데하이드 등의 반응 생성물은 HPLC로 분석하였다. 이런 화합물들은 잠재적으로 유해한 화합물이

고, 인체에 해로운 영향을 끼친다. 이번 연구결과는 친환경제품의 실내공기질에 대한 해로운 영향

에 대한 보기를 보여주었다.

Table 1. Conditions of HPLC analysis.

Item Analysis Conditions

HPLC Waters 600s, USA

Detector UV/Vis 360 nm

Column Nova-Pak C18(3.9×300 mm)

Mobile phases ACN/Water (55/45 V/V)

Analysis time 25 min

Injection volume 20 L

Column temperature 25℃

Flow rate 1.0 mL/min

Purge gas and flow He(99.99%), 100 mL/min

Table 2. Relative abundance of identified compounds emitted from natural paint.

Compounds Relative abundance

Toluene 547193

m, p–xylene 296857

Styrene 9221

o– xylene 56152

-pinene (peak 4) 2176031

-pinene (peak 6) 9870602

Table 3. Properties of peaks based on NIST-Saturn databases.

Peak number Molecular weight Molecular formula

1 47 -

2 84 / 128 CH2Cl2 / C2H2Cl2O2

3 100 / 128 C7H16 / C9H2O

5 136 C10H16

7 134 C10H14

8 136 C10H16

O

O OR1

R2

R3 R4

+ C

OR3

R4

R1

R2

R3

O

C

O

+C

R4

O

*

R2

R3

O

O O

R4

R1

O

O *

C

R1

R2

O

OH *

C

R1

R2

Hydropero ide channel

POZ(Primary ozonide)

Crigee Intermediate

Carbonyl compound

Fig. 1. Reaction mechanism between unsaturated hydrocarbon compounds and ozone.

Fig. 2. Schematic diagrams of chamber and sample holder.

Fig. 3. Experimental schedule.

(20 min)(10 min)(10 min)

A B C D E F

(120 min)

Start time

(1440 min) (1440 min)

-480 min -240 min -120 min 1440 min 2880 min

.

Fig. 4. A GC/MS chromatogram of gas-phase sample emitted from natural paint.

Elapsed time (min)

1400 1600 1800 2000 2200 2400

Ozo

ne

co

nce

ntr

atio

n (

pp

b)

0

200

400

600

800

1000

theoretical ozone (1000ppb)

blank ozone (1000ppb)

Fig. 5. Comparison of ozone concentration (theoretical vs. experimental, initial ozone

concentration = 1000 ppb).

Elapsed time (min)

1400 1600 1800 2000 2200 2400

Ozo

ne

co

nce

ntr

atio

n (

pp

b)

0

200

400

600

800

1000

1000 ppb

500 ppb

200 ppb100 ppb

Ozone injection (1440min)

Theoretical

Experimental

Fig. 6. Comparison of theoretical ozone to real ozone concentrations.

Elapsed time (min)

1400 1600 1800 2000 2200

Ct/C

0

0.0

0.3

0.6

0.9

1.2

1.5

Ozo

ne

co

nce

ntr

atio

n (

pp

b)

0

100

200

300

400

500

600

-pinene

Ozone (1000 ppb)

Ozone injection

Fig 7. Degradation profile of -pinene with ozone concentration using FTIR.

C0: -pinene concentration before ozone injection.

Ct: -pinene concentration at reaction time.

Elapsed time (min)

1400 1600 1800 2000 2200 2400

Ozone

concentr

ation (

ppb

)

0

100

200

300

400

500

600

1000 ppb

200 ppb

100 ppb

500 ppb

Injected ozone concentration (ppb)

(a) Ozone

Elapsed time (min)

1400 1600 1800 2000 2200 2400

Pa

rtic

le c

on

ce

ntr

atio

n (

pa

rtic

les/c

m3)

0

20000

40000

60000

80000

1000 ppb

500 ppb

200 ppb

100 ppb

Injected ozone concentration (ppb)

(b) Particle

Fig. 8. Variation of ozone and particle number concentration during the terpene/ozone

reaction in a chamber.

Ozone concentration (ppb)

0 200 400 600 800 1000 1200

Ma

xim

um

pa

rtic

le c

on

ce

ntr

atio

n (

pa

rtic

les/c

m3)

0

10000

20000

30000

40000

50000

60000

70000

80000

Fig. 9. Variation of maximum particle number concentration during terpene/ozone reaction.

Elapsed time (min)

1400 1450 1500 1550 1600

Nu

mb

er

co

nce

ntr

atio

n (

pa

rtic

les/c

m3)

0

5000

10000

15000

20000

25000

30000

Ma

ss c

on

ce

ntr

atio

n (

g/m

3)

0

2

4

6

8

10

Number

MassOzone injection (1440min)

(a) Particle number concentration and total particle mass concentration.

Particle diameter (nm)

10 100

dN

/dL

og

(Dp)

(pa

rtic

les/c

m3)

0

10000

20000

30000

40000

50000

60000

1467 min

1532 min

1663 min

1793 min

(b) Particle size distribution by monitoring SMPS.

Elapsed time (min)

1400 1500 1600 1700 1800

Me

an

dia

me

ter

(nm

)

0

20

40

60

80

100

120

140

(c) Change in mean particle diameter.

Fig. 10. Characterization of aerosol formation.

Elapsed time (min)

1400 1600 1800 2000 2200 2400

Ga

s c

on

ce

ntr

atio

n (

g/m

3)

0

10

20

30

40

50

60

Formaldehyde

Acetaldehyde

Acetone+Acrolein

Propionaldehyde

Ozone injection

Fig. 11. Secondary organic compounds formed by ozone/terpene reaction.