Characteristics And Health Impacts Of Atmospheric Volatile Organic Compounds At The Surrounding Area Of A Gasoline-Contaminated Remediation Site
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(2) 118. Journal of the Chinese Institute of Environmental Engineering, Vol. 14, No. 2 (2004). and water solubility compared to other gasoline constituents results in MTBE being transferred from gasoline to air and then to water or from gasoline directly to water. Contamination of drinking water has become a public health issue because MTBE is considered a possible human carcinogen by USEPA and has a disagreeable taste and odor at low ppb concentrations. Exposure to the ambient atmosphere containing VOCs would cause severely adverse effects on human health [3-4]. In general, VOCs are emitted mainly from fugitive sources, especially from oil refinery and/or petrochemical plants, rather than stationary sources [5-17]. Recently, emission of VOCs to the ambient air from gasoline-contaminated sites has been paid more attention. In order to prevent and control the emission of VOCs, Taiwan Environmental Protection Administration (TEPA) has passed an Act entitled “Volatile Organic Compounds Control and Emission Standards” on February 5th, 1997. Volatile organic compounds emitted from pumps, flanges, storage tanks, and flares are regulated by enforcement, which requests the oil refineries and petrochemical plants to reduce the fugitive emission of VOCs in order to meet the VOCs Control and Emission Standards. However, the concentration and emission of VOCs at the surrounding atmosphere of gasolinecontaminated sites before and after remediation process has not been thoroughly investigated in Taiwan. Thus, it is important to characterize ambient VOCs and to assess their health hazards at the gasoline-contaminated remediation site. In the past, cleanup goals were often established without regard to risk, mandating remediation of groundwater to background or non-detectable level, to maximum allowable contaminant levels, or to level of total petroleum hydrocarbons (TPH). However, there has been a significant regulatory shift toward riskbased standards and a growing acceptance of natural attenuation as an important component of petroleum site remediation since 1994 [18]. The risk assessment applied to contaminated sites is a technical procedure to determine site-specific cleanup goals. Recently, much of the focus of health risk assessment has been on the development of models that combine fate/transport modeling and exposure/risk assessment modeling for estimating the potential human health risk near remediation sites. The American Society of Testing Materials has developed Risk Based Corrective Actions (RBCA) guidelines (ASTM, 1995) for site remediation [19-24]. RBCA integrates U. S. EPA risk assessment practices with traditional site investigation and remedy selection activities in order to determine cost-effective measures for the protection of human health and environmental resources. CalTOX is a multimedia total exposure model for hazardous waste sites developed by the California Department of Toxic Substances Control, Human and. Ecological Risk Division. CalTOX is spreadsheetbased software that aids in assessing risk posed by some hazardous materials in the environment. The Exposure and Risk Assessment Decision Support System (DSS) developed by American Petroleum Institute (API) [25-26] is a tool for risk assessment. API DSS allows either a deterministic or a probabilistic risk analysis by evaluating the risk uncertainty. Both RBCA and API DSS estimate the human health risk that depends on the toxicity of the contaminants and on the human exposure factors. Quantifying potential health risk of a contaminated site would provide necessary support for decisions of the related management and remediation actions. The comparisons of those multipathway computer-based models have been conducted in several studies [27-29]. The objectives of this study were to investigate the characteristics of atmospheric VOCs at the surrounding area of a gasoline-contaminated site and to conduct the health risk assessment for evaluating the related health impacts after remediation process. The results would be useful for further evaluating whether the remediation of the gasoline-contaminated site has been fully accomplished or not.. METHODOLOGIES Gasoline-contaminated Remediation Site. A gasoline-contaminated remediation site located at the suburb of Chia-yi County, Taiwan was selected for this particular investigation. Farmlands, along with an oil transfer station and a nearby community surround the gasoline-contaminated remediation site. The community has population of approximately 2,000 and is thought as the sensitive site. Besides, an intercity highway (national HW #1) and a local road (county road #163) are neighbored to the gasoline-contaminated remediation site. The location of the gasoline-contaminated remediation site and its neighboring area is illustrated in Fig. 1. According to the report of Chinese Petroleum Corporation (CPC), gasoline fuel was spilled at a site nearby HW #1 in Chia-yi County from an underground pipeline, which is buried along the intercity highway. Since then, CPC has conducted the remediation of the gasoline-contaminated site by both soil vapor extraction and soil replacing for more than three years. Sampling Sites. In order to characterize the atmospheric VOCs at the surrounding area of the gasoline-contaminated remediation site, VOCs samples were collected once every three months from February 2002 to April 2003 (a total of six seasons). A sampling network was.
