二氯甲烷萃取-HPLC法测定水中的多菌灵

用二氯甲烷液-液萃取氮吹浓缩法萃取水和废水中的多菌灵,取浓缩纯化后的有机相直接进样到高效液相色谱仪,用二极管矩阵检测器检测,根据保留时间外标法定量。实验结果表明,采用此方法可将水体中的多菌灵快速有效地提取,并可获得较高的精密度和准确度。     

二氧化锰颗粒对Hela细胞DNA损伤的尺度依赖性毒作用(英文)

为了观察二氧化锰颗粒物所致的尺度依赖性DNA损伤作用,将纳米尺度二氧化锰颗粒物(Nano-MnO2)和常规尺度二氧化锰颗粒物(Nor-MnO2)所致的DNA损伤进行了对比研究.将Hela细胞分别暴露于不同浓度(0、100、200、400μg·mL-1)的Nano-MnO2和Nor-MnO2中,染毒24h,采用彗星实验检测Hela细胞的DNA损伤水平.结果表明:与对照组相比,Nano-MnO2和Nor-MnO2均可使彗尾DNA百分比(TailDNA%)和尾矩(TailMoment)显著增加(p<0.01);而在同一浓度水平上,Nano-MnO2所致的DNA损伤则比Nor-MnO2所致的DNA损伤更为严重(p<0.01).结果提示:二氧化锰颗粒对Hela细胞DNA损伤具有尺度依赖性毒作用,纳米尺度比常规尺度二氧化锰颗粒毒作用更强烈.     

开封市污灌区土壤重金属污染评价

通过分析污水灌溉在农业生产中的利弊及我国土壤的污染现状,运用内梅罗指数法及潜在生态危害指数法,分别参照国家土壤环境质量二级标准和土壤背景值对开封市污灌区土壤重金属污染状况进行了评价.结果表明,以二级标准为评价标准,评价结果为安全级别,以土壤背景值为评价标准,评价结果为轻度污染.但污灌区重金属含量明显超过清灌区重金属含量,Pb污染已达到中等污染水平,当地应采取有效措施以保护土壤免受污染.     

浙江省建筑材料放射性水平及居民受照剂量估算

报道了１９８８年－１９９５年浙江省建筑材料中放射性水平和所致居民剂量的计算结果。采用高纯锗γ能谱法测定了该地区的６种,１３９个建筑材料样品中放射性核素含量,并收集了１９８４年以前该地区另外５种,７７个建筑材料样品中的放射性水平数据。     

西北主要城市生活用水中氡及其剂量当量研究

分析了生活用水对室内空气中氡的贡献,并估算了水中氡剂量当量的大小．研究表明,西北地区主要大城市生活用水中氡的浓度差异较大,其中宝鸡和咸阳两市居民自备井水中氡的浓度较高,兰州市水中氡的浓度最高．西北地区主要城市生活用水中氡的释放量占室内总氡的3．30—24．47％,水中氡剂量当量不大,最高值为环境天然辐射剂量当量的17％左右．     

山区二级公路运营期常态交通风险评价

为客观准确地评价山区二级公路常态交通风险,将风险源分为动态风险源和静态风险源.首先,基于白化权函数的综合评价法建立事故后果模型,基于历史事故数据建立事故概率模型,以评价静态风险;其次,结合白化权函数和层次分析法(AHP)建立事故后果模型,采用有序Logit模型建立事故概率模型,以评价动态风险;最后综合动静态风险结果评价...     

