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Concentrations of volatile organic compounds in an industrial area of Korea
Atmospheric Environment 35 (2001) 2747}2756
Concentrations of volatile organic compounds in an industrial area of Korea Kwangsam Na , Yong Pyo Kim *, Kil-Choo Moon , Il Moon, Kochy Fung Global Environmental Research Center, Korea Institute of Science and Technology, P.O. Box 131, Cheongryang, Seoul 130-650, South Korea Department of Chemical Engineering, Yonsei University, Seodaemun-Ku, Shinchon-Dong 134 Seoul 120-749, South Korea Atm AA Inc. 23917 Craftsman Rd. Calabasas, CA 91302, USA Received 17 February 2000; accepted 8 June 2000
Abstract We measured and analyzed daily mean concentrations of volatile organic compounds (VOC) at Ulsan industrial and downtown sites from 3 to 8 June 1997. The industrial site is situated at the boundary of a petrochemical complex and the other is at downtown area in Ulsan. At each site, we collected ambient air samples in passivated stainless-steel containers by using constant #ow samplers and analyzed them by a GC-FID. At Ulsan industrial site, the concentrations and their daily variations of total VOC were higher than those at the downtown site. The concentrations of oxygenated hydrocarbons were the highest among seven hydrocarbon groups at both sites. The fraction of C }C light hydrocarbon concentrations to C }C hydrocarbons at Ulsan industrial site was higher than that in other industrial areas. It suggests that fugitive emissions of light hydrocarbons in Ulsan industrial areas might be higher than those of other industrial areas. Under favorable wind conditions, the in#uence of industrial emissions of VOC on the downtown hydrocarbon levels was observed. 2001 Elsevier Science Ltd. All rights reserved. Keywords: City of Ulsan; Emission sources; Hazardous organics; Fugitive emissions
1. Introduction During the last three decades, Korea has been industrialized rapidly and the side e!ect resulted in air quality problems in industrial areas, especially, in petrochemical industries. People in these areas began to concern seriously about the detrimental health e!ects by exposing to volatile organic compounds (VOC). Especially, public grievance becomes higher during summertime due to unpleasant odors. Korea has two large petrochemical complexes in Ulsan and Yochon. The two industrial areas have both petrochemical plants and oil-producing processes. There were a few studies on quantifying VOC concentrations in Yochon (Kim et al., 1997; Ghim et al., 1998), but VOC levels in Ulsan have not been quanti"ed yet.
* Corresponding author. Tel.: #82-2958-5816; fax: #822958-5805 E-mail address: [email protected] (Y.P. Kim).
Ulsan (35336 N and 129318 E) is located at the southeastern coastal part of Korea (Fig. 1). This area has a temperate climate. Since an oil re"nery was established in the mid 1960s, the city has become one of the largest industrial areas in Korea with 700 small and large plants such as petrochemical plant, oil re"nery processes, and other chemical plants. Among them, 400 business enterprises were designated as plants related to air pollutant emissions. At present, approximately 810,000 barrels of crude oil per day is processed in the oil re"nery. Also, Ulsan is the seventh largest city in Korea with population of about one million and an area of 1,055 km. Across the city, the Tae-Hwa River runs, and there are a few major ports in Ulsan Bay such as Ulsan port, On San port, and Banojin port. The amount of oil consumed by residents in the city of Ulsan in 1997 was about 910,000 kl. The number of vehicles in the city is in excess of 240,000, 78.9% being passenger vehicles, 15.2% trucks and 5.4% buses (Ulsan Metropolitan City, 1998). Thus, it is expected that the ambient VOC concentrations in
1352-2310/01/$ - see front matter 2001 Elsevier Science Ltd. All rights reserved. PII: S 1 3 5 2 - 2 3 1 0 ( 0 0 ) 0 0 3 1 3 - 7
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K. Na et al. / Atmospheric Environment 35 (2001) 2747}2756
Fig. 1. Map of location of the measurement sites in the city of Ulsan (D: downtown site; I: industrial site; P: petrochemical complex).
urban areas are a!ected by emissions from both petrochemical industries and urban activities. Korea Institute of Science and Technology (KIST) carried out an intensive "eld measurement study in June 1997 of "ne particles and VOC at two sites in Ulsan, one at downtown area and the other at industrial area. In the present study, "ve samples were obtained at each site. Since the sample number is not large, it is di$cult to make a meaningful statistical analysis. Therefore, it would be better to think of the results of VOC measurement as not representative values but rather episodic values during the study period. It warrants further studies in industrial areas in Korea. This paper describes the results of VOC measurements in Ulsan downtown and industrial areas and discusses the e!ects of industrial emissions on the downtown Ulsan area. 2. Experimental 2.1. Sampling VOC measurements were carried out at two locations as shown in Fig. 1. One is in the downtown area of Ulsan
(denoted as site D) and is approximately 200 m from a four-lane road and 5.5 km from the petrochemical complex. The sampling site D (about 18 m above the ground level) is on the top of a four-storey building at Hamwall Elementary School surrounded by residential and commercial areas. The other site is in the industrial area (denoted as site I) located at the northern boundary of the petrochemical complex. The distance between the two sites is about 5 km. The site I (about 9 m above the ground level) is on the top of a two-storey building at Seonam Elementary School about 0.5 km away from petrochemical plants, showing that this site is well characterized as a petrochemical industrial part of Ulsan. When wind from south is dominant, impacts of industrial emissions on the site D are expected. The sampling period was between 3 and 15 June 1997. Fine particles were collected for ion analysis and ambient air samples were collected for VOC analysis. The measurements of VOC were conducted between 3 and 8 June . Twenty-four hour averaged VOC concentrations were measured during the study period to observe the general feature of the VOC levels at the two sites. In this paper, only VOC data are presented and discussed. Integrated particle-free ambient air samples were collected in 6 l SUMMA canisters. The canisters were cleaned and evacuated by Atm AA (Calabasa, CA, USA). The initial vacuum pressure was 1.3;10\}1.3; 10\ atm (10\}10\ Torr). Flow rate of sample was controlled by a #ow controller to constant #ow of 10}15 ml min\ for 24-h sampling. To prevent accumulation of water and other contaminants, the sampler was operated prior to the sampling without attaching the can to allow purging all lines in sampler with clean particlefree dry air. The sampling equipment and procedure were conformed to US EPA TO-14 (US EPA, 1988). Table 1 summarizes meteorological conditions during the sampling period measured at the Meteorological Administration in Ulsan, apart from about 300 m of the site D. 2.2. Analysis Samples were shipped by air to Atm AA for analysis within 3 weeks of sampling. Jayanty (1989) has shown that selected organics in a stainless-steel canister revealed that most VOC were stable over a 2-week period. A subsequent study in preparation for a large-scale "eld study also demonstrated that ambient VOC are stable over a 1-month period when stored in passivated canisters (Fung et al., 1994). Hence, a 3-week delay between sampling and analysis will not lead to a serious change in VOC concentration. Samples were analyzed by using a high-resolution gas chromatography (GC) after cryogenic sample concentration as described previously (Grosjean and Fung, 1984). In brief, an aliquot of a canister air was metered into a trap immersed in liquid argon to concentrate the
K. Na et al. / Atmospheric Environment 35 (2001) 2747}2756
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Table 1 Daily mean meteorological data during the measurement period of June 1997 in Ulsan Date
Temperature (3C)
Relative humidity (%)
Wind speed (m s\)
3 4 5 6 7 8
18.8 19.0 17.9 18.0 18.6 18.9
72 77 85 84 82 81
4.3 4.2 3.2 6.0 4.4 3.9
Most frequent wind direction (%) SE (17)
SE (21)
ESE (17)
SSW (13) NW (34) NNW (26) E (28) SW (17) ENE (20)
Precipitations (mm) WNW (13) NNE (13) N (21) NW (19) NW (17) WNW (15)
* * * 11.8 * *
No precipitation.
