Methyl methacrylate (MMA) and alumina recovery from waste artificial marble powder pyrolysis

Journal of Material Cycles and Waste Management - Owing to various advantages of artificial marble compared to natural marble, its application has been rising exponentially, which has resulted in...     

Distribution of diatoms in the surficial sediments of the Mangyung-Dongjin tidal flat,west coast of Korea (Eastern Yellow Sea)

The relationship between the distribution of benthic diatoms and sediment characteristics of the Mangyung-Dongjin tidal flat on the west coast of Korea was investigated during June and July 1988. Diatoms were collected from the upper 5 mm of sediments at 60 sites along eight transect lines running perpendicular to the shore line. Of the 371 taxa encountered in the study area, 88% were pennate diatoms. Genera represented by the greatest number of species were Navicula, Nitzschia, Amphora, Cocconeis, Fragilaria and Achnanthes. The most abundant species were Paralia sulcata, Navicula sp. #1, N. arenaria and Cymatosira belgica; all were broadly distributed across the tidal flats. The 60 sites could be assigned to eight clusters with respect to similarity in species composition. Discriminant analysis showed that separation cluster was primarily related to the mean grain size of the sediment. The species could not be separated into groups based on similarities in occurrence; a high degree of spatial overlap was observed. The preferences of the more abundant species for grain size were, therefore, analysed by plotting numerical abundance against mean grain size. There were at least four patterns: species groups could be associated with finegrained sediments, those of intermediate size and coarser sediments and the last group showed no discernible pattern.     

Induction of cytochrome P4501A and endocrine disrupting effects of school incinerator residues

The emission of the dioxin-like compounds from on-site waste incinerators of seven schools in Kyonggi Province of Korea was evaluated by determination of the cytochrome P4501A(CYP1A) catalytic activity and antiestrogenic activity using cell culturemicrobioassay. The residue samples were extracted in a Soxhlet apparatus using toluene for 20 hr. The concentrated crude extractswere fractionated with a basic alumina column. Dioxin-like compounds were then extracted. Induction of CYP1A activity in a rat(H4IIE) hepatoma cell line was used as indicator of biologicaleffect of incinerator residues and measured as 7-ethoxyresorufin-O-deethylase(EROD) activities. The EROD activities of fraction II extracts (one of the two extracts) in the H4IIE cells were from 0.044±0.002 to 4.424±0.351 ng-TEQ g^-1 (TCDD Toxicity equivalent), showing relatively high inducing capacity. Antisetrogenicity of the extracts was measured as decrease in E₂-induced cell proliferation. Most of the extracts showed antiestrogenic activity in MCF7-BUS cell.The TEQ levels of the incinerator residues and the antiestrogenicactivities were in good correlation, strongly suggesting that thepotent toxic emissions were indeed produced from the on-site school waste semi-incinerators and could cause the antiestrogenicity.     

Seasonal characteristics of haze observed by continuous visibility monitoring in the urban atmosphere of Kwangju, Korea

Continuous visibility monitoring has been carried out inKwangju, Korea since May 1999. The total light extinctioncoefficient b _ext measured by a transmissometer andreveals seasonal trends in urban visual air quality,especially under hazy conditions with a visual range of lessthan 15 km. Seasonal atmospheric visibility under lowrelative humidity during the winter was observed to be betterthan during any other seasons. Summertime visibility wasseverely degraded due to highly increased light scattering byhygroscopic particles under high humidity atmosphericconditions. Visibility during spring and fall was alsomoderate. However, yellow sand in spring caused the lowestvisibility conditions over the measurement area for a fewdays. With continuous monitoring using the transmissometer,the daily average seasonal visual range was measured to be13.1, 9.2, 11.0, and 13.9 km in spring, summer, falland winter, respectively. Under the atmospheric humiditycondition less than 60%, visual range was observed tobe 16.1, 13.9, 15.1, and 16.6 km in spring, summer,fall, and winter, respectively. The mean light extinctionbudget by sulfate and nitrate aerosols was determined to bethe highest value of 63.71% during the summer and thelowest value of 27.08% during spring. During the `yellow sand dust' period, a mean light extinction budget by soil particles was estimated to be at an unusually high value of 44.22%.     

