Aerosol and Air Quality Research, 12: 1315–1326, 2012 Copyright © Taiwan Association for Aerosol Research ISSN: 1680-8584 print / 2071-1409 online doi: 10.4209/aaqr.2012.02.0035

Measurements and PCA/APCS Analyses of Volatile Organic Compounds in Kaohsiung Municipal Sewer Systems, Southern Taiwan Chin-Hung Huang, Kang-Shin Chen*, Hsin-Kai Wang Institute of Environmental Engineering, National Sun Yat-Sen University, Kaohsiung 80424, Taiwan ABSTRACT

This study measured 71 volatile organic compounds (VOCs) collected using stainless steel canisters at 15 monitoring sites in two main Kaohsiung municipal sewers, A-Sewer and B-Sewer, during winter and summer periods in 2008 and 2009. The results indicate that the overall average of total VOCs, TVOC, in A-Sewer was 1173.51 ± 187.69 μg/m3, which was about 40% higher than that in B-Sewer (689.22 ± 151.64 μg/m3). However, TVOC in the winter/dry season was about three (or five) times that in the summer/wet season for A-Sewer (or B-Sewer). For the A-Sewer, chlorinated organics, aromatics, and alkanes were predominant, and altogether contributed to about 90.0% of the TVOC in winter and about 70.6% in summer, with alkenes, ethers, ketones, and sulfur compounds as minor components. For B-sewer, aromatics, alkanes, and chlorinated organics were predominant, and altogether contributed to about 94.1% of the TVOC in winter and about 74.3% in summer, while others were minor ones. The principal component analysis (PCA) and absolute component scores (APCS) models indicate that the percentage source contributions for A-Sewer were solvent usage (31.65 ± 11.27%), oil refineries and storage leaks (28.71 ± 11.52%), auto paintings (19.14 ± 9.74%), asphalt plants (17.05 ± 8.73%), and others (3.45 ± 3.95%). The percentage source contributions for B-Sewer were printing factories (45.35 ± 9.19%), oil refineries and storage leaks (31.78 ± 8.59%), solvent usage (18.64 ± 8.50%), and dry cleaning (4.23 ± 4.70%). Keywords: Volatile organic compounds; Stainless canister; PCA; APCS.

INTRODUCTION

Modern cities operate sewage treatment plants that receive wastewater discharged from various sources, including industry, residential households, public institutions, and commercial facilities. Many studies have shown that industries such as oil refineries, plastic and chemical factories, surface-painting shops, and semiconductor manufacturers represent a major source of volatile organic compounds (VOCs) in the atmosphere (Nikolaou et al., 2002; Khwaja et al., 2008; Nian et al., 2008; Cai et al., 2010; Yuan et al., 2010; Leuchner et al., 2010; Vega et al., 2011). Emissions of VOCs into the atmosphere via sewer collection and treatment systems have also received considerable attention. This is mainly because discharges of wastewater to treatment systems via sewers are related to the transfer of volatile organic compounds from the aqueous to gaseous phase, causing various potential risks, such as worker exposure to toxic chemicals during wastewater collection and treatment, emissions of toxic air contaminants and photochemical precursors to the atmosphere, as well as * Corresponding author. Tel./Fax: +886-7-5254406 E-mail address: shin@mail.nsysu.edu.tw

accumulation of explosive gases in sewer confined environments. While several studies have focused on controlling VOCs in wastewater treatment systems (Atasoy et al., 2004; Hamoda, 2006; Cheng et al., 2008), related works have also shown that VOC emissions from manhole covers in the sewer systems should not be ignored (Corsi et al., 1992; Corsi et al., 1995; Escalas et al., 2003).

Despite numerous measurements of individual VOC species in the aqueous phase (Corsi et al., 1995; Kuo et al., 1997; Cheng et al., 2008; Gasperi et al., 2008; Oskouie et al., 2008), the individual gaseous species in a sewer system have seldom been addressed. Since a sewer is a poorly ventilated and confined space, VOCs may accumulate to high levels and pose a health risk to workers. Moreover, highly concentrated hydrocarbons in confined spaces may explode under unfavorable conditions, thus further threatening the environment and human life (Corsi et al., 1995). Understanding the levels of gaseous species in sewer systems is thus essential for environmental and safety concerns.

Kaohsiung City (22°38'N, 120°17'E), in southern Taiwan, is a heavily industrialized harbor city with around 1.52 million inhabitants and an area of around 153.6 km2. The many industrial parks located in and around the city include steel production plants, oil refineries, plastic and chemical factories, metal-making plants, power plants, and municipal waste incinerators. Kaohsiung City has two

Huang et al., Aerosol and Air Quality Research, 12: 1315–1326, 2012 1316

main sewer systems, A-Sewer and B-Sewer (Fig. 1). A-Sewer is approximately 14.5 km long, and collects about 195,000 tons of household and business wastewater a day. Among the many industries located along the A-Sewer are those that produce mechanical devices, electronic spare parts, chemicals and plastics. B-Sewer is approximately 10.8 km long, and collects about 112,000 ton of household and business wastewater a day. Among the many business located along the B-Sewer include those producing cement, paper, textiles, and mechanical devices. While other wastewater may come from agriculture and animal husbandry, both sewers are eventually discharged into the wastewater treatment plant near the coastal site (Fig. 1).

This study measured 71 VOCs in the gaseous phase in the two sewers in the winter/dry and summer/wet seasons in Kaohsiung City in southern Taiwan from 2008–2009. The characteristics and seasonal variations of VOCs are examined, and their dominant source contributions are assessed using PCA and APCS. The results are important for environmental and safety concerns, and form data base for assessing health risks in the future.

