the less-reported gaseous studies have primarily dealt with chemical process stream concentrations than indoor air quality (IAQ) concentration levels. Accordingly, the current study was conducted to establish the feasibility of applying visible-light-induced TiO₂ doped with sulfur (S) element to cleanse toluene and ehtyl benzene at IAQ levels. The S-doped TiO₂ was prepared by applying two popular processes and two well-known methods. For both target compounds, the two coating methods exhibited different photocatalytic oxidation (PCO) efficiency. Similarly, the two S-doping processes showed different PCO efficiency. These results indicate that the coating method and doping process are important parameters which can influence PCO efficiency. Meanwhile, it was found that the PCO efficiency of ethyl benzene was higher than that of toluene. In addition, the degradation efficiency of the target compounds increased as the relative humidity (RH) decreased. The PCO efficiency varied from 44% to 74% for toluene and from 68% to 95%, as the RH decreased. Consequently, it is suggested that with appropriate RH conditions, the visible-light-assisted photocatalytic systems can also become an important tool for improving IAQ.

In this study, we evaluated the photocatalytic oxidation efficiency of aromatic volatile hydrocarbons by using WO3–doped TiO2 nanotubes (WTNTs) under visible-light irradiation. One-dimensional WTNTs were synthesized by ultrasonic-assisted hydrothermal method and impregnation. XRD analysis revealed successful incorporation of WO3 into TiO2 nanotube (TNT) structures. UV-Vis spectra exhibited that the synthesized WTNT samples can be activated under visible light irradiation. FE-SEM and TEM images showed the one-dimensional structure of the prepared TNTs and WTNTs. The photocatalytic oxidation efficiencies of toluene, ethylbenzene, and o-xylene were higher using WTNT samples than undoped TNT. These results were explained based on the charge separation ability, adsorption capability, and light absorption of the sample photocatalysts. Among the different light sources, light-emitting-diodes (LEDs) are more highly energy-efficient than 8-W daylight used for the photocatalytic oxidation of toluene, ethylbenzene, and o-xylene, though the photocatalytic oxidation efficiency is higher for 8-W daylight.

The adequacy of urban air quality monitoring networks in the largest metropolitan city, Seoul was evaluated using multivariate analysis for SO2, NO2, CO, PM10, and O3. Through cluster analysis for 5 air pollutants concentrations, existing monitoring stations are seen to be clustered mostly by geographical locations of the eight zones in Seoul. And the stations included in the same cluster are redundantly monitoring air pollutants exhibiting similar atmospheric behavior, thus it can be seen that they are being operated inefficiently. Because monitoring stations groups representing redudancy were different depending on measurement items and several pollutants are being measured at the same time in each air monitoring station, it is seemed to be not easy to integrate or transmigrate stations. But it may be proposed as follows : the redundant stations can be integrated or transmigrated based on ozone of which measures are increasing in recent years and alternatively the remaining pollutants other than the pollutant exhibiting similar atmospheric behavior with nearby station’s can be measured. So it is considered to be able to operate air quality monitoring networks effectively and economically in order to improve air quality.

Unlike many laboratory-scale studies on absorption of organic compounds (VOCs), limited pilot-scale studies have been reported. Accordingly, the present study was carried out to examine operation parameters for the effective control of a hydrophilic VOC (methyl ethyl ketone, MEK) by applying a circular pilot-scale packed-absorption system (inside diameter 37 cm × height 167 cm). The absorption efficiencies of MEK were investigated for three major operation parameters: input concentration, water flow rate, and ratio of gas flow-rate to washing water amount (water-to-gas ratio). The experimental set-up comprised of the flow control system, generation system, recirculation system, packed-absorption system, and outlet system. For three MEK input concentrations (300, 350, and 750 ppm), absorption efficiencies approached near 95% and then, decreased gradually as the operation time increased, thereby suggesting a non-steady state condition. Under these conditions, higher absorption efficiencies were shown for lower input concentration conditions, which were consistent with those of laboratory-scale studies. However, a steady state condition occurred for two input concentration conditions (100 and 200 ppm), and the difference in absorption efficiencies between these two conditions were insignificant. As supported by an established gas-liquid absorption theory, a higher water flow rate exhibited a greater absorption efficiency. Moreover, as same with the laboratory-scale studies, the absorption efficiencies increased as water-to-gas ratios increased. Meanwhile, regardless of water flow rates or water-to-gas ratios, as the operation time of the absorption became longer, the pH of water increased, but the elevation extent was not substantial (maximum pH difference, 1.1).