hydrocarbons. The volume concentrated was in the range of 100}150 ml and was determined from the pressure changes of a 3 l #ask at controlled temperature caused by the air that passed through the trap into the #ask. The concentrated sample was revolatilized by heating the trap with hot water (&903C) and injected into a Hewlett-Packard 5890 Series II GC equipped with a #ame ionization detector (FID) and a 50 m long; 0.2 mm I.D. Ultra 1 methyl silicone column (HewlettPackard, USA). The detector signal was processed by a Shimadzu Class-VP Chromatography Data System (Shimadzu, Columbia, MD, USA). With subambient temperature programming, complete separation of the C hydrocarbons was achieved, negating the necessity of separate analyses for the light and heavy hydrocarbons. The analytical conditions were as follows: initial column temperature !553C held for 3 min followed by programming at 153C min\ to 403C and at 43C min\ to 1503C and held isothermal at 1503C for 15 min and at 253C min\ to a "nal temperature of 1953C. Carrier was H (2.1 kg cm\) and make-up gas was N (30 ml min\). Halocarbons were analyzed isothermally at 703C using two-dimensional capillary GC with electron capture detection (ECD). Strong electron capture sensitivity of GC-ECD allows these compounds to be measured without interference from the hydrocarbons despite their low ambient concentrations in many cases. A HewlettPackard 5710A GC was equipped with a 10-port and a 4-port valve (Valco, Austin, TX, USA) for sample loop injection, column switching and back#ush, and a Shimadzu CR501A Data Processor. One milliliter of air in the gas loop was injected into a pre-column (30 m long;0.53 mm I.D. DB-1, J&W Scienti"c, Folsom, CA, USA), which is served to isolate the fraction of the sample that contained the target compounds. With the 4-port valve, the unwanted fractions were vented and the desirable fraction was transferred to the analytical column (30 m long;0.32 mm I.D. DB-624, J&W Scienti"c, Folsom, CA, USA) for further separation and detection by the ECD. A splitter was used to transfer a fraction of the e%uent from the pre-column to the analytical col-
umn. Calibration standards from reputable manufacturers (Custom Blend, Scott-Marin Inc., Riverside, CA and Scotty IV Analyzed Gases, Scot Specialty Gases, San Bernadeno, CA, USA) were used to establish the retention times and detector responses of the ECD each time. The method had a lower quanti"able limit of &0.1 ppb for a 1 ml sample injection. The FID was calibrated each time with a National Institute of Standards and Technology, USA (NIST). 9.4 ppm propane standard (SRM 1666B) and all hydrocarbon concentrations were measured in reference to the SRM response. Multilevel calibration was obtained from di!erent dilutions of this standard. Occasionally, SRM 1811 was also used without dilution as a check for benzene and toluene. The GC-ECD was calibrated at 3 levels with standard mixtures (in Scotty IV cylinders) of chlorinated hydrocarbons from Scott Specialty Gases (CA, USA). Identi"cations were based on retention indices of the compounds referenced to n-alkanes that had been established previously using qualitative gaseous standard mixtures prepared in-house from liquid standard mixtures (Supelco (Bellefonte, PA, USA) catalog no. 4-8265, 4-8266, and 4-8267) and pure compounds (PolyScience Kit, PolyScience Corporation, Niles, IL and Aldrich, Milwaukee, WI, USA). Reproducibility, as determined from replicate analyses of standards and samples, was within 10% for compounds at concentrations above 5 ppbC and the lower quanti"able limit was &0.1 ppbC for a 100 ml of sample concentrated. Further, GC-MS was used for identi"cation con"rmation of the compounds that have been identi"ed by the GC-FID, and to determine qualitatively the nature of unknown peaks such as certain siloxanes which only present in some samples.
3. Results and discussion 3.1. General characteristics Table 2 lists the average concentrations of hydrocarbon groups measured on the basis of their chemical
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Table 2 Concentrations of C }C total hydrocarbon groups measured in Ulsan (unit: ppbC) Average$S.D.
Alkanes Alkenes Alkynes Aromatics Naphthenes Oxygenated hydrocarbons Halogenated hydrocarbons C }C Total hydrocarbons
Ulsan downtown site
Ulsan industrial site
95.4$33.9 45.3$19.1 4.0$0.9 65.3$30.0 21.5$7.2 126.5$33.8 6.2$3.3 364.2$114.4
210.7$87.6 131.8$93.4 5.5$0.8 92.2$19.3 31.9$13.7 829.7$1076.7 15.6$3.3 1317.3$1184.5
Table 3 Concentrations of the 20 most abundant species measured in Ulsan and another industrial area (unit: ppb) Downtown site
Industrial site
Yochon industrial site
Component
Avg$S.D.
Component
Avg$S.D.
Component
Avg$S.D.
Methanol/ethanol/acetone HxMCyTSiloxane Ethylene Propane Toluene n-Butane Propylene i-Pentane Acetylene Fluorotrimethyl silane Ethane n-Pentane i-Butane n-Hexane m-Xylene Benzene p-Xylene Methyl tertiary butyl ether o-Xylene 2-Methylpentane
15.7$3.7 7.8$9.7 6.9$4.2 5.0$1.9 3.9$0.5 3.5$1.9 2.1$1.1 2.0$1.0 1.9$0.4 1.7$2.3 1.6$0.6 1.5$0.8 1.4$0.4 1.1$0.4 1.1$0.6 1.1$0.6 1.0$0.6 0.9$0.4 0.9$0.4 0.8$0.3
Methanol/ethanol/acetone Ethylene Propylene Propane n-Butane Ethane n-Pentane Vinylchloride Toluene i-Pentane n-Hexane HxMCyTSiloxane p-Xylene Acetylene i-Butane 3-Methylpentane Benzene Cyclohexane Tetrahydrofuran i-Butylcyclopentane
467.8$533.4 29.1$31.5 11.7$9.5 9.5$3.5 7.7$3.8 5.7$3.2 4.7$3.1 4.0$1.8 3.9$0.9 3.8$2.1 3.5$2.1 3.2$3.1 2.7$1.7 2.7$0.4 2.7$1.2 2.2$1.2 2.1$0.8 1.5$1.5 1.4$1.4 1.4$3.0
Methanol Ethylene Propylene Propane Acetone/ethanol Ethane n/i-Propyl alcohol n-Hexane Vinylchloride n-Butane 1-Butene Acetylene Benzene Toluene 1,3-Butadiene n-Pentane n-Heptane i-Butane i-Pentane o-Xylene
26.1$30.1 23.2$16.2 16.7$10.2 10.5$4.7 9.6$7.1 7.2$3.0 5.7$9.5 3.7$2.5 3.3$4.2 3.1$2.9 2.5$1.9 2.2$0.7 2.1$1.0 2.0$1.0 1.9$2.5 1.8$1.1 1.7$2.0 1.6$0.9 1.4$0.6 1.3$0.9
Sampling period: November 1996}March 1997; Total number of samples: 21; 24 h sampling. Hexamethylcyclotrisiloxane.
structure. In this study, oxygenated hydrocarbons include alcohols, carbonyl compounds, and nitrile. Acrylonitrile was the only nitrile compound in the study. The daily mean concentration of total hydrocarbon at the site I, 1317.3 ppb is about 4 times higher than that of the site D, 364.2 ppbC due to larger emissions in the industrial area than in the downtown area. Oxygenated hydrocarbons at both sites are the most abundant in hydrocarbon classes. The standard deviations of the concentrations of oxygenated hydrocarbons, alkanes, and alkenes are high-
er at the site I than those at the site D, while those of aromatics are higher at the site D. As shown in Table 3, major fractions of alkanes, alkenes, and oxygenated hydrocarbons are C }C hydrocarbons. As will be dis cussed in Section 3.3, major emission sources of these compounds are petrochemical plants in Ulsan. Higher daily variations of their concentrations at the site I than at the site D are probably due to wider variations in emission amounts of these chemicals in the industrial area than in the downtown area.