SAMPLING AND ANALYSIS

The samples were collected at ten and five monitoring

sites for A-Sewer and B-Sewer, respectively (Fig. 1). Samples for a particular sewer were conducted from one site to the next during the same day. Since the distance and starting sample-time between two neighboring sites were all within 1 km and 10 min, and since the residence time of air is usually much longer than that of the wastewater in the sewer, the changes of VOC concentrations were thus assumed negligible during the sampling period. In southern Taiwan, the average rainfall is only around 18.40 mm during the winter season, yet is high as 430.63 mm during the summer season. Thus, winter and summer are herein referred to as dry and wet seasons, respectively. Sampling periods were therefore chosen on December 16–17, 2008 and on June 2–3, 2009 in order to study the variations between winter/dry and summer/wet seasons.

In compliance with the US-EPA Method TO-15 (USEPA, 1999), air samples were collected using 400 mL stainless steel canisters. At each monitoring site, a sampling tube was inserted approximately 1 m into the sewage through a pick hole on a manhole cover. Samples were then collected for 3 min using an air pump at a fixed flow rate of 100 mL/min. Temperature and pressure at each site were also measured in order to calculate VOC concentrations in μg/m3, which can be directly used to evaluate emission amounts of VOCs and possible cancer risks when needed in the future.

WWTP: Waste Water Treatment Plant

Legend

A-Sewer

B-Sewer

Sampling sites

Fig. 1. Location of the sampling sites for A- and B-Sewers in Kaohsiung City.

Taiwan

Taiwan Strait

Huang et al., Aerosol and Air Quality Research, 12: 1315–1326, 2012 1317

The air samples were then analyzed with a gas chromatograph (GC, Agilent 6890N) and a mass spectrometer (MS, Agilent 5973N). The GC oven temperature was initially programmed at 40°C, rising to 50°C after 2 min, and then increased at 8 °C/min to 230°C, then held for 10 min. Before sampling, all canisters were cleaned, moisturized, and checked for leaks to ensure a vacuum. Six-point calibrations for each species were conducted, yielding linear regression with the coefficient of determination, R2, above 0.995. The method of detection limit (MDL) for each species was

determined according to US-EPA Test Methods SW-846 (http://www.epa.gov/sw-846/pdfs/chap1.pdf). A known quantity of each standard substance was measured seven times, and the MDL for each species was three times the standard deviation from the seven tests. The MDLs for various species ranged from 0.26 to 4.38 μg/m3, with the precision ranging from 81–105% (Table 1). Laboratory blank samples were prepared and analyzed; all data were corrected with reference to a blank. Recovery efficiencies of 92–105% were achieved.

Table 1. Method of detection limit (MDL) and precision of 71 VOCs.

Groups VOC species CAS-no MDL (μg/m3) RPD (%) Alkanes Propane 00074-98-6 0.54 86

Butane 00106-97-8 0.95 103 Isobutane 00075-28-5 0.31 92 Cyclopenpane 00287-92-3 0.37 98 Pentane 00109-66-0 0.38 98 Isopentane 00078-78-4 0.38 95 Cyclohexane 00110-82-7 0.45 81 Hexane 00110-54-3 0.46 98 2-Methylpentane 00107-83-5 0.46 99 3-Methylpentane 00096-14-0 0.46 96 2,2-Dimethylbutane 00075-83-2 0.46 88 2,3-Dimethylbutane 00079-29-8 0.53 90 Methylcyclohexane 00108-87-2 0.52 83 3-Mehtylhexane 00589-34-4 0.53 97 2,3-Dimethylpentane 00565-59-3 0.53 94 2,4-Dimethylpentane 00108-08-7 0.53 95 Heptane 00142-82-5 1.76 90 n-Octane 00111-65-9 0.60 95 2-Methylheptane 00592-27-8 0.60 91 3-Methylheptane 00589-81-1 0.60 94 2,2,4-Trimethylpentane 00540-84-1 0.60 90 n-Nonane 00111-84-2 0.68 96 n-Decane 00124-18-5 0.75 91 n-Undecane 01120-21-4 0.83 97

Alkenes Propene 00115-07-1 0.26 96 1,3-Butadiene 00106-99-0 1.10 95 1-Butene 00106-98-9 0.41 104 Cis-2-Butene 00590-18-1 0.53 105 Trans-2-Butene 00624-64-6 0.64 97 Isoprene 00078-79-5 0.97 90 1-Pentene 00109-67-1 0.37 98 Cis-2-Pentene 00627-20-3 0.37 92 Trans-2-Pentene 00646-04-8 0.37 96 1-Hexene 00592-41-6 0.45 94

Aromatics Benzene 00071-43-2 2.55 94 Toluene 00108-88-3 2.55 98 Styrene 00100-42-5 0.55 93 Ethylbenzene 00100-41-4 0.56 94 m/p-Xylene 00108-38-3; 00106-42-3 0.56 94 o-Xylene 00095-47-6 0.56 96 n-Propylbenzene 00103-65-1 0.64 99 Isopropylbenzene 00098-82-8 3.33 96 1,2,3-Trimethylbenzene 00526-73-8 0.64 91 1,2,4-Trimethylbenzene 00095-63-6 0.64 99 1,3,5-Trimethylbenzene 00108-67-8 0.64 95

Huang et al., Aerosol and Air Quality Research, 12: 1315–1326, 2012 1318

Table 1. (continued).

