We report the synthesis and gas sensing properties of bare and ZnO decorated TeO2 nanowires (NWs). A catalyst assisted-vapor-liquid-solid (VLS) growth method was used to synthesize TeO2 NWs and ZnO decoration was performed using an Au-catalyst assisted-VLS growth method followed by a subsequent heat treatment. Structural and morphological analyses using X-ray diffraction (XRD) and scanning/transmission electron microscopies, respectively, demonstrated the formation of bare and ZnO decorated TeO2 NWs with desired phase and morphology. NO2 gas sensing studies were performed at different temperatures ranging from 50 to 400 oC towards 50 ppm NO2 gas. The results obtained showed that both sensors had their best optimal sensing temperature at 350 oC, while ZnO decorated TeO2 NWs sensor showed much better sensitivity towards NO2 relative to a bare TeO2 NWs gas sensor. The reason for the enhanced sensing performance of the ZnO decorated TeO2 NWs sensor was attributed to the formation of ZnO (n)/ TeO2 (p) heterojunctions and the high intrinsic gas sensing properties of ZnO.

PURPOSES : This study analyzes the characteristics of nitrogen oxide concentration by applying titanium dioxide to existing roads in urban areas, using correlation analysis and a generalized linear model. METHODS : To analyze the characteristics of nitrogen oxide concentration with/without applying titanium dioxide to the urban road segment, data acquisition was conducted for nitrogen oxide concentration, weather information, and traffic information, etc., and a correlation analysis was conducted for each factor, with/without applying titanium dioxide to the roads. In addition, nitrogen oxide concentration generation models with/without the application of titanium dioxide to the roads were estimated using a generalized linear model. RESULTS : The results demonstrate that relative humidity and temperature were found to be slightly correlated with the nitrogen oxide concentration, both with and without the application of titanium dioxide to the roads; however, wind speed, solar radiation, and traffic volume were found to have somewhat low correlation according to the results of a correlation analysis. Moreover, relative humidity, temperature, solar radiation, and traffic volume were significant when titanium dioxide was applied to the roads, based on the estimated model from a generalized linear model, and the wind speed, solar radiation, and traffic volume were significant for the absence of titanium dioxide on the roads. CONCLUSIONS : Analytical results indicated that the characteristics of nitrogen oxide concentration vary depending on the application of titanium dioxide to the roads. In particular, when titanium dioxide was applied to the roads, the relative humidity and temperature were analyzed; according to both analyses, i.e., correlation analysis and a generalized linear model, the nitrogen oxide concentration was affected.

Carbon supports for dispersed platinum (Pt) electrocatalysts in direct methanol fuel cells (DMFCs) are being continuously developed to improve electrochemical performance and catalyst stability. However, carbon supports still require solutions to reduce costs and improve catalyst efficiency. In this study, we prepare well-dispersed Pt electrocatalysts by introducing titanium dioxide (TiO2) into biomass based nitrogen-doped carbon supports. In order to obtain optimized electrochemical performance, different amounts of TiO2 component are controlled by three types (Pt/TNC-2 wt%, Pt/TNC-4 wt%, and Pt/TNC-6 wt%). Especially, the anodic current density of Pt/TNC-4 wt% is 707.0 mA g−1 pt, which is about 1.65 times higher than that of commercial Pt/C (429.1 mA g−1 pt); Pt/TNC-4wt% also exhibits excellent catalytic stability, with a retention rate of 91 %. This novel support provides electrochemical performance improvement including several advantages of improved anodic current density and catalyst stability due to the well-dispersed Pt nanoparticles on the support by the introduction of TiO2 component and nitrogen doping in carbon. Therefore, Pt/TNC-4 wt% may be electrocatalyst a promising catalyst as an anode for high-performance DMFCs.