K. Na et al. / Atmospheric Environment 35 (2001) 2747}2756
The concentrations of the 20 most abundant species based on the identi"ed VOC are shown in Table 3, along with the results of Yochon industrial area. Because oxygenated species were not always fully identi"ed, only quanti"ed species are presented in this table. Yochon has the most outputs of petrochemical products in Korea. The measurements in Yochon were carried out from at the end of November 1996 to March 1997 (Moon et al., 1998). The total number of samples at Yochon is 21 and the samples were collected for 24 h. This site is situated at the boundary of a petrochemical complex like Ulsan industrial site and about 1 km away from petrochemical plants. Therefore, the results of Yochon would be helpful to understand the characteristics of emissions and ambient levels of VOC in Korean industrial areas. Even if both Ulsan and Yochon have petrochemical plants and oil re"nery processes in common, the distribution and ranking of the compounds between two industrial sites are signi"cantly di!erent suggesting di!erent concentration characteristics of their own. For example, at Ulsan industrial site, the concentration of toluene is higher than benzene while the concentration of benzene concentration is comparable to that of toluene at Yochon industrial site. Especially, vinyl chloride, cyclohexane, and tetrahydrofuran (THF), n/i-propyl alcohol, and 1,3butadiene largely associated with petrochemical industries, rank high only at the industrial sites. Thus, these species are characteristic species in industrial ambient air. At the site I, methanol/ethanol/acetone (467.8 ppb) is the most abundant species, followed by ethylene (29.1 ppb), and propylene (11.7 ppb). At the site D, the concentration of methanol/ethanol/acetone (15.7 ppb) is also the highest, followed by hexamethylcyclotrisiloxane (7.8 ppb), ethylene (6.9 ppb), and propane (5.0 ppb). In the case of Yochon industrial area, methanol (26.1 ppb) is the most abundant compound, followed by ethylene (23.2 ppb), and propylene (16.7 ppb). Early in this study, methanol, ethanol, and acetone were not quanti"ed individually and were presented together. However, subsequent results showed that methanol was the main species. For most studies for industrial ambient air (Sexton and Westberg, 1983; Cheng et al., 1997; Mohan Rao et al., 1997), oxygenated compounds were not reported. So, in industrial areas, alkanes have been recognized as the most abundant in hydrocarbon groups. Therefore, the high concentrations of oxygenated hydrocarbons such as methanol, ethanol and acetone are interesting. In Ulsan and Yochon industries, methanol is imported from abroad, and used for making glacial acetic acid and methyl tertiary butyl ether (MTBE). Thus, it is likely that fugitive and evaporative emissions during shipping, transport, and storage are the major sources of methanol in the air. In urban areas, ethylene, propylene and acetylene are mainly emitted from vehicle exhausts (Nelson and
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Quigley, 1984). Especially, acetylene has been used as a tracer for vehicle exhausts due to its low photochemical reactivity. Thus, main source of the three species may be inferred from vehicle exhausts at the site D if the impact from industrial sources is ignored. In Ulsan and Yochon industrial complexes, ethylene is used as a raw material for production of polyethylene, vinyl chloride monomer, ethanol, and acetaldehyde, and propylene is for production of polypropylene, acrylonitrile, and propylene oxide. Acetylene is used for production of vinyl nitric acid, trichloroethylene and arcylic acid. Considering these as well as relatively low tra$c density in Ulsan industrial area compared with Ulsan downtown area, the high concentrations of ethylene, propylene and acetylene at the site I would be rather the emissions from petrochemical plants than vehicle exhausts. Propane is not present in gasoline and is emitted from vehicle exhausts and natural gas (Fujita et al., 1995; Na et al., 1998). In Korea, its major source in the urban area is known to be lique"ed petroleum gas (LPG) used for cooking and heating (Na et al., 1998), and for taxicab fuel. LPG for domestic uses is 100% propane. LPG composition of vehicle fuel depends on the seasons. For example, all taxicabs in Korea use 100% of butane fuel, 60}70 wt% for n-butane and 30}40 wt% for i-butane, during the period of April}November, while mixture gas (butane 70}90 wt%, propane 10}30 wt%) is used as fuel for taxicabs during December}March (Na et al., 1998). Therefore, in this study, high concentration of propane at the site D may be mainly due to LPG emissions from residential and commercial areas. In petrochemical industries, propane, butane, and pentane are mainly released from oil re"nery and petrochemical plants (Aronian et al., 1989; Wadden et al., 1994). Although the population around industrial area is smaller than that in downtown area, the propane concentration at the site I is higher than that at the site D, due to the higher propane emissions from oil re"nery and petrochemical plants. Major sources of butane are known to be the evaporation of gasoline and LPG used as vehicle fuel in the urban areas in Korea (Na et al., 1998). During the period of this study, fugitive emissions during refueling of butane to vehicles may add butanes into the atmosphere. Vehicular LPG and the evaporation of butane may in#uence high concentrations of butane in the downtown ambient air. The concentrations of butane and pentane are higher at the site I than those at the site D. The reason for this may be the emissions from oil re"nery and petrochemical plants. As shown in Table 3, at the site D, concentration of n-butane is higher than that of i-butane, and concentration of i-pentane is higher than that of n-pentane. In case of the two industrial sites, the order of concentration of butanes is similar to the site D, but n-pentane is higher than i-pentane. As urban areas typically show larger value of i-pentane than n-pentane
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(Colbeck and Harrison, 1985; Hansen and Palmgren, 1996; Brocco et al., 1997), higher concentration of npentane compared to i-pentane at the site I may be thought of as a characteristic of the ambient air in Ulsan industrial area. However, the reason for this reversal is unclear. In the present study, two siloxanes such as hexamethylcyclotrisiloxane and #uorotrimethylsilane were found. These species are classi"ed into silyl compounds. Under GC-MS, these compounds were found to contain heteroatoms. These silyl species are all lumped into the oxygenated hydrocarbon group. From our experiences with land"ll gas analysis, it is believed that these are not from analytical artifacts but from land"ll gas. There are two reclaimed lands in the city of Ulsan. Considering this fact, high concentrations of the two-silyl compounds may be attributed to the emissions from the reclaimed lands. 3.2. Concentrations of aromatic and halogenated hydrocarbons Many of the aromatic and halogenated hydrocarbons are harmful to human. Thus, the concentrations of these compounds are important to assess human risk. Table 4 presents the average concentrations of seven aromatic hydrocarbons. The mean concentration of total aromatics is higher at the site I (12.5 ppb) than that at the site D (8.9 ppb). In urban areas, it was reported that the fractions of aromatic hydrocarbons to total non-methane hydrocarbons in ppbC are in the range of 0.2}0.4 (Sexton and Westberg, 1980; Isidorov et al., 1983). In this study, the fraction at the site D (0.2) is a$liated with general urban air but not at the site I (0.1). Toluene is the major species at both sites. The concentration of benzene observed at the site I is approximately twice as high as the site D. There are two possible emission sources of benzene: vehicle exhausts and fugitive emissions from petroleum industries. Benzene is mainly emitted from vehicle exhausts in downtown area Table 4 Concentrations (ppb) of aromatic hydrocarbons measured in Ulsan (unit: ppb) Average$S.D.
Benzene Toluene Ethylbenzene m-Xylene p-Xylene o-Xylene Styrene Sum
Ulsan downtown site
Ulsan industrial site
1.2$0.3 3.9$0.5 0.7$0.3 1.1$0.4 1.0$0.5 0.9$0.4 0.3$0.2 8.9$4.0
2.1$0.8 3.9$0.9 0.9$0.3 1.1$0.4 2.7$1.7 1.1$0.4 0.8$0.4 12.5$2.6
(Derwent et al., 2000). Despite much lower tra$c density, the site I showed higher benzene concentration, most likely due to industrial emissions, as benzene is used as raw material to produce alkylbenzene, carprolactam, and styrene monomer at the petrochemical industries of Ulsan. Note that p-xylene concentration at the site I is the highest among xylenes as well as is higher than that of benzene. p-Xylene is used as raw material for the manufacturing of terephthalic acid at Ulsan petrochemical industries and has the highest commercial value in xylenes. Higher concentration of p-xylene at the site I may be caused by the release from petrochemical plants handling it. The average concentrations of C }C halogenated hy drocarbons measured in Ulsan area are presented in Table 5. The concentration of total halogenated hydrocarbons at the site I (8.3 ppb) is about twice as high as the site D (4.1 ppb). The rankings of halogenated hydrocarbons, however, are di!erent for both sites. At the site I, the concentration of vinyl chloride (4.0 ppb) is the highest, followed by 1,2-dichloroethane (2.1 ppb), and trichloroethylene (0.8 ppb). At the site D, chloroform is the highest (1.1 ppb), followed by 1,2-dichloroethane (0.9 ppb), and methylene chloride (0.8 ppb). The concentrations of tetrachloroethylene (perchloroethylene) and carbon tetrachloride are low with small variations between the two sites. Especially, perchloroethylene mainly emitted from dry cleaning is the below detection limit throughout this study period. It suggests that no major local sources of these species exits at both sites. Vinyl chloride is a hazardous air pollutant and human carcinogen. Its unit risk is known to be the highest among halogenated hydrocarbons (Seiber, 1996). The concentration of it at the site I is approximately 6 times higher than that at the site D. Since vinyl chloride is used in the production of polyvinylchloride (PVC) in petrochemical industries, high concentration of it at the site I may be attributable to emissions from polymer industries. Further, it suggests that air pollutants are transported from the industrial area to downtown one as there are no major emission sources of vinyl chloride in the urban areas. Chloroform is a mutagen and a suspect carcinogen (Singh et al., 1992). Its concentration is much higher at the site D (1.1 ppb) than that at the site I (0.2 ppb). Its concentration at the site D is higher than those measured at Sapporo (0.1 ppb) and Tokyo (0.8 ppb) in Japan (Study periods: 1991}1995), and populated areas of the United States (0.04 ppb) (Kelly et al., 1994; Nakajima and Kondo, 1998). The reason for much higher concentration of chloroform at the site D compared to other urban areas remains uncertain. 1,2-Dichloroethane is a bacterial mutagen and a suspect carcinogen. The concentration measured at the site I
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Table 5 Concentrations of halogenated hydrocarbons measured in Ulsan (unit: ppb) Average $S.D.
Vinyl chloride 1,1-Dichloroethane 1,2-Dichloroethane Methylene chloride Tetrachloroethylene Chloroform 1,1,1-Trichloroethane Carbon tetrachloride Trichloroethylene Sum
Ulsan downtown site
Ulsan industrial site
0.7$0.7 BDL 0.9$0.7 0.8$0.5 BDL 1.1$0.6 0.3$0.1 0.2$0.1 0.2$0.1 4.1$2.1
4.0$1.8 BDL 2.1$1.6 0.6$0.2 BDL 0.2$0.1 0.4$0.1 0.2$0.1 0.8$0.1 8.3$1.8
BDL: Below detection limit.
