Key Engineering Materials Vols. 277-279

Abstract: The association of air pollution with daily mortality due to cardiovascular disease, respiratory disease, and old age (65 or older) in Seoul, Korea was investigated in 1999 using daily values of TSP, PM10, O3, SO2, NO2, and CO. Generalized additive Poisson models were applied to allow for the highly flexible fitting of daily trends in air pollution as well as nonlinear association with meteorological variables such as temperature, humidity, and wind speed. To estimate the effect of air pollution and weather on mortality, LOESS smoothing was used in generalized additive models. The findings suggest that air pollution levels affect significantly the daily mortality.

Abstract: Multivariate analysis was conducted to analyze the relationship between air pollutants and meteorological variables measured in Seoul from January 1 to December 31, 1999. The first principal component showed the contrast effect between O3 and the other pollutants. The second principal component showed the contrast effect between CO, SO2, NO2, and O3, PM10, TSP. Based on the cluster analysis, three clusters represented different air pollution levels, seasonal characteristics of air pollutants, and meteorological conditions. Discriminant analysis with Air Environment Index (AEI) was carried out to develop an air pollution index function.

Abstract: This study focuses on ozone modeling using meteorological and air monitoring variables. Twenty seven (27) places in Seoul were measured for ozone values from January 1999 to December 1999. Air quality monitoring data consisted of CO, NO2, O3, PM10, TSP while meteorology data consisted of the daily maximum temperature, humidity and wind speed, and solar radiation. The complexity of environmental data dynamics often requires models covering non-linearity. Photochemical ozone pollution is the result of complex non-linear interactions between atmospheric pollutants and meteorology. The generalized additive model is favored because it is the most flexible, has the fewest statistical assumptions, and it can detect and fit potentially complex and nonlinear dependencies. For these reasons we modeled the daily ozone amount using a generalized additive model with smooth loess functions and compared it with a multiple linear regression model.

Abstract: This study was made to investigate the extent and degree of As contamination in waters and sediments influenced by previous mining activity in the abandoned Dongil Au-Ag mine. Arsenic species was also identified in surface waters and groundwater. The chemical form of As in sediments was examined using sequential extraction analysis. The major contamination source of As in the mine area is suggested to be tailings with elevated levels of 8,718 As mg/kg. This was associated with the release of high level of As into the water system in the study area. The pH values of water samples ranged from 7.7 to 10.1, which was neutral to strong alkaline due to buffering effect by high concentration of Ca and Mg dissolved from carbonate mineral and weathering of concrete. Stream waters contained high level of As within the range of 40.5 to 150.4 ㎍/L and most waters exceeded the permissible level (50 ㎍/L) of As for stream water in Korea. The concentration ratios of As(Ⅲ) to As (total), however, extended in the range of 5.8 to 75% and increased at low pH condition in stream waters. Arsenic concentration in sediments digested by aqua regia (HNO3+HCl) ranged from 162 to 2,077 mg/kg. The highest concentration of As may be due to the direct inflow of tailings. The relatively high percentage (17.1~35.3%) of As coprecipitated with amorphous Fe oxyhydroxides indicates that more severe contamination of As can occur by re-extracting due to changes of chemical environment such as reducing condition.

Abstract: This study was conducted to test the performance of various combinations of coagulants for effective wastewater treatment of the tire recycling industry. From the Jar-test results, two kinds of coagulants, namely AlSi-1 and PASi-1, were found to be effective in decreasing BOD and CODCr values from the polluted wastewater among various combinations of coagulants. In comparison to Al-based or Si-based singular salts, the Si-Al combined salts (PASi-1) exhibited a higher removal efficiency of 90% turbidity, 93% SS, 70∼85% BOD5 and 85∼91% CODCr at 15± 2°C, pH7.5∼9.5 and 2.0mM of coagulant dosage. At 30±2°C of tire recycling effluents, the combination effect was clearly shown in the removal of CODCr over a wider range of pH. The reaction mechanisms of AlSi-1 and PASi-1 were also schematically studied.

Abstract: A new type of biofilter, the rotating drum biotrickling filter (RDBF) system, was developed and operated to remove styrene from waste gas stream. Porous polyurethane foam sheets were used as a packing material for the RDBF and a pure culture of the Gram-positive bacterium Brevibacillus sp. SP1 was as an inoculum. The reactor showed a short start-up period of 18 days. Once uniform biofilms were developed on the packing, a high and stable removal of styrene over 95 % was observed at an incoming concentration of 200 ppmv and a retention time of 0.5 min. The maximum elimination capacity was estimated to be 125 g/m3/hr. The outstanding performance was attributed to an efficient gas-liquid mass transfer and proper supply of nutrient solution to the packing during the rotation of the drum. However, this performance of the RDBF was not maintained longer than 7 days because of the clogging of the open pores in the polyurethane foam due to an excessive growth of the biofilms. This result indicates that the RDBF has great potential as a gas purification system if a proper method to control the biofilm growth is developed.