Groups VOC species CAS-no MDL (μg/m3) RPD (%) m-Ethyltoluene 00620-14-4 0.64 97 p-Ethyltoluene 00622-96-8 0.64 91 o-Ethyltoluene 00611-14-3 0.64 93 m-Diethylbenzene 00141-93-5 0.71 95 p-Diethylbenzene 00105-05-5 0.71 92

Chlorinated organics Chloromethane 00074-87-3 1.02 92 Dichloromethane 00075-09-2 1.27 95 Dibromochloromethane 00124-48-1 4.08 94 Bromodichloromethane 00075-27-4 3.39 97 Chloroform 00067-66-3 1.85 92 Chloroethene 00075-01-4 1.04 94 1,1-Dichloroethene 00075-35-4 1.65 96 cis-1,2-Dichloroethene 00156-59-2 1.45 98 Trans-1,2-Dichloroethene 00156-60-5 1.25 96 1,1-Dichloroethane 00075-34-3 1.60 89 1,2-Dichloroethane 00107-06-2 0.89 88 Trichloroethene 00079-01-6 2.51 92 1,1,1-Trichloroethane 00071-55-6 0.92 88 1,1,2-Trichloroethane 00079-00-5 2.39 90 Tetrachloroethene 00127-18-4 2.90 97 1,2-Dichloropropane 00078-87-5 2.38 95

Sulfur compounds Carbon Disulfide 00075-15-0 1.05 98 Ketones Acetone 00067-64-1 2.01 95

2-Butanone 00078-93-3 2.26 86 Ethers 2-Methoxy-2-Methyl-Propane 01634-04-4 1.36 90

THE PCA/APCS RECEPTOR MODELS

In this study, principal component analysis (PCA) was applied to identify the influences of potential sources. PCA is frequently used in data reduction to identify a small number of factors that explain most of the variance observed in a larger number of variables. It was performed by utilizing the orthogonal transformation method with varimax rotation to determine the eigenvalues of variance matrix of original variables; usually, factors with eigenvalues > 1 were chosen. (Amaya et al., 2009; Wang et al., 2010). Once a factor is determined by PCA, it consists of patterns of variation of the factor loadings of input parameters. The factor loadings indicate the correlation of each species with each component and a species was said to load on a given component if the factor loading was 0.5 or greater for that component. The characteristics of a factor can then be inferred from the dominant pollutants, such as VOCs, PAHs and carbonyl compounds (Ho et al., 2002; Chang et al., 2009; Guo et al., 2009; Wang et al., 2010).

The variances of individual factors in PCA indicate the relative magnitudes among dominant potential sources. Their absolute contributions can then be determined by absolute principal component scores (APCS) using multiple regression of VOC mass concentrations (Ho et al., 2006; Chen et al., 2008). Like all other multivariate receptor models, the PCA and APCS models need adequate source profiles and degrees of freedom to perform the regressions. Furthermore, the two receptor models may not be able to separate sources that are similar. The problem of collinearity

can be solved by combining similar sources into single category (Ho et al., 2002; Chen et al., 2008; Wang et al., 2010). RESULTS AND DISCUSSION Characteristics of VOC Species in Sewers

Only averaged concentrations of each sewer were presented here. This is mainly due to the fact that many side-streams entered main streams and some VOCs might emit out of the sewers such that no clear trends can be observed on the effects of upper-stream concentrations on down-stream concentrations, which were also found by Corsi et al. (1995). Table 2 lists the overall mean concentrations of 71 VOC species obtained from ten and five sampling sites of A- and B-sewers, respectively, including winter/dry and summer/wet periods. In the A-Sewer, chloroethene (208.35 μg/m3), trichloroethene (107.85 μg/m3), toluene (94.23 μg/m3), and tetrachloroethene (90.46 μg/m3) were the most abundant species, followed by acetone (61.22 μg/m3), 1,1-dichloroethene (54.96 μg/m3), m/p-xylene (54.19 μg/m3), 2-methoxy-2-methyl-propane (53.55 μg/m3), cis-1,2-dichloroethene (27.38 μg/m3), 1,1,2-trichloroethane (27.21 μg/m3), o-xylene (23.95 μg/m3), isopentane (23.00 μg/m3), and pentane (20.08 μg/m3). Other species in the A-Sewer were below 20.00 μg/m3.

In the B-Sewer, m/p-xylene (200.50 μg/m3) and toluene (147.53 μg/m3) were the most abundant species, followed by o-xylene (62.24 μg/m3), ethylbenzene (53.19 μg/m3), and acetone (30.87 μg/m3). Other species in the B-Sewer were

Huang et al., Aerosol and Air Quality Research, 12: 1315–1326, 2012 1319

Table 2. Overall mean concentrations of VOCs for the two sewers (Unit: μg/m3).

A sewer (n = 20)

B sewer (n = 10)

A sewer (n = 20)

B sewer (n = 10)