(3) Chia-Wei Lee et al.: Characteristics and Health Impacts of Atmospheric Volatile Organic Compounds at the Surrounding Area of a Gasoline-contaminated Remediation Site. established to collect VOCs at 1.5 m above ground and the sampling time was from 11 AM to 2 PM. As illus-. 119. of VOCs further detected in this study included benzene, toluene, ethylbenzene, m,p-xylene, n-octane, and MTBE. Hydrocarbons and meteorological parameters were also continuously monitored and cor-. Fig. 2. Flowchart for sampling and analysis of ambient VOCs.. Fig. 1. Sampling location of atmospheric VOCs at the gasoline -contamination remediation site in the suburb of Chia-yi County, Taiwan.. trated in Fig. 1, the sampling network included five sampling sites located at the upwind site (site A), the nearby community (sites B and D), the gasolinecontaminated site (site C) and the downwind site (site E), respectively. Among them, site B was located at the downwind of highway and the upwind of gasolinecontaminated site. The location of these five sampling sites varied with the prevailing wind direction for different seasons. Sampling Methods. In this study, the sampling of VOCs was conducted by collecting ambient air through a multibed stainless steel trapping tubes by an air-sampling pump with constant flow rate. Fig. 2 illustrates the sampling and analytical procedures of ambient hydrocarbons (i. e. methane and non-methane hydrocarbons), atmospheric VOCs, and meteorological parameters (i. e. wind speed and wind direction). VOC samples were collected by multi-bed stainless steel trapping tubes at a flow rate of 0.15 L/min using air-sampling pumps (SKC, model 222-3) for approximately three hours, and the tubes were packed with three adsorbents in series: 125 mg Carbosieve S-III, 200 mg Carbontrap B, and 300 mg Carbontrap C (U. S. EPA Method TO-17). The types. related with the concentration of atmospheric VOCs at the surrounding area. Gas samples were collected by Tedlar bags using air- sampling pumps of 0.1 L/min (BUCK, model IH) and further analyzed with a THC analyzer (DANI, model 451). Analytical Methods. After being sampled by the multi-bed stainless steel trapping tubes, VOCs samples were further desorbed by a thermal desorption unit (TDU, TEKMAR, model 6000), separated by a gas chromatography with a capillary separation column (Supelco, model VOCOL, 60 m × 0.53 mm × 3.00 µm), and then analyzed by a gas chromatography with a flame ionization detector (GC/FID). The gas chromatography (HP, model 5890 Series II) was equipped with a cryo-focussing inlet system connected to a single split/splitless injector and detector, to which the capillary separation column was connected. The quality assurance and quality control data for the chemical analysis of VOCs samples. In this study, the error of retention time for the detectable VOCs as shown in the analytical spectrum of GC/FID ranged from 0.006 to 0.043 minutes. The accuracy of chemical analysis ranged from 96 to 102 % (95105%), while the analytical stability ranged from 96 to 101 % (95-105%). The detection limit of the analytical method for each compound ranged from 0.5 to 1.1 ng. The R2 of calibration curves must be higher than 0.995 and the recovery rate ranged from 90.1 to 94.6 % (90-110%). These results indicated that the analytical methods of VOCs (U. S. EPA TO-17) were satisfied with the proposed quality assurance.
(4) Journal of the Chinese Institute of Environmental Engineering, Vol. 14, No. 2 (2004). 120. RESULTS AND DISCUSSION. requirements. Health Risk Assessment. Methane and Non-Methane Hydrocarbons. In this study, API’s Decision Support System for Exposure and Risk Assessment (API-DSS, Version 2.0) [25-26] was used as the major tool for human health risk assessment. This software consists of four modules: Development of Risk Scenario module, Receptor Point Concentration module, Chemical Intake and Risk Calculation module, and Risk Presentation module. The major chemicals concerned in this study were BTEX and MTBE. The DSS includes databases assessed by various modules and contains chemical-specific fate and transport properties, toxicity properties for those chemicals. The inhalation intakes of on-site receptors were computed as follows: b × C a × IH × ET DI = a (1) BW where DI is the daily absorbed dose from inhalation (mg/kg-day); ba is the chemical- specific bioavailability for inhalation (mg/mg); Ca is the concentration of chemical in ambient air (mg/m3); IH is the inhalation rate (m3/hr); ET is the exposure time (hr/day); and BW is the body weight (kg). The chronic daily intake (CDI) is used for the assessment of carcinogenic risk and non-carcinogenic effects from chronic exposure and can be computed by averaging daily intake over the exposure period, DI × EF × ED (2) CDI = 365 × AT where CDI is the chronic daily-absorbed dose (mg/kgday); EF is the exposure frequency (day/year); ED is the exposure duration (year); and AT is the averaging time (years). Both cancer and non-cancer hazards were further assessed based on the field- measured concentration of BTEX and MTBE during the sampling period. The cancer and non-cancer hazards were compared with lifetime cancer risk criteria of 1.0 × 10-6 and noncancer hazard index of unity. The cancer and noncancer hazards were estimated by the following two equations, (a). Cancer hazard risk: R = CDI × SF (3). In this study, methane and non-methane hydrocarbons (MHC and NMHC) were continuously monitored in-situ at the surrounding area of the