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611.
反相乳液聚合制备阳离子聚丙烯酰胺及其絮凝性能评价 总被引:2,自引:0,他引:2
研究了单体浓度、单体配比、反应温度、引发剂用量等因素对所制备的阳离子聚丙烯酰胺特性粘度、转化率、阳离子度的影响,并对产品的污水絮凝性能进行了评价。较佳的制备条件为:单体浓度为45%,单体配比为7∶3,引发剂用量m(引发剂)/m(单体)为0.5%,引发温度为45℃。用红外光谱对共聚物进行了结构表征,结果表明聚合物中有六元氮杂环的存在,达到预定要求。对共聚物进行了油田污水絮凝性能评价,研究表明单独使用自制阳离子聚丙烯酰胺(CPAM)时浊度的去除率为86.22%,COD去除率为87.95%,与聚合氯化铝复配使用时浊度去除率提高到92.91%,COD去除率提高到92.68%。 相似文献
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Jun Wang Wei Xi Yonghua Xiao Chenjiang Ying Jia Long Hui Zhang Xi Chen Congda Mao Xiumin Li Lin Wang Shunqing Xu 《环境科学学报(英文版)》2014,26(10):2131-2137
Food has been documented as one of major routes for human exposure to environmental estrogens(EEs), but information on the occurrence of EEs in animal foodstuffs is still scarce.This study analyzed estrogenic activity in 16 types of animal foodstuffs(n = 142) collected from four cities(Wuhan, Guangzhou, Wenzhou and Yantai) of China by combined yeast estrogen screen(YES) bioassay and chemical analysis. By bioassay, all samples' extracts were found to induce estrogenic activities and the bioassay-derived 17β-estradiol equivalent(EEQbio) ranged from 8.29 to 118.32 ng/g. In addition, the samples were analyzed by liquid chromatography coupled to tandem mass spectrometry for further chemical analysis. 17β-Estradiol was found in all samples in this survey at levels of 0.44 to 15.04 ng/g.All samples had 33.1% detection rate of 17α-ethinylestradiol(EE2), and the maximum concentration was 2.80 ng/g. Bisphenol A and 4-nonylphenols were detected in 83.8% and83.1% of samples, with concentrations up to 12.56 ng/g and 35.76 ng/g, respectively.However, the concentrations of estrone, diethylstilbestrol and 4-t-octylphenol were found to be below the limit of detection. A comparison of EEQbiomeasured from the YES assay and EEQchemcalculated from chemical analysis showed good correlation(R2= 0.84). Based on the results, the YES assay can be used as a rapid pre-screening method for monitoring the levels of estrogenic activity in large numbers of animal foodstuffs, and chemical analysis used in combination can be used for the identification of specific EEs. 相似文献
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氯化石蜡(chlorinated paraffins, CPs)是我国目前广泛应用在工业生产中的阻燃剂和增塑剂,其中短链氯化石蜡(short chain chlorinated paraffins, SCCPs)作为新污染物,因具有持久性、高毒性、长距离迁移特性和生物蓄积性等持久性有机污染物(persistent organic pollutants, POPs)特性引起了国内外的关注,尤其是SCCPs的环境赋存对环境健康的危害亟需进一步研究. 国内对SCCPs的研究集中在分析方法与环境行为等方面,对SCCPs的环境健康效应研究较少. 本文总结了近年来SCCPs分析方法的研究进展,并对其环境健康效应进行了梳理. 结果表明,SCCPs已被证实具有潜在的毒性效应,并且随着时间的推移,SCCPs在环境介质中的暴露浓度越来越高,因此SCCPs的环境外暴露对人体健康的潜在威胁越来越大. 研究显示,我国尚未停止SCCPs的生产与使用,因此在我国“十四五”规划之际,应加快SCCPs分析方法的研究进程,利用高分辨质谱将SCCPs的分析方法规范与标准化,并且在研究SCCPs的环境行为、迁移转化机制与毒性效应的基础上,深入开展SCCPs人体暴露风险与健康效应评估的研究,建立有效的环境健康风险评价模型与机制. 相似文献
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Solution culture and pot experiments were carried out to investigate the effects of root damage on phytoextraction of heavy metals. In hydroponics, roots of corn (Zea mays L.) seedlings were pretreated with heating stress, and then were exposed to 250 microM Pb+250 microM EDTA solutions for 7d. The results showed that the preheating treatment significantly increased Pb transportation from roots to shoots. In pot experiments, the effect of hot EDTA solution (95 degrees C) on the accumulation of heavy metal in the shoot of corn and pea (Pisum sativum L.) was also examined. Compared to normal EDTA (25 degrees C) treatment, application of hot EDTA solution to the soil surface increased the total removal of Pb in shoots of corn and pea by about 8- and 12-fold, respectively, in an artificially multimetal-contaminated soil. In addition, hot EDTA solution increased the shoot Cu removal by about 6-fold for corn and 9-fold for pea, respectively, in a naturally Cu-contaminated soil. These results suggested that exposure of roots to high temperature could increase the efficiency of EDTA on the accumulation of heavy metals in shoots. This new approach can help to minimize the amount of chelate applied in the field and reduce the potential risk of heavy metals' leaching. 相似文献
619.
