Studies on the Efficiency of Hydrogen Selenide Generation with Different Acid Media by Continuous Flow Hydride Generation Atomic Absorption Spectrometry

The efficiency of hydrogen selenide generation by HCl, HBr, H₂SO₄, HClO₄ and HNO₃ was studied with varying NaBH₄ concentrations by continuous flow hydride generation AAS. HBr showed higher efficiency (≈20%) than the conventionally used HCl. The optimum concentration of reagents were 5 M HBr, with 0.5% NaBH₄ and 6 M HCl with 1% NaBH₄. The efficiency followed the order HBr>HCl>HClO₄>H₂SO₄>HNO₃. The sensitivity and detection limits were 0.16 μg L⁻¹ and 0.15 μg L⁻¹ with HBr, and, 0.19 μg L⁻¹ and 0.17 μg L⁻¹ with HCl. The calibration graphs were linear in the range of 2–25 μg L⁻¹ for both the acids. Se⁶⁺ was reduced to Se⁴⁺ in 1 M HCl with the addition of solid KBr (4% final solution) with 60 minutes heating at 70 °C and compared to the commonly used 6 M HCl with 15 minutes boiling. Pre-reduction with KBr showed signal enhancement by 5 to 10% in the range 2–25 μg L⁻¹ of Se⁴⁺. The application of the method to SRM 1640 demonstrated that results were in good agreement with the certified values. Groundwater samples from a suburban area were analyzed and reported.     

Nonclassical Attack on a Quantum Key Distribution System

The article is focused on research of an attack on the quantum key distribution system and proposes a countermeasure method. Particularly noteworthy is that this is not a classic attack on a quantum protocol. We describe an attack on the process of calibration. Results of the research show that quantum key distribution systems have vulnerabilities not only in the protocols, but also in other vital system components. The described type of attack does not affect the cryptographic strength of the received keys and does not point to the vulnerability of the quantum key distribution protocol. We also propose a method for autocompensating optical communication system development, which protects synchronization from unauthorized access. The proposed method is based on the use of sync pulses attenuated to a photon level in the process of detecting a time interval with a signal. The paper presents the results of experimental studies that show the discrepancies between the theoretical and real parameters of the system. The obtained data allow the length of the quantum channel to be calculated with high accuracy.     

W(Ⅵ)-二苯基乙醇酸-2,2′-联吡啶极谱波研究及应用于岩溶地下水分析

在0.05 mol/L硫酸溶液中,W(Ⅵ)与二苯基乙醇酸络合在-0.70 V(vs.SCE)产生一灵敏的阴极极谱催化波,体系中加入2,2′-联吡啶后,W(Ⅵ)配合物的极谱波明显增高,峰电位负移到-0.80 V,标准曲线斜率变大,体系的稳定性显著提高。W(Ⅵ)在0.02~50 ng/mL范围与峰高呈良好线性关系,检出限达1.8×10-11mol/L。实验确定了最佳条件,拟定了不经分离富集直接测定岩溶地下水中痕量钨的方法。此外对极谱波的性质进行了探讨,证明该极谱波为配合物吸附催化氢波,讨论了阳离子表面活性物质对催化氢波的影响及相关作用机理。     

轨道交通产业全产业链的韧性-脆弱性研究

首先,论述了韧性-脆弱性理论,界定了韧性-脆弱性的内涵．其次,分析了全产业链的产业韧性-脆弱性的形成机理,包括全产业链韧性-脆弱性和轨道交通产业全产业链韧性-脆弱性两个概念的界定．第三,构建了轨道交通产业全产业链韧性-脆弱性评价指标,内部评价指标来自于企业管理水平等5个影响因子,外部评价指标来自于资源禀赋等3个影响因子．第四,实证分析了轨道交通产业全产业链韧性-脆弱性评价,得出8个指标分别影响该产业全产业链韧性-脆弱性的情况是：企业规模、技术密集度、交通成本和对外开发程度这4个指标的影响显著,劳动力成本对产业影响程度不大,消费购买力和专利申请数及政策支持影响不显著．最后,从提高产业技术创新能力等5个方面,提出缓解轨道交通产业全产业链韧性-脆弱性的对策建议．     

ONE‐DIMENSIONAL TEMPORALLY DEPENDENT ADVECTION–DISPERSION EQUATION IN POROUS MEDIA: ANALYTICAL SOLUTION

Abstract Analytical solutions of one‐dimensional advection–dispersion equation in semi‐infinite longitudinal porous domain are obtained in this work. The solute dispersion parameter is considered temporally dependent along uniform flow. The first‐order decay term, which is inversely proportional to the dispersion coefficient, is also considered. Initially, the space domain is not solute free. Analytical solutions are obtained for uniform and varying pulse‐type input. A new time variable is introduced. The Laplace transform technique is used to get the analytical solutions.     