Aerosol Optical and Radiative Properties Observed at Anmyeon and Jeju, Korea in the Spring of 2000 and 2001

The radiative properties of atmospheric aerosols are determined by their masses, chemical characteristics, and optical properties, such as aerosol optical depth (AOD), Åstrom;ngström parameter (α) and single scattering albedo (SSA). In particular, the aerosol optical properties determine the surface temperature perturbation that may give some information in understanding regional atmospheric radiative forcing. To understand the radiative forcing and regional source of an aerosol, the present study focused on the analysis of the aerosol optical properties based on two different observations in the spring season, during the special Asian dust storm period. The Korean Global Atmosphere Watch Observatory (KGAWO), at Anmyeon Island, and the ACE-Asia super-site, at Gosan, Jeju Island, have measured radiations and aerosols since 2000. The sites are located in the mid-west and south of the Korean peninsula, which are strongly affected by the Asian dust coming from China every spring. The aerosol optical properties, measured by ground-based sun and sky radiometers, over both sites were analyzed to gain an understanding of the radiation and climate properties.The probability distributions of the aerosol optical depths were rather narrow, with a modal value of approximately 0.38 at both sites during 2001 and 2002. The Ångström parameter frequency distributions showed two peaks at Anmyeon GAW, but only one peak at the Jeju ACE-Asia super site. One peak, around 0.63, characterizes the situation of a day having Asian dust, the second peak, around 1.13, corresponded to the relatively dust-free cases. The correlation between the aerosol optical depth and the Ångström exponents resulted in a wide range of the Ångström parameter, α, over a wide range of optical depths at Anmyeon, whereas a narrow range of α, with moderate to low values for the AOD at Jeju. Under dust free conditions the single scattering albedo (SSA) decreased with wavelength, while in the presence of Asian dust,the SSA either stayed neutral, or increased slightly with wavelength at Anmyeon, and showed higher value than Jeju. The change in the surface temperature was highly correlated with increases in the aerosol optical depth at Anmyeon to a greater extent than at Jeju.     

近期和长远时段内北极生态系统结构受到的影响

生物在物种水平上对全球气候变暖和紫外线B(UV-B)辐射增强的反应受到其群落内其他物种以及生态系统内养分循环的调节,所有的这些反应将会导致生态系统结构的变化.根据高纬度地区坏境因子的可能变化而做的控制试验表明,由夏季变暖而引起苔原植被的变化要小于增加施肥而引起的变化,试验涉及的某些环境因子对北极生态系统的结构有非常强烈地影响,但是这些影响因地区而异,观测结果表明,处于最寒冷地区的植物群落和无脊椎动物群落对全球气候变暖和紫外线B辐射的增强反应最为强烈.尽管微生物量和养分储存量相对稳定,北极无脊椎动物群落还是很可能会对全球变暖产生迅速的反应.试验结果显示,加强紫外线B辐射会改变革兰氏阴性细菌和真菌的群落组成结构,但不会对植物群落的组成产生影响.由夏季气温升高而提高的植物生产力将会控制食物网的动态变化,以苔原植被和亚极地森林植物为基础的食物网中的营养流动会明显地影响到几种优势动物种群数量的周期性波动,在某些年分这些动物的种群数量会达到峰值.小型啮齿动物和食叶昆虫如秋毛虫种群数量的周期性变化则会影响苔原和森林苔原植物的组成结构和多样性,同时也会影响到一些专性捕食者和寄生虫的变化.在暖冬,雪表形成冰壳可能会减少旅鼠的植物食物来源,然而较深的雪也可以使它们免受雪地表面上捕食者对它们的捕食.在芬诺斯堪的亚地区,已有证据表明小型啮齿类动物群落结构和种群动态的显著变化会导致专门以小型啮齿类动物为食物的捕食者的数量减少.气候还可能改变昆虫在白桦森林生态系统中的作用,因为暖冬可以增加这些昆虫卵的成活率,并且扩大其分布范围.此外,在夏季困扰驯鹿的昆虫会由于夏季气候的变暖而扩大其分布范围、增加种群数量并且种群更为活跃;同时在另一方面也会对驯鹿不利,即那些昔日驯鹿/北美驯鹿的避难场所--冰川和未融的成片的雪--在这样温暖的夏季则可能会消失.     

近期和长远时段内北极生态系统功能受到的影响

长期以来,就营养物质和碳循环而言,北极生态系统降低了初级生产力；能量,水和温室气体交换的水平已引起了局部和区域性的小幅度降温.大气CO2中的碳沉积在广袤而寒冷的有机土壤中,冰雪覆盖的低矮植被产生高的反射率,都影响了局部气候.然而,北极生态系统功能的许多方面都对气候变化及其产生的生物多样性影响敏感.当前的北极气候导致了低的有机物质分解速率,因此,尽管有机物和元素输入量较低,但北极生态系统还是趋向于积累有机物和元素,土壤中氮和磷等可利用元素结果成为促进碳固定以及生物量和有机物进一步积累的关键性限制因素.气候变暖可能增加特别是土壤中的碳和元素的周转,起初可能导致元素的丢失,但最后会慢慢的恢复.在北极生态系统中,单个物种和物种多样性已经明显地影响了元素的输入和滞留,另一方面,从长远来看,尽管CO2和紫外线增加对植物组织化学、分解和氮固定的影响可能变得重要,但对整个生态系统来说,影响可能很小.碳循环的示踪气体主要形式是CO2和CH4,大多数碳以CO2的形式损失,这些CO2是由植物和土壤生物产生.来自潮湿苔原生态系统以CH4形式释放的碳大约是CO2形式的5％,而且在没有任何其他变化的情况下,对变暖作出响应.冬天过程和植物类型也影响CH4释放和能量在生物圈和大气之间的交换,因为反射率从冬末到夏天存在很大的变化,在冬末,雪反射了入射的大部分光线,在夏天,生态系统吸收了入射的大部分光线,所以在所有的陆地生态系统中,北极生态系统在能量交换方面表现出巨大的季节性变化.植被深刻地影响北极生态系统水和能量交换.在冰雪覆盖期间,反射率从苔原、森林苔原、落叶林、常绿林依次降低.灌木和树增加了雪的深度,反过来又使冬天的土壤温度增加,因此,由气候变化而引起的未来植被方面的变化很可能深远地改变区域的气候.     