gasoline-contaminated remediation site. Field measurements of hydrocarbons indicated that methane concentration maintained almost constant and varied slightly with sampling location and season. Methane concentrations of approximately 2.5-2.7 ppm were observed in the ambient atmosphere since methane was mainly emitted from the natural and agricultural sources and evenly distributed in the atmosphere, which concurred with previous researches [10-11]. However, non-methane hydrocarbons varied significantly with both sampling location and season, since they were emitted mainly from the surrounding anthropogenic sources including stationary, mobile, and fugitive sources. Further investigation on NMHC concentration at various sampling sites showed that the lowest NMHC concentration was always observed at the upwind (site A) of the gasoline-contaminated remediation site (site A), while the highest NMHC concentration was generally observed at sites B, C, and D, which were located near the gasolinecontaminated site. The concentration of NMHC at the downwind site (site E) was generally lower than that of the sites B, C and D. The results suggested that NMHC might be emitted from source(s) near sites B, C and D. Consequently, it might be reasonable to assume that NMHC could be emitted from either gasoline-contaminated remediation site or automobile exhaust gas on the neighboring highway. The concentration contour of non-methane hydrocarbons for various wind direction cases is illustrated in Fig. 3. The concentration contours were generally perpendicular to wind direction and paralleled to the nearby highway or local road. Moreover, the maximum concentration did not appear at locations around site C, the gasoline-contaminated site, which indicated that ambient VOCs might be emitted from the spilled gasoline fuel. However, the gasoline-contaminated site was neighboring to the nearby highway on which automobiles’ exhaust gas also contributed VOCs to ambient atmosphere. Consequently, further analysis of VOCs’ characteristics and fingerprints is crucial for identifying major emission source(s) of atmospheric VOCs at the gasoline-contaminated remediation site.. (b).Non-cancer hazard risk: HI =. I RfD. (4). where R is the cancer hazard risk; CDI is the cancer daily average exposure dosage (mg/kg-day); SF is the cancer hazard slope (kg-day/mg); HI is the non-cancer hazard risk; I is the non-cancer exposure dosage (mg/kg-day); and RfD is the non-cancer reference exposure dosage (mg/kg-day).. Characteristics of Atmospheric VOCs. The analytical spectrum of field sampled atmospheric VOCs measured by GC/FID is illustrated in Fig. 4. Although several atmospheric VOCs could be qualitatively detected with the GC/FID, six VOCs.
(5) Chia-Wei Lee et al.: Characteristics and Health Impacts of Atmospheric Volatile Organic Compounds at the Surrounding Area of a Gasoline-contaminated Remediation Site. including benzene, toluene, ethylbenzene, m,p-xylene, n-octane, and MTBE were further quantified in this study since they were the major component of gasoline fuel. Measurement of these VOCs was highly required for identifying the influence of the spilled gasoline on atmospheric VOCs in the ambient air.. 121. major atmospheric VOCs observed in the ambient air. However, a few high boil-point hydrocarbons were also detected in some gas samples. It suggested that the nearby community was not only affected by VOCs emitted from the gasoline-contaminated remediation site but also from other unidentified local sources. In compari-. Fig. 4. Analytical spectrum of atmospheric VOCs measured with a GC/FID.. son with other seasons, the first season demonstrated very high concentration of m,p-xylene, especially at sites B and C. Relatively high concentrations of toluene and n-octane were found in the second and the third seasons. High concentrations of these VOCs were observed when as winds were blown from the westward directions (i. e. northwest and southwest winds), which therefore migrated VOCs to the sampling region. The results concurred with the facts that two VOCs sources, both gasoline-contaminated soil gas and tail exhausts from highway, are located at the westward upwind of the sampling region. Fingerprints of Atmospheric VOCs. Fig. 3. Concentration contour of non-methane hydrocarbons for various wind directions.. Sample number, concentration range and average of the measured VOCs during the investigation period are summarized in Table 1. Table 1 shows that m,p-xylene (in the first season) and toluene and n-octane (in the second season) were the. As mentioned earlier, agricultural farmlands surround the sampling region where a intercity highway and a local road nearby. In addition to the gasoline-contaminated site and highway traffic, there were only very few gasoline related VOCs emission sources in the agricultural fields. Therefore, it wouldn’t be surprised that the concentrations of atmospheric VOCs in the sampling region were much lower than those in the metropolitan [16, 30-31] and industrial areas [15, 32-33]. Both soil gas emitted from the gasoline-contaminated site and tail gas emitted from automobiles on the nearby highway were thought as two major VOCs sources. It can be further proved by the fact that the lowest VOCs concentration always found at the upwind site (site A) of sampling region for different seasons with wind directions varied from the southwest to the northeast. The results concurred quite well with the field measurements of non-methane hydrocarbons..
