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排序方式： 共有515条查询结果，搜索用时 15 毫秒
61.
根据湄洲湾海域2005年丰、平、枯三个水期的海水监测及2005年9月的湄洲湾表层沉积物监测数据对湄洲湾的环境质量进行评价。结果显示,湄洲湾海域水质综合指数(WQI)全年平均为0.69,除了F1站位枯水期为1.04,轻度污染,其余的均小于1.0,全年综合评价为清洁,但受气候及水文条件的影响,丰水期和枯水期有两个站位呈富营养化状态;表层沉积物综合质量指标平均值为0.52,综合评价为清洁,但铜、砷、镉的单因子污染指数平均值介于0.5~1.0之间,说明表层沉积物已被这三个因子玷污。 相似文献
62.
Axel Durand Zanna Chase Ashley T. Townsend Taryn Noble Emily Panietz Karsten Goemann 《International journal of environmental analytical chemistry》2016,96(2):119-136
Microwave-assisted digestion permits a rapid and total dissolution of sediments and various other sample types, allowing easier and more accurate multi-element determinations. In this study, we present an optimised microwave digestion method for the complete digestion of 200 mg of carbonate-rich sediments. The optimised method prevents the formation of precipitates and assures a complete dissolution of the material. The optimised method involves treatment with concentrated hydrochloric acid (HCl) prior to microwave digestion, which prevents the formation of an insoluble calcium fluoride precipitate associated with the use of hydrofluoric acid (HF). Three different certified reference samples along with a pure calcium carbonate standard and a carbonate-rich in-house marine sediment sample were considered. Sediments were found to only be partially digested if insufficient HF was present, while a noticeable fluoride-based precipitate was found if excess HF was present. Twenty elements were analysed using sector field inductively coupled plasma mass spectrometry (ICP-MS) (Al, Ag, Ba, Ca, Cd, Co, Cr, Cu, Fe, Mg, Mn, Mo, Na, Ni, Sr, Th, Ti, U, V and Zn). A total sample digestion with average elemental recoveries above 90% was obtained by reacting carbonate-rich samples with HCl on a hotplate at 150°C for 2 h (time for the total release of generated CO2), prior to any microwave digestion step. This extra step prevented the accumulation of gas in the sealed vessels during digestion, which would otherwise influence the carbonate chemical equilibria and make insoluble calcium available for precipitation. After this initial treatment, the improved digestion method consisted of microwave attack employing a mix of concentrated HCl, nitric acid (HNO3) and HF (4 mL/10 mL/2 mL), followed by evaporation on a hotplate. The limits of detection (LOD) obtained using the optimised microwave protocol and ICP-MS measurements were below 0.1 µg/kg for the trace elements and below 0.2 mg/kg for major elements. 相似文献
63.
Jiří Čmelík Zdeňka Nainarová Petr Ryšánek 《International journal of environmental analytical chemistry》2015,95(12):1090-1098
The developed and tested method is based on the acid volatile sulphur (AVS) releasing from a sample of sediment by acidification with hydrochloric acid and sequential absorption of released hydrogen sulphide into the absorption solution of sodium hydroxide. Total sulphur absorbed in the absorption solution is subsequently determined by inductively coupled plasma optical emission spectrometry (ICP-OES) technique. The method was tested using both model and real samples of the river sediment. Obtained results were compared with the results of iodometric determination as the method routinely used for the AVS determination. In case of using ICP-OES with purge and trap, there is no spectral interference of calcium; therefore for the determination of sulphur, it is possible to use atomic emission line of sulphur S I 180.7 nm. The tested method provides the results comparable with the iodometric method within the range of tested concentrations. The detection limit (LOD) of this method is 0.09 mg· S2? ? L?1 in the absorption solution which corresponds to 0.23 mg S2?·kg?1 in a sediment. Value of LOD is comparable with the iodometric determination. 相似文献
64.
A detailed statistical examination of replicated data used to certify platinum-group elements (PGEs) in environmental reference material BCR-723 is presented. Certification of Pt, Pd, and Rh concentrations in BCR-723 was based on 16, eight, and nine accepted data sets, respectively. Each accepted data set contained six replicated measurements for each PGE, and the statistical properties of these concentration data were examined, i.e. 96 for Pt, 48 for Pd, and 54 for Rh. This level of investigation has received limited attention but is critical in furthering our understanding of PGE variability and representativeness. Concentrations of Pt, Pd, and Rh were shown to differ significantly between accepted data sets. Palladium and Pt differed in their quantification between detection techniques. Additionally, Pd and Pt concentrations varied significantly between laboratories using a similar definitive method (inductively coupled plasma-isotope dilution mass spectrometry). The distribution of Pd concentrations was found to be bimodal, with a secondary population exhibiting a contamination signal of about 15%. The secondary population, not previously reported in BCR-723, is likely a measurement artifact and not due to a nugget effect. Comparisons of BCR-723 with other environmental media from Europe, i.e. airborne particulate matter, tunnel dust, and road-deposited sediment, indicated that Pd is uncommonly low in BCR-723 (6.0?ng?g?1) and is generally not representative in terms of its distribution relative to Pt and Rh. Serious consideration should be given to developing a new PGE certified environmental reference material. 相似文献
65.
海底界面Scholte波具有衰减小、传播距离远等特点,可应用于水下目标探测与海底参数反演。在实际海洋环境中,海水与弹性海底之间的沉积层会对Scholte波的激发和传播产生显著影响。该文利用缩比原理设计并开展水池实验研究,将实际海洋环境按1:5000的比例缩比至实验室水池尺度,利用声压场Scholte波识别方法在包含沉积层的实验环境下对Scholte波的激发与传播规律进行探究。实验结果表明,该实验条件下,1 mm厚度的沉积层时海底界面依然有Scholte波激发,但沉积层的存在会增大其衰减;而厚度超过1 mm的沉积层会导致Scholte波无法激发。根据缩比原理,实验环境对应为声源频率10 Hz、水深3000 m、沉积层厚度5 m的实际海洋环境,即在上述实际海洋环境中,海底界面Scholte波仍可以正常激发,而厚度大于5 m的粉沙质沉积层会导致Scholte波无法激发。 相似文献
66.
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. 相似文献
67.
Dr. Erik A. Toorman 《Rheologica Acta》1997,36(1):56-65
68.
ABSTRACTA 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. 相似文献
69.
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. 相似文献
70.
M. Meyer Yu. L. Raikher O. Sandre A. Bée V. Cabuil V. Dupuis P. Licinio R. Perzynski 《The European physical journal. E, Soft matter》2008,26(4):355-360
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%. 相似文献