The analysis of organic mercury compounds using liquid chromatography with on-line atomic fluorescence spectrometric detection

A new method for the analysis of organic mercury compounds is reported. The organomercurials are separated by high-performance liquid chromatography (HPLC). The compounds are converted to mercury(0) in a continuous-flow system by means of an oxidizing and a subsequent reducing solution. The elemental mercury generated is swept into the cell of an atomic fluorescence spectrometer (AFS) by a stream of argon. The compositions of the oxidizing solution, which contains peroxodisulphate and copper(II) in dilute sulphuric acid, and the reducing solution, which contains alkaline tin(II) chloride, were optimized, as were the gas–liquid separator (GLS), the condensing system and the geometry of the reaction coils. The method is applied to extracts of certified reference material (CRM) and to river sediments. High concentrations of methylmercury were found in the sediment samples. At one location, the presence of ethylmercury is derived from the sample chromatogram.     

小型可变坡水槽的结构及其特点

可变坡水槽作为研究水流及泥沙运动特性和水力学实验的一种设备已被广泛应用，本文论述了作者所研制的小型可变坡水槽的结构及其特点。     

An Exner-based coupled model for two-dimensional transient flow over erodible bed

Transient flow over erodible bed is solved in this work assuming that the dynamics of the bed load problem is described by two mathematical models: the hydrodynamic model, assumed to be well formulated by means of the depth averaged shallow water equations, and the Exner equation. The Exner equation is written assuming that bed load transport is governed by a power law of the flow velocity and by a flow/sediment interaction parameter variable in time and space. The complete system is formed by four coupled partial differential equations and a genuinely Roe-type first order scheme has been used to solve it on triangular unstructured meshes. Exact solutions have been derived for the particular case of initial value Riemann problems with variable bed level and depending on particular forms of the solid discharge formula. The model, supplied with the corresponding solid transport formulae, is tested by comparing with the exact solutions. The model is validated against laboratory experimental data of different unsteady problems over erodible bed.     

Isotope Geochemical Studies on Carbonates of Quaternary Glacio-Lacustrine Lake Sediments as indicators of Paleoenvironment

Selected silty “summer” and argillaceous “winter” layers of profiles of the rhythmically bedded glacio-lacustrine ice-marginal lake sediment of the Dehlitz-Leipzig varved clay (Leipziger Tieflandsbucht, Central Germany) have been examined for isotope composition (¹⁸O/¹⁶O, ¹³C/¹²C) of carbonate and organic fraction. In addition, mineralogical and grain size compositions were determined. The results show 1) a change in source of carbonate sediment (provenance) through time; 2) the oxygen isotope ratios differed between the “summer” and “winter” layers of varves couplets due to different rates of sedimentation; 3) anoxic events occurred in the lake; 4) carbon isotope ratios suggest organics in lake sediments which were derived from land and the primary productivity was low in the lake itself. In the study of cold-climatic lake sediments, isotope investigations can efficiently be used as additional paleosedimentological and facies indicators.     

核素随水-悬浮泥沙-底泥沙迁移模型

考虑了泥沙吸附和解吸、沉降和再悬浮对水相和泥沙相核素浓度的影响,根据质量守恒定律、吸附动力学方程和泥沙工程学建立了河流核素迁移的整体模型,进而得到分相模型.运用所得的模型对资江核电站排出的Sr在河流中迁移转化进行模拟,模拟结果表明所建模型基本上能反映Sr在水体中随水-悬浮泥沙-底泥沙的迁移规律.     

