Polychlorinated dibenzo-p-dioxins and dibenzofurans from food salt samples processed by heat treatment in Korea

Eight samples of processed food salt collected from five plants in Korea were analyzed for 2,3,7,8-substituted polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) using liquid-liquid extraction, clean-up procedures, and high resolution gas chromatography-high resolution mass spectrometry. The study included the analyses of two kinds of salt product sample: bamboo-salt and parched salt. The levels of toxic PCDD/Fs found in the salt product samples were extremely low: the results revealed TEQ levels ranging between the sub pg TEQ/g and sub fg TEQ/g. The differences in the TEQ values of toxic PCDD/F were observed between the salt product samples, which were treated with different frequency of baking using four different fuels (firewood, pine wood, pine resin, and indirect heating by gas) at temperatures from 300 to 2000 degrees C. In bamboo-salt samples, the concentrations and TEQ values of toxic PCDD/Fs ranged between 0.57-66 pg/g and 5.7x10(-5)-0.64 pg TEQ/g, respectively. PCDD/Fs levels in bamboo-salts baked by firewood were found to be higher than those baked by pinewood or pine resin. In parched salt samples, the concentrations and TEQ values of toxic PCDD/Fs ranged between 0.97-3.7 pg/g and 0.0097-0.017 pg TEQ/g, respectively. The data was discussed regarding the concentration and the distribution pattern of congeners.     

Fluctuations of exposure rate at regional radiation monitoring stations in Korea

Based on hourly means of exposure rate between August 2000 and July 2001 at nine Regional Radiation Monitoring Stations (RRMS) in Korea, we analyzed spatio-temporal characteristics of exposure rate. The mean and fluctuations of exposure rates were 99 and 3.8 nGy h(-1), respectively. The hourly exposure rate over 9 RRMS indicated a diurnal pattern with the exposure rates reaching a maximum between 5:00 and 8:00 a.m. in the early morning and a broad minimum between 4:00 and 10:00 p.m. in the afternoon. The fluctuations of exposure rate in the inland areas were less than 3.2 nGy h(-1), and those of exposure rate in coastal areas were larger than 3.9 nGy h(-1). The frequency distribution of exposure rates had one peak around the mean and was to be skewed to the right or positively skewed and its tails were fatter than those of a normal distribution. The interrelations of exposure rates at each station generally decreased with the distance between the stations. Empirical orthogonal function (EOF) analysis showed that almost all (99.9%) of exposure rate fluctuations were described by simultaneous variations. The spatial distribution of the first EOF modes of actual, low-pass (periods longer than one month) and high-pass (periods shorter than one month) exposure rate series were similar to each other.     

首都大学生的自然灾害认知调查与减灾教育建议

2006年国际减灾日的主题是"减灾始于学校",了解学生的灾害认知水平有助于减灾教育工作的有效开展。以北京5所高校的大学生为调查对象,通过问卷方式调查大学生对自然灾害的关注程度、防灾意识、灾害理论知识、应急行为知识以及对减灾教育的看法。问卷统计结果表明:大学生总体的灾害认知水平较低,现行减灾教育方式和内容与学生的期望有较大偏差。在此基础上,提出了减灾教育内容要将学生"该知道的"与"想知道的"相结合,通过演练演习等方式提高学生的防灾应急实际技能等减灾教育建议。     

一氯二乙基铝装置危险源辨识及预防措施

一氯二乙基铝装置为甲类火灾危险装置。通过对一氯二乙基铝装置工艺流程及各单元工艺特点的详细分析,危险源的辨识从物料危险性、工艺过程危险性、工艺操作危险性等角度展开,从而确定出该装置的重大风险因素。在对一氯二乙基铝装置危险源辨识和分析的基础上,对各工艺单元提出相应的控制措施,预防事故发生。     

现有评价方法在油气长输管道工程安全评价中的应用

油气长输管道工程的安全评价工作正在成为新建及在役管道安全运行的保障。针对目前国内已开展的油气长输管道工程安全评价现状,结合自身安全评价工作实践,对现有评价方法在油气长输管道工程安全评价中的应用进行了讨论,并提出相应建议。     

脱除NOx新型吸附剂的性能测试

通过试验测试CNA－208和CNA－255两种吸附剂脱除氮氧化物（NOx）的动态吸附容量和吸附NOx前后的燃点，考察了NOx对这两种吸附剂燃性能的影响以及CNA－208用作脱除NOx吸附剂的可靠性及其替CNA－255的可行性。     

柳州市城市土地利用空间格局演化特征分析

在GIS空间分析和统计分析模型的支持下，运用多种数学模型对柳州市土地利用空间格局演化从土地利用的数量结构和空间格局变化的两方面进行定量分析，通过比较定量分析结果，得出研究区土地利用空间格局变化表现为土地利用结构日趋合理、城市圈层由外向内土地利用多样性降低、土地利用功能集聚趋势加强、城市逐渐由工业导向型向居住、公共设施导向型转化等特征。     

GaAs PHEMT器件的可靠性评估方法研究

本文从GaAs PHEMT器件的失效机理出发,总结了PHEMT器件的几种可靠性评估方法:利用沟道区碰撞电离率对PHEMT器件的热电子退化的评估方法、高频C-V法对肖特基势垒接触退化的可靠性表征方法、用于欧姆接触退化表征的温度斜坡快速评价方法以及2DEG结构引起PHEMT器件失效的可靠性评估方法.     

Development of vermicast from sludge and powdered oyster shell

Soil acidification is one of the rising land degradation issues facing world agriculture. The risk of acidification is currently being assessed as part of agriculture productivity and sustainable theme. This study was conducted to produce a new vermicomposting cast as a recycling resource derived from municipal sewage sludge and waste oyster shell. The earthworm, Eisenia Andrei, was fed under different conditions. The most suitable mixture was 77:23 w/w% of sewage sludge and waste oyster shell. Powdered oyster shell (POS) sludge blend provided a stable pH, due to its buffering capacity during vermiculture because of the Ca²⁺ and OH^? release effect. The vermicast products fulfilled the cast standards of Korea Ministry of Environment for all the parameters such as moisture content, pH, salinity, organic carbon, TKN, Phosphate, and heavy metals. Slowly released organic matter when added to soil improves the capacity of the soil to hold nutrients for plants, improve soil aeration for roots, and improves soil drainage. This product will be an addition to already-commercialized sludge vermicast as a higher value product.     

A new approach to characterize biodegradation of organics by molecular mass distribution in landfill leachate

This study provides biodegradability of organics in leachate according to their molecular mass distributions (<0.5, 0.5 to 1, 1 to 3, 10, and >10 KDa). Organics with molecular mass values lower than 0.5 KDa were the predominant species in the raw leachate filtrate, and the aerated lagoon process was very effective in treating these highly biodegradable organics; the Fenton's oxidation process was very effective in treating not-so-biodegradable organics with molecular mass values higher than 0.5 KDa, but a portion of these organics were converted into organics <0.5 KDa after Fenton's oxidation. An oxygen uptake measurement using a respirometer was more sensitive than a conventional biochemical oxygen demand measurement to evaluate bioactivities, especially when bioactivities were low.