固相萃取-气相色谱法对河水与海水中36种农药残留的同时测定

应用固相萃取和气相色谱技术建立了河水和海水中36种常用农药(7种有机氯、11种有机磷、8种拟除虫菊酯、4种酰胺、2种苯胺和4种唑类杂环)的分析方法.采用Oasis HLB柱为水样富集萃取柱,考察了洗脱溶剂、上样体积、pH值和离子强度等因素对萃取效果的影响,采用无水硫酸钠和NH2柱进行除水和净化.目标农药在0.9 ～2 600 μg/L范围内线性良好;以PCB103为内标物,2,4,5,6-四氯间二甲苯、环氟菌胺和氟丙菊酯为替代物,实际河水、海水的加标回收率分别为62% ～124%、64% ～132%,相对标准偏差(n=3)分别为0.2% ～9.6%、0.1% ～12.2%;方法检出限为0.10 ～1.0 ng/L.方法快速、灵敏、准确,已成功应用于福建九龙江入海口表层水样的分析.     

氢化物-原子荧光法测定排污河水中砷

采用氢化物－原子荧光法测定排污河水中砷,讨论并确定了试验的最佳测定条件,结果表明,方法的检出限为０．１０μｇ．Ｌ＾－１,相对标准偏差为３．５％,回收率为９０％～１１０％。     

Laboratory and field evaluation of diffusive gradient in thin films (DGT) for monitoring levels of dissolved mercury in natural river water

The diffusive gradient in the thin films (DGT) technique was tested to measure dissolved mercury (Hg) both in laboratory aqueous solutions and in situ in river water. For this purpose, a commercial ready-to-use and specific-for-Hg DGT device was used. Each sampler consisted of a filter membrane-agarose gel as the diffusive layer and a Spheron-Thiol resin in polyacrylamide gel as the binding agent. Basic performance assays at the laboratory with this type of DGT unit confirmed the applicability of Fick's first law for DGT measurements. The diffusion coefficient of MeHg in the agarose diffusive gel was 8.50?×?10^?6?cm² s^?1 at 25°C. Several field studies were also carried out in two different rivers of the Ebro River basin (NE Spain) affected by Hg wastes released by the chlor-alkali industry. Hg concentrations determined by DGT were generally much lower than the results obtained through direct measurements of the river water. In addition, the results of a time series experiment also performed in the field show that the amount of Hg accumulated in the resin does not increase at all with the exposure time. This may be explained by the underestimation of the truly dissolved Hg fraction due to the formation of a biofilm layer on the surface of the samplers, thus clogging the filter and preventing Hg species from diffusing through it. Consequently, it was demonstrated that the DGT technique presents important limitations for measuring Hg in polluted rivers characterised by a high biomass load (eutrophic), whereas its performance was demonstrated to be correct in oligotrophic waters.     

Fate of branched-chain fatty acids in anaerobic environment of river sediment

The fate of six different branched-chain fatty acids (BCFAs) in an anaerobic environment of a river sediment was studied in vitro by culturing enrichment consortia. The anaerobic consortium of BCFA-degrading genus degraded BCFAs with tertiary carbons through β-oxidation, followed by methanogenesis by methane-producing anaerobic bacteria. The consortium could not degrade BCFAs with quaternary carbon. Degree of branching at the alpha or beta position along the carbon chain interfered with the beta-oxidation mechanisms of the branched-chain fatty acid.     

Some Results about Duality and Exact Penalization

In this paper, we introduce the concept of the valley at 0 augmenting function and apply it to construct a class of valley at 0 augmented Lagrangian functions. We establish the existence of a path of optimal solutions generated by valley at 0 augmented Lagrangian problems and its convergence toward the optimal set of the original problem and obtain the zero duality gap property between the primal problem and the valley at 0 augmented Lagrangian dual problem. Moreover, we establish the exact penalization representation results in the framework of valley at 0 augmented Lagrangian.     