무분별한 이산화탄소 배출로 인한 지구온난화는 이상기후와 생태계 파괴 등을 초래함으로써 인간의 삶에 심각한 영향을 미치고 있다. 이러한 문제의 근본 원인인 이산화탄소 배출을 저감하는 방법으로 본 연구에서는 자가-가교 성질이 있는 P(GMA-g-PPG)-co-POEM) (SP) 공중합체와 상용 고분자인 polyvinylpyrrolidone (PVP)를 혼합하여 블렌드 고분자 분리막을 제조하는 방법을 제시하였다. PVP 함량에 따른 분리막의 이산화탄소/질소 투과 특성을 확인하였으며, PVP의 함량이 증가 할수록 투과도는 감소하고 선택도는 증가하는 결과를 보였다. 특히 PVP 함량이 30 wt%인 경우, 투과도는 순수 SP 고분자의 CO2 투과도인 72.9 GPU에서 12.6 GPU로 감소하였으나, CO2/N2 선택도는 28.1에서 50.4로 약 79% 증가하였다. 이는 SP 공중합체와 PVP 사이의 수소결합으로 인해 고분자 사슬이 더욱 조밀하게 배열되기 때문인 것으로 볼 수 있으며, 이를 FT-IR, TGA, XRD, SEM을 통해 분석하였다. 따라서, 본 연구에서는 SP/PVP 고분자 블렌드 내 PVP의 함량을 조절함으로써 분리막의 투과도 및 선택도를 손쉽게 조절할 수 있음을 확인하였다.

The purpose of this study is to evaluate the performance of a tube and badge type NO2 passive air sampler. The principle of the method is a colorimetric reaction of NO2 with N-1-naphthylethylendiamine under acidic conditions. The sampling rates for the tube and badge type passive air samplers was determined 12.3 ± 4.4 mL/min and 27.3 ± 4.9 mL/min, respectively, as obtained from the slope of the linear correlation between the NO2 mass collected by the passive air sampler and the NO2 concentration with the NO2 analyzer. The tube and badge type passive air sampler were moderately correlated with a correlation coefficient of 0.9112. The measurement for the precision and accuracy of the passive air sampling was carried out with duplicate measurement of passive air samplers. The passive air sampler had good precision and accuracy for measuring NO2 in atmosphere. A good correlation was observed between the passive air sampler and the NO2 analyzer with a coefficient of determination of 0.9153 (tube type) and 0.9514 (badge type). This passive air sampler would be suitable for the NO2 concentration monitoring in atmosphere.

The objectives of this study were to characterize the factors affecting exposure to the VOCs and NO2 in the vicinity of Gwangyang industrial complex. The VOCs and NO2 levels were measured for residents of an exposure group (industrial area within 5 km) and a control group (15 km farther), respectively using the VOCs and NO2 filter badge as a passive sampler from August to September 2006. The means of indoor, outdoor, workplace and personal exposure levels of benzene were 1.10 ppb, 0.94 ppb, 1.85 ppb and 2.35 ppb respectively in the exposure group. The means regarding toluene for the exposure group were 9.29 ppb indoor, 8.09 ppb outdoor, 14.5 ppb workplace, 14.2 ppb personal exposure. The means regarding ethylbenzene were 4.96 ppb(indoor), 4.45 ppb(outdoor), 6.84 ppb (workplace), 6.10 ppb(personal exposure), and the means regarding xylene were 0.10 ppb(indoor, outdoor), 0.18 ppb(workplace) 0.17 ppb(personal exposure). The means for the indoor, outdoor, workplace and personal exposure level of NO2 were 18.40 ppb, 18.51 ppb, 18.59 ppb, 18.80 ppb respectively in the exposure group. Correlations between personal exposures and workplace concentrations of individual VOCs and NO2 exposures, and each of the microenvironment was statistically significant.

In order to understand the contribution of seaweed aquaculture to nutrients and carbon cycles in coastal environments, we measured the nutrients & carbon uptake rates of Porphyra yezoensis Ueda sampled at Nakdong-River Estuary using a chamber incubation method from November 2011 to April 2012. It was observed that the production rate of dissolved oxygen by P. yezoensis (n=30~40) was about 68.8±46.0 μmol gFW -1 h-1 and uptake rate of nitrate, phosphate and dissolved inorganic carbon (DIC) was found to be 2.5±1.8 μmol gFW -1 h-1, 0.18±0.11 μmol gFW -1 h-1 and 87.1±57.3 μmol gFW -1 h-1, respectively. There was a positive linear correlation existed between the production rate of dissolved oxygen and the consumption rates of nitrate, phosphate and DIC, respectively, suggesting that these factors may serve as good indicators of P. yezoensis photosynthesis. Further, there was a negative logarithmic relationship between fresh weight of thallus and uptake rates of nutrients and CO2, which suggested that younger specimens (0.1~0.3 g) were much more efficient at nutrients and CO2 uptake than old specimens. It means that the early culturing stage than harvesting season might have more possibilities to be developed chlorosis by high rates of nitrogen uptake. However, N & C demanding rates of Busan and Jeollabuk-do, calculated by monthly mass production and culturing area, were much higher than those of Jeollanam-do, the highest harvesting area in Korea. Chlorosis events at Jeollabuk-do recently might have developed by the reason that heavily culture in narrow area and insufficient nutrients in maximum yield season (Dec.~Jan.) due mostly to shortage of land discharge and weak water circulation. The annual DIC uptake by P. yezoensis in Nakdong-River Estuary was estimated about 5.6×103 CO2 ton, which was about 0.03% of annual carbon dioxide emission of Busan City. Taken together, we suggest more research would be helpful to gain deep insight to evaluate the roles of seaweed aquacul-ture to the coastal nutrients cycles and global carbon cycle.

