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711.
论述了近年来国内在稀释测定生化需氧量(BOD5)中有关稀释倍数的研究成果;分析评价了一些确定稀释倍数的数理公式;总结了稀释法测定BOD5的基本要求。 相似文献
712.
试验了废水中的丙溴磷气相色谱分析方法。以大口径毛细管柱分离废水中的丙溴磷,分别采用氮磷检测器(NPD)和电子捕获检测器(ECD)检测,得到了良好的分离效果和较高的灵敏度,方法检测限为0.002mg/L(绝对检测量最低可达2pg,NPD)和0.0008mg/L(绝对检测量最低可达0.8pg,ECD)。该方法中,采用双柱双检测器,排除了误检和其他物质的干扰,保证了分析结果的可靠性。 相似文献
713.
The geography and climate of the Santiago basin are, in general, unfavorable for the diffusion of air pollutants. Consequently, extreme events occur frequently during the high pollution season extending from April to August. The meteorological conditions concurrent with those extreme events are mainly associated with the leading edges of coastal lows that bring down the base of the semipermanent temperature inversion reducing the dirunal growth of the surface mixed layer. In order to produce an objective 12 to 24-hour episode forecast, a two-way multivariate discriminant analysis has been used in the definition of a meteorological air-pollution potential index (MAPPI), separating high and low meteorological air-pollution potential days. The same procedure has been applied in the selection of the most efficient predictors for the MAPPI objective forecast, based on 12 and 24 UTC radiosonde data at Quintero, about 100 km to the NW of Santiago. Results indicate about 70% correctly forecasted days, with satisfactory skill-scores relative to persistency. The strong persistency characterizing the most efficient predictors in the 12-hour objective forecast scheme, makes the prediction of the first and last days of any particular air-pollution potential episode particularly difficult. To overcome this problem, a new set of predictors based on continuous measurements near the level of the top of the temperature inversion layer (900 hPa during air-pollution episodes) is being tested. Preliminary results indicate that the time-integrated zonal wind component at that level is a reliable precursor for both the onset and the end of air-pollution potential episodes. 相似文献
714.
A magnetic carbon composite, Fe3O4/C composite, was fabricated by one-step hydrothermal synthesis, modified by heat treatment under an inert atmosphere (N2), and then used as an adsorbent for ciprofloxacin (CIP) removal. Conditions for the modification were optimized according to the rate of CIP removal. The adsorbent was characterized by Fourier transform infrared spectroscopy, X-ray diffraction measurements, vibrating-sample magnetometry, scanning electron microscopy, transmission electron microscopy, and N2 adsorption/desorption isotherm measurements. The results indicate that the modified adsorbent has substantial magnetism and has a large specific area, which favor CIP adsorption. The effects of solution pH, adsorbent dose, contact time, initial CIP concentration, ion strength, humic acid and solution temperature on CIP removal were also studied. Our results show that all of the above factors influence CIP removal. The Langmuir adsorption isotherm fits the adsorption process well, with the pseudo second-order model describing the adsorption kinetics accurately. The thermodynamic parameters indicate that adsorption is mainly physical adsorption. Recycling experiments revealed that the behavior of adsorbent is maintained after recycling for five times. Overall, the modified magnetic carbon composite is an efficient adsorbent for wastewater treatment. 相似文献
715.
采用过硫酸钾(KSP)氧化法对有序介孔碳FDU-15进行了改性处理,制备了羧基化改性有序介孔碳FDU-15-KSP,对其进行了表征,并将其用于典型难降解染料罗丹明B的吸附。表征结果显示:KSP氧化处理可提高介孔碳上的羧基含量,但并未破坏其二维六方有序结构。实验结果表明:与FDU-15相比,FDU-15-KSP对罗丹明B的吸附性能显著提高,常温下的饱和吸附量由136.99 mg/g提高到196.08 mg/g;吸附p H为7时吸附效果最好,经60 min吸附后吸附过程基本达到平衡,温度升高有利于吸附的进行;FDU-15-KSP对罗丹明B的吸附过程较符合Langmuir等温吸附模型,是一个自发的、吸热的熵驱动过程;FDU-15-KSP对罗丹明B的吸附行为遵循Lagergren准二级动力学方程,吸附过程以化学吸附为主。 相似文献
716.