Alkanes Isopropylbenzene ND 1.50 ± 4.74 Propane 2.79 ± 2.47 ND 1,2,3-Trimethylbenzene 4.71 ± 8.28 2.85 ± 4.59 Butane 11.96 ± 11.73 6.38±10.28 1,2,4-Trimethylbenzene 18.75 ± 7.52 10.00 ± 10.24Isobutane 6.20 ± 6.50 2.12±3.97 1,3,5-Trimethylbenzene 4.96 ± 7.24 3.46 ± 5.05 Cyclopenpane 3.36 ± 7.41 ND m-Ethyltoluene 10.90 ± 13.59 6.51 ± 8.29 Pentane 20.08 ± 22.83 12.68±21.40 p-Ethyltoluene 5.12 ± 2.73 3.06 ± 3.23 Isopentane 23.00 ± 19.78 10.76±8.40 o-Ethyltoluene 5.37 ± 2.79 3.37 ± 4.90 Cyclohexane 4.93 ± 9.93 0.88±2.78 m-Diethylbenzene 0.56 ± 1.98 ND Hexane 13.54 ± 16.14 6.79±7.59 p-Diethylbenzene 0.10 ± 0.46 ND 2-Methylpentane 12.80 ± 14.49 4.51±3.65 Chlorinated organics 3-Methylpentane 9.86 ± 11.92 3.21±2.85 Chloromethane 1.11 ± 2.40 4.39 ±8.68 2,2-Dimethylbutane 2.66 ± 4.36 0.67±1.20 Dichloromethane 5.71 ± 5.01 3.51 ±2.98 2,3-Dimethylbutane 1.95 ± 2.74 0.54±1.22 Dibromochloromethane ND ND Methylcyclohexane 2.79 ± 4.00 3.63±9.62 Bromodichloromethane ND 1.95 ±4.13 3-Mehtylhexane 8.15 ± 8.20 2.24±3.27 Chloroform 13.83 ± 9.83 10.66 ±8.00 2,3-Dimethylpentane 2.66 ± 4.41 0.59±1.35 Chloroethene 208.35 ± 98.52 2.07 ±3.67 2,4-Dimethylpentane 1.95 ± 4.59 ND 1,1-Dichloroethene 54.96 ± 43.77 4.87 ±5.41 Heptane 7.47 ± 4.68 1.71±3.64 cis-1,2-Dichloroethene 27.38 ± 22.58 1.49 ±4.72 n-Octane 10.01 ± 5.59 5.08±8.80 Trans-1,2-Dichloroethene 11.38 ± 50.87 0.71 ±2.25 2-Methylheptane 3.46 ± 6.35 0.98±2.06 1,1-Dichloroethane 1.98 ± 0.83 ND 3-Methylheptane 4.47 ± 7.55 2.36 ± 4.60 1,2-Dichloroethane 17.05 ± 50.17 0.41 ±1.29 2,2,4-Trimethylpentane 5.29 ± 12.70 3.51 ± 1.17 Trichloroethene 107.85 ± 32.32 1.80 ±3.96 n-Nonane 4.30 ± 10.12 2.51 ± 5.35 1,1,1-Trichloroethane ND 0.54 ±1.72 n-Decane 3.74 ± 8.57 9.89 ± 4.99 1,1,2-Trichloroethane 27.21 ± 9.95 ND n-Undecane 2.85 ± 6.22 6.21 ± 6.63 Tetrachloroethene 90.46 ± 27.05 4.00 ±9.45

Alkenes 1,2-Dichloropropane 0.47 ± 2.11 ND Propene 11.88 ± 16.20 6.41 ± 7.06 1,4-Dichlorobenzene 3.58 ± 1.13 1.31 ±4.15 1,3-Butadiene 3.26 ± 7.78 0.52 ± 1.66 Sulfur compounds 1-Butene 14.48 ± 22.11 6.57 ± 7.93 Carbon Disulfide 6.39 ± 7.53 3.92 ±5.48 Cis-2-Butene 2.47 ± 4.16 0.54 ± 1.19 Ketones Trans-2-Butene 1.84 ± 2.88 0.27 ± 0.86 Acetone 61.22 ± 61.32 30.87±17.26Isoprene 1.71 ± 2.32 1.18 ± 2.81 2-Butanone 8.75 ± 10.15 ND 1-Pentene 3.29 ± 9.59 0.41 ± 1.30 Ethers Cis-2-Pentene 1.34 ± 2.21 0.13 ± 0.40 2-Methoxy-2-Methyl-Propane 53.55 ± 39.12 8.67 ±6.82 Trans-2-Pentene 3.28 ± 5.08 0.11 ± 0.34 1-Hexene 1.04 ± 2.07 0.94 ± 2.08

Aromatics TVOC Benzene 6.05 ± 8.98 ND Dry season 1766.98 1178.19 Toluene 94.23 ± 57.38 147.53 ± 103.09 Wet season 580.04 200.26 Styrene 6.03 ± 14.43 7.40 ± 12.61 Overall 1173.51 689.22 Ethylbenzene 19.04 ± 17.95 53.19 ± 50.46 TSD m/p-Xylene 54.19 ± 49.01 200.50 ± 80.57 Dry season 51.24 56.80 o-Xylene 23.95 ± 17.69 62.24 ± 30.79 Wet season 17.18 6.55 n-Propylbenzene 3.46± 4.68 2.13 ± 3.99 Overall 187.69 151.64

below 30.00 μg/m3 (Table 2). The overall average of all measured VOC species, TVOC, in the A-Sewer was 1173.51 ± 187.69 μg/m3, which was about 40% higher than that of the B-Sewer (689.22 ± 151.64 μg/m3). Seasonal Variations of Hydrocarbon Groups

The VOC concentrations in the two sewers varied significantly between the winter/dry and summer/wet seasons. Figs. 2 and 3 present their concentrations and percentage compositions classified in seven hydrocarbon

groups, respectively. For the A-Sewer during the winter/dry season, chlorinated organics (990.47 μg/m3; 56.1%) were predominant, followed by aromatics (399.00 μg/m3; 22.6%), alkanes (199.25 μg/m3; 11.3%), ethers (61.84 μg/m3; 3.5%), alkenes (56.82 μg/m3; 3.2%), ketones (49.20 μg/m3; 2.8%), and sulfur compounds (10.40 μg/m3; 0.5%). For the A-Sewer in the summer/wet season, chlorinated organics (152.15 μg/m3; 26.2%) were predominant, followed by alkanes (141.29 μg/m3; 24.4%), aromatics (115.84 μg/m3; 20.0%), ketones (90.74 μg/m3; 15.6%), ethers (45.26 μg/m3;

Huang et al., Aerosol and Air Quality Research, 12: 1315–1326, 2012 1320

Fig. 2. Average concentrations of seven hydrocarbon groups for the A- and B-Sewers during winter/dry and summer/wet seasons.

7.8%), alkenes (32.37 μg/m3; 5.6%), and sulfur compounds (2.38 μg/m3; 0.4%).

