The chlorination of municipal drinking water supplies leads to the formation of so-called disinfection by-products(DBPs), many of which have been reported to cause harmful health effects based on animal studies. This study was conducted: 1) to observe seasonal changes in the major DBPs at four sampling sites on a drinking water distribution system located in Chunchon, Kangwon Do; and 2) to examine the effects of major water quality parameters on the formation of DBPs. During the field sampling, the water temperature, pH, and total and free chlorine residuals were all measured. The water samples were then analyzed for total organic carbon(TOC) and eight disinfection by-products in the laboratory. Chloroform, dichloroacetic acid, and trichloroacetic acid were the major constituents of the measured DBPs. The concentrations of the total DBPs were highest in fall, particularly in October, and lowest in summer. The concentrations of the total DBPs increased with increasing TOC concentrations. Multiple regression analyses showed that the concentrations of chloroform, bromodichloromethane, and chloral hydrate were linearly correlated with the pH. Other water parameters were not included in the regression equations. Accordingly, these results suggest that TOC and pH are both important factors in the formation of DBPs.

The photodegradation of benzene was studied in an aqueous solution using a medium pressure Hg-lamp. In this study, persulfate, nitrate, nitrite, chloride, and sulfate ions were all tested as sensitizers. The persulfate, nitrate, and nitrite ions exhibited a sensitizing effect in the photodegradation of benzene, whereas no detectable effects were observed with the sulfate and chloride ions. When nitrite ions were used as the sensitizer, the photodegradation of benzene ran through a maximum value and thereafter decreased with an increasing nitrite concentration. The resulting build-up of nitrite ions seemed to scavenge the hydroxyl radicals. When nitrite ions were present along with persulfate ions, the photodegradation of benzene was inhibited.

The effects of ozone on chloroplast development in barley seedlings during greening was investigated based on ultrastructural changes in the chloroplasts and band pattern changes in the chloroplast thylakoid membrane proteins. In this analysis of the chloroplast thylakoid membrane thylakoid protein band pattern by SDS-PAGE, none of the 24-hour greening bands included were clearer than the control. This means that the ozone treatment produced a dealy in chloroplast development and decreased the amount of thylakoid membrane proteins. LHC II chloroplast band of developing barley seedlings treated with 0.5 and 1.0 ppm ozone during the last 4 hours of the 24-hour greening period was weaker than the other bands. This result indicates that ozone affects the LHC II protein complex of the chloroplast thylakoid membrane. When investigating the ultastructural changes in ozone-treated chloroplast, the main site affected by 0.5 ppm ozone was the chloroplast grana, thereby explaining the delayed chloroplast development during the early phase of greening. In addition, there was also a structural change in the stromal grana of the ozone treated chloroplast during the middle phase of greening. The effects of ozone on the chloroplast of barley seedlings during the last phase of 48-hour greening were more functionally inhibiting than structural changes.

Methane combustion over perovskite-type oxides prepared using the malic acid method was investigated. To enhance the catalytic activity, the perovskite oxides were modified by the substitution of metal into their A or B site. In addition, the reaction conditions, such as the temperature, space velocity, and partial pressure of the methane were varied to understand their effect on the catalytic performance. With the LaCoO3-type catalyst, the partial substitution of Sr or Ba into site A enhanced the catalytic activity in the methane combustion. With the LaBO3(B=Co, Fe, Mn, Cu)-type catalyst, the catalytic activities were exhibited in the order of Co>Fe Mn>Cu. Futhermore, the partial substitution of Co into site B enhanced the catalytic activity, whereas an excess amount of Co decreased the activity. The surface area and catalytic activity of the perovskite catalysts prepared using the malic acid method showed higher values than those prepared using the solid reaction method. The catalytic activity was enhanced with decreased methane concentration and with a decrease in the space velocity.

In order to understand the wintertime intermittent characteristics of the trans-boundary air pollutant transport observed in East Asia, a numerical simulation of the long-range transport of pollutants was applied using an atmospheric transport model(STEM-II). The numerical simulation was carried out for the entire month of January 1997 and specific atmospheric aerosol (including sulfate, nitrate, and other ion compounds0 observation data were compared from four observation sites(Cheju Island, Kanghwa Island, Dazaifu, and Fukue Island). The observation data revealed that concentration peaks were intermittently observed at 3 to 4-day intervals plus the four observation sites exhibited a very similar spatial variation. The horizontal and spatial scale of the heavily polluted air masses was analyzed based on numerical results. The mechanism of the intermittent transport of air pollutants was clearly explained by a comparison of the observed data with the numerical output. It was found that the wind pattern variations associated with the synoptic scale pressure system changes play an extremely important role in the transport of pollutants in this region.

Transboundary air pollution has recently become an area of increasing scientific interest and political concern as countries are receiving air pollutants from their neighbors. In order to gain a better understanding of the long-range transport processes of air pollutants and the source-receptor relationships among neighboring countries, an atmospheric transport model coupled with a RAMS(Regional Atmospheric Modeling System) model was applied to the East Asia region during the entire month of January 1993. The scalar transport option of the RAMS model was used to calculate special atmospheric constituents such as trace gases or aerosols. The sulfate production in clouds and rainwater and its removal processes by dry and wet deposition were considered. The sulfate budget from source regions to receptor regions was estimated by analysing the source-receptor relationships. When a specific receptor site revealed a sulfate value higher than the sulfate concentration based on its own source origin, this was taken to indicate long-range transport from another source region. The contribution ratio from various source region was calculated. The contribution ratio of dry and wet deposition was higher on the main continent of the East region. Furthermore, the high deposition amounts were identified on the west coast of Korea and the East China Sea.

A series of simulations were carried out to test the accuracy of a CFD (Computational Fluid Dynamics) model for flow and dispersion problems around buildings. The basic equations involved are Reynolds-averaged Navier-Stokes equations. Two different cases were selected to estimate the accuracy of a CFD model. Case 1 adopted Euler equations, which are obtained by neglecting the viscous fluxes, which can be closed by the $textsc{k}$-$\varepsilon$model for a turbulent close problem. The results of both cases were compared with wind tunnel data. The results for Case 2 were closer to the wind both cases were compared with wind tunnel data. The results for Case 2 were closer to the wind tunnel data than Case 1. Accordingly, this indicates that the inclusion of viscous fluxes in a CFD model is required for the simulation of flow and 야spersion around buildings.