The present study aims to evaluate the characteristics of atmospheric polycyclic aromatic hydrocarbons (PAHs) pollution in roadside and residential areas of two Korean metropolitan cities (Seoul and Incheon) and a background area (Seokmolee). This purpose was established by analyzing temporal and spacial concentration distribution of total and 7 individual PAHs, which were extracted from ambient particulate matters, and by utilizing a multivariate statistical method (principal component analysis, PCA) for the qualitative determination of potential PAH sources. Target PAHs included benzo(a)anthracene (BaA), benzo(a)pyrene (BaP), benzo(b)fluoranthene (BbF), benzo(k)fluoranthene (BkF), chrysene (Chr), dibenzo(a,h)anthracene (DahA), and indeno(1,2,3-cd)pyrene (IcdP). For all surveyed sites, the concentrations of total PAHs were higher in winter season than in other seasons. However, the concentrations of individual PAHs varied with surveyed sites. In both residential and roadside sites of Seoul and Incheon, BbF revealed the highest atmospheric levels. For all 7 target PAHs, the ambient concentrations were higher in Seoul and Incheon than in a background area (Seokmolee). In both residential and roadside areas, the concentrations of 4 target PAHs (BaA, BbF, BkF, DahA) were higher in Incheon than in Seoul. However, both the residential and roadside Chr concentrations were comparable in Seoul and Incheon. In addition, the residential IcdP concentrations were higher in Incheon than in Seoul, whereas the roadside concentrations were higher in Seoul. The roadside and residential BaP concentrations exhibited the reverse result to the IcdP concentrations. An PCA analysis suggested that atmospheric PAHs in both residential and roadside areas would be due to combined effects of several potential sources such as gasoline- and diesel-fueled vehicles, coal/oil combustion, and waste incineration.

This study evaluated the applicability of visible-light-driven N- and S-doped titanium dioxide(TiO2) for the control of low-level dimethyl sulfide(DMS) and dimethyl disulfide(DMDS). In addition, a photocatalytic unit(PU)-adsorption hybrid was evaluated in order to examine the removal of DMS and DMDS which exited the PU and a gaseous photocatalytic byproduct(SO2) which was generated during the photocatalytic processes. Fourier-Tranform-Infrared(FTIR) spectrum exhibited different surface characteristics among the three-types of catalysts. For the N- and S-doped TiO2 powders, a shift of the absorbance spectrum towards the visible-light region was observed. The absorption edge for both the N- and S-doped TiO2 was shifted to λ 720 nm. The N-doped TiO2 was superior to the S-doped TiO2 in regards to DMS degradation. Under low input concentration(IC) conditions(0.039 and 0.027 ppm for DMS and DMDS, respectively), the N-doped TiO2 revealed a high DMS removal efficiency(above 95%), but a gradual decreasing removal efficiency under high IC conditions(7.8 and 5.4 ppm for DMS and DMDS, respectively). Although the hybrid system exhibited a superior characteristic to PU alone regarding the removal efficiencies of both DMS and DMDS, this capability decreased during the course of a photocatalytic process under the high IC conditions. The present study identified the generation of sulfate ion on the catalyst surface and sulfur dioxide(maximum concentrations of 0.0019 and 0.0074 ppm for the photocatalytic processes of DMS and DMDS, respectively) in effluent gas of PU. However, this generation of SO2 would be an insignificant addition to indoor air quality levels.