(2.1 ppb) is much higher than that observed at the site D (0.9 ppb). By comparison, the mean concentrations of 1,2-dichloroethane at seven sites in selected US cities range from 0.1 to 1.5 ppb (Singh et al., 1982). Hence, the concentration at the site D is similar to that of selected US cites, but that at the site I is comparatively high. 3.3. Inyuence of emissions on ambient air of Ulsan To observe the e!ect of fugitive emissions on ambient air of industrial areas, "rst we tried to calculate the fractions of C }C (light hydrocarbon concentrations) and C }C (heavy hydrocarbon concentrations) to total hydrocarbons. Secondly, we compared the percent of alkanes, alkenes, and aromatics to total VOC (sum of alkanes, alkenes, and aromatics) concentrations (ppbC) for Ulsan and Yochon industrial sites, Korea, Edmonton industrial area, Canada (Cheng et al., 1997), Thane indus-
trial area, India, (Mohan Rao et al., 1997), and other urban areas (Moschonas and Glavas, 1996). As illustrated in Fig. 2, in the case of Edmonton industrial site, alkenes include alkenes, alkynes, diene, alicyclic, and halogenated hydrocarbons. The fractions of light hydrocarbon concentrations (56.8, 69.8, and 66.5% at Ulsan D, Ulsan I, and Yochon sites, respectively), in total VOC are higher than those of heavy hydrocarbon concentrations (43.2, 30.2, and 33.5% at Ulsan D, Ulsan I, and Yochon sites, respectively). Higher fractions of light hydrocarbons at the site I compared to the site D may be due to fugitive emissions of light hydrocarbons like ethane, propane, butane, pentane, ethylene, and propylene emitted from storage tank, #are stack, pump, compressor seal, pipeline valves, and #anges, etc. As shown in Fig. 2, there is a di!erence in hydrocarbon compositions among Ulsan sites D and I, and Yochon
Fig. 2. Comparision of fraction of hydrocarbon groups to total hydrocarbons at the downtown and industrial sites (Ulsan: this study; Yochon: Kim et al., 1997; Edmonton: Cheng et al., 1997; Thane: Mohan Rao et al., 1997; Sydney, Hamburg, Chicago, and Osaka: Moschonas and Glavas, 1996).
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site: 45.2, 48.5, and 43.3% for alkanes, 21.5, 30.3, and 41.5% for alkenes, and 33.3, 21.2, and 15.2% for aromatics at the sites D and I, and Yochon site, respectively. Alkanes constitute the highest fraction in the total hydrocarbon among the three sites, but each has a distinct di!erence in concentration rank between aromatics and alkenes. The concentration rank of aromatics is higher than that of alkenes at the site D. In contrast, the order of concentrations between two classes is reverse at the site I. In Fig. 2, Ulsan site D and other urban sites show similar composition patterns with alkanes being the highest, followed by alkenes and aromatics. Thus, the VOC levels in Ulsan site D appear to belong to a typical urban air. Although all of Ulsan, Yochon, Edmonton, and Thane include similar industrial sources such as petrochemical plant and oil re"nery process, Ulsan and Yochon industrial sites show di!erent rank of hydrocarbon compositions compared to Thane and Edmonton industrial sites. In other words, the two industrial sites in Korea have higher fraction of alkenes to total VOC compared to other industrial areas. This suggests that the e!ect of fugitive emissions of light hydrocarbons in Ulsan and Yochon industrial areas might be higher than other industrial areas. Namely, the two industrial ambient air may be more a!ected by leakage than other industrial areas. For reducing the ambient concentrations of total VOC in Ulsan and Yochon industrial area, controlling fugitive emissions may be required. During the two days of 3 and 7 June, higher total VOC concentrations at the site D (413.7 and 454.5 ppbC, respectively), were observed compared with those of the other days. For the two days, the frequencies of wind direction from the industrial areas were 52 and 65%, respectively. On 4, 5, and 6 June (376.4, 377.8, and
167.3 ppbC, respectively), the frequencies of wind direction from the site I were 25, 29, and 10%, respectively. Comparatively, lower concentrations were observed during these 3 days. It shows that ambient concentrations of VOC at the site D may be a!ected by industrial emissions. To determine the additional in#uence of industrial emissions on ambient air of the site D, the concentration ratios of ethylene to total C }C hydrocarbons (ethane, ethylene, acetylene, propane, n/i-butane, n/i-pentane) are estimated are shown in Fig. 3 along with other urban areas (Hester and Harrison, 1995; Moschonas and Glavas, 1996; Morikawa et al., 1998). As shown in this "gure, the fraction of Ulsan site D (26.6%) is higher than any other urban area ranging from 10.4 to 19.5%. As mentioned earlier, in an urban setting, ethylene is the major components of vehicle exhausts. Hence, it can be thought that its concentration depends upon the number of vehicles. Seoul, the capital of Korea, has about 40 times more vehicles than in Ulsan downtown area in comparable area. However, it is noted that the ethylene concentration (6.9 ppb) at Ulsan site D is higher than that measured at Seoul (4.0 ppb). Higher concentration of ethylene in Ulsan industrial area (29.1 ppb) may a!ect higher fraction of ethylene in C }C hydrocarbons in Ulsan downtown atmosphere compared to other urban area.
4. Summary Ambient concentrations of C }C volatile organic compounds were quanti"ed. At Ulsan industrial site, the concentrations of total VOC were about 4 times higher
Fig. 3. Comparison of the concentration compositions of ethylene on total C }C at Ulsan industrial and downtown sites, and other urbans (Ulsan: this study; Chicago and Sydney: Moschonas and Glavas, 1996; London: Hester and Harrison, 1995; Osaka: Morikawa et al., 1998; Copenhagen: Hansen and Palmgren, 1996).
K. Na et al. / Atmospheric Environment 35 (2001) 2747}2756
than those at the downtown site. Oxygenated hydrocarbons had the highest concentration of seven hydrocarbon groups. The distribution and ranking of the major compounds between the two sites were signi"cantly di!erent suggesting di!erent emission characteristics of the two sites. At the downtown site, the concentrations of species closely related to vehicle exhausts (ethylene, propylene and acetylene) and evaporative emissions (butanes and pentanes) were high, whereas the concentrations of ethylene, propylene, vinyl chloride, cyclohexane and tetrahydrofuran largely associated with petrochemical industries were high at the industrial site. Relatively, high portion of C }C light hydrocarbon in Ulsan industrial area was observed compared to other industrial areas. It suggests that the e!ect of fugitive emissions of the light hydrocarbons in Ulsan industrial area might be higher than that of the other industrial areas. For reducing the ambient VOC in Ulsan industrial area, controlling fugitive emissions may be required. From the results of the higher concentration of vinyl chloride and higher fraction of ethylene in C }C hydro carbons compared to other urban area, it is identi"ed that industrial emissions of VOC a!ect on the downtown ambient air by transport.
Acknowledgements This work was supported by the Ministry of Environment, Korea and Korea Institute of Science and Technology.
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Modeling and Measurement Studies: a Perspective through San Joaquin Valley Air Quality Study and AUSPEX. Air and Waste Management Association, Pittsburg, PA. Fujita, E.M., Watson, J.G., Chow, J.C., Magliano, K.L., 1995. Receptor model and emissions inventory source apportionments of nonmethane organic gases in California's San Joaquin Valley and San Francisco Bay area. Atmospheric Environment 29, 3019}3035. Ghim, Y.S., Song, C.H., Shim, S.G., Kim, Y.P., Moon, K.C., 1998. Comparative study of volatile organic compound concentrations in the Yochon industrial estate during spring and fall. Journal of Korean Air Pollution Research Association 14, 153}160. Grosjean, D., Fung, K., 1984. Hydrocarbons and carbonyls in Los Angeles air. Journal of Air Pollution Control Association 34, 537}543. Hansen, A.B., Palmgren, F., 1996. VOC air pollutants in Copenhagen. The Science of the Total Environment 189/190, 451}457. Hester, R.E., Harrison, R.M., 1995. Volatile Organic Compounds in the Atmosphere. The Royal Society of Chemistry, Milton Road, Cambridge, pp. 46}47. Isidorov, V.A., Zenkevich, J.G., Scotte, B.V., 1983. Volatile organic compounds in the atmosphere of forests. Atmospheric Environment 17, 1347}1353. Jayanty, R.K.M., 1989. Evaluation of sampling and analytical methods for monitoring toxic organics in air. Atmospheric Environment 23, 777}782. Kelly, T.J., Mukund, R., Spicer, C.W., Pollack, A.J., 1994. Concentrations and transformations of hazardous air pollutants. Environmental Science and Technology 28, 378A}387A. Kim, Y.P., Lee, J.H., Jin, H.C., Moon, K.C., 1997. Concentrations of particulate and gaseous ionic and organic species in the ambient air of the Yochon industrial estate. Journal of Korean Air Pollution Research Association 13, 269}284. Mohan Rao, A.M., Pandit, G.G., Sain, S., Sharma, S., Krishnamoorthy, T.M., Nambi, K.S.V., 1997. Non-methane hydrocarbons in industrial locations of Bombay. Atmospheric Environment 31, 1077}1085. Moon, K.C., Kim, Y.P., Shim, S.G., Ghim, Y.S., Kim, J.S., Kim, J.Y., 1998. Air quality study for the Yochon industrial estate. Proceedings of 91th Annual Meeting of AWMA, San Diego, USA, Paper C98-TP44.06. Morikawa, T., Wakamatsu, S., Tanka, M., Uno, I., Kamiura, T., Maeda, T., 1998. C }C Hydrocarbon concentrations in central Osaka. Atmospheric Environment 32, 2007}2016. Moschonas, N., Glavas, S., 1996. C }C Hydrocarbons in the atmosphere of Athens, Greece. Atmospheric Environment 30, 2769}2772. Na, K., Kim, Y.P., Ghim, Y.S., 1998. Concentrations of C }C volatile organic compounds in ambient air in Seoul. Journal of Korean Air Pollution Research Association 14, 95}105. Nakajima, T., Kondo, H., 1998. Concentrations of chlorinated hydrocarbons in urban atmosphere. Journal of Japan Society Air Pollution 33, 42}49. Nelson, P.F., Quigley, S.M., 1984. The hydrocarbons composition of exhaust emitted from gasoline fueled vehicles. Atmospheric Environment 18, 2769}2772. Seiber, J.M., 1996. Toxic air contaminants in urban atmospheres: experience in California. Atmospheric Environment 30, 751}756.