Concentration of trace elements in feathers of waterfowl,Korea

Cadmium (Cd), lead (Pb), chromium (Cr), copper (Cu), manganese (Mn), zinc (Zn), and iron (Fe) were analyzed in the breast feather of white-fronted geese (Anser albifrons, n?=?15), mallards (Anas platyrhynchos, n?=?4), and spot-billed ducks (Anas poecilorhyncha, n?=?13) found dead in Gimpo, Korea. All of the mallards and eight of the 13 spot-billed ducks had embedded shot. Concentrations of Pb, Cr, Cu, Mn, Zn, and Fe were significantly different among waterfowl species. Mallards with embedded shot had relatively higher Pb, Cr, Mn, and Fe concentrations than the other species. Cd and Cr in feathers of waterfowl species were within the range reported for other birds, and no specimen exceeded the tentative threshold effect levels of Cd (2 μg/g dry weight (dw)) and Cr (2.8 μg/g dw) for birds. However, Pb in feathers of all four mallards and two spot-billed ducks exceeded the threshold for deleterious effects (>4 μg/g dw). Essential elements such as Cu, Mn, Zn, and Fe in the feather of waterfowl species were not at toxic levels and within the background or normal range for the homeostatic mechanisms.     

Development of conflict techniques for left-turn and cross-traffic at protected left-turn signalized intersections

To design comprehensive traffic safety measures, the risk of the occurrence of traffic accidents must be objectively evaluated. It is difficult, however, to evaluate the effects of traffic measures in terms of the change in the number of traffic accidents, because traffic accidents are unpredictable and rare events. Therefore, this study used a traffic conflict technique to objectively evaluate traffic safety at intersections. In this study, traffic conflicts that occur at the time of a signal violation were differentiated according to type, and a traffic conflict technology was developed that would consider the severity of each type of conflict. To apply this method, traffic images were collected from the Jungja intersection and the Naejung intersection in Sungnam City, Korea and were analyzed using traffic data by means of image procedure technology. The analyses showed that of the four levels of differentiated conflict conditions, the Level 1 condition occurred most often, followed by Level 2, which occurred much less frequently than Level 1. Level 3 (serious conflicts) and Level 4 (dangerous conflicts: accidents) conditions were not detected.     

Detection and Molecular Characterization of Human Noroviruses in Korean Groundwater Between 2008 and 2010

RT-PCR, nucleotide sequencing, and phylogenetic analysis were performed for genotyping and molecular characterization of noroviruses isolated from Korean groundwater. Among 160 samples collected from 80 sites between 2008 and 2010, 14 samples (8.7?%) from 12 sites were positive for noroviruses (NoVs). The percentages of NoV-positive samples in 2008, 2009, and 2010 were 22.2, 3.2, and 0?%, respectively, representing a yearly decrease. GII-positive samples (n?=?9, 5.6?%) outnumbered GI-positive samples (n?=?5, 3.1?%). The genotypes of the GI NoVs were GI.2, GI.5, and GI.6, and the genotypes of the GII NoVs were all GII.4. One sample, HM623465, was very similar to CUK-3 and CBNU2 and two GII.4 sequences isolated from the stool of Korean gastroenteritis patients. A BLASTN search revealed several nucleotide sequences highly similar to those of NoVs isolated in this study. The original isolation sources for these similar NoVs were mostly stool (n?=?731, 80.0?%) and groundwater (n?=?135, 14.8?%), and all the countries from which they were isolated were almost in Asia (96.0?%); specifically, China (n?=?192, 21.0?%), Japan (n?=?383, 41.9?%), Korea (n?=?296, 32.4?%), and other Asian countries (n?=?6, 0.7?%). These results suggest that Korean groundwater might be contaminated with NoVs from the stool of infected patients and that these NoVs in turn cause new cases of gastroenteritis through a typical fecal-oral route with region-specific circulation. Therefore, it is important to properly treat sewage, which may include waterborne viruses and manage point sources in groundwater for national health and sanitation. In addition, continuous molecular surveillance remains important for understanding circulating NoVs.