This study was designed to evaluate qualitatively and quantitatively the pollutant compositions, which were emitted from three types of mosquito repellents(MRs)(mat-, liquid-vaporized, and coil-type) by utilizing a 50-L environmental chamber. A qualitative analysis revealed that 42 compounds were detected on the gas chromatography/ mass spectrometer system, and that the detection frequency depended upon chemical types. Nine of the 42 compounds exhibited a detection frequency of 100%. Four aromatic compounds(benzene, ethyl benzene, toluene, and xylene) were detected in all test MRs. The concentration equilibriums in the environmental chamber were achieved within 180 min after sample introduction. The coil-type MR represented higher chamber concentrations as compared with the mat- or liquid-vaporized-type MR, with respect to the target compounds except for naphthalene. In particular, the chamber concentrations of ethyl benzene, associated with the use of coil-type MR, were between 0.9 and 65 mg m-3, whereas those of mat- and liquid-vaporized-type MRs were between 0.5 and 2.0 mg m-3and 0.3 and 1.4 mg m-3, respectively. However, naphthalene concentrations in the chamber, where a liquid-vaporized-type MR was placed, were measured as between 17.8 and 56.3 mg m-3, but not detected in the chamber, where a mat- or coil-type MR was placed. The empirical model fitted well with the time-series concentrations in the environmental chamber(in most cases, determination coefficient, R2 ≳ 0.9), thereby suggesting that the model was suitable for testing emissions. In regards to the target compounds except for benzene, although they were emitted from the MRs, health risk from individual exposure to them were estimated not to be significant when comparing exposure levels with no observed adverse exposure levels or lowest observed adverse exposure levels of corresponding compounds. However, it was concluded that the use of MRs could be an important indoor source as regards benzene.

Present study was designed to characterize the concentrations of major roadside air pollutants in Daegu and to compare with those of Seoul and Busan. Evaluated were the exceedance frequence of mean concentrations of target compounds(CO, NO2, O3, PM10, SO2) and the relationship for time variation. Two air pollution monitoring stations(one roadside station and one residential station) in Daegu were selected for this study. In addition, one roadside monitoring station from each of Seoul and Busan was chosen for the comparison of Daegu monitoring stations. The data analyzed in the current study were collected from 1998 to 2000 by Daegu Regional Environmental Management Office. The roadside concentrations of NO2 and PM10 and the exceedance frequency of ambient air standard levels in Daegu were higher than those of Seoul and Busan. Except O3, the roadside concentrations of all target compounds showed following three distinguished patterns; first, possibly due to increased traffic density, the concentrations increased from 0500 to 0900(LST), second, the concentrations decreased from 0900 to 1700(LST) possibly due to the increased wind velocity and decreased traffic density, and finally, increased traffic density, the concentrations increased again from 1700 to 2100(LST). An implication was that major air pollution sources shifted from residential area to road-area during rush hours.

Present study evaluated the low-temperature destruction of n-hexane and benzene using mesh-type transition-metal platinum(Pt)/stainless steel(SS) catalyst. The parameters tested for the evaluation of catalytic destruction efficiencies of the two volatile organic compounds(VOC) included input concentration, reaction time, reaction temperature, and surface area of catalyst. It was found that the input concentration affected the destruction efficiencies of n-hexane and benzene, but that this input-concentration effect depended upon VOC type. The destruction efficiencies increased as the reaction time increased, but they were similar between two reaction times for benzene(50 and 60 sec), thereby suggesting that high temperatures are not always proper for thermal destruction of VOCs, when considering the destruction efficiency and operation costs of thermal catalytic system together. Similar to the effects of the input concentration on destruction efficiency of VOCs, the reaction temperature influenced the destruction efficiencies of n-hexane and benzene, but this temperature effect depended upon VOC type. As expected, the destruction efficiencies of n-hexane increased as the surface area of catalyst, but for benzene, the increase rate was not significant, thereby suggesting that similar to the effects of the reaction temperature on destruction efficiency of VOCs, high catalyst surface areas are not always proper for economical thermal destruction of VOCs. Depending upon the inlet concentrations and reaction temperatures, almost 100% of both n-hexane and benzene could be destructed. The current results also suggested that when applying the mesh type transition Metal Pt/SS catalyst for the better catalytic pyrolysis of VOC, VOC type should be considered, along with reaction temperature, surface area of catalyst, reaction time and input concentration.