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Sexton, K., Westberg, H., 1980. Ambient hydrocarbon and ozone measurements downwind of a large automotive painting plant. Environmental Science and Technology 14, 329}332. Sexton, K., Westberg, H., 1983. Photochemical ozone formation from petroleum re"nery emissions. Atmospheric Environment 17, 467}475. Singh, H.B., Salas, L.J., Stiles, R.E., 1982. Measurements of selected light hydrocarbons over the Paci"c Ocean: latitudinal and seasonal variations. Environmental Science and Technology 16, 872}880. Singh, H.B., Salas, L., Viezee, W., Sitton, B., Fepek, R., 1992. Measurement of volatile organic chemicals at selected sites in California. Atmospheric. Environment 26A, 2929}2946.
Ulsan Metropolitan City, 1998. Statistical Yearbook of Ulsan, Korea. US EPA, 1988. Method TO14: determination of volatile organic compounds (VOCs) in ambient air using SUMMA passivated canister sampling and gas chromatographic analysis. In Compendium of Methods for the Determination of Toxic Organic ompounds in Ambient Air. EPA/600/4-89/017, O$ce of Research and Development, Research Triangle Park, NC, USA. Wadden, R.A., Sche!, P.A., Uno, I., 1994. Receptor modeling of VOCs-ll. Development of VOC control functions for ambient ozone. Atmospheric Environment 28, 2507}2521.
Concentrations of volatile organic compounds in an industrial area of Korea Kwangsam Na , Yong Pyo Kim *, Kil-Choo Moon , Il Moon, Kochy Fung Global Environmental Research Center, Korea Institute of Science and Technology, P.O. Box 131, Cheongryang, Seoul 130-650, South Korea Department of Chemical Engineering, Yonsei University, Seodaemun-Ku, Shinchon-Dong 134 Seoul 120-749, South Korea Atm AA Inc. 23917 Craftsman Rd. Calabasas, CA 91302, USA Received 17 February 2000; accepted 8 June 2000
Abstract We measured and analyzed daily mean concentrations of volatile organic compounds (VOC) at Ulsan industrial and downtown sites from 3 to 8 June 1997. The industrial site is situated at the boundary of a petrochemical complex and the other is at downtown area in Ulsan. At each site, we collected ambient air samples in passivated stainless-steel containers by using constant #ow samplers and analyzed them by a GC-FID. At Ulsan industrial site, the concentrations and their daily variations of total VOC were higher than those at the downtown site. The concentrations of oxygenated hydrocarbons were the highest among seven hydrocarbon groups at both sites. The fraction of C }C light hydrocarbon concentrations to C }C hydrocarbons at Ulsan industrial site was higher than that in other industrial areas. It suggests that fugitive emissions of light hydrocarbons in Ulsan industrial areas might be higher than those of other industrial areas. Under favorable wind conditions, the in#uence of industrial emissions of VOC on the downtown hydrocarbon levels was observed. 2001 Elsevier Science Ltd. All rights reserved. Keywords: City of Ulsan; Emission sources; Hazardous organics; Fugitive emissions
1. Introduction During the last three decades, Korea has been industrialized rapidly and the side e!ect resulted in air quality problems in industrial areas, especially, in petrochemical industries. People in these areas began to concern seriously about the detrimental health e!ects by exposing to volatile organic compounds (VOC). Especially, public grievance becomes higher during summertime due to unpleasant odors. Korea has two large petrochemical complexes in Ulsan and Yochon. The two industrial areas have both petrochemical plants and oil-producing processes. There were a few studies on quantifying VOC concentrations in Yochon (Kim et al., 1997; Ghim et al., 1998), but VOC levels in Ulsan have not been quanti"ed yet.
* Corresponding author. Tel.: #82-2958-5816; fax: #822958-5805 E-mail address: [email protected] (Y.P. Kim).
Ulsan (35336 N and 129318 E) is located at the southeastern coastal part of Korea (Fig. 1). This area has a temperate climate. Since an oil re"nery was established in the mid 1960s, the city has become one of the largest industrial areas in Korea with 700 small and large plants such as petrochemical plant, oil re"nery processes, and other chemical plants. Among them, 400 business enterprises were designated as plants related to air pollutant emissions. At present, approximately 810,000 barrels of crude oil per day is processed in the oil re"nery. Also, Ulsan is the seventh largest city in Korea with population of about one million and an area of 1,055 km. Across the city, the Tae-Hwa River runs, and there are a few major ports in Ulsan Bay such as Ulsan port, On San port, and Banojin port. The amount of oil consumed by residents in the city of Ulsan in 1997 was about 910,000 kl. The number of vehicles in the city is in excess of 240,000, 78.9% being passenger vehicles, 15.2% trucks and 5.4% buses (Ulsan Metropolitan City, 1998). Thus, it is expected that the ambient VOC concentrations in
1352-2310/01/$ - see front matter 2001 Elsevier Science Ltd. All rights reserved. PII: S 1 3 5 2 - 2 3 1 0 ( 0 0 ) 0 0 3 1 3 - 7
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Fig. 1. Map of location of the measurement sites in the city of Ulsan (D: downtown site; I: industrial site; P: petrochemical complex).
urban areas are a!ected by emissions from both petrochemical industries and urban activities. Korea Institute of Science and Technology (KIST) carried out an intensive "eld measurement study in June 1997 of "ne particles and VOC at two sites in Ulsan, one at downtown area and the other at industrial area. In the present study, "ve samples were obtained at each site. Since the sample number is not large, it is di$cult to make a meaningful statistical analysis. Therefore, it would be better to think of the results of VOC measurement as not representative values but rather episodic values during the study period. It warrants further studies in industrial areas in Korea. This paper describes the results of VOC measurements in Ulsan downtown and industrial areas and discusses the e!ects of industrial emissions on the downtown Ulsan area. 2. Experimental 2.1. Sampling VOC measurements were carried out at two locations as shown in Fig. 1. One is in the downtown area of Ulsan
(denoted as site D) and is approximately 200 m from a four-lane road and 5.5 km from the petrochemical complex. The sampling site D (about 18 m above the ground level) is on the top of a four-storey building at Hamwall Elementary School surrounded by residential and commercial areas. The other site is in the industrial area (denoted as site I) located at the northern boundary of the petrochemical complex. The distance between the two sites is about 5 km. The site I (about 9 m above the ground level) is on the top of a two-storey building at Seonam Elementary School about 0.5 km away from petrochemical plants, showing that this site is well characterized as a petrochemical industrial part of Ulsan. When wind from south is dominant, impacts of industrial emissions on the site D are expected. The sampling period was between 3 and 15 June 1997. Fine particles were collected for ion analysis and ambient air samples were collected for VOC analysis. The measurements of VOC were conducted between 3 and 8 June . Twenty-four hour averaged VOC concentrations were measured during the study period to observe the general feature of the VOC levels at the two sites. In this paper, only VOC data are presented and discussed. Integrated particle-free ambient air samples were collected in 6 l SUMMA canisters. The canisters were cleaned and evacuated by Atm AA (Calabasa, CA, USA). The initial vacuum pressure was 1.3;10\}1.3; 10\ atm (10\}10\ Torr). Flow rate of sample was controlled by a #ow controller to constant #ow of 10}15 ml min\ for 24-h sampling. To prevent accumulation of water and other contaminants, the sampler was operated prior to the sampling without attaching the can to allow purging all lines in sampler with clean particlefree dry air. The sampling equipment and procedure were conformed to US EPA TO-14 (US EPA, 1988). Table 1 summarizes meteorological conditions during the sampling period measured at the Meteorological Administration in Ulsan, apart from about 300 m of the site D. 2.2. Analysis Samples were shipped by air to Atm AA for analysis within 3 weeks of sampling. Jayanty (1989) has shown that selected organics in a stainless-steel canister revealed that most VOC were stable over a 2-week period. A subsequent study in preparation for a large-scale "eld study also demonstrated that ambient VOC are stable over a 1-month period when stored in passivated canisters (Fung et al., 1994). Hence, a 3-week delay between sampling and analysis will not lead to a serious change in VOC concentration. Samples were analyzed by using a high-resolution gas chromatography (GC) after cryogenic sample concentration as described previously (Grosjean and Fung, 1984). In brief, an aliquot of a canister air was metered into a trap immersed in liquid argon to concentrate the
K. Na et al. / Atmospheric Environment 35 (2001) 2747}2756
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Table 1 Daily mean meteorological data during the measurement period of June 1997 in Ulsan Date
Temperature (3C)
Relative humidity (%)
Wind speed (m s\)
3 4 5 6 7 8
18.8 19.0 17.9 18.0 18.6 18.9
72 77 85 84 82 81
4.3 4.2 3.2 6.0 4.4 3.9
Most frequent wind direction (%) SE (17)
SE (21)
ESE (17)
SSW (13) NW (34) NNW (26) E (28) SW (17) ENE (20)
Precipitations (mm) WNW (13) NNE (13) N (21) NW (19) NW (17) WNW (15)
* * * 11.8 * *
No precipitation.
