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931.
测定苯胺类化合物pH控制范围及调节方法的研究   总被引:4,自引:0,他引:4  
介绍了NEDA法反应机理及其酸度、pH调节方法对实验结果的影响,叙述了合理调整pH控制范围及改进pH调节方法,可以得到最大灵敏度、最佳分析效果及理想的实验方法。该方法可在化工、纺织、染料、生态、环境保护等相关领域广泛应用。  相似文献   
932.
本文研究了北京地区4种类型5个石灰性土壤样品对锰的吸附、及其与土壤各理化性质的关系。在每克土壤加入25ml10~200gMn/ml的剂量范围内,土壤对锰的吸附极好的遵从Freundrich等温方程,而是否符合Langmuir等温方程则与加入的锰溶液浓度有关,当其小于120 gMn/ml时,则能较好地符合Langmuir方程;这一现象说明,土壤具有两种或两种以上的吸附位。在土壤各理化性质中主要是粘粒含量和阳离于交换总量(CEC)影响到锰的吸附。但在锰溶液浓度较低时,各土壤理化性质均与土壤吸附锰量无显著相关。平衡溶液的pH强烈影响土壤吸附锰的能力,当pH由4上升至7左右时,土壤对锰的吸附急剧增加,pH值再上升,土壤吸附锰量的增加趋于平缓。  相似文献   
933.
This study reports on the analysis of emissions and fuel consumption from motor vehicles using a modal approach. The four standard driving modes are idling, accelerating, cruising, and decelerating. On-road data were collected using instrumented test vehicles traveling many times through the urban areas of Hong Kong. A model was developed for estimating vehicular fuel consumption and emissions as a function of instantaneous speed and driving mode. Piecewise interpolation functions were proposed for each nonidling driving mode. Idling emission and fuel consumption rates were estimated as negative exponential functions of idling time. Preliminary modeling results showed good agreements for the test vehicles and indicated that the on-road measurements are feasible for the development of modal emission and fuel consumption models.  相似文献   
934.
Many traditional water quality standards are based on extreme percentiles; often, there is the risk of making wrong decisions with these standards because of high estimation uncertainty. Standards expressed as fuzzy intervals in the form of [trigger, enforcement limitation] make it possible to control the risks for the discharger and the consumer simultaneously. With fuzzy interval compliance, corrective action is initiated when the trigger is exceeded; noncompliance is declared when the enforcement limitation is exceeded. Fuzzy intervals would digest the risks that are inherent when a single enforcement limitation is used to determine compliance; the risks can be further lowered when the fuzzy intervals are based on less extreme percentiles. This paper proposes several alternatives to using a single extreme percentile standard for regulating water quality or waste discharge. A case study using municipal effluent water quality data was included that suggests methods to determine compliance with fuzzy interval standards.  相似文献   
935.
报道了夏季蔬菜中有机磷农药残留量的调查。结果表明:在西红柿、青椒和豆角中,乐果平均残留量为0.081mg/kg,甲基对硫磷为0.015mg/kg,二嗪农为0.003mg/kg,而敌敌畏在这三种蔬菜中均未检出。夏季蔬菜中农药残留量的超标率甲基对硫磷>乐果>二嗪农>敌敌畏。三种蔬菜中,豆角的有机磷农药检出率最高,其次为青椒、西红柿。  相似文献   
936.
大气环境中汞的形态及其分析方法   总被引:24,自引:0,他引:24  
陈乐恬  张晓山 《环境化学》1999,18(6):584-588
本文引用了近二十年来与大气环境中汞的形态和分析方法有关的20多篇文章,对各种方法的优缺点进行了比较。  相似文献   
937.
利用废铁屑和粉煤灰的电化学原理处理印染废水的方法研究   总被引:15,自引:0,他引:15  
提出一种改进的铁屑法处理印染废水 ,对其机理进行探讨 ,并确定工艺条件为 p H4.0 ,处理时间 3 0 min,铁屑和粉煤灰的投加率分别为 5 %和 6%时 ,CODcr可降至 40 0 mg/L以下 ,去除率达 77%以上 ,脱色率 95 %以上 ,是一种高效可行的印染废水预处理方法  相似文献   
938.
中国CDM项目开发现状及存在问题分析研究   总被引:1,自引:0,他引:1  
清洁发展机制(CDM)是国际社会实现温室气体减排的履约机制之一。目前中国已成为CDM市场的主要输出国,但在CDM项目开发过程中还存在很多问题,例如区域分布不平衡、碳排放权交易标准不统一、缺乏激励机制等。在经济发展和节能减排的双重压力下,中国政府声明将严格遵守《巴黎协定》,正在积极落实已提出的到2020年控制温室气体排放行动目标,并向联合国提交了到2030年的"国家自主贡献"行动目标。中国的积极行动推动了全球气候问题的解决。  相似文献   
939.
To investigate the cause of fine particulate matter (particles with an aerodynamic diameter less than 2.5 µm, PM2.5) pollution in the heating season in the North China Plain (specifically Beijing, Tianjin, and Langfang), water-soluble ions and carbonaceous components in PM2.5 were simultaneously measured by online instruments with 1-hr resolution, from November 15, 2016 to March 15, 2017. The results showed extreme severity of PM2.5 pollution on a regional scale. Secondary inorganic ions (SNA, i.e., NO3?+SO42+ NH4+) dominated the water-soluble ions, accounting for 30%-40% of PM2.5, while the total carbon (TC, i.e., OC + EC) contributed to 26.5%-30.1% of PM2.5 in the three cities. SNA were mainly responsible for the increasing PM2.5 pollution compared with organic matter (OM). NO3? was the most abundant species among water-soluble ions, but SO42- played a much more important role in driving the elevated PM2.5 concentrations. The relative humidity (RH) and its precursor SO2 were the key factors affecting the formation of sulfate. Homogeneous reactions dominated the formation of nitrate which was mainly limited by HNO3 in ammonia-rich conditions. Secondary formation and regional transport from the heavily polluted region promoted the growth of PM2.5 concentrations in the formation stage of PM2.5 pollution in Beijing and Langfang. Regional transport or local emissions, along with secondary formation, made great contributions to the PM2.5 pollution in the evolution stage of PM2.5 pollution in Beijing and Langfang. The favourable meteorological conditions and regional transport from a relatively clean region both favored the diffusion of pollutants in all three cities.  相似文献   
940.
In this study,the thermal stability of a Fe_2 O_3 catalyst for mercury oxidation was significantly improved by doping with Al_2 O_3.After 1 hr,the catalyst doped with 10 wt.% Al_2 O_3 still exhibited a mercury conversion efficiency of 70.9%,while the undoped sample even lost its catalytic activity.Doping with Al_2 O_3 retarded the collapse of the catalyst mesoporous structure during high-temperature calcination,and the doped samples maintained a higher specific surface area,smaller pore size,and narrower pore size distribution.Transmission electron microscope images revealed that after calcination at 350℃,the average size of the catalyst grains in Fe_2 O_3 was 23.4 nm;however,the corresponding values for 1%Al_2 O_3/Fe_2 O_3,3%Al_2 O_3/Fe_2 O_3,and 10%Al_2 O_3/Fe_2 O_3 were only 13.3,7.1,and 4.7 nm,respectively.Results obtained from X-ray diffraction and thermogravimetry coupled with differential scanning calorimetry confirmed that doping with Al_2 O_3 also retards the crystallization of the catalysts at high temperature,constraining catalyst grains to a smaller size.  相似文献   
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