In order to reduce roadside and indoor air pollution for volatile organic compounds VOC), it may be necessary to apply photocatalyst-coated construction materials. This study evaluated the technical feasibility of the application of TiO2 photocatalysis for the removal of VOC present in roadside or indoor air. The photocatalytic removal of five target VOC was investigated: benzene, toluene, ethyl benzene and o,m,p-xylenes. Variables tested for the current study included ultraviolet(UV) light intensity coating materials, relative humidity (RH), and input concentrations. Prior to performing the parameter tests, adsorption of VOC onto the current experiment was surveyed, and no adsorption was observed. Stronger UV intensity provided higher photocatalytic destruction(PCD) efficiency of the target compounds. For higher humidity, higher PCD efficiency was observed. The PCD efficiency depended on coating material. Contrary to certain previous findings, lower PCD efficiencies were observed for the experimental condition of higher input concentrations. The current findings suggested that the four parameters tested in the present study should be considered for the application of photocatalyst-coated construction materials in cleaning VOC of roadside or indoor air.

This study evaluated the technical feasibility of the application of TiO2 photocatalysis for the removal of volatile hydrocarbons(VHC) at low ppb concentrations commonly associated with non-occupational indoor air quality issues. A series of experiments was conducted to evaluate five parameters (relative humidity (RH), hydraulic diameter (HD), feeding type (FT) of VHC, photocatalytic oxidation (PCO) reactor material (RM), and inlet port size (IPS) of PCO reactor) for the PCO destruction efficiencies of the selected target VHC. None of the target VHC presented significant dependence on the RH, which are inconsistent with a certain previous study that reported that under conditions of low humidity and a ppm toluene inlet level, there was a drop in the PCO efficiency with decreasing humidity. However, it is noted that the four parameters (HD, RM, FT and IPS) should be considered for better VHC removal efficiencies for the application of TiO2 photocatalytic technology for cleansing non-occupational indoor air. The PCO destruction of VHC at concentrations associated with non-occupational indoor air quality issues can be up to nearly 100%. The amount of CO generated during PCO were a negligible addition to the indoor CO levels. These abilities can make the PCO reactor an important tool in the effort to improve non-occupational indoor air quality.

Petroleum refineries have been considered as an important emission source for atmospheric volatile hazardous air pollutants(HAPs). The emission source includes petroleum refinery processes and process equipment. The control strategy for volatile HAPs requires emission estimations of these pollutants. However, systematic methods of volatile HAPs emission from petroleum refineries have not yet been established. Accordingly, present study surveyed the estimation method of volatile HAPs emitted from the petroleum refinery processes and process equipment. The emission estimation methods for the petroleum refinery processes are applied for 11 petroleum refining facilities: fluidized catalytic cracking, thermal cracking, moving bed catalytic cracking, compressed engine, blowdown system, vacuum distilled column condensator, natural gas or distilled boiler, natural gas or distilled heater, oil boiler, oil heater and flare. Four emission estimation methods applied for the petroleum refinery process equipment are as follows: average emission factor approach, screening ranges approach, EPA correlation approach and unit-specific correlation approach. The process equipment for which emission factors are available are valves, pump seals, connectors, flanges and open-ended lines.

