Effects of Metsulfuron-Methyl on the Microbial Population and Enzyme Activities in Wheat Rhizosphere Soil

The effects of metsulfuron-methyl, a sulfonylurea herbicide, on the wheat soil microorganisms were evaluated by the methods of microbial inoculation culture, and the activities of three enzymes were measured using the colorimetric method. The tolerant microorganisms that can resist 500 μ g·g^?1 metsulfuron-methyl in the counting culture medium were studied specially. Metsulfuron-methyl distinctly inhibited the common aerobic heterotriphic bacteria, but the effects on common fungi and common actinomycete were not evident. In the meantime, the number of tolerant fungi increased greatly in the rhizosphere after the application of metsulfuron-methyl in contrast to the significant decrease of the amount of tolerant actinomycete. It indicates that fungi might turn into the dominant microbial type and actinomycete is the sensitive factor in the soil polluted by sulfonylurea residues. The population of aromatic compounds–decomposing bacteria, aerobic azotobacter, and nitrite bacteria all increased in the earlier period, but the aerobic azotobacter decreased rapidly in number 30 days later, and the amount of nitrite bacteria also showed a temporary decrease with time 15 days later. However, the denitrifying bacteria just began to increase significantly after the crops had grown for 50 days. The amount of sulfur-oxidizing bacteria gradually decreased with the growth of crops, and so were the sulfate-reducing bacteria after metsulfuron-methyl application. To all types of microorganisms, there were more microbes in rhizosphere samples than those in nonrhizosphere except aerobic azotobacter. It means the growth of wheat root system can stimulate the growth of most microorganisms. The activities of hydrogen peroxidase and polyphenol oxidase in soil samples after metsulfuron-methyl application were notably lower than those in the control, and the difference of the activities between the samples of rhizosphere and nonrhizosphere was evident. On the contrary, the activity of dehydrogenase was not inhibited by the application of metsulfuron-methyl, and the rhizosphere effect was not obvious either.     

离子色谱法测定钻井废水中的Cl-、Br-

利用离子色谱法测定钻井废水中的Cl~-、Br~-,实验结果表明,该方法能准确分析测定样品中的Cl~-和Br~-,相对标准偏差小于2%。同时该方法降低了干扰因素的影响,缩短了分析时间,提高了工作效率,能对钻井废水中的Cl~-和Br~-进行有效的分离,样品的加标回收率达到87%~109%,能准确测定Cl~-和Br~-。同时与硝酸银滴定法测定钻井废水中的Cl~-相比较,当样品中Br~-含量小于Cl~-和Br~-总含量的10%时,两种方法测定Cl~-含量的相对偏差小于5%。     

限速值对信号交叉口交通安全的影响分析

为研究交叉口进口道车辆限速值对交叉口的安全和运行产生的影响,通过微观仿真平台,分析车辆在交叉口限速分别为30,38和46 km/h时的车均延误、车均行程时间,并将车辆行驶轨迹输入安全辅助评价(SSAM)软件中展开分析。结果表明,车辆限速值的提高对车均延误的影响不大,但会减小车辆在进口道的车均行程时间。另外,限速值从30 km/h提高到46 km/h,引起的碰撞时间(TTC)、后侵占时间(PET)数值变化不显著,但使总冲突数从42个增加到59个。     

1961—2010年上海市各量级降水的多尺度变化特征研究

为了详尽地了解气候变化下上海市降水变化特征,合理开发管理城市水资源,利用上海市10个地方气象站1961—2010年逐日降水数据,综合利用累积距平、滑动平均、线性倾向估计、百分位、去趋势波动等方法系统分析近50年来上海市10个站点降水指标的季节、年际、年代际变化特征。研究发现:1)研究区降水经历了1960s、1970s年代的下降期,1980s、1990s和2000s年代的快速增长期,最早出现变化的是上海市南部地区,但是变化幅度最大、变化趋势最为复杂的是市区徐家汇站;2)研究区季节降水分配不均,且市区与郊区存在较大的数值差异,变化幅度上,各站点夏季、冬季降水呈显著增加趋势,春季和秋季降水呈不显著下降趋势;3)研究区各站点降水强度有增强趋势,主要表现在暴雨量级以下降水频次变少,但是总量增多,且暴雨与大暴雨以上量级降水频次增多,空间上各站点响应时间与幅度存在差异;4)基于百分位和DFA两种方法计算的极端降水研究都表明,研究区各站点极端降水呈显著增强趋势,两种方法计算的市区徐家汇站5年滑动降水量年递增率分别为20.1 mm·(10a)~(-1)和28.3 mm·(10a)~(-1)。     

