Jia-Lin Wang

Assessment of reducing ozone forming potential for vehicles using liquefied petroleum gas as an alternative fuel

Liquefied petroleum gas (LPG) is currently used in a small fleet of taxis as an alternative fuel to gasoline in Taipei, Taiwan as part of an incentive program promoted by Taiwan EPA to improve urban air quality. Under the test procedure in accordance with the US FTP-75 protocol to simulate an average urban driving pattern, the exhaust from four LPG and four gasoline-powered vehicles was analyzed for the percent composition of NMHCs. Emission factors for individual NMHCs were apportioned from the emission factors of total hydrocarbon based on chemical composition of the exhaust from both types of vehicles. After adjusting for ozone formation potential (OFP) by maximum incremental reactivity, the average OFP for LPG vehicles was estimated to be only 52.8% (g-O3/veh-km) of the gasoline vehicles, or 3.3% of ozone reduction in Taipei metropolitan area, should all taxis be converted to LPG fuel. Composition analysis of the local LPG revealed that propane, butane and isobutane were the three major components and negligible amounts of alkenes were also found. In addition, the leakage from a LPG service station was substantially smaller than from a gasoline service station because of the closed design with the LPG pumping systems.

Traffic-related air pollution and cardiovascular mortality in central Taiwan

In this study, the relationship between cardiovascular mortality and traffic-related air pollutants (NO(2), CO, PM(10), and six volatile organic compounds (VOCs), propane, iso-butane, propylene, benzene, meta-, para-, and ortho-xylenes) was investigated. The concentrations of NO(2), PM(10) and CO from 1993 to 2006 were measured at a fixed-site air monitoring station, and VOC data from 2003 to 2006 were obtained from a photochemical assessment monitoring site in an urban area in central Taiwan. Outcome variables were data on mortality due to cardiovascular diseases (ICD-9-CM 410-411, 414, 430-437) from 1993 to 2006. Cardiovascular mortality averaged 1.5 cases, ranging between 0 and 9 cases per day. Daily air pollution levels ranged from 0.5 to 80.5ppb for NO(2) and from 0.1 to 3.8ppm for CO. From the subset of data from 2003 to 2006, daily average values ranged from 0.6 to 17.5ppb for propane, 0.3 to 6.7ppb for iso-butane, 0.3 to 6.7ppb for propylene, 0.2 to 3.8ppb for benzene, 0.3 to 26.0ppb for m,p-xylene, and 0.02 to 7.6ppb for o-xylene. Poisson generalized additive model was used to estimate the effects of elevated air pollutant levels on daily mortality, adjusting for meteorological conditions and temporal trends. Single-pollutant model showed that cardiovascular mortality was significantly associated with NO(2) lagged 2 days, and with propane, iso-butane, and benzene lagged 0 day. The relative risk for an interquartile range increase in air pollutant levels was 1.053 for NO(2), 1.064 for propane, 1.055 for iso-butane, and 1.055 for benzene. In conclusion, daily cardiovascular mortality showed association with data on acute exposure to traffic air pollutants in Taichung, which is an important factor to consider in studying cardiovascular mortality in urban environments.

Automated gas chromatography with cryogenic / sorbent trap for the measurement of volatile organic compounds in the atmosphere

An automated gas chromatographic system was constructed to easily adapt either the cryogenic trap or chemical sorbent trap for preconcentrating ambient levels of volatile organic compounds. Remarkable similarity in chromatograms from C3 to C10 was found between these two enrichment methods, except that the sorbent trap did not quantitatively trap the C2-hydrocarbons. In contrast to cryogenic trapping, the chromatographic conditions for more volatile compounds were substantially improved using the sorbent trap. Water interference on the porous-layer open tubular column was also better managed using the sorbent trap for the continuous analysis of humid room air. The similarity in peak profiles between the GC-flame ionization detection (FID) and a commercial GC-MS system, regardless of concentration levels, facilitated compound identification on the FID chromatograms based on a field mission involving analysis of 106 air samples.