(6) Journal of the Chinese Institute of Environmental Engineering, Vol. 14, No. 2 (2004). 122. they were close to either gasoline-contaminated site or Despite of seasonal variation, the fingerprints of highway. Although site A showed relatively low atmospheric VOCs at various sampling sites are concentrations of atmospheric VOCs, the most illustrated in Fig. 5. Similar to NMHC, VOCs were abundant VOCs were always higher at sampling sites B, C and D whereas Table 1. Sample number, concentration range and average of atmospheric VOCs at various seasons. Sample No. (n). Season First. 5. Second. 5. Third. 5. Fourth. 5. Fifth. 5. Sixth. 5. MTBE (ppbv). Benzene (ppbv). n-Octane (ppbv). Toluene (ppbv). Ethylbenzene (ppbv). m,p-Xylene (ppbv). 0.11~0.71 (0.32) 0.15~0.36 (0.20) 0.10~0.29 (0.20) 0.10~0.19 (0.15) 0.03~0.06 (0.05) 0.04~0.31 (0.12). 0.18~0.29 (0.22) 0.24~0.48 (0.38) 0.16~0.35 (0.25) 0.14~0.32 (0.22) 0.06~0.15 (0.10) 0.08~0.41 (0.18). 0.15~0.30 (0.24) 0.19~1.80 (0.67) 0.12~0.36 (0.24) 0.12~0.34 (0.22) 0.04~0.08 (0.06) 0.06~0.15 (0.11). 0.16~0.24 (0.21) 1.09~1.57 (1.40) 0.17~0.58 (0.38) 0.15~0.55 (0.35) 0.05~0.21 (0.10) 0.08~0.80 (0.30). 0.13~0.16 (0.14) 0.23~0.27 (0.25) 0.12~0.19 (0.15) 0.10~0.18 (0.15) 0.04~0.08 (0.07) 0.04~0.21 (0.10). 0.13~7.97 (2.43) 0.35~0.44 (0.38) 0.20~0.35 (0.28) 0.15~0.33 (0.26) 0.02~0.05 (0.04) 0.09~0.55 (0.20). ( ) represents the average concentration of atmospheric VOCs.. Table 2. Concentration ratio of toluene and benzene (T/B) at various sampling locations and seasons. Season. Date Year/M/D. Time. Wind Direction. A. B. C. D. E. First. 2002/03/01. Northwest. 0.83. 1.11. 1.14. 0.79. 0.89. Second. 2002/04/15. Southwest. 4.54. 3.43. 3.27. 3.36. 4.38. Northwest. 1.06. 1.96. 2.00. 1.43. 1.05. Third. 2002/07/22. 11 AM | 2 PM. Fourth. 2002/10/19. Northwest. 1.07. 2.25. 2.20. 1.41. 1.00. Fifth. 2003/01/24. Northeast. 0.80. 1.50. 0.90. 0.90. 0.90. Sixth. 2003/04/01. Northwest. 1.00. 1.90. 1.80. 1.80. 1.00. 11 AM Exhaust gasa － | 2 PM － － Exhaust gas [12-13] Exhaust gas [14] － － Exhaust gas [15] － － a sampling on the highway in current study. －. 2.00~2.30. － － －. 1.6~2.1 1.6~2.0 2.3~2.7. n-octane and toluene. Sites B, C and D demonstrated relatively high concentrations of m,p-xylene and toluene. Site E usually had the lowest concentration of atmospheric VOCs except for toluene. In comparison with various seasons, the first and the second seasons (Spring and Summer of 2002) demonstrated relatively high concentrations of atmospheric VOCs. The seasonal variations of VOCs levels might result from many factors such as wind direction, wind speed and traffic conditions near site. The distribution of atmospheric VOCs at various sampling sites and seasons is illustrated in Fig. 6. Overall speaking, the concentrations of atmospheric VOCs were relatively low except for the first and the second seasons. During the first and the second seasons, a consistent variation of VOCs at various sampling sites was observed. For instance, m,p-xylene. was the major VOCs in the first season, while toluene and n-octane were the most abundant VOCs in the second season. The results might attribute to the transportation of VOCs from local and/or regional sources to the sampling region by the prevailing wind. The concentration ratios of toluene and benzene (T/B) at various sampling locations and seasons are summarized in Table 2. Table 2 shows that T/B ratio varied significantly with seasons and locations. The T/B ratios in the first and the fifth seasons were relatively lower, while the T/B ratios in the second season were relatively higher than other seasons. In addition to these three seasons, the T/B ratios at sites A, B, C, D and E were in the range of 1.00-1.07, 1.902.25, 1.80-2.20, 1.41-1.80 and 1.00-1.05, respectively. In comparison with other studies [12-15], the T/B ratio of tail-pipe exhaust gas on the highway (2.0-2.3).