Abstract: The carbon isotope ratios in foxtail seeds, which grow well anywhere such as a residential street, roadside, empty lot, field etc., were measured by EA/IRMS (Elemental Analyzer/ Isotope Ratio Mass Spectrometer). The samplings were carried out in two ways. One set of foxtail seeds was sampled at 11 different locations to examine the effect of the traffic frequency in Daejeon and its suburbs. The other set was collected in three separate areas to examine the distance effect from the roadside. The d13C values of foxtails were increased at a distance from the center of Daejeon City. According to the results for the other set to examine the distance effect from the roadside, the d13C values of foxtails grown close to the roads were lower than those far away from the road. It means that the roadside foxtails are highly affected by automobile exhaust gases. This effect strongly decreased as the distance from the road increased, because the pollution gases by the vehicles diluted well with the air, even at 5 m from the road. We propose that these results can be used in the monitoring of the hazardous atmospheric pollutants caused by fossil fuel in addition to the monitoring of carbon dioxide.

Abstract: The response of Quercus mongolica, one of the major tree species in Northeast Asia and the most dominant deciduous tree in Korea, was studied in relation to elevated CO2 and the addition of nitrogen to soil in terms of its physiology and growth over two years. Plants were grown from seed at two CO2 conditions (ambient and 700 µL L-1) and with two levels of soil nitrogen supply (1.5 mM and 6.5 mM). Elevated CO2 was found to significantly enhance the photosynthesis rate and water use efficiency by 2.3-2.7 times and by 1.3-1.8 times, respectively. Over time within a growing season, there was a decreasing trend in the photosynthesis rate. However, the decrease was slower especially in two-year-old seedlings grown in elevated CO2 and high nitrogen conditions, suggesting that their physiological activity lasted relatively longer. Improved photosynthesis and water use efficiency as well as prolonged physiological activity under high CO2 condition resulted in an increase in biomass accumulation. That is, in elevated CO2, total biomass increased by 1.7 and 1.2 times, respectively, for one- and two-year-old seedlings with low nitrogen conditions, and by 1.8 and 2.6 times with high nitrogen conditions. This result indicates that the effect of CO2 on biomass is more marked in high nitrogen conditions. This, therefore, shows that the effect of CO2 is accelerated by the addition of nitrogen. With the increase in total biomass, the number of leaves and stem diameter increased significantly, and more biomass was allocated in roots, resulting in structural change. Overall, the elevated CO2 markedly stimulated the physiology and growth of Q. mongolica. This demonstrates that Q. mongolica is capable of exploiting an elevated CO2 environment. Therefore, it will remain a dominant species and continue to be a major CO2 sink in the future, even though other resources such as nitrogen can modify the CO2 effect.

Abstract: Ceramides are well-known second messengers which mediate apoptosis, proliferation, differentiation in mammalian cells, but the physiological roles of phytosphingosines are poorly understood. We hypothesized that one of the phytosphingosine derivatives, N-acetylphytosphingosine (NAPS) can induce apoptosis in human leukemia Jurkat cell line and increase apoptosis in irradiated MDA-MB-231 cells. We first examined the effect of NAPS on apoptosis of Jurkat cells. NAPS had a more rapid and stronger apoptotic effect than C2-ceramide in Jurkat cells and significant increase of apoptosis was observed at 3 h after treatment. In contrast, the apoptosis induced by C2-ceramide was observed only after 16 h of treatment. NAPS induced apoptosis was mediated by caspase 3 and 8 activation and inhibited by z-VAD-fmk. Ceramide plays a pivotal role in radiation induced apoptosis. We postulated that exogenous treatment of NAPS sensitizes tumor cells to ionizing radiation, since NAPS might be used as a more effective alternative to C2-ceramide. As expected, NAPS decreased clonogenic survival of irradiated MDA-MB-231 cells dose dependently, and apoptosis of irradiated cells in the presence of NAPS was increased through the caspase activation. Taken together, NAPS is an effective apoptosis-inducing agent, which can be readily synthesized from yeast sources, and is a potent alternative to ceramide for the further study of ceramide associated signaling and the development of radiosensitizing agent.

Abstract: In order to investigate the levels of heavy metal contamination and to assess the risk of the adverse health effects on human exposure to toxic heavy metals influenced by past mining activities, environmental geochemical surveys were undertaken around abandoned metal mine sites (Okdong Cu-Pb-Zn, Dokok Au-Ag-Cu and Hwacheon Au-Ag-Pb-Zn mines). High concentrations of heavy metals were found in tailings from the Okdong (72 As mg/kg, 53.6 Cd mg/kg, 910 Cu mg/kg, 1,590 Pb mg/kg, 5,720 Zn mg/kg), the Dokok (254 As mg/kg, 98.2 Cd mg/kg, 2,550 Cu mg/kg, 4,200 Pb mg/kg, 18,020 Zn mg/kg) and the Hwacheon (72 As mg/kg, 12.4 Cd mg/kg, 580 Pb mg/kg, 1,300 Zn mg/kg) mines. Elevated levels of As, Cd, Pb and Zn were also found in agricultural soils from these mine areas. Human risk effects are classified into a cancer effect and a toxic (noncancer) effect. The hazard index representing a toxic risk for As was higher value than 1.0 in the Okdong and the Hwacheon mine sites, as was that for Cd in the Okdong and Dokok mine sites. Therefore, toxic risks for As and Cd exist via exposure (ingestion) to the contaminated soil, groundwater and rice grains in these mine areas. The cancer risk for As by the consumption of groundwater used as drinking water from the Okdong and the Hwacheon mine areas was 7E-4 and 1E-4, respectively. These risk levels exceed the acceptable risk (1 in 100,000) for regulatory purposes.