Abstract: The level of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans
(PCDD/Fs) concentration in blood of 4 chemists conducting dioxin analysis at a laboratory was estimated. The level of PCDDF/s concentration ranged from 4.48 pg I-TEQ/g-fat to 8.17 pg ITEQ/ g-fat (mean level : 6.19 pg I-TEQ/g-fat, median level : 6.07 pg I-TEQ/g-fat, standard deviation in this study : 1.51 pg I-TEQ/g-fat). The level of PCDD/Fs in bloods of the chemists in this study is not higher compared with other studies in Korea. The portion of PCDFs to the total PCDD/F I-TEQ concentration in this study was found to be over 80%. This is not the case in other
countries where the portion of PCDDs to the total TEQ in blood was generally much higher than that of PCDFs. In Korea, the portion of PCDFs to the total PCDD/F I TEQ concentration in food was higher than that of PCDDs. In other countries, the portion of PCDFs was relatively lower. It is considered that the portion of PCDFs in blood has interrelation with that of PCDFs in food in both Korea and other countries.
Abstract: Anaerobically digested sludge was seeded in a mesophilic UASB reactor and the sludge was monitored for seven months to better understand the start-up process of the reactor. The reactor was fed with synthetic wastewater containing glucose. As the COD loading rate increased stepwise (from 1 to 4 g COD l-1 d-1), the methane production rate increased. COD removal efficiency was maintained to be greater than 90% after day 36. Maximum value of the methane production rate
(6.0-6.5 l d-1) was achieved from day 152 and remained stable afterward. Although the reactor showed steady performance in terms of COD removal efficiency and methane production under constant hydraulic retention time (HRT) or COD loading rates, physicochemical and microbial properties of UASB sludge kept changing during the initial 5 months of operation. Specific methanogenic activity
was initially negligible but increased until day 150, and then remained constant (0.72 + 0.11 g CH4-COD g-1 VSS d-1) afterward. Sludge volume index showed that the settling ability of UASB sludge gradually improved until it reached a plateau in day 120. Improved settling-ability could provide a basis for keeping bed height constant despite shortened HRT. The mean diameter of the UASB sludge gradually increased until approximately day 150 and maintained a maximum value (0.48 mm) afterward. Confocal laser scanning microscopy revealed F420-based autofluorescence of physical and optical sections of UASB sludge, suggesting the locations of autofluorescent methanogens in the UASB sludge during the start-up period. During the initial operation of the reactor, autofluorescence showed random and uneven distribution inside the sludge. However, autofluorescence appeared as an inner layer near the edge of the sludge with time, suggesting more abundant or active methanogens in this layer. The highest autofluorescence was observed in the range of 20 to 28 µm depth from the surface of granule as determined by optical slicing of UASB sludge. The results obtained in this study provide insight into UASB sludge development that involves dynamic changes in physicochemical and microbial aspects during the start-up period.
Abstract: Toxicity screening tests using the Reserve Electron Transfer (RET) and Electron Transfer (ETr) assays were performed with five wastewater samples amended with trickling filter (TF) or activated sludge (AS) biomass. In the case of untreated samples, Home Life domestic wastewater (HLD/W) showed the lowest inhibition, followed by domestic sewage (DS), hospital wastewater (H/W), East Straus wastewater (ES/W), and Mills wastewater (M/W) from both ETr and RET assays. After 12 hours of treatment at 20°C, DS with AS biomass had the lowest % inhibition from the RET assay, followed by DS with TF, HLD/W with TF, H/W with TF, M/W with TF, and M/W with AS. AS biomass reduced more toxicity from DS than TF biomass whereas acclimated TF biomass reduced significantly more toxicity than AS biomass, indicating the importance of acclimation. M/W was
most toxic and resistant to biodegradation among six wastewater samples. No nitrification occurred with M/W and ES/W. While there was significant nitrification with DS treated by AS biomass, little nitrification by TF biomass occurred even with DS, HLD/W, and H/W. It appears that nitrification is significantly inhibited by M/W and ES/W even when mixed with domestic sewage. It appears that there is a strong relationship between the TIC/TC ratio and % inhibition.
Abstract: Growth and reproduction of Porphyra kuniedae from the southern coast of Korea were investigated. Biomass, plant size and occurrence of reproductive structures were monitored every other week from November 2001 to March 2002. Release of zygotospores and monospores from the plants was induced and the number of spores was counted in the laboratory culture every month. Biomass and plant size were found to be inversely correlated with water temperature. The maximum values in biomass and plant size were observed in mid-January with the lowest water temperature, and the values decreased with the increase of water temperature. Based on the cohort analysis, three cohorts started in late November, one to two cohorts were added every other week, and the maximum was eight in mid-January. The percentage of matured plants in the field was the highest in January. In the laboratory culture test, zygotospores were released more than monospores from large plants in late December while monospores were released much more than zygotospores since late January.
Abstract: Silicon oxide deposition on fine alumina powders by plasma-enhanced chemical vapor deposition (PECVD) at atmospheric pressure was carried out in a circulating fluidized bed reactor. To deposit silicon oxide on alumina powders, the organo-silicon source precursors (tetraethoxysilane (TEOS) and hexamethyldisiloxane (HMDSO)) and oxygen were used as the reactant gases while helium and argon were used as the dilute gases. The surface property of
plasma-treated alumina powder varies from hydrophobic to hydrophilic in the surface composition with variation of the discharge power. In oxygen-containing atmospheres, chemical composition of the deposited film is more inorganic with increasing the discharge power and the flow ratio of O2/precursor for both organo-silicon precursors.
Abstract: In small buildings and residences in Korea, unvented or improperly vented combustion appliances are used to heat rooms. These heaters are mostly gas-fired portable equipment used for auxiliary heating. Although their maintenance cost is very low, unvented gas-fired heaters emit air contaminants such as carbon dioxide and carbon monoxide. If there is inadequate ventilation and even a little fresh air with oxygen comes into the appliances, combustion occurs less efficiently and heaters generate more air contaminants. Natural ventilation is the best way to prevent air pollution in small buildings. Outdoor air has a lot of oxygen and can reduce air pollution. The objective and scope of this research is to predict the distribution of indoor air pollution, according to the results of field measurements and CFD (Computational Fluid Dynamics) simulations. In a room of 6.4m×3.1m×2.6m in size, air contaminants (CO2 and CO) and air temperature were measured in two instances--with natural ventilation and without natural ventilation. After comparing the results obtained with computer simulation and field measurements, passive control methods to improve indoor air quality in a room are proposed.
Abstract: Recently, patterning and analyzing complex data of behaviors of animals in response to external stimuli such as toxic chemicals has become focus of attentions. In this paper, an energy minimization model to extract the features of response behavior of chironomids under toxic treatment is proposed, which is applied on the image of velocity vectors. The model is based on the improved active contour model and the variation of the energy values produced by the evolving active contour. We attempt to implement an adaptive computational method to characterize the changes in response behaviors of chironomids after treatment with an insecticide, diazinon. Active contour is formed around each collection of velocities to gradually evolve to find the optimal boundaries of velocity collections through processes of energy minimization. The energy minimization model effectively reveals characteristic patterns of behavior for the treatment versus no treatment, and identifies changes in behavioral states as the time progressed.
Abstract: Ammonia generated from decomposition of a large amount of garbage, causes a serious environmental pollution. And also, carbon monoxide is notoriously a toxic compound and oxidized in the atmosphere to give carbon dioxide which causes green house effect or ozone depletion. We have investigated the possibility of carbonylation and amination, and proposed the reaction mechanisms for the photochemical transformation of carbon monoxide in aqueous methanol.