Evaluated were household THMs exposure associated with the use of municipal tap water treated with chlorine and with ozone-chlorine. The current study measured the THMs concentrations in the tap water and indoor and outdoor air in the two types of household, along with an estimation of THMs exposure from water ingestion, showering, and the inhalation of indoor air. Chloroform was the most abundant THMs in all three media, yet no bromoform was detected in any sample. Contrary to previous findings, the fall water THMs concentrations exhibited no significant difference between the chlorine and ozone-chlorine treated water. However, the spring median chloroform concentration in the tap water treated with chlorine (17.6 ppb) was 1.3 times higher than that in the tap water treated with ozone-chlorine (13.4 ppb). It is suggested that the effects of the water parameters should be considered when evaluating the advantage of ozone-chlorine disinfection for THMs formation over chlorine disinfection. The indoor air THMs concentration trend was also consistent with the water concentration trend, yet the outdoor air THMs concentrations did not differ significantly between the two types of household. The indoor to outdoor air concentration ratios were comparable with previous studies. The THMs exposure estimates from water ingestion, showering, and the inhalation of indoor air suggested that, for the residents living in the surveyed households, their exposure to THMs in the home was mostly associated with their household water use, rather than the indoor air. The THMs exposure estimates from tap water ingestion were similar to those from showering.

Air pollution from the Daegu industrial complex (DIC) in Korea has been a common nuisance and cause of complaints for nearby residents. The current study measured the indoor and outdoor levels of six VOC (benzene, toluene, ethylbenzene, and three isomeric xylenes) at two residential areas with a different proximity to the DDIC, plus the ambient levels at two industrial areas within the boundary of the DDIC. The QA/QC program included the range of correlation coefficient (0.94～0.99) for calibration curves, within the permissible range. Toluene was the most abundant VOC in the ambient air both in residential and industrial areas. Both indoor and outdoor air concentrations of all target VOC except benzene were higher in residential area near the DIC compared to that further away from the DIC. Moreover, the ambient air concentrations of all target VOC except benzene for two industrial sites (A and B) were significantly higher than the outdoor or indoor air concentrations in the two residential areas. The findings further suggested that VOC ambient levels measured in a residential area near the DIC be used as a potential indicator of odor-causing unidentified air pollutants transported from the DIC. Moreover, it was found that the elevated ambient toluene levels outweighed the indoor sources with respect to the environmental exposure of residents nearby the DIC. However, in the residential area further away from the DIC, the toluene indoor sources outweighed the outdoor sources.

