Analysis of the major factors affecting the visibility degradation in two stations.

UNLABELLED: There are four types of PM10 (particulate matter with an aerodynamic diameter <10 microm) episodes that occur frequently in central Taiwan: long-range transport with dust storms (DS), long-range transport with frontal pollution (FP), river dust (RD), and stagnant weather (SW). During the periods of the four episodes, poor visibility usually results. Multiple linear regression was applied to visibility using eight potential influential variables (temperature, relative humidity, wind speed, PM2.5, PM2.5-10, SO2, NO2, and NO) as independent variables. Of the eight variables, PM2.5 showed the greatest explainable percentage of about 48.6% and 58.1% for Taichung and Wuchi stations, respectively. This suggested that PM2.5 was the most important contributor to reduced visibility. Compared with other type of episodes, the aerosols tended to be offine size during the SWepisodes. This is the main reason that the poorest visibility occurred during the SWepisodes. Good correlation between visibility and secondary inorganic salts (NH4+, NO3, and SO4(2-)) were found at Taichung station (r = 0.71) and Wuchi station (r = 0.81), suggesting that secondary inorganic salts did contribute significantly to the degradation ofvisibility. The visibility degradation due to the effects ofNO3- was much higher than that due to SO4(2-) and NH4+ in the urban area, whereas the visibility degradation due to the effects of NO3 , SO42-, and NH4+ did not show significant diference in the rural area. IMPLICATIONS: Of the eight potential influential variables, PM2.5 showed the greatest effects on reduced visibility. Compared with other type of episodes, the aerosols tend to be fine size during the episodes of stagnant weather. This is the main reason why the poorest visibility occurred during the SW episodes. Good correlations between visibility and secondary inorganic salts (NH4+, NO3-, and SO4(2-)) suggested that secondary inorganic salts did contribute significantly to the degradation of visibility. Among the three inorganic salts, nitrates played a leading role for visibility degradation in urban areas in central Taiwan.

Polycyclic aromatic hydrocarbons in household dust near diesel transport routes.

A river-dredging project has been undertaken in Nantou, Taiwan. A large number of diesel vehicles carrying gravel and sand shuttle back and forth on the main roads. Ten stations along major thoroughfares were selected as the exposure sites for testing, while a small village located about 9 km from a main traffic route was selected as the control site. Levels of household dust loading at the exposure sites (60.3 mg/m(2)) were significantly higher than those at the control site (38.2 mg/m(2)). The loading (µg/m(2)) of t-PAHs (total polycyclic aromatic hydrocarbons) in the household dust at the exposure sites was significantly higher (P < 0.05) than was the case at the control site. The diagnostic ratios of PAHs showed that diesel emissions were the dominant source of PAHs at the exposure sites. The lack of a significant correlation between the concentrations of Fe and t-PAHs suggested that the t-PAHs in household dust might come from diverse sources. However, a significant correlation (P = 0.003) between the concentrations of Mo and t-PAHs implied that the most of the t-PAHs in the household dust might have resulted from diesel emissions. The lifetime cancer risks of BaP(eq) from household dust exposure were markedly higher than those resulting from inhalation exposure.

Anomalous luminescence phenomena of indium-doped ZnO nanostructures grown on Si substrates by the hydrothermal method.

In recent years, zinc oxide (ZnO) has become one of the most popular research materials due to its unique properties and various applications. ZnO is an intrinsic semiconductor, with a wide bandgap (3.37 eV) and large exciton binding energy (60 meV) making it suitable for many optical applications. In this experiment, the simple hydrothermal method is used to grow indium-doped ZnO nanostructures on a silicon wafer, which are then annealed at different temperatures (400°C to 1,000°C) in an abundant oxygen atmosphere. This study discusses the surface structure and optical characteristic of ZnO nanomaterials. The structure of the ZnO nanostructures is analyzed by X-ray diffraction, the superficial state by scanning electron microscopy, and the optical measurements which are carried out using the temperature-dependent photoluminescence (PL) spectra. In this study, we discuss the broad peak energy of the yellow-orange emission which shows tendency towards a blueshift with the temperature increase in the PL spectra. This differs from other common semiconductors which have an increase in their peak energy of deep-level emission along with measurement temperature.