This study conducted comparison and data analysis of evaluation results from three kinds of monitoring methods for indoor air quality monitoring, which are Korean Official test method for indoor air quality, monitoring method by gas analyzer, and continuous measurement by using sensor. NO₂, one of indoor air pollutants, was selected as a evaluation factor for this study because it is commonly generated during the operation of potable gas range. Monitoring results of NO₂ concentration from three subjected methods show that background concentration of NO₂, before operation of portable gas range, was 43.05~50.22ppb. On the other hand, NO₂ concentration for four and half hours (4½) after gas range operation was 64.31~69.89ppb in average. Average concentration of NO₂ during first thirty (30) minutes was increased about 33.85~49.39% than the concentration of NO₂ before operation of gas range. </br>In general, monitoring results by utilizing NO₂ gas analyzer was 8.1% higher than the results by continuous measurement using sensor method. In case of monitoring method using sensor, the results was lower about 6.1% than Korean official test method, and lower about 11.7~3.2% than NO₂ gas analyzer. Especially, change rate of concentration for first thirty (30) minutes measured by Korean official test method was 50ppb/hr, which is 44.4% lower than the change rate from NO₂ gas analyzer, 90ppb/hr, and 43.2% lower than results from sensor, 88ppb/hr. </br>In accordance with this study, it is concluded that monitoring frequency for indoor air quality management must be shorten during the time period having significant change rate of NO₂ concentration. In other words, air quality monitoring must be considered characteristics of concentration changes as well as accuracy of measurement.

Personal or population exposure to hazardous air pollutants has often been assessed by time-weighted average model with combining concentrations of indoor environments and time-activity pattern, which were mainly a single measurement. However, daily levels of air pollutants in indoor environments may greatly be changed because of source emission, ventilation, decay rate and so on. Subsequently exposure by a single measurement in indoor environments could not be assessed properly. In this study, we measured the consecutive 21 daily indoor and outdoor measurements of nitrogen dioxide (NO₂) with 37 houses and 19 shops such as restaurants and coffee shops beside street by using of passive samplers. Considering that average concentration during 21 days was true value, paired t-test was conducted. Daily variations of NO₂ in houses with constant or low emission source were different from those in restaurants with irregular or high emission source. These results can be explained that the NO₂ emission of indoor sources could affect the validity of measurement periods.

In this study, we estimated nitrogen dioxide (NO₂) concentrations in microenvironments where residential indoor, residential outdoor, other indoors, and transportation using measured personal exposure and multiple linear regression analysis of time-weighted average model, and compared with measured NO₂ concentration in microenvironments. Measured residential indoor, outdoor and other indoor NO₂ concentration was 22.22±9.59 ppb, 23.64±9.62 ppb, and 22.07±13.90 ppb, respectively. NO₂ concentrations in residential indoor and outdoor, total outdoor, other indoor, and transportation by multiple regression analysis were significantly estimated as 20.48 ppb, 32.79 ppb, 24.35 ppb, and 28.82 ppb, respectively (p= 0.000). Measured and estimated NO₂ concentration were similar with each other, therefore NO₂ concentrations in each microenvironment were able to be estimated using time-weighted average model and personal exposure with multiple regression analysis.