Determination of halogen levels in marine geological samples

ABSTRACT

A method for determining levels of fluorine (F), chlorine (Cl), bromine (Br), and iodine (I) in marine geological samples using wavelength dispersive X-ray fluorescence is presented here. Samples are prepared as pressed powder pellets. The method makes full use of the advantages of the ability of the modern X-ray fluorescence spectrometer to detect ultra-light elements and high-powered X-rays. A series of calibration standards with an appropriate concentration range was developed using a standard addition method. Empirical coefficients were used to correct for matrix effects in the case of F and Cl, the rhodium Kα -Compton peak was used as internal standard for Br matrix corrections, and the rhodium Kb-Compton peak was used to correct for the matrix effect on I. For % concentration of the analyte, the precision (relative standard deviation) of the method was <5%. For concentrations <0.1%, the relative standard deviation depended heavily on the count rates (or concentration). The accuracy of the method was validated by comparison of the results to similar reference materials. The detection levels of this method (counting time100 s) were 100, 5, 0.5, and 10 µg g^?1 for F, Cl, Br, and I, respectively. The method was here used to determine the levels of halogens in samples of 19 marine sediments (China, Russia, Canada, American), 10 marine manganese nodules (China, Russia, American, Germany, India, Japan), 4 cobalt-rich crust reference materials (Russia, China), reference materials, and 3 phosphorites.     

Magneto-orientational properties of ionically stabilized aqueous dispersions of Ni(OH)2 nanoplatelets

Magnetic and orientational behavior of nickel hydroxide nanoplatelets ionically stabilized in a liquid matrix is studied. Under an applied field the platelets orient their faces normal to its direction. For characterization of the individual behavior of dispersed and non-interacting particles three techniques are used: SAXS, SQUID and magneto-optics. Analysis reveals that nickel hydroxide in a platelet phase is paramagnetic with a pronounced anisotropy of the intrinsic susceptibility, the major component of which (in the direction normal to platelet face) exceeds the minor one by about 25%.     

粘土悬浮液明渠流的减阻现象

水和粘土悬浮液在水槽中的流动试验证明，在粗糙边界上的粘土悬浮液明渠流阻力明显小于清水流．在同样水力条件下粘土悬液的时均流速比清水流速大得多．当悬液浓度较高时，流动阻力系数比清水流阻力系数的一半还小．实验表明粘土悬液的高粘性和屈服应力抑制了紊动的发展，减小了紊动剪力，导致阻力降低．对于光滑边界湍流，粘土悬液的阻力系数与清水流的相近，不发生减阻现象     

海底沉积物声特性与海水深度变化关系的研究

海底沉积物声特性的实验室测量结果,相对原位直接测量,将由于测量环境的改变而发生变化。其中海水深度(压强)的改变是影响海底沉积物声传播速度、声传播衰减系数的因素之一。文章以现有海底沉积物纵波传播速度理论为依据,分析了海水深度(压强)影响海底沉积物声传播速度、声传播衰减系数的原因;设计了海底沉积物声特性实验室仿真测量系统,并根据实验数据获得海水深度(压强)影响海底沉积物声传播速度、声传播衰减系数的变化规律。     

Adaptation and validation of QuEChERS method for the simultaneous analysis of priority and emerging pollutants in sediments by gas chromatography—mass spectrometry

A Quick, Easy, Cheap, Effective, Rugged and Safe (QuEChERS) method has been adapted and validated for the simultaneous determination of priority (16 PAHs, 12 PCBs and 7 organochlorine pesticides (OCPs)) and emerging (carbamazepine, 9 musks and 6 sunscreens) pollutants in sediments by Gas Chromatography-Mass Spectrometry (GC-MS). The sample preparation was adapted by modifying the nature of the extraction solvent and optimising clean-up and evaporation steps. The method was validated by the analysis of spiked estuarine and marine sediments. Analytical performances were evaluated in terms of linearity, accuracy, precision and detection limits. The method shows good linearity (coefficients of determination > 0.998) and repeatability (RSD < 10%). Obtained recoveries are acceptable, ranging from 62% to 131% for all the compounds. Detection limits are estimated to range from 0.01 ng/g to 3.18 ng/g. This developed method offers the ability to detect and quantify several priority and emerging pollutants at low concentration levels in sediments.