Cryogen free automated gas chromatography for the measurement of ambient volatile organic compounds

An automated gas chromatographic system was constructed for measuring ambient volatile organic compounds (VOCs). Preconcentration of the VOCs was performed by using two separated sorbent traps of different combinations with each designated for either low or high boiling VOCs. Both traps and their associated valve systems were integrated as a complete system sharing a common sample inlet. Precise temperature controls for desorption relied on the use of a process controller with proportional-integral-derivative algorithm to throttle the current supply. No additional cryo-focusing stage prior to the column was needed owing to the flash heating capability for desorption. Other than the cryogen free preconcentration and focusing, the separation of VOCs of large volatility difference was also performed without cryogen. The system employed an Al2O3/KCl porous-layer open tubular column for separating C3-C7 compounds; and a DB-1 column for C6-C12. This automated GC system has been deployed in a Taiwan Environmental Protection Agency urban air quality monitoring station of Taiwan for continuous measuring C3-C7 ozone precursors. Excellent correlation between the car exhaust type of compounds measured by our GC system and carbon monoxide measured by a non-dispersive infrared spectrometer was observed, suggesting the automated GC system was robust and reliable.

Concentration distributions of anthropogenic halocarbons over a metropolitan area

Abstract A method coupling trace gas analysis with air sampling was employed to examine relative emission strengths of several regulated halocarbons. A total of 51 air samples were taken in a random manner throughout the Taipei metropolitan area within one hour period. Several background air samples were also collected on the east coast of Taiwan to provide baseline conditions. The concentrations of CFC-11 (CCl 3 F), CFC-113(CCI 2 FCCIF 2 ), and CCl 4 throughout the city were found to be uniform and close to the background levels, suggesting emissions were insignificant. By contrast, the variability in concentrations for CFC-12 (CCI 2 F 2 ) and CH 3 CCl 3 were large and exhibited area dependence, implying significant usage.

Construction of an automated gas chromatography/mass spectrometry system for the analysis of ambient volatile organic compounds with on-line internal standard calibration

An automated sampling and enrichment apparatus coupled with a gas chromatography/mass spectrometry (GC/MS) technique was constructed for the analysis of ambient volatile organic compounds (VOCs). A sorbent trap was built within the system to perform on-line enrichment and thermal desorption of VOCs onto GC/MS. In order to improve analytical precision, calibration accuracy, and to safe-guard the long-term stability of this system, a mechanism to allow on-line internal standard (I.S.) addition to the air sample stream was configured within the sampling and enrichment apparatus. A sub-ppm (v/v) level standard gas mixture containing 1,4-fluorobenzene, chloropentafluorobenzene, 1-bromo-4-fluorobenzene was prepared from their pure forms. A minute amount of this I.S. gas was volumetrically mixed into the sample stream at the time of on-line enrichment of the air sample to compensate for measurement uncertainties. To assess the performance of this VOC GC/MS system, a gas mixture containing numerous VOCs at sub-ppb (v/v) level served as the ambient air sample. Various internal standard methods based on total ion count (TIC) and selective ion monitoring (SIM) modes were attempted to assess the improvement in analytical precision and accuracy. Precision was improved from 7-8% RSD without I.S. to 2-3% with I.S. for the 14 target VOCs. Uncertainties in the calibration curves were also improved with the adoption of I.S. by reducing the relative standard deviation of the slope (Sm%) by an average a factor of 4, and intercept (Sb%) by a factor of 2 for the 14 target VOCs.

Construction and validation of automated purge-and-trap-gas chromatography for the determination of volatile organic compounds.

An automated purge-and-trap chromatographic system for the determination of dissolved volatile organic compounds in aqueous samples was built in the laboratory with minimum cost both in the construction and routine operation. This system was built upon a commercial gas chromatograph with full automation capability using self-developed hardware and software. The use of a multi-sorbent bed quantitatively trapped a wide range of volatile organic compounds at ambient temperature, including the extremely volatile ones such as dichlorofluoromethane (CFC-12). Flash heating for rapid desorption and adequate plumbing for minimizing dead volume resulted in excellent chromatographic separation at above-ambient temperatures, which eliminated the need for cryogen for cooling at the head of the column, a second refocusing stage, or entire GC oven for refocusing. This cryogen-free system was tested with standard solutions and environmental samples for determining hydrocarbons with flame ionization detection, and halogenated compounds with electron-capture detection. An innovative method was also developed for validating the systems linearity for extremely volatile compounds. By introducing ambient air, which usually contains constant levels of anthropogenic halocarbons, e.g., CFC-12 and CFC-11 (CCl3F), the need to prepare aqueous standards containing extremely volatile compounds is avoided, hence providing a convenient method for evaluating a purge-and-trap system.