Meanwhile, for the B-sewer in the winter/dry season, aromatics (926.11 μg/m3; 78.6%) were predominant, followed by alkanes (111.87 μg/m3; 9.5%), chlorinated organics (70.55 μg/m3; 6.0%), alkenes (28.14 μg/m3; 2.4%), ketones (21.71 μg/m3; 1.8%), ethers (12.53 μg/m3; 1.1%), and sulfur compounds (7.29 μg/m3; 0.6%). For the B-Sewer in the summer/wet season, aromatics (81.34 μg/m3; 40.6%) were predominant, followed by alkanes (62.62 μg/m3; 31.3%), ketones (40.04 μg/m3; 20.0%), alkenes (6.02 μg/m3; 3.0%), chlorinated organics (4.89 μg/m3; 2.4%), ethers (4.80 μg/m3; 2.4%), and sulfur compounds (0.54 μg/m3; 0.3%).

The wintertime mean TVOC was 1766.98 ± 51.24 μg/m3 and 1178.19 ± 56.80 μg/m3 for the A-Sewer and B-Sewer, respectively; while the summertime mean TVOC was 580.04 ± 17.18 μg/m3 and 200.26 ± 6.55 μg/m3 for the A-Sewer and B-Sewer, respectively. That is, TVOC in the winter/dry season was about three (or five) times that during

the summer/wet season for the A-Sewer (or B-Sewer). Most VOC species in the two sewer systems are thus more diluted during the summer/wet period than during winter/dry period, except for ketones. For instance, the acetone concentration was higher during the summer/wet season (90.74 μg/m3 for A-sewer; 40.04 μg/m3 for B-Sewer) than in the winter/dry season (49.20 μg/m3 for A-Sewer; 21.71 μg/m3 for B-Sewer). As is well known, acetone is an important solvent in the chemical and semiconductor industries (Cheng et al., 2008; Lu et al., 2009). Given its high polarity and easy dissolution in water, acetone may enter a sewer system, with rains causing higher concentrations during the summer/wet period than those during the winter/dry period. Wu et al. (2006) observed similar results, in which acetone was easily found in the sewer system in Shin-Chu Industrial Park in northern Taiwan owing to its high volatility.

In summary, chlorinated organics, aromatics, and alkanes were the three predominant compounds in the two sewers,

Huang et al., Aerosol and Air Quality Research, 12: 1315–1326, 2012 1321

Fig. 3. Average composition (%) of seven hydrocarbon groups for the A- and B-Sewers during winter/dry and summer/wet seasons.

cumulatively contributing to about 85.1% of the TVOC for the A-Sewer, and 91.2% for the B-Sewer. Chlorinated organics dominated the A-Sewer, since they are largely used for organic solvents and oil emulsion cleaners in industrial parks (Wilkie et al., 1996; Orchard et al., 2000; Ndon et al., 2000; Escalas et al., 2003; Rule et al., 2006). However, aromatics dominated the B-Sewer, which are largely used in the plastic, painting and resin industries (Cheng et al., 2008). Source Identification Using PCA and APCS

Table 3 of PCA results shows that five dominant factors for the A-Sewer are FC1 (33.29%), FC2 (24.80%), FC3 (16.39%), FC4 (14.48%), and FC5 (2.51%), which explain 91.38% of total variance. After combining individual species loadings in each factor, APCS results for the A-Sewer were determined and displayed in Fig. 4. Solvent usages (31.65 ± 11.27%) were the first contributor, correlated with chlorinated-containing species of chloroform, 1,2-dichloroethane, trichloroethene, 1,2-dichloropropane, and

1,1,2-trichloroethane. These VOCs are mainly used as metal degreasers, adhesives, and carpet cleaning agents (Sidropoulos et al., 2009; Ongwandee et al., 2011). Oil refineries and storage leaks (28.71 ± 11.52%) were the second contributor, correlated with species of isobutane, pentane, isopentane, cyclohexane, hexane, 2-methylpentane, 3-methylpentane, 2,2-dimethylbutane, 2,3-dimethylbutane, propene, 1,3-butadiene, 1-butene, cis-2-butene, trans-2-butene, isoprene, and 2-methoxy-2-methyl-propane (Badol et al., 2008). Auto paintings (19.14 ± 9.74%) were the third contributor, correlated with species of 3-mehtylheptane, toluene, ethylbenzene, m/p-xylene, o-xylene, n- propylbenzene, m-ethyltoluene, p-ethyltoluene, o-ethyltoluene, m-diethylbenzene, and p-diethylbenzene (Yuan et al., 2010). Asphalt plants (17.05 ± 8.73%) were the fourth contributor, correlated with species of propane, butane, methylcyclohexane, 3-methylhexane, 2,2,4-trimethylpentane, 1,2,3-trimethylbenzene, 1,2,4-trimethylbenzene, and 1,3,5-trimethylbenzene (Vega et al., 2000). Others (3.45 ± 3.95%) were the fifth contributor, correlated with styrene.

Table 3. Factor loadings of PCA results for A-Sewer.

Compounds Factor

FC1 FC2 FC3 FC4 FC5 Propane 0.85 Butane 0.55 0.80 Isobutane 0.73 Cyclopenpane 0.50 Pentane 0.87 Isopentane 0.90 Cyclohexane 0.92 Hexane 0.86 2-Methylpentane 0.81 3-Methylpentane 0.78 2,2-Dimethylbutane 0.83 2,3-Dimethylbutane 0.80 Methylcyclohexane 0.71 3-Mehtylhexane 0.73

Huang et al., Aerosol and Air Quality Research, 12: 1315–1326, 2012 1322

Table 3. (continued).