hydrocarbons. The volume concentrated was in the range of 100}150 ml and was determined from the pressure changes of a 3 l #ask at controlled temperature caused by the air that passed through the trap into the #ask. The concentrated sample was revolatilized by heating the trap with hot water (&903C) and injected into a Hewlett-Packard 5890 Series II GC equipped with a #ame ionization detector (FID) and a 50 m long; 0.2 mm I.D. Ultra 1 methyl silicone column (HewlettPackard, USA). The detector signal was processed by a Shimadzu Class-VP Chromatography Data System (Shimadzu, Columbia, MD, USA). With subambient temperature programming, complete separation of the C hydrocarbons was achieved, negating the necessity of separate analyses for the light and heavy hydrocarbons. The analytical conditions were as follows: initial column temperature !553C held for 3 min followed by programming at 153C min\ to 403C and at 43C min\ to 1503C and held isothermal at 1503C for 15 min and at 253C min\ to a "nal temperature of 1953C. Carrier was H (2.1 kg cm\) and make-up gas was N (30 ml min\). Halocarbons were analyzed isothermally at 703C using two-dimensional capillary GC with electron capture detection (ECD). Strong electron capture sensitivity of GC-ECD allows these compounds to be measured without interference from the hydrocarbons despite their low ambient concentrations in many cases. A HewlettPackard 5710A GC was equipped with a 10-port and a 4-port valve (Valco, Austin, TX, USA) for sample loop injection, column switching and back#ush, and a Shimadzu CR501A Data Processor. One milliliter of air in the gas loop was injected into a pre-column (30 m long;0.53 mm I.D. DB-1, J&W Scienti"c, Folsom, CA, USA), which is served to isolate the fraction of the sample that contained the target compounds. With the 4-port valve, the unwanted fractions were vented and the desirable fraction was transferred to the analytical column (30 m long;0.32 mm I.D. DB-624, J&W Scienti"c, Folsom, CA, USA) for further separation and detection by the ECD. A splitter was used to transfer a fraction of the e%uent from the pre-column to the analytical col-
umn. Calibration standards from reputable manufacturers (Custom Blend, Scott-Marin Inc., Riverside, CA and Scotty IV Analyzed Gases, Scot Specialty Gases, San Bernadeno, CA, USA) were used to establish the retention times and detector responses of the ECD each time. The method had a lower quanti"able limit of &0.1 ppb for a 1 ml sample injection. The FID was calibrated each time with a National Institute of Standards and Technology, USA (NIST). 9.4 ppm propane standard (SRM 1666B) and all hydrocarbon concentrations were measured in reference to the SRM response. Multilevel calibration was obtained from di!erent dilutions of this standard. Occasionally, SRM 1811 was also used without dilution as a check for benzene and toluene. The GC-ECD was calibrated at 3 levels with standard mixtures (in Scotty IV cylinders) of chlorinated hydrocarbons from Scott Specialty Gases (CA, USA). Identi"cations were based on retention indices of the compounds referenced to n-alkanes that had been established previously using qualitative gaseous standard mixtures prepared in-house from liquid standard mixtures (Supelco (Bellefonte, PA, USA) catalog no. 4-8265, 4-8266, and 4-8267) and pure compounds (PolyScience Kit, PolyScience Corporation, Niles, IL and Aldrich, Milwaukee, WI, USA). Reproducibility, as determined from replicate analyses of standards and samples, was within 10% for compounds at concentrations above 5 ppbC and the lower quanti"able limit was &0.1 ppbC for a 100 ml of sample concentrated. Further, GC-MS was used for identi"cation con"rmation of the compounds that have been identi"ed by the GC-FID, and to determine qualitatively the nature of unknown peaks such as certain siloxanes which only present in some samples.
3. Results and discussion 3.1. General characteristics Table 2 lists the average concentrations of hydrocarbon groups measured on the basis of their chemical
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Table 2 Concentrations of C }C total hydrocarbon groups measured in Ulsan (unit: ppbC) Average$S.D.
Alkanes Alkenes Alkynes Aromatics Naphthenes Oxygenated hydrocarbons Halogenated hydrocarbons C }C Total hydrocarbons
Ulsan downtown site
Ulsan industrial site
95.4$33.9 45.3$19.1 4.0$0.9 65.3$30.0 21.5$7.2 126.5$33.8 6.2$3.3 364.2$114.4
210.7$87.6 131.8$93.4 5.5$0.8 92.2$19.3 31.9$13.7 829.7$1076.7 15.6$3.3 1317.3$1184.5
Table 3 Concentrations of the 20 most abundant species measured in Ulsan and another industrial area (unit: ppb) Downtown site
Industrial site
Yochon industrial site
Component
Avg$S.D.
Component
Avg$S.D.
Component
Avg$S.D.
Methanol/ethanol/acetone HxMCyTSiloxane Ethylene Propane Toluene n-Butane Propylene i-Pentane Acetylene Fluorotrimethyl silane Ethane n-Pentane i-Butane n-Hexane m-Xylene Benzene p-Xylene Methyl tertiary butyl ether o-Xylene 2-Methylpentane
15.7$3.7 7.8$9.7 6.9$4.2 5.0$1.9 3.9$0.5 3.5$1.9 2.1$1.1 2.0$1.0 1.9$0.4 1.7$2.3 1.6$0.6 1.5$0.8 1.4$0.4 1.1$0.4 1.1$0.6 1.1$0.6 1.0$0.6 0.9$0.4 0.9$0.4 0.8$0.3
Methanol/ethanol/acetone Ethylene Propylene Propane n-Butane Ethane n-Pentane Vinylchloride Toluene i-Pentane n-Hexane HxMCyTSiloxane p-Xylene Acetylene i-Butane 3-Methylpentane Benzene Cyclohexane Tetrahydrofuran i-Butylcyclopentane
467.8$533.4 29.1$31.5 11.7$9.5 9.5$3.5 7.7$3.8 5.7$3.2 4.7$3.1 4.0$1.8 3.9$0.9 3.8$2.1 3.5$2.1 3.2$3.1 2.7$1.7 2.7$0.4 2.7$1.2 2.2$1.2 2.1$0.8 1.5$1.5 1.4$1.4 1.4$3.0
Methanol Ethylene Propylene Propane Acetone/ethanol Ethane n/i-Propyl alcohol n-Hexane Vinylchloride n-Butane 1-Butene Acetylene Benzene Toluene 1,3-Butadiene n-Pentane n-Heptane i-Butane i-Pentane o-Xylene
26.1$30.1 23.2$16.2 16.7$10.2 10.5$4.7 9.6$7.1 7.2$3.0 5.7$9.5 3.7$2.5 3.3$4.2 3.1$2.9 2.5$1.9 2.2$0.7 2.1$1.0 2.0$1.0 1.9$2.5 1.8$1.1 1.7$2.0 1.6$0.9 1.4$0.6 1.3$0.9
Sampling period: November 1996}March 1997; Total number of samples: 21; 24 h sampling. Hexamethylcyclotrisiloxane.
structure. In this study, oxygenated hydrocarbons include alcohols, carbonyl compounds, and nitrile. Acrylonitrile was the only nitrile compound in the study. The daily mean concentration of total hydrocarbon at the site I, 1317.3 ppb is about 4 times higher than that of the site D, 364.2 ppbC due to larger emissions in the industrial area than in the downtown area. Oxygenated hydrocarbons at both sites are the most abundant in hydrocarbon classes. The standard deviations of the concentrations of oxygenated hydrocarbons, alkanes, and alkenes are high-
er at the site I than those at the site D, while those of aromatics are higher at the site D. As shown in Table 3, major fractions of alkanes, alkenes, and oxygenated hydrocarbons are C }C hydrocarbons. As will be dis cussed in Section 3.3, major emission sources of these compounds are petrochemical plants in Ulsan. Higher daily variations of their concentrations at the site I than at the site D are probably due to wider variations in emission amounts of these chemicals in the industrial area than in the downtown area.