采用模板法在CuO外包裹一层具有介孔结构的SiO_2,制备了CuO/AC@SiO_2。采用X射线衍射仪对CuO/AC@SiO_2的结构和催化活性位点进行了表征。通过固定床气固吸附实验,研究了CuO/AC@SiO_2对H_2S的吸附脱除性能。表征结果显示,CuO是催化氧化H_2S的活性中心,被氧化成Cu2O后吸附脱除H_2S的性能下降。实验结果表明:CuO/AC吸附H_2S时的有效穿透时间为117 min,CuO/AC@SiO_2的有效穿透时间提高到141 min,CuO/AC@SiO_2对H_2S的吸附性能明显提高;以Cu(NO_3)_2为前驱体的CuO/AC@SiO_2对H_2S的吸附量高于以Cu(AC)_2为前驱体;在Cu(NO_3)_2为前驱体、m(正硅酸乙酯)∶m(CuO/AC)=0.7、吸附温度为90℃的最佳条件下,CuO/AC@SiO_2对H_2S的吸附量达17.40 mg/g。 相似文献
717.
The role of automated feedback in training and retaining biological recorders for citizen science
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René van der Wal Nirwan Sharma Chris Mellish Annie Robinson Advaith Siddharthan 《Conservation biology》2016,30(3):550-561
The rapid rise of citizen science, with lay people forming often extensive biodiversity sensor networks, is seen as a solution to the mismatch between data demand and supply while simultaneously engaging citizens with environmental topics. However, citizen science recording schemes require careful consideration of how to motivate, train, and retain volunteers. We evaluated a novel computing science framework that allowed for the automated generation of feedback to citizen scientists using natural language generation (NLG) technology. We worked with a photo‐based citizen science program in which users also volunteer species identification aided by an online key. Feedback is provided after photo (and identification) submission and is aimed to improve volunteer species identification skills and to enhance volunteer experience and retention. To assess the utility of NLG feedback, we conducted two experiments with novices to assess short‐term (single session) and longer‐term (5 sessions in 2 months) learning, respectively. Participants identified a specimen in a series of photos. One group received only the correct answer after each identification, and the other group received the correct answer and NLG feedback explaining reasons for misidentification and highlighting key features that facilitate correct identification. We then developed an identification training tool with NLG feedback as part of the citizen science program BeeWatch and analyzed learning by users. Finally, we implemented NLG feedback in the live program and evaluated this by randomly allocating all BeeWatch users to treatment groups that received different types of feedback upon identification submission. After 6 months separate surveys were sent out to assess whether views on the citizen science program and its feedback differed among the groups. Identification accuracy and retention of novices were higher for those who received automated feedback than for those who received only confirmation of the correct identification without explanation. The value of NLG feedback in the live program, captured through questionnaires and evaluation of the online photo‐based training tool, likewise showed that the automated generation of informative feedback fostered learning and volunteer engagement and thus paves the way for productive and long‐lived citizen science projects. 相似文献
718.
719.
Mi Ni Qiong Wu Junli Wang Jian H. Ren Dian P. Zhang 《Journal of environmental science and health. Part. B》2013,48(12):777-785
AbstractBacillus spp. have long been used as biocontrol agents because of their efficient broad-spectrum antimicrobial activity. We identified a novel strain of Bacillus atrophaeus, named JZB120050, from soil. B. atrophaeus JZB120050 had a strong inhibitory effect against Botrytis cinerea and many other phytopathogens. Gas chromatography-mass spectrometry showed that B. atrophaeus JZB120050 produced many secondary metabolites, such as alkanes, alkenes and acids; some of which were related to pathogen inhibition. Enzyme activity analysis showed that B. atrophaeus JZB120050 secreted cell-wall-degrading enzymes, including chitinase, glucanase and protease, which degraded fungal cell walls. Both the novel glucanase gene bglu and chitinase gene chit1 were cloned and heterologously expressed in Escherichia coli and the products showed strong enzyme activity. In addition, B. atrophaeus JZB120050 secreted siderophores and formed a significant biofilm. Future studies should focus on these antimicrobial factors to facilitate widespread application in the field of agricultural biocontrol. 相似文献
720.
含铬(Ⅵ)污水对地下水、土壤污染的研究 总被引:6,自引:1,他引:5
通过模拟含铬(Ⅵ)污水的土壤淋滤过程,结合受污染区域土壤垂直含铬分布分析,研究了含铬污水渗漏对地下水、土壤的污染。结果表明:含铬污水在亚粘土、亚砂土、砂土中的平均渗透系数分别为6.02×10-6cm/s、3.87×10-4cm/s、5.32×10-4cm/s。含铬污水排放会在土壤中沉积铬,引起土壤污染,并污染地下水。 相似文献