Compounds Factor

FC1 FC2 FC3 FC4 FC5 2,3-Dimethylpentane 0.66 2,4-Dimethylpentane 0.51 Heptane 0.52 n-Octane 0.66 2-Methylheptane 0.65 3-Methylheptane 0.70 2,2,4-Trimethylpentane 0.50 0.84 n-Nonane 0.52 n-Decane 0.56 n-Undecane 0.63 Propene 0.96 1,3-Butadiene 0.77 1-Butene 0.86 Cis-2-Butene 0.82 Trans-2-Butene 0.84 Isoprene 0.76 1-Pentene 0.72 Cis-2-Pentene 0.73 Trans-2-Pentene 0.65 1-Hexene 0.58 0.50 Benzene 0.65 0.52 Toluene 0.58 0.78 Styrene 0.70 Ethylbenzene 0.82 m/p-Xylene 0.88 o-Xylene 0.83 n-Propylbenzene 0.76 1,2,3-Trimethylbenzene 0.85 1,2,4-Trimethylbenzene 0.86 1,3,5-Trimethylbenzene 0.86 m-Ethyltoluene 0.80 p-Ethyltoluene 0.85 o-Ethyltoluene 0.84 m-Diethylbenzene 0.82 p-Diethylbenzene 0.80 Chloromethane 0.86 Dichloromethane 0.80 Chloroform 0.95 Chloroethene 0.86 1,1-Dichloroethene 0.88 cis-1,2-Dichloroethene 0.79 Trans-1,2-Dichloroethene 0.88 1,1-Dichloroethane 0.85 1,2-Dichloroethane 0.98 Trichloroethene 0.96 1,1,2-Trichloroethane 0.94 Tetrachloroethene 0.55 1,2-Dichloropropane 0.94 Carbon Disulfide 0.72 Acetone 0.72 2-Butanone 0.83 2-Methoxy-2-Methyl-Propane 0.85 Eigenvalue 21.97 16.37 10.82 9.56 1.66 % Total variance 33.29 24.80 16.39 14.48 2.51 Cumulative % 33.29 58.09 74.48 88.87 91.38

Huang et al., Aerosol and Air Quality Research, 12: 1315–1326, 2012 1323

Fig. 4. Average percentage source contributions (% of calculated mass ± SD) to VOCs of APCS results for A- and B-Sewer.

Table 4 of PCA results shows that four dominant factors for the B-Sewer are FC1 (42.33%), FC2 (29.79%), FC3 (15.91%), and FC4 (3.38%), which explain 91.40% of total variance. Similarly, after combining individual species loadings in each factor, APCS results for the B-Sewer were determined and displayed in Fig. 4. Printing factories (45.35 ± 9.19%) were the first contributor, correlated with species of methylcyclohexane, heptane, n-octane, 2-methylheptane, 3-methylheptane, n-nonane, n-decane, n-undecane, propene, cis-2-Butene, trans-2-Butene, cis-2-Pentene, toluene, styrene, ethylbenzene, m/p-xylene, o-xylene, n-propylbenzene, isopropylbenzene, 1,2,3-trimethylbenzene, and 1,2,4-trimethylbenzene (Yuan et al., 2010). Oil refineries and storage leaks (31.78 ± 8.59%) were the second contributor, correlated with species of butane, isobutane, pentane, isopentane, cyclohexane, hexane, 2-methylpentane, 3-methylpentane, 2,2-dimethylbutane, 2,3-dimethylbutane, 1,3-butadiene, 1-butene, isoprene, trans-2-pentene, 1-hexene, and 2-methoxy-2-methyl-propane (Badol et al., 2008). Solvent usages (18.64 ± 8.50%) were the third contributor, correlated with species of chloromethane, dichloromethane, chloroform, chloroethene, 1,1-dichloroethene, cis-1,2-dichloroethene, 1,2-dichloroethane, 1,1,1-Trichloroethane, and acetone (Ongwandee et al.,

2011). Dry cleanings (4.23 ± 4.70%) were the fourth contributor, correlated with species of trichloroethene and tetrachloroethene (Vega et al., 2000; Nikolaou et al., 2002). CONCLUSIONS

This study identified 71 volatile organic compounds in seven hydrocarbon groups from Kaohsiung municipal sewers from 2008–2009. Measurement results indicate that the concentrations of most VOC species during the winter/ dry season were higher than those during the summer/wet season. The three most abundant hydrocarbon groups in the two sewers were chlorinated organics, aromatics, and alkanes.

Five principal factors were determined for A-Sewer using PCA, accounting for 91.38% of total variance. The APCS results indicate that the pre-dominant source contributors for A-Sewer were solvent usages (31.65 ± 11.27%), oil refineries and storage leaks (28.71 ± 11.52%), auto paintings (19.14 ± 9.74%), asphalt plants (17.05 ± 8.73%), and others (3.45 ± 3.95%). Four principal factors were determined for B-Sewer using PCA, accounting for 91.40% of total variance. The APCS results indicate that the pre-dominant source contributors for B-Sewer were printing factories (45.35 ±

(b) B-Sewer

Printing factory = 45.35 ± 9.19%

Oil refinery and storage = 31.78 ± 8.59%

Solvent use = 18.64 ± 8.50%

Dry cleaning = 4.23 ± 4.70%

(a) A-Sewer

Solvent use = 31.65 ± 11.27%

Oil refinery and storage = 28.71 ± 11.52%

Auto paints = 19.14 ± 9.74%

Others = 3.45 ± 3.95% Asphalt plant =

17.05 ± 8.73%

Huang et al., Aerosol and Air Quality Research, 12: 1315–1326, 2012 1324

Table 4. Factor loadings of PCA results for B-Sewer.