(7) Chia-Wei Lee et al.: Characteristics and Health Impacts of Atmospheric Volatile Organic Compounds at the Surrounding Area of a Gasoline-contaminated Remediation Site. and the characteristics of VOCs sampled at sites B and C were quite similar to the characteristics of VOCs emitted from tail-pipe exhaust gas. The results indicated that atmospheric VOCs sampled at site B (the downwind of highway and the upwind of gasoline-contaminated site) and site C (the gasolinecontaminated site) were mainly attributed to the tailpipe exhaust gas emitted from automobiles driven on. 123. second season ranged from 3.27 to 4.54, which were quite similar to the T/B ratio of 3.8-4.2 for 92unleaded gasoline. It suggested that, in the second season, the atmospheric VOCs were mainly attributed from the fugitive emission of spilled gasoline. Further investigation on the fingerprints of ambient VOCs was to determine the mass ratio of benzene, toluene, ethylbenzene and m,p-xylene (BTEX).. Fig. 6. Distribution of atmospheric VOCs at various locations and seasons.. Fig. 5. Fingerprints of atmospheric VOCs at various sampling locations.. the nearby highway. However, the T/B ratios in the. The mass ratios of BTEX for different seasons at various sampling locations are summarized in Table 3. In order to characterize the component of tail gas, VOCs were sampled and analyzed from tail pipes as well as on highway in this study. It reveals that the BTEX ratio of the tail gas was 1.6:3.2:1.0:2.5. Similar to T/B ratios, the BTEX ratios varied very much with seasons and locations. However, the BTEX ratios in current study were not similar to those of the other studies [12-14,16-17]. It might result from the difference of vehicles’ emissions in different studies. In spite of the first, the second, and the fifth seasons, the BTEX ratios at sites B, C and D were similar to tail gas. Concurred with the T/B ratios, results from BTEX ratios suggested that ambient VOCs were mainly attributed to the exhaust of tail gas from the nearby highway. Moreover, the BTEX ratios at site A (upwind site) and site E (downwind site) were also quite similar with each other in three seasons. It.
(8) Journal of the Chinese Institute of Environmental Engineering, Vol. 14, No. 2 (2004). 124. suggested that the background concentrations of VOCs in ambient atmosphere did not vary much although some VOCs might be emitted from tail gas and spilled oil.. The health risks exposed to VOCs for those residences who lived in the surrounding area of the gasoline-spilled site were further assessed using API’s. Health Risk Assessment Table 3. Concentration ratio of benzene, toluene, ethylbenzene, and m,p-xylene (BTEX) at various sampling locations and seasons. Season First Second Third Fourth Fifth Sixth Exhaust gasa Exhaust gas [12-13] Exhaust gas [14] Exhaust gas [16] Exhaust gas [17] a. A 1.8:2.1:1.0:8.2 1.0:4.5:1.0:1.5 1.3:1.4:1.0:1.7 1.4:1.5:1.0:1.5 1.5:1.3:1.0:0.5 2.0:2.0:1.0:2.3. B 1.3:1.4:1.0:56.9 1.8:6.3:1.0:1.5 1.6:3.1:1.0:2.0 1.3:3.0:1.0:1.6 1.9:2.6:1.0:0.6 2.0:3.8:1.0:2.6. C 1.4:1.6:1.0:16.9 1.9:6.3:1.0:1.8 1.7:3.4:1.0:2.0 1.4:3.1:1.0:1.7 1.3:1.1:1.0:0.6 1.8:3.0:1.0:1.5 1.6:3.2:1.0:2.5 3.4:6.2:1.0:4.9 4.1:6.6:1.0:2.2 3:7:1:5 3:7:1:4. D 1.8:1.4:1.0:0.8 1.7:5.6:1.0:1.3 1.8:2.6:1.0:1.8 1.8:2.5:1.0:1.8 1.3:1.2:1.0:0.7 1.5:2.8:1.0:1.6. E 1.3:1.1:1.0:3.1 1.2:5.2: 1.0:1.5 1.4:1.4: 1.0:1.9 1.3:1.3: 1.0:1.9 1.3:1.1: 1.0:0.7 1.7:1.7 :1.0:1.7. sampling on the highway in current study. Table 4.. Inhalation exposure scenario for DSS estimation [26]. Parameters Body weight (BW) Lifetime (AT) Exposure frequency (EF) Exposure duration (ED) Inhalation rate (IH) Bioavailability (ba) Benzene SF Benzene RfD Toluene RfD Ethylbenzene RfD Xylenes RfD MTBE RfD. Table 5.. Unit kg year day/year year m3/hr mg/mg (mg/kg-day)-1 mg/kg-day mg/kg-day mg/kg-day mg/kg-day mg/kg-day. Value 70 70 365 30 1.25 1 2.9×10-2 1.7×10-3 0.114 0.290 0.200 0.857. The health hazard index obtained from health risk assessment [34].. Chemicals Benzene. First 8.3×10-7. SECOND 1.4×10-6. Benzene Ethylbenzene MTBE Toluene Xylenes Total. 