PCDD/F Measurement at a High-Altitude Station in Central Taiwan: Evaluation of Long-Range Transport of PCDD/Fs during the Southeast Asia Biomass Burning Event

Recent biomass burning in Southeast Asia has raised global concerns over its adverse effects on visibility, human health, and global climate. The concentrations of total suspended particles (TSPs) and other vapor-phase pollutants (CO and ozone) were monitored at Lulin, an atmospheric background station in central Taiwan in 2008. To evaluate the long-range transport of persistent organic pollutants (POPs) during the Southeast Asia biomass burning event, the atmospheric polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) were also measured at Lulin station. The atmospheric PCDD/F and TSP concentrations measured at Lulin station ranged from 0.71-3.41 fg I-TEQ/m(3) and 5.32-55.6 microg/m(3), respectively, during the regular sampling periods. However, significantly higher concentrations of PCDD/Fs, TSPs, CO, and ozone were measured during the spring season. These high concentrations could be the result of long-range transport of the products of Southeast Asia biomass burning. During the Southeast Asia biomass burning event (March 18-24, 2008), an intensive observation program was also carried out at the same station. The results of this observation program indicated that the atmospheric PCDD/F concentration increased dramatically from 2.33 to 390 fg I-TEQ/m(3) (March 19, 2008). The trace gas (CO) of biomass burning also significantly increased to 232 ppb during the same period, while the particle-bound PCDD/Fs in the TSP increased from 28.7 to 109 pg I-TEQ/g-TSP at Lulin station during the burning event. We conclude that there was a significant increase in the PCDD/F concentration in ambient air at a high-altitude background station in central Taiwan during the Southeast Asia biomass burning event.

Assessment of removal efficiency of perfluorocompounds (PFCs) in a semiconductor fabrication plant by gas chromatography.

This study investigated a gas chromatographic (GC) method to assess the destruction or removal efficiency (DRE) of local scrubbers on five perfluorocompounds (PFCs), i.e., SF(6), NF(3), CF(4), C(2)F(6), and C(3)F(8), which are very potent greenhouse gases used in a semiconductor fabrication plant. Air samples taken at inlets and outlets of local scrubbers were analyzed by a self-constructed multi-column GC system equipped with thermal conductivity detection. Three packed columns were integrated into the heart-cut GC system to allow simultaneous analysis of the five target PFCs. The Porapak Q pre-column performs rough separation and cuts eluent groups to two analytical columns for optimal separation. The Molecular Sieve - 5A column separated NF(3), CF(4), and C(3)F(8) and the second Porapak Q separated SF(6) and C(2)F(6). Linearity was greater than 0.995 (R(2)) for the five PFCs, and the reproducibility was about 4% (relative standard deviation) for NF(3), and better than 0.5% for the other four PFCs. DRE for the combustion (CB) and electric-thermal types of local scrubbers was evaluated by taking into account the in-line dilution from air and fuel gases. Both flow and tracer methods were employed to deduce the dilution factors (DFs). For the tracer method, helium was employed as the tracer and injected upstream of the scrubbers and thus mixed with the exhaust gas. With this method, the DFs were determined to be in the range from 4.8 to 5.9 for the CB unit, significantly higher than the value of 3.3 based on the flow method. The DREs for the CB unit for C(3)F(8) were greater than 90% and between 40% and 50% for CF(4).

Sub-second thermal desorption of a micro-sorbent trap for the analysis of ambient volatile organic compounds.

This study investigates a novel approach of fast thermal desorption on a micro-sorbent trap for analyzing ambient volatile organic compounds (VOCs) by gas chromatography with flame ionization detection. Unlike conventional approaches, the temperature feedback mechanism for temperature control was abandoned, which often poses a limit to the heating speed due to slow response of the sensor and the control algorithm. Instead, a series of programmed a.c. pulses was given to the Ni-Cr wire coiled around the micro-trap to perform instant heating from room temperature to 250 degrees C within a fraction of a second, maintained at 250 degrees C during injection, and subsequently to 300 degrees C for trap cleaning. Temperature fluctuation around a high temperature set point could be maintained within +/- 10 degrees C. Significant improvement in resolution and peak height was obtained compared to a trap with temperature feedback and control algorithm. While keeping resolution at a satisfactory level, the sub-second desorption approach allows faster chromatography and at the same time increases the sensitivity of VOC analysis.