Factors affecting the quantitative uncertainty of the estimated short-term intake. Part II—Practical examples

ABSTRACT

The effects of the spread of residue concentrations in the samples derived from the selected supervised trials and the number of trials were studied on the magnitude and uncertainty of the short-term dietary intakes calculated with the proposed new procedure (IESTI_p) and that one used currently by the FAO (Food and Agriculture Organization) and WHO (World Health Organization) Joint meeting on Pesticide Residues (JMPR) (IESTI_c). The residue data of 10 pesticides were obtained from supervised trials conducted on apples and pears. The methods described in Part I were used for the calculations of the uncertainty. The results indicate that the ratio of IESTI_P to IESTI_c (φ_IESTI) is directly proportional to the ratio of the estimated maximum residue level (MRL), recommended by the JMPR; to the highest residue (HR) observed in supervised trials, and it may have a wide range depending on the particular conditions. The φ_IESTI becomes greater with the increase of the difference between the mrl or maximum residue limit (MRL, established by the Codex Alimentarius Commission, CAC) and HR, and becomes smaller if the difference between the large portion (LP) and unit mass (U) decreases. The φ_IESTI ranged between 2 and 5.1 in the 16 cases examined indicating that the IESTI_p calculation method leads to higher intake estimates. The ratio of CV_IESTIp and CV_IESTIc ranged typically between 0.62 and 1.71. It rapidly increased up to 12 trials. For a larger number of trials, the ratio remained practically constant (1.69–1.71). The processing factor (PF) equally affects the MRL and HR values, therefore, it will not practically influence the φ_IESTI. The uncertainty of the estimated median residues depends on the spread and number of values in the residue datasets, which affects the uncertainty of the conversion factor (CF) and subsequently the uncertainty of the estimated IESTI_p. Residue values obtained from minimum nine independent trials are required for the correct calculation of the 95% confidence intervals of the calculated median residues. The uncertainty of the analytical results directly affects the median, HR values and indirectly the calculated mrl and the MRL derived from it. Therefore, it should also be considered for the calculation of the combined uncertainty of the conversion factors. For the correct interpretation of the results of dietary exposure calculations, the upper 95% confidence limit of the short-term intake should also be considered. However, it is not the current practice of regulatory agencies or JMPR.     

煤层气开采过程中渗透率模型比较研究

为了得到煤层气开采过程中渗透率的准确预测模型,分析了不同泊松比和孔隙压力下的储层孔隙率变化规律,通过理论分析对4种经典渗透率模型进行了比较研究。研究结果表明: P&M模型和C&B模型对泊松比敏感度较小,改进P&M模型和S&D模型对泊松比敏感度较大;改进P&M模型能有效反映渗透率变化趋势,在p＜1.4 MPa和p＞4.1 MPa时k/k0数值拟合度较高;P&M模型和S&D模型不能准确描述p＜1.4 MPa时k/k0变化情况,而在p＞1.4MPa时k/k0数值拟合度较高;煤层渗透率随孔隙压力增大表现为“U”型趋势,包含低孔隙压力骤减区、中孔隙压力稳定区和高孔隙压力稳步升高区3个阶段,改进P&M和S&D模型更能表现煤层气渗透率随孔隙压力变化趋势。     

常压法测定煤层瓦斯含量的误差分析

为了校正脱气法和常压法测量瓦斯含量的误差。通过理论分析、模型计算和实验对比的方法,研究煤样气体自然成分含二元和三元混合气体时的误差来源。查明气体成分为N2和CH4时,该误差可通过系数法进行修正;气体成分含CO2,CH4和N2 3种气体时,误差可通过扩展的langmuir模型修正。水分对测定误差的影响为:烟煤中含氧官能团与水优先结合后,影响煤孔网吸附点的可达性,导致水分与测定误差线性相关;无烟煤表面积大且表面官能团减少,水分的优先吸附使煤表面性质更均匀,水分与气体分子竞争煤表面的相同吸附点,水分与测定误差负相关。该结论对煤层瓦斯含量测定方法的选择和修正有重要意义。     

水-力耦合对含瓦斯煤渗透率影响的试验研究

以贵州矿区突出煤层40~60目的型煤试件为研究对象,借助自主研发的三轴渗流设备开展了不同含水率及有效应力条件下的三轴渗流试验,系统研究了含瓦斯煤渗透率受水-力耦合作用的演化趋势,根据试验结果推导了上述两因素与含瓦斯煤渗透率间的量化关系式,研究成果对贵州瓦斯灾害防治和煤层气勘探开发提供理论依据。