Use of heavy liquid density separation to remove pyrite from sediment samples for radiocarbon dating     

《Quaternary Geochronology》2015

Sample preparation protocols for concentrating organic material from sediments for radiocarbon dating often include a large number of steps and the use of hazardous chemicals. Thus, these protocols are often problematic for pollen-poor sediments as material can get lost or may become degraded. Pyrite in samples for radiocarbon dating hinders an effective graphitisation process and thus needs to be removed during sample preparation. Standard protocols require the use of nitric acid, a strong oxidant that corrodes organic material. Therefore, the use of nitric acid needs to be avoided when preparing pollen-poor but pyrite-rich sediments.We present a method that minimises the sample preparation steps by replacing acid treatment with heavy liquid separation. Using non-toxic LST at a density of 2.0 g cm⁻³ is shown to be effective for separating the organic fraction from sulphides, silicates and carbonates. We applied this method to pyrite-rich and pollen-poor sediments from Western Australia that had previously been problematic to date. The successful AMS radiocarbon dating of all samples pre-treated with LST demonstrates the effectiveness of this method.  相似文献   

Organic matter mineralisation in the hypolimnion of an eutrophic Maar lake   总被引：2，自引：0，他引：2  

Sven Fahrner  Michael Radke  Dorothée Karger  Christian Blodau 《Aquatic Sciences - Research Across Boundaries》2008,70(3):225-237

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The Origin and Distribution of Salts on Alluvial Fans in The Atacama Desert,Northern Chile     

I. A. Berger  R. U. Cooke 《地球表面变化过程与地形》1997,22(6):581-600

The Atacama Desert has been predominantly hyperarid since the middle Miocene. Combined ionic and X-ray diffraction analysis shows that calcium sulphate is prevalent on three similar alluvial fans in salar basins across a transect of different environments in Antofagasta Province, northern Chile. Differences between the fans were largely due to the effect of local factors on salt input, secondary redistribution and deposit preservation. Thus carbonate was notable in the High Andes (fan C) and Pre-Cordillera (fan B), whereas in the Central Valley (fan A) greater qualities of the more soluble salts (chlorides and nitrates) probably reflect the higher level of aridity and an oceanic source (the camanchaca). Calcium sulphate distribution on the alluvial fans and on adjacent hilltops indicates an aeolian origin. Evidence from the Pre-Cordillera (fan B), however, suggests that salt input may have been episodic, related to changes in conditions within the general aridity and possibly to stone pavement and soil development. Calcium sulphate sources range from an input in Andean precipitation and the camanchaca to abundant regional evaporite deposits. It is probable, however, that products of Andean volcanism constitute the dominant primary source of calcium sulphate, and that the salt has subsequently been distributed widely within the endoreic basins of the region by a combination of groundwater, surface flow and the wind. © 1997 John Wiley & Sons, Ltd.  相似文献   

INTERRELATIONSHIP BETWEEN WATER QUALITY AND GROUNDWATER FLOW DYNAMICS IN A SMALL WETLAND SYSTEM ALONG A SANDY HILL RIDGE     

H. DE MARS  A. C. GARRITSEN 《水文研究》1997,11(4):335-351

Detailed modelling of the hydrological setting of fen meadows appears to be possible provided that detailed information on geomorphology, hydrochemistry and piezometric heads is available for a number of years. In the Laegieskamp, a small wetland reserve located in the central part of The Netherlands, a piezometric monitoring network was sampled for water quality analysis and piezometric heads between 1986 and 1992. Average yearly discharge and recharge periods were used for FLOWNET calculations. First, the models were used to determine, with the help of information on water quality, the hydrological systems in the study area. Secondly, they were used to define the present and past hydrological setting of a fen meadow in the reserve. The hydrological systems and water quality in the study area have changed considerably over the past 65 years. At present the fen meadow is mainly fed by precipitation. The mineral-rich conditions favouring the fen meadow vegetation are thought to be maintained thanks to a clayey peat layer and an oscillating shallow water body that prevents rapid leaching of minerals. The sulphate content in the fen exhibits a pattern of temporal variation, which is related to the severity of the annual drought. Our study showed that groundwater flow is mainly lateral, instead of the assumed vertical infiltration of groundwater in previous regional studies. This led us to the conclusion that conservation and restoration perspectives are much better than previously expected. The polluted middle, deep groundwater is not a major threat to this fen at the moment. © 1997 John Wiley & Sons, Ltd.  相似文献   

藻酸双酯钠片剂的薄膜包衣工艺研究     

黎华  赵峡  赛向阳 《中国海洋大学学报(自然科学版)》2005,35(2):306-308

为了提高产品质量的稳定性,实验研究了采用新菲尔对藻酸双酯钠片剂进行薄膜包衣的方法,并运用正交试验确定了薄膜包衣的最佳工艺条件为：藻酸双酯钠片剂硬度为3～4kg／mm^2,包衣液浓度为11％,喷液流量为0．19kg／min,片芯水分为5．0％。采用新菲尔包制的薄膜衣片与藻酸双酯钠糖衣片相比较具有阻湿性能好,片剂增重小,工时短等优点。  相似文献   