3.9×10-2 2.0×10-4 1.1×10-4 6.5×10-4 5.0×10-3 4.5×10-2. 6.8×10-2 3.6×10-4 7.1×10-4 4.4×10-4 7.9×10-3 7.4×10-2. DSS. The inhalation exposure scenario for risk assessment of on-site population is shown in Table 4 [26]. For cancer risk assessment, benzene was the. Cancer hazard risk Third Fourth -7 4.1×10 3.6×10-7 Non-cancer hazard risk Hazard index 1.9×10-2 1.7×10-2 -5 5.9×10 8.5×10-5 4.2×10-5 2.2×10-5 -4 8.4×10 8.1×10-4 -4 2.1×10 2.8×10-4 -2 2.0×10 1.8×10-2. Fifth 3.6×10-7. Sixth 4.1×10-7. 1.7×10-2 9.5×10-5 5.3×10-5 1.3×10-3 8.7×10-5 1.8×10-2. 2.0×10-2 1.1×10-4 3.3×10-5 4.2×10-4 2.4×10-4 2.0×10-2. only carcinogen considered in this study. Based on the field measurements during six sampling seasons, the lifetime cancer risks for benzene exposure ranged.
(9) Chia-Wei Lee et al.: Characteristics and Health Impacts of Atmospheric Volatile Organic Compounds at the Surrounding Area of a Gasoline-contaminated Remediation Site. from 3.6×10-7 to 1.4 × 10-6. Even though the risk estimated for the second season was slightly higher than 1.0 × 10-6, the mean value of six seasons was less than the criteria of one part per million. Besides, the assessed total non-cancer hazard indices for BTEX and MTBE ranged from 1.8 × 10-2 to 7.4 × 10-2, which were much less than the hazard index of unity (see Table 5). Therefore, both estimated cancer and noncancer hazard risks show that atmospheric VOCs at the surrounding area of the gasoline-contaminated site would not cause significant health effects on the nearby community. SUMMARY AND CONCLUSIONS This study investigated the characteristics of ambient VOCs in the atmosphere at the surrounding area of a gasoline-contaminated remediation site by conducting a field measurement of protocol. Results obtained from the field measurement protocol indicated that the concentration of NMHC at the upwind site was always lower than the downwind site. Major VOCs observed in the sampling region were noctane, toluene, and m,p-xylene. However, the observation of high boil-point compounds in several cases suggested that the atmospheric VOCs at nearby community were not only emitted from the gasolinecontaminated remediation site but also from other unidentified local sources. This study revealed that the T/B ratios of atmospheric VOCs were similar to the T/B ratio of tail-pipe exhaust gas. It suggested that atmospheric VOCs were mainly attributed to the tailpipe exhaust gas rather than the spilled gasoline fuel. In addition to T/B ratios, similar trends were also observed for the BTEX ratios. Health risk assessment indicated that the mean lifetime cancer risk for nearby population was less than 1×10-6, while the total noncancer hazard indexes were less than unity. Both estimated cancer and non-cancer hazard risks show that atmospheric VOCs at the surrounding area of the gasoline-contaminated remediation site would not cause significant health impacts on nearby population. Based on the health risk assessment, this study concluded that the gasoline-contaminated site has been successfully remedied and would not cause further health problems on the neighboring residences. ACKNOWLEDGEMENTS This study was performed under the auspicious of Environmental Protection Bureau (EPB) of Chia-yi County, Taiwan. The authors would like to express their great appreciation to the EPB of Chia-yi County for its financial support. Special thanks also went to Central Technology Co., Ltd. for its constant assistance in monitoring of ambient hydrocarbons.. 