The Secondary Products by Ozone-initiated Reaction with ... - koasas

The Secondary Products by Ozone-initiated Reaction with Terpenes Emitted from Natural Paint

Sang-Guen Jung

1),2)

1)

, Rheo B. Lamorena , Woojin Lee

Kil-Choo Moon

1)

1),*

and Shin-Do Kim

1)

, Gwi-Nam Bae ,

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), 3

which results in the increase of particle counts ranging from 8,000 to 70,000 particles/cm . 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: [email protected]

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. Suc h 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, 2 000). 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 3

the chamber is 1 m (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 thre e 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 dryi ng 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

-1

instrumental resolution in the range from 650 to 3700 ㎝ .

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.

2

A 10 mL of paint was applied on a 100 x 90 mm 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 (Q 1) is equal to outlet flow (Q 2). 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 semivolatile 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 4

3

after the injection of ozone. The peak concentration (7 x 10 particles/cm ) 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 coul d 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.

3

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

References Aschmann, S. M., Arey, J., Atkinson, R (2002) OH radical formation from the gas-phase reactions of O3 with a series of terpene. Atmospheric Environmental, 36, 4347-4355. ASTM D 5197 (1997) Standard test method for determination of formaldehyde and other carbonyl compounds in air (active sampler methodology). Atkinson, R. (2003) Gas-phase tropospheric chemistry of biogenic volatile organic compounds: a review. Atmos. Environ. Supp., 37(2), S197-S219. Bonn, B., Schuster, G., and Moortgat, G. K. (2002) Influence of water vapor on the process of new particle formation during monoterpene ozonolysis. J. Phys. Chem. A, 106, 2869 -2881.

Fan, Z., Lioy, P., Weschler, C., Fiedler, N., Kipen, H., and Zhang, J. (2003) Ozone-initiated reactions with mixures of volatile organic compounds under simulated indoor conditions. Environ. Sci. Technol. 37, 1811-1821. Fick, J., Pommer, L., Andersson, B., Nilsson, C. (2002) A study of the gas-phase ozonolysis of terpene: the impact of radicals formed during the reaction. Atmospheric Environment 36, 3299-3308. Fjallstrom, P., Andersson, B., Nilsson C., Andersson, K. (2002) Drying of linseed oil paints: a laboratory study of aldehyde emissions. Industrial Crops and Product 16, 173-184. Fortmann, R., Roache, N., Chang, J. C. S., Guo, Z. (1998) Characterization of emissions of volatile organic compounds from interior alkyd paint. J. Air & Waste Manage. Assoc., 48, 931-940. Grosjean, D., Williams, E. L., and Seinfeld, J. H. (1992) Atmospheric oxidation of selected terpenes and related carbonyls: gas-phase carbonyl products. Environ. Sci. Technol., 26(8), 1526-1533. Jenkin, M. E., Shallcross, D. E., Harvey, J. N. (2000) Development and application of a possible mechanism for the generation of cis-pinic acid from the ozonolysis of - and pinene. Atmospheric Environment, 34, 2837-2850. Kelly, N. A. (1982) Characterization of fluorocarbon-film bags as smog chambers. Environ. Sci. Technol., 16(11), 763-770. Koch, S., Winterhalter, W., Uherek, E., Kollof, A., Neeb, P., and Moortgat, G.K. (2000) Formation of new particles in the gas-phase ozonolysis of monopterpenes. Atmospheric Environment, 34, 4031-4042. Liu, X., Mason, M., Krebs, K., and Sparksk, L. (2004) Full-scale chamber investigation and simulation of air freshener emissions in the presence of ozone. Environ. Sci. Technol., 38, 2802-2812. Morrison, G. C, and Nazaroff, W. W. (2002) Ozone interactions with carpet: secondary emissions of aldehydes. Environ. Sci. Technol., 36, 2185-2192. Odum, J. R., Hoffmann, T., Bowman, F., Collins, D. Flagan, R.C., Seinfield, J.H. (1996) Gas/particle partitioning and seconday organic aerosol yields. Environ. Sci. Technol., 30, 2580-2585. Reiss, R., Ryan, P. B., Koutrakis, P,, and Tibbetts, S. J. (1995) Ozone reactive chemistry on interior latex paint. Environ. Sci. Technol., 29, 1906-1912. Reissell, A., Harry, C., Aschmann, S.M., Atkinson, R., and Arey, J. (1999) Formation of acetone from the OH radical an O 3-initiated reactions of a series of monoterpenes.

J.