Compounds Factor

FC1 FC2 FC3 FC4 Butane 0.86 Isobutane 0.81 Pentane 0.87 Isopentane 0.50 0.80 Cyclohexane 0.80 Hexane 0.82 2-Methylpentane 0.86 3-Methylpentane 0.77 2,2-Dimethylbutane 0.86 2,3-Dimethylbutane 0.58 0.78 Methylcyclohexane 0.79 0.50 3-Mehtylhexane 0.65 2,3-Dimethylpentane 0.52 Heptane 0.83 n-Octane 0.97 2-Methylheptane 0.90 3-Methylheptane 0.86 2,2,4-Trimethylpentane n-Nonane 0.95 n-Decane 0.94 n-Undecane 0.98 Propene 0.72 1,3-Butadiene 0.78 1-Butene 0.53 0.71 Cis-2-Butene 0.72 Trans-2-Butene 0.76 Isoprene 0.85 1-Pentene 0.52 Cis-2-Pentene 0.88 Trans-2-Pentene 0.54 0.74 1-Hexene 0.82 Toluene 0.95 Styrene 0.76 Ethylbenzene 0.89 m/p-Xylene 0.95 o-Xylene 0.93 n-Propylbenzene 0.85 Isopropylbenzene 0.84 1,2,3-Trimethylbenzene 0.80 1,2,4-Trimethylbenzene 0.82 1,3,5-Trimethylbenzene 0.58 m-Ethyltoluene 0.66 p-Ethyltoluene 0.66 o-Ethyltoluene 0.52 Chloromethane 0.72 Dichloromethane 0.74 Bromodichloromethane 0.55 Chloroform 0.77 0.51 Chloroethene 0.80 1,1-Dichloroethene 0.81 cis-1,2-Dichloroethene 0.78 Trans-1,2-Dichloroethene 0.65 1,2-Dichloroethane 0.80 Trichloroethene 0.52 0.73 1,1,1-Trichloroethane 0.80

Huang et al., Aerosol and Air Quality Research, 12: 1315–1326, 2012 1325

Table 4. (continued).

Compounds Factor

FC1 FC2 FC3 FC4 Tetrachloroethene 0.78 Carbon Disulfide 0.55 Acetone 0.94 2-Methoxy-2-Methyl-Propane 0.87 Eigenvalue 24.97 17.57 9.39 1.99 % Total variance 42.33 29.79 15.91 3.38 Cumulative % 42.33 72.11 88.02 91.40

Notes: Only factor loadings > 0.5 are listed and > 0.7 appear in bold.

9.19%), oil refineries and storage leaks (31.78 ± 8.59%), solvent usages (18.64 ± 8.50%), and dry cleanings (4.23 ± 4.70%). Since the species and concentrations of VOCs in a sewer may be changed at different time or different day, the results in this work give a preliminary understanding of the behaviors of VOCs in the two sewer systems. ACKNOWLEDGEMENTS

The authors would like to thank Professor M. S. Chou in the Institute of Environmental Engineering, National Sun Yat-Sen University and Professor C.T. Lin in the Department of Marine Environmental Engineering, National Kaohsiung Marine University for their assistance during the course of field measurement and laboratory analysis. This work was supported by the Kaohsiung Municipal Government in Taiwan under contract NO. KMG-73.

REFERENCES Amaya, F.U., Cristina, L.M., Enrique, R. and Maria Luisa,

F.M. (2009). Source Identification of Heavy Metals in Pastureland by Multivariate Analysis in NW Spain. J. Hazard. Mater. 165: 1008–1015.

Atasoy, E., Dogeroglu, T. and Kara, S. (2004). The Estimation of NMVOC Emissions from an Urban-scale Wastewater Treatment Plant. Water Res. 38: 3265–3274.

Badol, C., Locoge, N. and Galloo, J.C. (2008). Using a Source-receptor Approach to Characterise VOC Behaviour in a French Urban Area Influenced by Industrial Emissions. Part II: Source Contribution Assessment Using the Chemical Mass Balance (CMB) Model. Sci. Total Environ. 389: 429440.

Chang, C.C., Wang, J.L., Candice, S.C., Liu, S.C. and Shiu, C.J. (2009). Source Characterization of Ozone Precursors by Complementary Approaches of Vehicular Indicator and Principal Component Analysis. Atmos. Environ. 43: 1771–1778.

Cai, C., Geng, F., Tie, X., Yu, Q. and An, J. (2010). Characteristics and Source Apportionment of VOCs Measured in Shanghai, China. Atmos. Environ. 44: 5005–5014.

Chen, K.S., Wang, H.K., Peng, Y.P., Wang, W.C., Chen, C.H. and Lai, C.H. (2008). Effects of Open Burning of Rice Straw on Concentrations of Atmospheric Polycyclic Aromatic Hydrocarbons in Central Taiwan. J. Air Waste

Manage. Assoc. 58: 1318–1327. Cheng, W.H., Hsu, S.K. and Chou, M.S. (2008). Volatile

Organic Compound Emissions from Wastewater Treatment Plants in Taiwan: Legal Regulations and Costs of Control. J. Environ. Manage. 88: 1485–1494.

Corsi, R.L., Chang, D.P.Y. and Schroeder, E.D. (1992). A Modeling Approach for VOC Emissions from Sewers. Water Environ. Res. 64: 734–741.

Corsi, R.L., Quigley, C.J., Melcer, H. and Bell, J. (1995). Aromatic VOC Emissions from a Municipal Sewer Interceptor. Water Sci. Technol. 31: 137–145.

Escalas, A., Guadayol, J.M., Cortina, M., Rivera, J. and Caixach, J. (2003). Time and Space Patterns of Volatile Organic Compounds in a Sewage Treatment Plant. Water Res. 37: 3913–3920.

Gasperi, J., Garnaud, S., Rocher, V. and Moilleron, R. (2008). Priority Pollutants in Wastewater and Combined Sewer Overflow. Sci. Total Environ. 407: 263–272.

Guo, W., He, M., Yang, Z., Lin, C., Quan, X. and Men, B. (2009). Distribution, Partitioning and Sources of Polycyclic Aromatic Hydrocarbons in Daliao River Water System in Dry Season, China. J. Hazard. Mater. 164: 1379–1385.