125. REFERENCES 1. U. S. EPA, “Soil Screening Guidance: User’s Guide,” U. S. EPA, EPA-540/R-96/ 018 (1996). 2. Kao, C. M. and C. C. Wang, “Control of BTEX Migration by Intrinsic Bioremediation at A Gasoline Spill Site,” Wat. Res., 34(13), 3413-3423 (2000). 3. Atkinson, R., “Gas-phase Tropospheric Chemistry of Organic Compounds: A Review,” Atmos. Environ., 24A, 1-41 (1990). 4. Tso, T. L., “Research Report of CPC in Taiwan, 87-CPC-M-007-004,” National Tsing-hua University, Hsinchu, Taiwan, ROC (1998). (in Chinese) 5. Tsai, J. H., H. L. Chiang, Y.C. Hsu, H. C. Weng and C. Y. Yang, “The Speciation of Volatile Organic Compounds (VOCs) from Motorcycle Engine Exhaust at Different Driving Modes,” Atmos. Environ., 37, 2485-2496 (2003). 6. Tsai, J. H., H. L. Chiang, Y. Y. Liu and C. Y. Yang, “Volatile Organics Profiles and Photochemical Potentials from Motorcycle Engine Exhaust,” J. A&WMA, 53, 516-522 (2003). 7. Hsieh, C. C. and J. H. Tsai, “VOC Concentration Characteristics in Southern Taiwan,” Chemosphere, 50, 545-556 (2002). 8. Fukui, Y. and P. V. Doskey, “An Enclosure Technique for Measuring Nonmethane Organic Compound Emissions from Grasslands,” J of Environ. Quality, 25, 601-610 (1991). 9. Guenther, A., “Seasonal and Spatial Variations in Natural Volatile Organic Compound Emission,” Ecological Applications, 7(1), 34-45 (1997). 10. Duffy, B. L. and P. F. Nelson, “Nom-Methane Exhaust Composition in The Sydney Harbour Tunnel:A Focus on Benzene and 1,3-Butadiene,” Atmos. Environ., 30, 2759-2768 (1996). 11. Singh, H. and P. Zimmerman, “Atmospheric Distribution and Sources of Nonmethane Hydrocarbons,” Nriagu, J. O. （ Ed. ） Gaseous Pollutants: Characterization and Cycling. Wiley, New York, pp.177-235 (1992). 12. Scheff, P. A., C. B. Keil, J. Graf-teterycz, J. Y. Jeng and R. A. Wadden, “The Composition of Organic Emissions in Car and Diesel Bus Parking Facilities,” Proc. American Industrial Hygiene Conf. (1992). 13. Scheff, P. A., R. A. Wadded, “Receptor Modeling of Volatile Organic Compounds Emission Inventory and Validation,” ES&T, 27(4) (1993). 14. Wadden, R. A., “Source Discrimination of ShortTerm Hydrocarbon Samples Measured Aloft,”.
(10) 126. Journal of the Chinese Institute of Environmental Engineering, Vol. 14, No. 2 (2004). ES&T, 20(5), 206-208 (1986). 15. Yang, G. L., “The Concentrations of C6-C10 Hydrocarbons in the Ambient Air of Taiwan,” Master Thesis, Department of Atomic Science, National Tsing Hua University, Taiwan (1991). (in Chinese) 16. Smith, D. L., G. F. Evans and T. A. Lumpkin, “Measurements of VOCs from TAMS Network,” J. A&WMA, 42(10), 1319-1323 (1992). 17. Chiang, P. C., “The Development and Application of Receptor Model in Central and Northern Taiwan”， ROC EPA Report，EPA-82-E3F1-0901 (1993). (in Chinese) 18. U. S. EPA, “MTBE Fact Sheet #2, Remediation of MTBE Contaminated Soil and Groundwater,” U. S. EPA, EPA-510/F-97/015 (1998). 19. American Society for Testing and Materials (ASTM), “Standard Guide for Risk-Based Corrective Action Applied at Petroleum Release Sites,” ASTM E1739-95 (1995). 