체계적으로 분석된 대구지역의 PM10 오염도의 시간적 및 공간적 특성과 대조지역에서 측정된 PM10 오염도에 근거하여 대구지역의 PM10 오염에 대한 저감 방안이 다음과 같이 제시된다. 대구시의 지역특성에 따른 PM10 관리의 관점에서 볼 때 대구지역의 PM10 관리는 다른 지역보다는 도로변 또는 도로변 인근지역, 그리고 공업지역에서 우선적으로 이루어져야 하고 지역적으로 PM10 관리 전략을 달리하여야 함을 제시하고 있다. 남산동, 삼덕동 및 대명동을 포함하여 도로변 또는 도로변 인근의 주택에 거주하는 주민의 PM10으로부터 건강 위해성을 줄이기 위해서는 자동차 교통 관리가 가장 우선적으로 수행되어야 한다. 한편, 노원동과 중리동을 포함한 공업지역 또는 인근에 거주하는 주민의 PM10으로부터 건강 위해성을 줄이기 위해서는 자동차 교통 관리 보다는 공단 배출 PM10 관리가 가장 우선적으로 수행되어야 한다. 나아가, 본 연구결과에 기초할 때, 비록 만성영향과 밀접한 관련이 있는 평균농도는 모든 지역에서 PM10 대기환경 기준치 이하로 나타났지만, 급성영향과 밀접한 관련이 있는 최대 농도와 결코 낮지 않은 PM10 대기환경 기준치를 초과하는 빈도수를 고려할 때, 대구지역의 PM10 관리는 지속적으로 수행되어야 함이 강조된다. 대구지역의 시간대 별 PM10 관리 관점에서 볼 때, 대구의 일반 주거지역의 PM10 관리는 오전 10시에서 오후 1 3시에 집중되어야 효율적인 PM10 관리가 될 수 있음을 의미한다. 공업지역인 중리동과 노원동의 경우, 다소 이른 오전 7시부터 오후 1 2시 사이에 PM10 관리가 집중되어야 효율적인 PM10 관리가 될 수 있을 것이다. 반면에 상업/주거 지역인 삼덕동과 대명동 그리고 도로변 지역인 남산동의 경우, 특정 시간대가 아닌 거의 전 시간대에 걸쳐 PM10 관리해야 하고 특히 자동차 배출 PM10 관리대책 수립이 시급하다. 대구지역의 요일 별 PM10 관리 관점에서 볼 때, 모든 지역에 대하여 일요일과 월요일의 PM10 농도가 낮게 나타났으므로 화요일에서 토요일까지 집중되는 것이 PM10관리가 효율적으로 수행될 수 있음을 의미한다. 대구지역의 월 별 PM10 관리 관점에서 볼 때, 모든 지역에서 하절기인 7월, 8월 및 9월에 낮은 농도를 나타내었고, 동절기인 11월 2월 보다는 오히려 이른 봄인 3월에 최대 농도를 나타내고 있으므로 모든 지역에서 3월에는 특별한 PM10 관리가 이루어져야 하고, 특히 근본적인 문제점인 중국의 황사현상을 저감하기 위한 중국과의 외교적인 노력이 요구된다. 대구지역의 계절 별 PM10 관리 관점에서 볼 때, 계절적으로는 모든 지역에서 봄철에 가장 PM10 농도, 그 다음이 겨울, 가을 그리고 여름의 순으로 나타났다. 봄철의 가장 높은 PM10 농도와 여름철의 가장 낮은 PM10 농도는 앞의 월별 PM10 농도 변화에서도 설명된 바와 같이 각각 황사와 장마의 영향 때문인 것으로 사료된다. 여름과 가을 보다 높은 PM10 농도를 나타내는 겨울철의 경우, 난방 연료 사용의 증가로 인한 영향을 받는 것으로 사료되므로 청정연료 사용의 확대가 권장된다. 대부분의 경우, 대조지역에서 측정된 PM10 농도가 대구의 여섯 개 대기오염측정 지점에서 측정된 PM10 농도 보다 낮게 나타났고, 일부는 일반주거지역인 만촌동과 유사하게 나타났다. 따라서, 대구의 PM10 측정망 중에서 만촌동이 주위 PM10 오염원의 영향을 가장 적게 받는 주거지역임을 함께 고려할 때 대구시의 PM10 관리목표는 만촌동의 PM10 수준으로 유지함이 바람직한 것으로 제안된다.

This study was designed to evaluate the exposure to benzene by residents in neighborhoods near a major roadways, by persons waiting buses, and by drivers and service station attendants while refueling. It was confirmed that the outdoor air benzene concentrations near the major roadways were higher than those further away from the sources. However, neither the indoor air nor breath concentrations were different for two specified residential areas. Smoking was confirmed as an important factor for the indoor air benzene levels. Persons waiting buses, drivers and service station attendants were exposed to elevated benzene levels compared to even the residents in neighborhoods near a major roadways. The mean benzene concentration at bus stop was 2.7 to 6.9 times higher than the mean ambient air concentration. The mean benzene concentrations in the breathing zone of drivers and service station attendants were 95 to 160 and 120 to 202 times higher than the mean ambient air concentrations, respectively.

This study examined the carbon dioxide (CO_2) pollution inside vehicles under low ventilation condition and evaluated the Air Quality System (AQS) for in-vehicle air quality using two techniques. The low ventilation condition is not recommended in order to keep oxygen-rich condition inside vehicles. Under the low ventilation condition, the in-vehicle CO_2 concentrations exceeded 1,000 ppm, the air quality guidelines in the United States, Western Europe, and Japan, indicating more oxygen deficiency inside vehicles. On the contrary, with the AQS-on condition, the in-vehicle CO_2 concentrations were less than 1,000 ppm for most of the driving time, indicating that the AQS could solve the problem of CO_2 accumulation inside vehicles under the low ventilation condition. The AQS test conducted by comparing carbon monoxide (CO) and volatile organic compound (VOC) concentrations inside two vehicles indicated that the AQS effectively decreased the in-vehicle concentrations by 21 to 36%, as compared to medium ventilation condition with the windows closed, the vent opened, and air conditioning on. In addition, The AQS test conducted by comparing the interior and exterior concentrations indicated that the AQS effectively decreased the in-vehicle concentrations by 18 to 31%, as compared to medium ventilation condition.