This study presents residential indoor and outdoor exposure concentrations distributions of volatile organic compounds (VOCs, benzene, toluene, xylene) and nitrogen dioxide (NO₂) in industrial area (case) and agricultural area (control) during 5 days. Concentrations of VOCs and NO₂ were measured with passive samplers in residential indoor and outdoor. Most of benzene, toluene and NO₂ mean concentrations in case area were higher than those in control area. Considering the indoor and outdoor ratios (I/O) were higher than 1, the residence might be have the sources of indoor air pollutants such as smoking and using of gas range. Residential indoor concentrations of benzene, toluene, and NO₂ with indoor smokers were higher than those and without indoor smokers. In conclusion, it is suggested that personal exposures to air pollutants might be affected by indoor sources as well as outdoor pollutants emitted from industrial complex, and indoor air quality and outdoor air quality should be simultaneously considered to reduce the personal exposure to air pollutants.

Indoor, outdoor, and personal nitrogen dioxide (NO₂) exposures were studied in a population of housewives. Daily Indoor and outdoor NO₂ concentrations were measured and compared with simultaneously personal exposures of 17 housewives for 7 consecutive days in 17 houses. In this study, indoor and outdoor NO₂ samples at home were collected only while the housewives were at home samples. Time activity patterns and house characteristics were used to determine the effects of these factors on personal exposure. Since housewives spent their times in indoor houses with mean of 78.3%, their NO₂ exposures were associated with indoor houses NO₂ levels (r= 0.89) rather than outdoor NO₂ level (r= 0.85). Contribution of indoor NO₂ concentration on personal exposure was estimated by 70.77% by using of mass balance model. The close association between measured indoor NO₂ concentrations and measured personal exposure and contribution of indoor NO₂ concentration suggests that measuring indoor concentrations of NO₂ in the home is sufficient to estimate personal exposure accurately.

Exposure to nitrogen dioxide (NO₂) can produce adverse health effects. Various indoor and outdoor combustion sources make NO₂ the most ubiquitous pollutant in the indoor environment. Indoor air quality can be affected by indoor sources, ventilation, decay and outdoor levels. Although technologies exist to measure these factors, direct measurements are often difficult. In the present paper, we used a mass balance model and regression analysis, penetration factor (ventilation rate divided by the sum of ventilation rate and deposition constant) and source strength factor (source strength divided by the sum of ventilation rate and deposition constant) were calculated using multiple indoor and outdoor measurements with 10 houses. Subsequently, mean contributions of indoor and outdoor sources were 28.86% and 81.09%, respectively, suggesting that both indoor and outdoor sources had contributions to indoor concentrations of NO₂.

Indoor air quality can be affected by indoor sources, ventilation, outdoor levels, and removal. Various indoor and outdoor combustion sources make nitrogen dioxide(NO2), which is a by-product of high temperature fossil fuel combustion. Especially, the presence of gas ranges and smoking have been identified as two of the major factors contributing to indoor NO2 exposures. In this study, the relative efficiencies for NO2 removal by a large number of materials are presented. This work has demonstrated that reactions with indoor surfaces represents a significant sink for NO2, and that these reactions currently are effecting a considerable degree of control over indoor NO2 levels. It seems that this control could be enhanced by judicious selection of furnishings and construction materials. Improved understanding of that rates and mechanisms of the removal process will permit optimization of the process for indoor air quality improvement.

Indoor air quality tends to be the dominant contributor to personal exposure, because most people spend over 80% of their time indoors. In this study, indoor and outdoor NO2 concentrations were measured simultaneously with personal exposures of 30 university students in weekday and weekend in Daegu, Korea. House characteristics and subject's activity pattern were used to determine the effects on personal exposure. Since university students spent most of their times indoor, their NO2 exposure was associated with indoor NO2 level during both weekday and weekend in spite of different time activity. Using a time-weighted average model, NO2 exposures of university students were estimated by NO2 measurements in indoor home, indoor school, and outdoor home. In conclusion, major personal exposure to NO2 resulted from air quality of indoor environment at house.

Indoor air quality can be affected by indoor sources, ventilation, decay and outdoor levels. Although technologies exist to measure these factors, direct measurements are often difficult. The purpose of this study was to develop an alternative method to characterize indoor environmental factors by multiple indoor and outdoor measurements. Using a mass balance model and regression analysis, penetration factor (ventilation rate divided by the sum of ventilation rate and deposition constant) and source strength factor (source strength divided by the sum of ventilation rate and deposition constant) were calculated using multiple indoor and outdoor measurements. Subsequently, the ventilation rate and NO2 generation rate were estimated. Mean of ventilation rate was 1.41 ACH in houses, assuming a residential NO2 deposition constant of 0.94 hr-1. Mean generation rate of NO2 was 16.5 ppbv/hr. According to house characterization, inside smoking and family number were higher NO2 generation rates, and apartment was higher than single-family house. In conclusion, indoor environmental factors were effectively characterized by this method using multiple indoor and outdoor measurements.