Hamoda, M.F. (2006). Air Pollutants Emissions from Waste Treatment and Disposal Facilities. J. Environ. Sci. Health., Part A 41: 77–85.

Ho, K.F., Lee, S.C. and Chiu, G.M.Y. (2002). Characterization of Selected Volatile Organic Compounds, Polycyclic Aromatic Hydrocarbons and Carbonyl Compounds at a Roadside Monitoring Station. Atmos. Environ. 36: 57–65.

Ho, K.F., Cao, J.J., Lee, S.C. and Chan, C.K. (2006). Source Apportionment of PM2.5 in Urban Area of Hong Kong. J. Hazard. Mater. B138: 73–85.

Khwaja, H.A. and Narang, A. (2008). Carbonyls and Non-methane Hydrocarbons at a Rural Mountain Site in Northeastern United States. Chemosphere 71: 2030–2043.

Kuo, H.W., Chiang, T.F., Lo, I.I., Lai, J.S., Chan, C.C. and Wang, J.D. (1997). VOC Concentration in Taiwan’s Household Drinking Water. Sci. Total Environ. 208: 41–47.

Leuchner, M. and Rappenglück, B. (2010). VOC Source-receptor Relationships in Houston during TexAQS-II. Atmos. Environ. 44: 4056–4067.

Lu, H., Cai, Q.Y., Wen, S., Chi, Y., Guo, S., Sheng, G., Fu, J. and Blance, A.L. (2009). Carbonyl Compounds in the

Huang et al., Aerosol and Air Quality Research, 12: 1315–1326, 2012 1326

Ambient Air of Hazy Days and Clear Days in Guangzhou, China. Atmos. Res. 94: 363–372.

Ndon, U.J., Randall, A.A. and Khouri, T.Z. (2000). Reductive Dechlorination of Tetrachloroethylene by Soil Sulfate-reducing Microbes under Various Electron Donor Conditions. Environ. Monit. Assess. 60: 329–336.

Nian, H.C., Liu, H.W., Wu, B.Z., Chang, C.C., Chiu, K.H. and Lo, J.G. (2008). Impact of Inclement Weather on the Characteristics of Volatile Organic Compounds in Ambient Air at the Hsinchu Science Park in Taiwan. Sci. Total Environ. 399: 41–49.

Nikolaou, A.D., Golfinopoulos, S.K., Kostopoulou, M.N., Kolokythas, G.A. and Lekkas, T.D. (2002). Determination of Volatile Organic Compounds in Surface Waters and Treated Wastewater in Greece. Water Res. 36: 2883–2890.

Ongwandee, M., Moonrinta, R., Panyametheekul, S., Tangbanluekal, C. and Morrison, C. (2011). Investigation of Volatile Organic Compounds in Office Buildings in Bangkok, Thailand: Concentrations, Sources, and Occupant Symptoms. Build. Environ. 46: 1512–1522.

Orchard, B.J., Doucette, W.J., Chard, J.K. and Bugbee, B. (2000). A Novel Laboratory System for Determining Fate of Volatile Organic Compounds in Planted Systems. Environ. Toxicol. Chem. 19: 888–894.

Oskouie, A.K., Lordi, D.T., Granato, T.C. and Kollias, L. (2008). Plant-specific Correlations to Predict the Total VOC Emissions from Wastewater Treatment Plants. Atmos. Environ. 42: 4530–4539.

Rule, K.L., Conber, S.D.W., Ross, D., Thornton, A., Makropoulos, C.K. and Rautiu, R. (2006). Survey of Priority Substances Entering Thirty English Wastewater Treatment Works. Water Environ. J. 20: 177–184.

Sidiropoulos, C. and Tsilingiridis, G. (2009). Improved Sectoral Allocation of NMVOC Emissions from Solvent Use in Greece. Sci. Total Environ. 407: 4075–4083.

U.S. Environmental Protection Agency (1999).

Determination of Volatile Organic Compounds (VOCs) in Air Collected in Specially Prepared Canister and Analyzed by Gas Chromatography/Mass Spectrometry (GC/MS), Second Edition Compendium Method TO-15.

Vega, E., Mugica, V., Carmona, R. and Valencia, E. (2000). Hydrocarbon Source Apportionment in Mexico City Using the Chemical Mass Balance Receptor Model. Atmos. Environ. 34: 4121–4129.

Vega, E., Sánchez-Reyna, G., Mora-Perdomo, V., Iglesias, G.S., Arriaga, J.L., Limón-Sánchez, T., Escalona-Segura, S. and Gonzalez-Avalos, E. (2011). Air Quality Assessment in a Highly Industrialized Area of Mexico: Concentrations and Sources of Volatile Organic Compounds. Fuel 90: 3509–3520.

Wang, H.K., Huang, C.H., Chen, K.S., Peng, Y.P. and Lai, C.H. (2010). Measurement and Source Characteristics of Carbonyl Compounds in the Atmosphere in Kaohsiung City, Taiwan. J. Hazard. Mater. 179: 1115–1121.

Wilkie, P.J., Hatzimihalis, G., Koutoufides, P. and Connor, M.A. (1996). The Contribution of Domestic Sources to Level of Key Organic and Inorganic Pollutants in Sewage: The Case of Melbourne, Australia. Water Sci. Technol. 34: 63–70.

Wu, B.Z., Feng, T.Z., Sree, U., Chiu, K.H. and Lo, J.G. (2006). Sampling and Analysis of Volatile Organics Emitted from Wastewater Treatment Plant and Drain System of an Industrial Science Park. Anal. Chim. Acta 576: 100–111.

Yuan, B., Shao, M., Lu, S. and Wang, B. (2010). Source Profiles of volatile Organic Compounds Associated with Solvent Use in Beijing China. Atmos. Environ. 44: 1919–1926.

Received for review, February 14, 2012 Accepted, April 29, 2012