二甲亚砜捕获-高效液相色谱测定天然水体中羟基自由基的光化学生成

利用二甲亚砜捕获羟基自由基定量生成甲醛,甲醛与1,3-环己二酮和氨衍生反应,衍生产物在400 nm的激发波长下,在460 nm处具有特征荧光,建立了一个新的高效液相色谱分离、荧光检测水体中光学反应产生的羟基自由基的方法.考察了捕获剂用量、酸度、温度、时间以及衍生试剂用量对羟基自由基测定的影响,在优化的实验条件下,该方法对羟基自由基的定量下限为0.066μmol·L-1.采用建立的方法对湖水、海水以及湿地水在氙灯模拟光源以及太阳光下羟基自由基光化学生成进行了初步研究,表明太阳光照下羟基自由基的生成速率约为氙灯光照下羟基自由基生成速率的两倍以上,说明羟基自由基在实际自然条件下的生成速率有可能被低估.天然水体中的羟基自由基的生成与水体成分密切相关,由铁和可溶性有机质(DOM)光照产生羟基自由基的机理较为复杂,DOM和铁的相互作用对天然水体中羟基自由基的光化学生成影响有待于进一步研究.     

轻质油中间原料储罐腐蚀现状及对策

对近年来加工原料劣质化后轻质油中间原料储罐腐蚀问题突出和腐蚀导致的安全事故多发的现状进行了论述,介绍了中国石化轻质油中间原料储罐的调研情况和发现的主要问题,从多个方面提出了轻质油中间原料储罐的防腐对策.     

高超声速钝锥等离子体鞘套电波传播特性研究

目的改进现阶段地面指控站对临近空间高超声速飞行器的通信和测控效果。方法采用计算流体动力学技术模拟钝锥体在不同高超声速飞行条件下的头身部绕流流场特性,并运用相关公式建立钝锥等离子体鞘套电磁模型。然后运用改进的移位算子时域有限差分方法计算电磁波经过等离子体鞘套的传播特性。结果计算结果表明,电磁波在等离子体鞘套内的传播特性在频率处于最大等离子体频率附近时发生转折,电磁波通过等离子体鞘套的透射效果与飞行工况和入射波条件密切相关。相对其他入射角度,当电磁波垂直于飞行体物面入射到等离子体鞘套尾部时的电磁波衰减较小。飞行高度增加或飞行速度减小时,等离子体鞘套对电磁波的衰减效应将减弱。结论该研究可为有效测控临近空间高超声速飞行器、缓解再入通讯中断现象提供一定的技术突破方法。     

Design and demonstration of a next-generation air quality attainment assessment system for PM2.5 and O3

Due to the increasingly stringent standards, it is important to assess whether the proposed emission reduction will result in ambient concentrations that meet the standards. The Software for Model Attainment Test—Community Edition (SMAT-CE) is developed for demonstrating attainment of air quality standards of O₃ and PM_2.5. SMAT-CE improves computational efficiency and provides a number of advanced visualization and analytical functionalities on an integrated GIS platform. SMAT-CE incorporates historical measurements of air quality parameters and simulated air pollutant concentrations under a number of emission inventory scenarios to project the level of compliance to air quality standards in a targeted future year. An application case study of the software based on the U.S. National Ambient Air Quality Standards (NAAQS) shows that SMAT-CE is capable of demonstrating the air quality attainment of annual PM_2.5 and 8-hour O₃ for a proposed emission control policy.     

昆山市大气 PM 2．5中无机元素污染特征研究

应用SEM－EDS结合XRF法测定了2013年8月－2014年5月昆山市7个不同地区大气PM2．5中无机元素的污染水平。研究发现,昆山地区一共可检出40种无机元素,其中主要的22种元素浓度范围在3.02～1113 ng／m3之间,合计为3784 ng／m3;PM2．5中无机元素季节变化明显,呈现春秋季高,夏冬季低的变化特点。无机元素的空间变化不大。通过富集因子的研究,Sc、Ni、Cu、Zn、As、Br、Cd、Pb、Se、Ag、Sn、Sb和Tl等13种元素EF＞10,富集程度非常高,说明人类活动对这些元素的贡献较大。