Pollution Potential of Some Triazole Pesticides

Abstract

The widespread occurrence of pesticides, especially in the groundwater has stimulated research into the behavior of these agrochemicals in the environment. In this work a simple model to describe the fate of the two triazole fungicides Flutriafol and Flusilazol in a silt soil is presented. For this purpose we constructed mini-columns of soil, on which we applied the two fungicides, the percolation waters and the soils were collected at different times and the pesticides quantified in these samples. In the first part, these experiments were carried out outdoors during a period of 6 months on the silt soil and in a second part, we did similar indoor experiments with the same soil and with two others. To complete our work, we studied the adsorption of these two compounds on these three types of soil with batch equilibrium experiments. The results demonstrate that the fungicide Flusilazol is an immobile compound in soil, being strongly adsorbed whatever the nature of the soil. The Flutriafol is slightly to moderately mobile in the different soils, being less adsorbed.     

Modeling the drainage and groundwater table above the collecting pipe through 2D groundwater models

In order to understand the effects of the landfill operation on groundwater flow behavior, 2D horizontal groundwater simulation model was carried out. The model saved the memory of computer and time consumption comparing with 3D groundwater flow model. However, the most difficulty is the assignment of collecting pipe boundary in the study site. Therefore, 2D vertical model was applied to calculate the change of groundwater table above the collecting pipe. This paper paid attention to examine the validation of the assignment of the collecting pipe boundary by applying the results of 2D vertical model. 2D horizontal model was coupled with the recharge model to solve the partial differential equation of groundwater flow. Finite difference method and iterative successive over relaxation were applied. The drainage volume of leachate collection was summed up in the whole landfill site and compared with the average volume of treated waste water. The study demonstrated that the results of 2D vertical model validated and can be applied to 2D horizontal groundwater flow simulation.     

废物库周围地下水中的放射性核素分布研究

中国工程物理研究院核物理与化学研究所原工作地点 (老点 )存在两个放射性废物库 5 37 1和 5 37 2。年内分别在库周围取地下水 (或土 ) 6次 ,对 5 37 1得到地下水和泥土中的铀含量大约为 1.2 7μg L和 3.0 μg L ,对5 37 2得到的地下水中的90 Sr含量约为 5 .35× 10 - 3 Bq L。上列数据与本底无明显差异。可见 ,5 37 1废物库周围地下水中铀含量与生活区河水中含量无明显差异 ,5 37 2废物库周围地下水中锶含量与生活区河水中含量也无明显差异。至今未监测到两个废物库中的放射性核素对周围地下水中的明显影响     

离子色谱法测定地下水中的乙酸根含量

对地下水样品除氯后，选用1．35mmol／LNa2CO3-1．00mmol／LNaHCO3混合溶液作淋洗液，用离子色谱法测定地下水样品中乙酸根的含量，乙酸根浓度在0～5．00mg／L范围内与电导率峰高呈线性关系，线性回归方程为H=15950．6c-442．7，相关系数为0．9994，方法的检出限为0．05mg／L，加标回收率为101％-110％，测定结果的相对标准偏差为2．3％。     

Multi-residue procedure for the analysis of pesticides in groundwater: Application to samples from the comunidad Valenciana,Spain

Summary A simple multi-residue procedure has been developed and applied to the analysis of pesticides in groundwater samples from the Comunidad Valenciana, a predominantly agricultural area on the Mediterranean coast of Spain. The procedure includes a liquid-liquid extraction, after addition of NaCl on the samples, and a subsequent analysis by capillary gas chromatography using a dual detection system with electron capture and nitrogen-phosphorous detectors. This allows the determination of more than 30 compounds (organophosphorous, organochlorine and pyrethroid pesticides) at the low ppb (g l^–1) levels. Detection limits obtained varied between 0.01 g l^–1 (lindane, fonofos) and 0.5 g l^–1 (cypermethrin). An additional injection of the sample extracts into a gas chromatograph equipped with a column of different polarity and electron capture detector is used for the confirmation of chromatographic peaks. The recommended procedure has been applied to 66 ground water samples. Pesticides, including organophosphorus and organochlorine compounds were detected in 31 of them, in levels ranging from 0.02 to 0.7 g l^–1.