Recently, bathes have been suspected to an important source of indoor exposure to volatile organic compounds(VOCs). Two experiments were conducted to evaluate chloroform exposure and corresponding body burden by exposure routes while bathing. Another experiment was conducted to examine the chloroform dose during dermal exposure and the chloroform decay in breath after dermal exposure. The chloroform dose was determined based on exhaled breath analysis. The exhaled breath concentration measured after normal baths (2.8 ㎍/㎥) was approximately 13 times higher that measured prior to normal bathes (0.2 ㎍/㎥). Based on the means of the normalized post exposure chloroform breath concentration, the dermal exposure was estimated to contribute to 74% of total chloroform body burden while bathing. The internal dose from bathing (inhalation plus dermal) was comparable to the dose estimated from daily water ingestion. The risk associated with a weekly, 30-min bath was estimated to be 1 x 10^-5, while the risk from daily ingestion of tap water was to be 0.5 × 10^-5 for 0.15 1 and 6.5 × 10^-5 for 2.0 1. Chloroform breath concentration increased gradually during the 60 minute dermal exposure. The breath decay after the dermal exposure showed two-phase mechanism, with early rapid decay and the second slow decay. The mathematical model was developed to describe the relationship between water and air chloroform concentrations, with R^2 = 0.4 and p<0.02.

The pyrolysis reactions of atomic hydrogen with chloroform were studied in a 4 cm i.d, tubular flow reactor with low flow velocity (518 ㎝/sec) and a 2.6 ㎝ i.d. tubular flow reactor with high flow velocity (1227 ㎝/sec). The hydrogen atom concentration was measured by chemiluminescence titration with nitrogen dioxide, and the chloroform concentrations were determined using a gas chromatography. The chloroform conversion efficiency depended on both the chloroform flow rate and linear flow velocity, but did not depend on the flow rate of hydrogen atom. A computer model was employed to estimate a rate constant for the initial reaction of atomic hydrogen with chloroform. The model consisted of a scheme for chloroform-hydrogen atom reaction, Runge-Kutta 4th-order method for integration of first-order differential equations describing the time dependence of the concentrations of various chemical species, and Rosenbrock method for optimization to match model and experimental results. The scheme for chloroform-hydrogen atom reaction included 22 elementary reactions. The rate constant estimated using the data obtained from the 2.6 cm i.d. reactor was to be 8.1 × 10 exp (-14) ㎤/molecule-sec and 3.8 × 10 exp (-15) ㎤/molecule-sec, and the deviations of computer model from experimental results were 9% and 12%, for the each reaction time of 0.028 sec and 0.072 sec, respectively.

Two experiments were conducted to evaluate breathing zone air quality in Taegu, using automatic analyzers for four air quality standards(SO2, NO2, CO, and O3). First, air target compounds were measured for 8 to 12 hours in each of two commercial areas and five residential areas. Second, air target compounds were hourly measured for 24 hours in each of two commercial areas, two residential areas, and an industrial complex area. Based on the first experiment the breathing zone air was more polluted in the commercial area as compared to the residential area, while the second experiment showed that the breathing zone air was polluted rather in the residential area as compared to the commercial area. The second experiment also indicated that there was some variation of breathing zone air concentration with time and measuring sites. Diurnal variation of breathing zone air concentrations was consistent with previous studies which measured at building height. The highest breathing zone air concentration was shown in Seongseo industrial complex area. An unusual finding of this study was that SO2 concentration in the breathing zone air of Bisandong, a typical residential area of Taegu, was higher than that of other residential areas, even higher than that of Seongseo industrial complex area.