Patterns of Genetic Diversity in Remaining Giant Panda Populations 总被引:12,自引:0,他引:12
Zhi Lu † Warren E. Johnson Marilyn Menotti-Raymond Naoya Yuhki Janice S. Martenson Susan Mainka ‡ Huang Shi-Qiang § Zheng Zhihe Guanghan Li Wenshi Pan † Xiarong Mao † Stephen J. O'Brien†† 《Conservation biology》2001,15(6):1596-1607
Abstract: The giant panda ( Ailuropoda melanoleuca ) is among the more familiar symbols of species conservation. The protection of giant panda populations has been aided recently by the establishment of more and better-managed reserves in existing panda habitat located in six mountain ranges in western China. These remaining populations are becoming increasingly isolated from one another, however, leading to the concern that historic patterns of gene flow will be disrupted and that reduced population sizes will lead to diminished genetic variability. We analyzed four categories of molecular genetic markers (mtDNA restriction-fragment-length polymorphisms [RFLP], mtDNA control region sequences, nuclear multilocus DNA fingerprints, and microsatellite size variation) in giant pandas from three mountain populations (Qionglai, Minshan, and Qinling) to assess current levels of genetic diversity and to detect evidence of historic population subdivisions. The three populations had moderate levels of genetic diversity compared with similarly studied carnivores for all four gene measures, with a slight but consistent reduction in variability apparent in the smaller Qinling population. That population also showed significant differentiation consistent with its isolation since historic times. From a strictly genetic perspective, the giant panda species and the three populations look promising insofar as they have retained a large amount of genetic diversity in each population, although evidence of recent population reduction—likely from habitat loss—is apparent. Ecological management to increase habitat, population expansion, and gene flow would seem an effective strategy to stabilize the decline of this endangered species. 相似文献
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在“九五”期间 ,江苏省地震局深入调查研究 ,把握主要矛盾 ,深化各项改革 ,狠抓实事实办 ,强化政府行政职能 ,加强宣传力度 ,加强地方地震机构建设 ,注重规划和计划的制订与实施 ,不断理顺拨款渠道 ,健全地方财政对地震事业投入的预算体制 ,健全行政规章、规范管理行为 ,加强法规建设、强化法制管理。经努力 ,各项工作取得了明显成效 ,1 996~ 1 999年 ,全局各类经费总来源为前 4年的 3 1倍 ;地震监测系统的数字化、通讯系统的计算机网络化、分析预报系统的应急决策指挥系统现代化建设取得明显进展。地震监测预报工作为保障全省经济建设顺利进行 ,维护社会稳定作出重要贡献。全局职工的住房得到明显改善 ,4年中在宁职工人均增加住房面积约 2 0m2 。人均总收入也较从前有大幅度提高。新建园艺绿地面积约 4 0 0 0m2 。工作体会主要是 ,领导班子同心协力是搞好工作的关键 ,广大职工的积极性是搞好工作的基础 ,各级领导坚持“两手抓”是搞好工作的根本 ,领导干部始终不懈地讲学习、讲政治、讲正气是搞好工作的前提 相似文献