Indoor air quality is affected by source strength of pollutants, ventilation rate, decay rate, outdoor level, and so on. Although technologies measuring these factors exist directly, direct measurements of all factors are not always practical in most field studies. The purpose of this study was to develop an alternative method to estimate these factors by application of multiple measurements. For the total duration of 30 days, daily indoor and outdoor NO2 concentrations were measured in 30 houses in Brisbane, Australia, and for 21 days in 40 houses in Seoul, Korea, respectively. Using a box model by mass balance and linear regression analysis, penetration factor (ventilation divided by sum of air exchange rate and deposition constant) and source strength factor (emission rate divided by sum of air exchange rate and deposition constant) were calculated. Subsequently, the ventilation and source strength were estimated. In Brisbane, the penetration factors were 0.59±0.14 and they were unaffected by the presence of a gas range. During sampling period, geometric mean of natural ventilation was estimated to be 1.10±1.51 ACH, assuming a residential NO2 decay rate of 0.8 hr-1 in Brisbane. In Seoul, natural ventilation was 1.15±1.73 ACH with residential NO2 decay rate of 0.94 hr-1. Source strength of NO2 in the houses with gas range (12.7±9.8 ppb/hr) were significantly higher than those in houses with an electric range (2.8±2.6 ppb/hr) in Brisbane. In Seoul, source strength in the houses with gas range were 16.8±8.2 ppb/hr. Conclusively, indoor air quality using box model by mass balance was effectively characterized.

Indoor and outdoor nitrogen dioxide (NO2) concentrations were measured and compared with measurements of personal exposures of 95 persons in Seoul, Korea and 57 persons in Brisbane, Australia, respectively. Time activity diary was used to determine the impact on NO2 exposure assessment and microenvironmental model to estimate the personal NO2 exposure. Most people both Seoul and Brisbane spent their times more than 90% of indoor and more than 50% in home, respectively. Personal NO2 exposures were significantly associated with indoor NO2 levels with Pearson coefficient of 0.70 (p<0.01) and outdoor NO2 levels with Pearson coefficient of 0.66 (p<0.01) in Seoul and of 0.51 (p<0.01) and of 0.33 (p<0.05) in Brisbane, respectively. Using microenvironmental model by time weighted average model, personal NO2 exposures were estimated with NO2 measurements in indoor home, indoor office and outdoor home. Estimated NO2 measurements were significantly correlated with measured personal exposures (r = 0.69, p<0.001) in Seoul and in Brisbane (r = 0.66, p<0.001), respectively. Difference between measured and estimated NO2 exposures by multiple regression analysis was explained that NO2 levels in near workplace and other outdoors in Seoul (p = 0.023), and in transportation in Brisbane (p = 0.019) affected the personal NO2 exposures.

The personal exposures of nitrogen dioxide(NO2), microenvironmental levels and daily time activity patterns on Seoul subway station workers were measured from February 10 to March 12, 1999. Personal NO2 exposure for 24 hours were 29.40±9.75 ppb. NO2 level of occupational environment were 27.87±7.15 ppb in office, 33.60±8.64 ppb in platform and 50.13±13.04 ppb in outdoor. Personal exposure time of subway station workers was constituted as survey results with 7.94±3.00 hours in office, 2.82±1.63 hours in platform and 1 hours in outdoor. With above results, personal NO2 exposure distributions on subway station workers in Seoul were estimated with Monte Carlo simulation which uses statistical probabilistic theory on various exposure scenario testing. Some of distributions which did not have any formal patterns were assumed as custom distribution type. Estimated personal occupational NO2 exposure using time weighted average (TWA) model was 31.29±5.57 ppb, which were under Annual Ambient Standard (50 ppb) of Korea. Though arithmetic means of measured personal NO2 exposure was lower than that of occupational NO2 exposure estimated by TWA model, considering probability distribution type simulated, probability distribution of measured personal NO2 exposures for 24 hours was over ambient standard with 3.23%, which was higher than those of occupational exposure (0.02%). Further research is needed for reducing these 24 hour NO2 personal excess exposures besides occupational exposure on subway station workers in Seoul.