Geophys. Res., 104(D11), 13869-13879. Rohr, A. C., Weschler C. J., Koutrakis, P., and Spengler, J. D. (2003) Generation and quantification of ultrafine particles through terpene/ozone reaction in a chamber setting. Aeros. Sci. Tech., 37, 65-78. Sack, T. M., and Steele, D. H. (1992) A survey of household products for volatile organic compounds. Atmospheric Environment, 26A(6), 1063-1070. Sarwar, G., Corsi, R., Allen, D., Weschler, C. (2003) The significance of secondary organic aerosol formation and growh in buildings: experimental and computational evidence. Atmospheric Environment, 37, 1365-1381. USA. EPA. (1991) Sick Building Syndrome (SBS) Indoor Air Facts No. 4 (revised). Available from: URL: http://www.epa.gov/iaq/pubs/sbs.html USA, EPA, (1999) Determination of formaldehyde in ambient air using absorbent cartridge followed by high performance liquid chromatography (HPLC). Compendium Method TO 11A. Wainman, T., Zhang, J., Weschler, C. J., Lioy, P. J. (2000) Ozone and limonene in indoor air: a source of submicron particle exposure. Environ. Health Perspec., 108(12), 1139 -1145. Weschler, C. J., Hodgson, A. T., and Wooley, J. D. (1992) Indoor chemistry: ozone, volatile organic compounds, and carpets. Environ. Sci. Technol., 26, 2371-2377. Weschler, C. J., and Shields, H. C. (1996) Production of the hydroxyl radical in indoor air. Environ. Sci. Technol., 30, 3250-3258. Weschler, C. J., and Shields, H. C. (1999) Indoor ozone/terpene reactions as a source of indoor particles. Atmospheric Environment, 33, 2301-2312. Weschler, C. J. (2000) Ozone in indoor environments: concentration and chemistry. Indoor Air 2000, 10, 269-288. Wilkins, C. K., Wolkoff, P., Clausen, P. A., Hammer, M., Nielsen, G. D. (2003) Upper airway irritation of terpene/ozone oxidation products (TOPS). Dependence on reaction time, relative humidity an initial ozone concentration. Toxic. Lett., 143, 109-114. Wolkoff, P. (1999) Photocopier and indoor air pollution. Atmospheric Environment, 33, 2129-2130. Wolkoff, P., Clausen, P. A, Wilkins, C. K., Nielsen, G. D. (2000) Formation of strong airway irritants in terpene/ozone mixtures. Indoor Air, 10, 82-91.

천연 페인트로부터 방출되는 털핀류와 오존 반응에

의한 이차 오염물질 생성 정상근 1)

1),2)

1)

, Rheo B. Lamorena , 이우진

1),*

한국과학기술연구원 대기자원연구센터,

초

1)

1)

, 배귀남 , 문길주 , 김신도

2)

2)

서울시립대학교 환경공학과

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.

Table 2.

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

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

OH

*

O Hydropero ide channel

R1 C R2 O

* O

O R1 O O

O

R1

O

R2

R4

R3

+

C

O

R4 Carbonyl compound

Crigee Intermediate

R2 R4

R3

C

R2

O

R1

R3

O R1

POZ (Primary ozonide)

O

O

+

C

R3*

C

R2

R4

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

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

A

B

C

(10 min)

(10 min)

(20 min)

-480 min

-240 min

D

(120 min)

-120 min

E

F

(1440 min)

(1440 min)

Start time

Fig. 3. Experimental schedule.

1440 min

2880 min

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

Ozone concentration (ppb)

1000

800

600

400

200 theoretical ozone (1000ppb) blank ozone (1000ppb) 0 1400

1600

1800

2000

2200

2400

Elapsed time (min)

Fig. 5. Comparison of ozone concentration (theoretical vs. experimental, initial ozone concentration = 1000 ppb).

1000


Ozone injection (1440min) 800

Theoretical Experimental 1000 ppb

600

400 500 ppb 200

200 ppb

100 ppb

0 1400

1600

1800

2000

2200

2400

Elapsed time (min)

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

1.5

600 Ozone injection

-pinene Ozone (1000 ppb)

400

Ct/C0

0.9 300 0.6 200 0.3

0.0 1400


500

1.2

100

1600

1800

2000

0 2200

Elapsed time (min)

Fig 7. Degradation profile of -pinene with ozone concentration using FTIR. C0: -pinene concentration before ozone injection. Ct: -pinene concentration at reaction time.

600 Injected ozone concentration (ppb) 1000 ppb 500 ppb 200 ppb 100 ppb


500

400

300

200

100

0 1400

1600

1800

2000

2200

2400

Elapsed time (min)

(a) Ozone

Particle concentration (particles/cm3)

80000 Injected ozone concentration (ppb) 1000 ppb 500 ppb 200 ppb 100 ppb

60000

40000

20000

0 1400

1600

1800

2000

2200

2400

Elapsed time (min)

(b) Particle Fig. 8.

Variation of ozone and particle number concentration during the terpene/ozone reaction in a chamber.

3

Maximum particle concentration (particles/cm )

80000 70000 60000 50000 40000 30000 20000 10000 0 0

200

400

600

800

1000

1200


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

10 Number Mass

Ozone injection (1440min) 25000

8

20000 6 15000 4 10000 2

5000

0 1400

1450

1500

1550

Mass concentration (g/m3)

Number concentration (particles/cm3)

30000

0 1600

Elapsed time (min)

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

60000 1663 min

dN/dLog(Dp) (particles/cm3)

50000 1532 min 40000

30000 1467 min 20000 1793 min 10000

0 10

100

Particle diameter (nm)

(b) Particle size distribution by monitoring SMPS.

140

Mean diameter (nm)

120

100

80

60

40

20

0 1400

1500

1600

1700

Elapsed time (min)

(c) Change in mean particle diameter. Fig. 10. Characterization of aerosol formation.

1800

60

Gas concentration (g/m3)

50

40

30

20

10

0 1400

Formaldehyde Acetaldehyde Acetone+Acrolein Propionaldehyde

Ozone injection

1600

1800

2000

2200

2400

Elapsed time (min)

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