Coordinates with Non-Singular Curvature for a Time Dependent Black Hole Horizon

A naive introduction of a dependency of the mass of a black hole on the Schwarzschild time coordinate results in singular behavior of curvature invariants at the horizon, violating expectations from complementarity. If instead a temporal dependence is introduced in terms of a coordinate akin to the river time representation, the Ricci scalar is nowhere singular away from the origin. It is found that for a shrinking mass scale due to evaporation, the null radial geodesics that generate the horizon are slightly displaced from the coordinate singularity. In addition, a changing horizon scale significantly alters the form of the coordinate singularity in diagonal (orthogonal) metric coordinates representing the space-time. A Penrose diagram describing the growth and evaporation of an example black hole is constructed to examine the evolution of the coordinate singularity.     

FLUCTUATIONS AND FUTURE TREND OF CLIMATE, GLACIERS AND DISCHARGE OF ■R■MQI RIVER IN XINJIANG

Based on the analyses of various data available of the rümqi River, Xinjiang, it is found that the warming trend of the climate in recent years is mainly accompanied by the decrease in precipitation, discharge, and glacial mass balance. Since the Little Ice Age, the temperature has increased by 0.5—1.0℃, while the precipitation, glacial volume and annual discharge have decreased by 50 mm, 41% and 11%, respectively. It is possible that the trend would last for the next 10—15 years.     

An adaptive local grid refinement and peak/valley capture algorithm to solve nonlinear transport problems with moving sharp-fronts

Highly nonlinear advection–dispersion-reaction equations govern numerous transport phenomena. Robust, accurate, and efficient algorithms to solve these equations hold the key to the success of applying numerical models to field problems. This paper presents the development and verification of a computational algorithm to approximate the highly nonlinear transport equations of reactive chemical transport and multiphase flow. The algorithm was developed based on the Lagrangian-Eulerian decoupling method with an adaptive ZOOMing and Peak/valley Capture (LEZOOMPC) scheme. It consists of both backward and forward node tracking, rough element determination, peak/valley capturing, and adaptive local grid refinement. A second-order tracking was implemented to accurately and efficiently track all fictitious particles. Shanks’ method was introduced to deal with slowly converging case. The accuracy and efficiency of the algorithm were verified with the Burger equation for a variety of cases. The robustness of the algorithm to achieve convergent solutions was demonstrated by highly nonlinear reactive contaminant transport and multiphase flow problems.     

Sensitive adsorptive stripping voltammetric method for direct determination of trace concentration of lead in the presence of cupferron in natural water samples

This paper reports the use of an adsorptive voltammetric technique for Pb(II) determination using cupferron as a selective complexing agent. After accumulation of the complex onto a hanging mercury drop electrode, the electrode potential was scanned with differential pulse modulation and the reduction current of lead was observed at about??0.5?V. Under optimum conditions (5?×?10^?4?mol?L^?1 cupferron concentration, 0.1?mol?L^?1 acetate buffer (pH 5.5), adsorption at??50?mV for 30?s) the detection limit was 5.1?×?10^?10?mol?L^?1. The relative standard deviation of five measurements for low lead concentration was 3.1%. The accuracy of the method was tested by analysing certified reference material (SPS-WW1 Waste Water). Finally, the method was successfully applied to the determination of Pb(II) in river water samples without any pretreatments.     

二维过渡金属二硫化物中自旋能谷耦合的谷电子学

电子的电荷自由度与自旋自由度是现代电子器件的基础核心之一。随着二维材料,尤其是二维过渡族硫化物(TMDCs)的研究深入,另一个自由度——能谷——也引起了人们极大的研究兴趣。由于TMDCs中自旋与能谷的强耦合,自旋(能谷)可以通过能谷(自旋)方便地进行调控和探测,为电子自旋和能谷的相关领域提供了新的手段和方法。文章首先对能谷自由度以及TMDCs中自旋与能谷的强耦合进行了介绍,然后介绍基于圆偏振光激发和自旋注入两种方式进行的自旋调控和探测的理论和实验工作,最后对基于能谷的自旋调控进行了总结和展望。