K. Na et al. / Atmospheric Environment 35 (2001) 2747}2756
The concentrations of the 20 most abundant species based on the identi"ed VOC are shown in Table 3, along with the results of Yochon industrial area. Because oxygenated species were not always fully identi"ed, only quanti"ed species are presented in this table. Yochon has the most outputs of petrochemical products in Korea. The measurements in Yochon were carried out from at the end of November 1996 to March 1997 (Moon et al., 1998). The total number of samples at Yochon is 21 and the samples were collected for 24 h. This site is situated at the boundary of a petrochemical complex like Ulsan industrial site and about 1 km away from petrochemical plants. Therefore, the results of Yochon would be helpful to understand the characteristics of emissions and ambient levels of VOC in Korean industrial areas. Even if both Ulsan and Yochon have petrochemical plants and oil re"nery processes in common, the distribution and ranking of the compounds between two industrial sites are signi"cantly di!erent suggesting di!erent concentration characteristics of their own. For example, at Ulsan industrial site, the concentration of toluene is higher than benzene while the concentration of benzene concentration is comparable to that of toluene at Yochon industrial site. Especially, vinyl chloride, cyclohexane, and tetrahydrofuran (THF), n/i-propyl alcohol, and 1,3butadiene largely associated with petrochemical industries, rank high only at the industrial sites. Thus, these species are characteristic species in industrial ambient air. At the site I, methanol/ethanol/acetone (467.8 ppb) is the most abundant species, followed by ethylene (29.1 ppb), and propylene (11.7 ppb). At the site D, the concentration of methanol/ethanol/acetone (15.7 ppb) is also the highest, followed by hexamethylcyclotrisiloxane (7.8 ppb), ethylene (6.9 ppb), and propane (5.0 ppb). In the case of Yochon industrial area, methanol (26.1 ppb) is the most abundant compound, followed by ethylene (23.2 ppb), and propylene (16.7 ppb). Early in this study, methanol, ethanol, and acetone were not quanti"ed individually and were presented together. However, subsequent results showed that methanol was the main species. For most studies for industrial ambient air (Sexton and Westberg, 1983; Cheng et al., 1997; Mohan Rao et al., 1997), oxygenated compounds were not reported. So, in industrial areas, alkanes have been recognized as the most abundant in hydrocarbon groups. Therefore, the high concentrations of oxygenated hydrocarbons such as methanol, ethanol and acetone are interesting. In Ulsan and Yochon industries, methanol is imported from abroad, and used for making glacial acetic acid and methyl tertiary butyl ether (MTBE). Thus, it is likely that fugitive and evaporative emissions during shipping, transport, and storage are the major sources of methanol in the air. In urban areas, ethylene, propylene and acetylene are mainly emitted from vehicle exhausts (Nelson and
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Quigley, 1984). Especially, acetylene has been used as a tracer for vehicle exhausts due to its low photochemical reactivity. Thus, main source of the three species may be inferred from vehicle exhausts at the site D if the impact from industrial sources is ignored. In Ulsan and Yochon industrial complexes, ethylene is used as a raw material for production of polyethylene, vinyl chloride monomer, ethanol, and acetaldehyde, and propylene is for production of polypropylene, acrylonitrile, and propylene oxide. Acetylene is used for production of vinyl nitric acid, trichloroethylene and arcylic acid. Considering these as well as relatively low tra$c density in Ulsan industrial area compared with Ulsan downtown area, the high concentrations of ethylene, propylene and acetylene at the site I would be rather the emissions from petrochemical plants than vehicle exhausts. Propane is not present in gasoline and is emitted from vehicle exhausts and natural gas (Fujita et al., 1995; Na et al., 1998). In Korea, its major source in the urban area is known to be lique"ed petroleum gas (LPG) used for cooking and heating (Na et al., 1998), and for taxicab fuel. LPG for domestic uses is 100% propane. LPG composition of vehicle fuel depends on the seasons. For example, all taxicabs in Korea use 100% of butane fuel, 60}70 wt% for n-butane and 30}40 wt% for i-butane, during the period of April}November, while mixture gas (butane 70}90 wt%, propane 10}30 wt%) is used as fuel for taxicabs during December}March (Na et al., 1998). Therefore, in this study, high concentration of propane at the site D may be mainly due to LPG emissions from residential and commercial areas. In petrochemical industries, propane, butane, and pentane are mainly released from oil re"nery and petrochemical plants (Aronian et al., 1989; Wadden et al., 1994). Although the population around industrial area is smaller than that in downtown area, the propane concentration at the site I is higher than that at the site D, due to the higher propane emissions from oil re"nery and petrochemical plants. Major sources of butane are known to be the evaporation of gasoline and LPG used as vehicle fuel in the urban areas in Korea (Na et al., 1998). During the period of this study, fugitive emissions during refueling of butane to vehicles may add butanes into the atmosphere. Vehicular LPG and the evaporation of butane may in#uence high concentrations of butane in the downtown ambient air. The concentrations of butane and pentane are higher at the site I than those at the site D. The reason for this may be the emissions from oil re"nery and petrochemical plants. As shown in Table 3, at the site D, concentration of n-butane is higher than that of i-butane, and concentration of i-pentane is higher than that of n-pentane. In case of the two industrial sites, the order of concentration of butanes is similar to the site D, but n-pentane is higher than i-pentane. As urban areas typically show larger value of i-pentane than n-pentane
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(Colbeck and Harrison, 1985; Hansen and Palmgren, 1996; Brocco et al., 1997), higher concentration of npentane compared to i-pentane at the site I may be thought of as a characteristic of the ambient air in Ulsan industrial area. However, the reason for this reversal is unclear. In the present study, two siloxanes such as hexamethylcyclotrisiloxane and #uorotrimethylsilane were found. These species are classi"ed into silyl compounds. Under GC-MS, these compounds were found to contain heteroatoms. These silyl species are all lumped into the oxygenated hydrocarbon group. From our experiences with land"ll gas analysis, it is believed that these are not from analytical artifacts but from land"ll gas. There are two reclaimed lands in the city of Ulsan. Considering this fact, high concentrations of the two-silyl compounds may be attributed to the emissions from the reclaimed lands. 3.2. Concentrations of aromatic and halogenated hydrocarbons Many of the aromatic and halogenated hydrocarbons are harmful to human. Thus, the concentrations of these compounds are important to assess human risk. Table 4 presents the average concentrations of seven aromatic hydrocarbons. The mean concentration of total aromatics is higher at the site I (12.5 ppb) than that at the site D (8.9 ppb). In urban areas, it was reported that the fractions of aromatic hydrocarbons to total non-methane hydrocarbons in ppbC are in the range of 0.2}0.4 (Sexton and Westberg, 1980; Isidorov et al., 1983). In this study, the fraction at the site D (0.2) is a$liated with general urban air but not at the site I (0.1). Toluene is the major species at both sites. The concentration of benzene observed at the site I is approximately twice as high as the site D. There are two possible emission sources of benzene: vehicle exhausts and fugitive emissions from petroleum industries. Benzene is mainly emitted from vehicle exhausts in downtown area Table 4 Concentrations (ppb) of aromatic hydrocarbons measured in Ulsan (unit: ppb) Average$S.D.
Benzene Toluene Ethylbenzene m-Xylene p-Xylene o-Xylene Styrene Sum
Ulsan downtown site
Ulsan industrial site
1.2$0.3 3.9$0.5 0.7$0.3 1.1$0.4 1.0$0.5 0.9$0.4 0.3$0.2 8.9$4.0
2.1$0.8 3.9$0.9 0.9$0.3 1.1$0.4 2.7$1.7 1.1$0.4 0.8$0.4 12.5$2.6
(Derwent et al., 2000). Despite much lower tra$c density, the site I showed higher benzene concentration, most likely due to industrial emissions, as benzene is used as raw material to produce alkylbenzene, carprolactam, and styrene monomer at the petrochemical industries of Ulsan. Note that p-xylene concentration at the site I is the highest among xylenes as well as is higher than that of benzene. p-Xylene is used as raw material for the manufacturing of terephthalic acid at Ulsan petrochemical industries and has the highest commercial value in xylenes. Higher concentration of p-xylene at the site I may be caused by the release from petrochemical plants handling it. The average concentrations of C }C halogenated hy drocarbons measured in Ulsan area are presented in Table 5. The concentration of total halogenated hydrocarbons at the site I (8.3 ppb) is about twice as high as the site D (4.1 ppb). The rankings of halogenated hydrocarbons, however, are di!erent for both sites. At the site I, the concentration of vinyl chloride (4.0 ppb) is the highest, followed by 1,2-dichloroethane (2.1 ppb), and trichloroethylene (0.8 ppb). At the site D, chloroform is the highest (1.1 ppb), followed by 1,2-dichloroethane (0.9 ppb), and methylene chloride (0.8 ppb). The concentrations of tetrachloroethylene (perchloroethylene) and carbon tetrachloride are low with small variations between the two sites. Especially, perchloroethylene mainly emitted from dry cleaning is the below detection limit throughout this study period. It suggests that no major local sources of these species exits at both sites. Vinyl chloride is a hazardous air pollutant and human carcinogen. Its unit risk is known to be the highest among halogenated hydrocarbons (Seiber, 1996). The concentration of it at the site I is approximately 6 times higher than that at the site D. Since vinyl chloride is used in the production of polyvinylchloride (PVC) in petrochemical industries, high concentration of it at the site I may be attributable to emissions from polymer industries. Further, it suggests that air pollutants are transported from the industrial area to downtown one as there are no major emission sources of vinyl chloride in the urban areas. Chloroform is a mutagen and a suspect carcinogen (Singh et al., 1992). Its concentration is much higher at the site D (1.1 ppb) than that at the site I (0.2 ppb). Its concentration at the site D is higher than those measured at Sapporo (0.1 ppb) and Tokyo (0.8 ppb) in Japan (Study periods: 1991}1995), and populated areas of the United States (0.04 ppb) (Kelly et al., 1994; Nakajima and Kondo, 1998). The reason for much higher concentration of chloroform at the site D compared to other urban areas remains uncertain. 1,2-Dichloroethane is a bacterial mutagen and a suspect carcinogen. The concentration measured at the site I
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Table 5 Concentrations of halogenated hydrocarbons measured in Ulsan (unit: ppb) Average $S.D.