The Role of Multiphase Chemistry in the Oxidation of Dimethylsulphide (DMS). A Latitude Dependent Analysis     

F. Campolongo  A. Saltelli  N. R. Jensen  J. Wilson  J. Hjorth 《Journal of Atmospheric Chemistry》1999,32(3):327-356

A kinetic model for the OH-initiated homogeneous gas phase oxidation of dimethylsulfide (DMS) in the atmosphere (Saltelli and Hjorth, 1995), has been extended here to include the liquid phase chemistry. The updated model has then been employed to predict the temperature dependency of the MSA/nss-SO42- ratio. Model predictions have been compared with observational data reported in Bates et al. (1992). Sensitivity and uncertainty analysis has been performed in a Monte Carlo fashion to identify which are the important uncertainties on the input parameters and which are the possible combinations of parameter values that could explain the field observations. Results of the analysis have indicated that the temperature dependencies of the interactions between gas phase and liquid phase chemistry may to a large extent explain the observed T-dependence of the MSA/nss- SO42- ratio. The potential role of multi-phase atmospheric chemistry, not only in the case of SO2 but also of other oxidation products of DMS and, particularly, of DMS itself, has been highlighted.  相似文献   

Negative effects of blue mussel (Mytilus edulis) presence in eelgrass (Zostera marina) beds in Flensborg fjord,Denmark     

Hanne Fogh Vinther  Jens Sund Laursen  Marianne Holmer 《Estuarine, Coastal and Shelf Science》2008

The effect of blue mussel (Mytilus edulis) presence in eelgrass (Zostera marina) beds was studied from June 2004 to July 2005 in Flensborg fjord, Denmark. The field experiments were conducted at two stations, one with only Z. marina (Eelgrass station) present and one where M. edulis were present in the Z. marina beds (Mixed station). Zostera marina parameters were measured (growth of leaves, shoot density, leaf length, and nutrient content) in combination with epiphyte cover and sediment parameters (sulphate reduction rates, sediment nutrient fluxes, organic content, C, N and P content) to examine possible positive and negative effects of the mussels on eelgrass performance. The fluxes of ammonium from the sediments were stimulated at all sampling dates at the Mixed station, and possibly stimulated epiphyte growth at this station. Further ¹⁵N signals in epiphytes from the Mixed station suggested that excretion products from the mussels were important nitrogen sources at this station. Sulphate reduction rates were enhanced at the Mixed station and also sediment sulphide concentrations increased under mussel influence, which may have resulted in sulphide toxicity and decreased growth of Z. marina at this station. The study indicates that for Z. marina beds in Flensborg Fjord the effects of M. edulis in seagrass beds are primarily negative, and raises the question whether this leads to negative effects on the stability and expansion of Z. marina beds.  相似文献   

溶剂萃取法制取晶球状硫酸钾   总被引：3，自引：1，他引：2       下载免费PDF全文

李丽娟  李纪泽 《盐湖研究》1998,6(4):28-33

提出了溶剂萃取法制取晶球状硫酸钾产品的新工艺。从理论上研究了硫酸钾晶体从溶液中析出的推动力、析出浓度和溶液的过饱和度。并在年产500吨规模中间试验基础上,研究了盐析和溶剂萃取水形成过饱和状态的机理。  相似文献   

盐渍土地区岩土工程勘察中水土腐蚀性评价探讨——以渭北东部卤阳湖(卤泊滩)地区为例     

牛宝琪  王佳武  董小恒  胡建刚  兰文娟  侯龙俊  李法军 《陕西地质》2012,30(2):73-78

卤阳湖(俗称卤泊滩)地处关中平原东部,东西长约30 km,南北宽1.5～7 km,总面积124 km2。卤阳湖土壤盐碱化严重,不宜农作物生长,对其开发中遇到的主要问题是盐渍土勘察、腐蚀性评价和地基处理。卤泊滩地基土属于硫酸盐渍土。  相似文献   

地下水石油烃生物降解作用研究     

焦珣 《上海国土资源》2012,33(2):16-20,33

在对某石油污染场地地质、水文地质条件、污染源污染方式调查基础上,根据地下水样测试结果,分析了地下水石油烃污染分布特征、污染晕中指示生物降解作用的电子受体、代谢产物以及重要地球化学参数的变化规律,通过计算矿物饱和指数和采用含水层介质X射线矿物衍射方法研究了污染晕中矿物沉淀反应,计算了含水层的氧化容量。结果表明：由于SO42-背景浓度值较高,硫酸盐还原是污染场地地下水石油烃生物降解的优势反应;菱铁矿、黄铁矿和FeS的沉淀反应是HS-、Fe2＋浓度异常的原因;SO42-的氧化容量在含水层中的氧化容量（OXC）所占比例最大,可进一步推断硫酸盐还原反应是引起污染场地地下水石油烃生物降解的优势反应。  相似文献