20. American Society for Testing and Materials (ASTM), “Risk-Based Decision Making Performance Assessment Study Bulletin #1,” ASTM (1999). 21. American Society for Testing and Materials (ASTM), “Risk-Based Decision Making Performance Assessment Study Bulletin #2,” ASTM (2000). 22. American Society for Testing and Materials (ASTM), “ Standard Provisional Guide for Riskbased Corrective Action,” ASTM PS104-98 (1998). 23. American Society for Testing and Materials (ASTM), “Standard Provisional Guide for Riskbased Corrective Action,” ASTM E2081-00 (2001). 24. Groundwater Services Inc., “RBCA (Risk based Corrective Action) 1.3a,” Software, Version 1.3a (1995). 25. Sprague, R., H. Jr and H. J. Watson (editors), “Decision Support Systems: Putting Theory into Practice,” Third edition, Prentice-Hall, Inc., New Jersey, USA (1993). 26. American Petroleum Institute (API), “Exposure and Risk Assessment Decision Support System (DSS),” Software, Version 2.0 (1999).. 27. Chang, S. H., C. Y. Kuo, J. W. Wang and K. S. Wand, “Comparison of RBCA and CalTOX for Setting Risk-based Cleanup Levels based on Inhalation Exposure,” Chemosphere, 56, 359-367 (2004). 28. Khan, F. I. and T. Husain, “Risk-based Monitored Natural Attenuation-A Case Study,” Journal of Hazardous Materials, B85, 243–272 (2001). 29. Hetrick, D. M. and S. J. Scott, “Fate and Exposure Models: Selecting the Appropriate Model for a Specific Application SESOIL and AT123D models, ” J. Soil Contam., 7 (3), 301–309 (1998). 30. Chiang, Y. C., “Characteristics and Source Identification of Atmospheric Volatile Organic Compounds in Taipei, ” Master Thesis, Graduate Institute of Environmental Engineering, National Taiwan University, Taiwan (1993). (in Chinese) 31. Edgerton S. A., M. W. Holdren, D. L. Smith and J. J. Shah, “Inter-Urban Comparison of Ambient Volatile Organic Compound Concentrations in U. S. Cities,” J. A&WMA, 39 (5), 729-732 (1989). 32. Chang, F. H., “A Study of Air Toxics Characteristics in the Vicinity of a Petro- chemical Industrial Park,” Master Thesis, Department of Environmental Engineering, National Cheng Kung University, Taiwan (1994). (in Chinese) 33. Yeh, M. P. and J. G. Lo, “The Analysis Methods of Volatile Organic Compound in Ambient Air (1),” Proc. of the 10th Air Pollution Control and Technology Conf., CIEnvE, pp.651-356 (1993). (in Chinese) 34. Chia-yi EPB, “Evaluation of Gasolinecontaminated Remediation Site at 274.3K of Highway # 1,” ROC Chia-yi EPB Report (2003). (in Chinese). Discussions of this paper may appear in the discussion section of a future issue. All discussions should be submitted to the Editor-in-chief within six months. Manuscript Received: January 4, 2004.
(11) Chia-Wei Lee et al.: Characteristics and Health Impacts of Atmospheric Volatile Organic Compounds at the Surrounding Area of a Gasoline-contaminated Remediation Site. 127. 汽油污染場址整治後環境空氣中揮發性有機物特性及健康風險評估 李家偉 1,* 1. 羅卓卿 2. 陳威錦 2. 袁. 菁3. 袁中新 2. 國立高雄第一科技大學環境與安全衛生工程系 2. 3. 國立中山大學環境工程研究所. 國立高雄大學土木與環境工程學系. 關鍵詞：汽油污染整治場址、揮發性有機物、甲苯/苯比值、健康風險評估. 摘. 要. 本研究以某整治後之汽油污染場址為研究對象，探討場址附近環境空氣中揮發性有機物之特性，並評估 鄰近社區居民吸入揮發性有機物所產生之健康風險。本研究自 2002 年 2 月起至 2003 年 4 月止，在整治後之 污染場址及周圍地區設置包含 5 個採樣點之揮發性有機物採樣網，進行近地表揮發性有機物之採樣。空氣中 揮發性有機物係以多重床式不銹鋼吸附管進行採樣，經熱脫附後以 GC-FID 進行定量分析，空氣中甲烷及非 甲烷碳氫化合物亦於現場進行連續偵測。本研究結果顯示，就非甲烷總碳氫化合物而言，污染場址上風處背 景採樣點之濃度多半低於場址下風處。空氣中揮發性有機物主要為正辛烷、甲苯及間,對-二甲苯，其中甲苯 與苯濃度之比值，與汽車尾氣排放之比值相似，而苯、甲苯、乙苯、間,對-二甲苯之比值亦有相同趨勢。此 結果顯示，污染場址空氣中揮發性有機物受汽車尾氣排放之影響較大，而受場址本身逸散之影響則較小。本 研究另以風險模式推估污染場址鄰近居民吸入揮發性有機物所造成之健康風險。在致癌風險部分，居民吸入 苯之致癌機率小於百萬分之一；而在非致癌風險部分，揮發性有機物之總危害指數亦未超過基準值，顯示吸 入空氣中揮發性有機物對鄰近社區居民健康之影響並不顯著。.
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