Vinyl chloride 1,1-Dichloroethane 1,2-Dichloroethane Methylene chloride Tetrachloroethylene Chloroform 1,1,1-Trichloroethane Carbon tetrachloride Trichloroethylene Sum
Ulsan downtown site
Ulsan industrial site
0.7$0.7 BDL 0.9$0.7 0.8$0.5 BDL 1.1$0.6 0.3$0.1 0.2$0.1 0.2$0.1 4.1$2.1
4.0$1.8 BDL 2.1$1.6 0.6$0.2 BDL 0.2$0.1 0.4$0.1 0.2$0.1 0.8$0.1 8.3$1.8
BDL: Below detection limit.
(2.1 ppb) is much higher than that observed at the site D (0.9 ppb). By comparison, the mean concentrations of 1,2-dichloroethane at seven sites in selected US cities range from 0.1 to 1.5 ppb (Singh et al., 1982). Hence, the concentration at the site D is similar to that of selected US cites, but that at the site I is comparatively high. 3.3. Inyuence of emissions on ambient air of Ulsan To observe the e!ect of fugitive emissions on ambient air of industrial areas, "rst we tried to calculate the fractions of C }C (light hydrocarbon concentrations) and C }C (heavy hydrocarbon concentrations) to total hydrocarbons. Secondly, we compared the percent of alkanes, alkenes, and aromatics to total VOC (sum of alkanes, alkenes, and aromatics) concentrations (ppbC) for Ulsan and Yochon industrial sites, Korea, Edmonton industrial area, Canada (Cheng et al., 1997), Thane indus-
trial area, India, (Mohan Rao et al., 1997), and other urban areas (Moschonas and Glavas, 1996). As illustrated in Fig. 2, in the case of Edmonton industrial site, alkenes include alkenes, alkynes, diene, alicyclic, and halogenated hydrocarbons. The fractions of light hydrocarbon concentrations (56.8, 69.8, and 66.5% at Ulsan D, Ulsan I, and Yochon sites, respectively), in total VOC are higher than those of heavy hydrocarbon concentrations (43.2, 30.2, and 33.5% at Ulsan D, Ulsan I, and Yochon sites, respectively). Higher fractions of light hydrocarbons at the site I compared to the site D may be due to fugitive emissions of light hydrocarbons like ethane, propane, butane, pentane, ethylene, and propylene emitted from storage tank, #are stack, pump, compressor seal, pipeline valves, and #anges, etc. As shown in Fig. 2, there is a di!erence in hydrocarbon compositions among Ulsan sites D and I, and Yochon
Fig. 2. Comparision of fraction of hydrocarbon groups to total hydrocarbons at the downtown and industrial sites (Ulsan: this study; Yochon: Kim et al., 1997; Edmonton: Cheng et al., 1997; Thane: Mohan Rao et al., 1997; Sydney, Hamburg, Chicago, and Osaka: Moschonas and Glavas, 1996).
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site: 45.2, 48.5, and 43.3% for alkanes, 21.5, 30.3, and 41.5% for alkenes, and 33.3, 21.2, and 15.2% for aromatics at the sites D and I, and Yochon site, respectively. Alkanes constitute the highest fraction in the total hydrocarbon among the three sites, but each has a distinct di!erence in concentration rank between aromatics and alkenes. The concentration rank of aromatics is higher than that of alkenes at the site D. In contrast, the order of concentrations between two classes is reverse at the site I. In Fig. 2, Ulsan site D and other urban sites show similar composition patterns with alkanes being the highest, followed by alkenes and aromatics. Thus, the VOC levels in Ulsan site D appear to belong to a typical urban air. Although all of Ulsan, Yochon, Edmonton, and Thane include similar industrial sources such as petrochemical plant and oil re"nery process, Ulsan and Yochon industrial sites show di!erent rank of hydrocarbon compositions compared to Thane and Edmonton industrial sites. In other words, the two industrial sites in Korea have higher fraction of alkenes to total VOC compared to other industrial areas. This suggests that the e!ect of fugitive emissions of light hydrocarbons in Ulsan and Yochon industrial areas might be higher than other industrial areas. Namely, the two industrial ambient air may be more a!ected by leakage than other industrial areas. For reducing the ambient concentrations of total VOC in Ulsan and Yochon industrial area, controlling fugitive emissions may be required. During the two days of 3 and 7 June, higher total VOC concentrations at the site D (413.7 and 454.5 ppbC, respectively), were observed compared with those of the other days. For the two days, the frequencies of wind direction from the industrial areas were 52 and 65%, respectively. On 4, 5, and 6 June (376.4, 377.8, and
167.3 ppbC, respectively), the frequencies of wind direction from the site I were 25, 29, and 10%, respectively. Comparatively, lower concentrations were observed during these 3 days. It shows that ambient concentrations of VOC at the site D may be a!ected by industrial emissions. To determine the additional in#uence of industrial emissions on ambient air of the site D, the concentration ratios of ethylene to total C }C hydrocarbons (ethane, ethylene, acetylene, propane, n/i-butane, n/i-pentane) are estimated are shown in Fig. 3 along with other urban areas (Hester and Harrison, 1995; Moschonas and Glavas, 1996; Morikawa et al., 1998). As shown in this "gure, the fraction of Ulsan site D (26.6%) is higher than any other urban area ranging from 10.4 to 19.5%. As mentioned earlier, in an urban setting, ethylene is the major components of vehicle exhausts. Hence, it can be thought that its concentration depends upon the number of vehicles. Seoul, the capital of Korea, has about 40 times more vehicles than in Ulsan downtown area in comparable area. However, it is noted that the ethylene concentration (6.9 ppb) at Ulsan site D is higher than that measured at Seoul (4.0 ppb). Higher concentration of ethylene in Ulsan industrial area (29.1 ppb) may a!ect higher fraction of ethylene in C }C hydrocarbons in Ulsan downtown atmosphere compared to other urban area.
4. Summary Ambient concentrations of C }C volatile organic compounds were quanti"ed. At Ulsan industrial site, the concentrations of total VOC were about 4 times higher
Fig. 3. Comparison of the concentration compositions of ethylene on total C }C at Ulsan industrial and downtown sites, and other urbans (Ulsan: this study; Chicago and Sydney: Moschonas and Glavas, 1996; London: Hester and Harrison, 1995; Osaka: Morikawa et al., 1998; Copenhagen: Hansen and Palmgren, 1996).
K. Na et al. / Atmospheric Environment 35 (2001) 2747}2756
than those at the downtown site. Oxygenated hydrocarbons had the highest concentration of seven hydrocarbon groups. The distribution and ranking of the major compounds between the two sites were signi"cantly di!erent suggesting di!erent emission characteristics of the two sites. At the downtown site, the concentrations of species closely related to vehicle exhausts (ethylene, propylene and acetylene) and evaporative emissions (butanes and pentanes) were high, whereas the concentrations of ethylene, propylene, vinyl chloride, cyclohexane and tetrahydrofuran largely associated with petrochemical industries were high at the industrial site. Relatively, high portion of C }C light hydrocarbon in Ulsan industrial area was observed compared to other industrial areas. It suggests that the e!ect of fugitive emissions of the light hydrocarbons in Ulsan industrial area might be higher than that of the other industrial areas. For reducing the ambient VOC in Ulsan industrial area, controlling fugitive emissions may be required. From the results of the higher concentration of vinyl chloride and higher fraction of ethylene in C }C hydro carbons compared to other urban area, it is identi"ed that industrial emissions of VOC a!ect on the downtown ambient air by transport.
Acknowledgements This work was supported by the Ministry of Environment, Korea and Korea Institute of Science and Technology.
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