Ant composition and activity patterns as determined by pitfall trapping and other methods in three habitats in the semi-arid Karoo

The diversity and abundance of epigaeic ant species were determined across three habitats (riverine areas, gently sloping grassland areas and steep slope areas) in summer (November–December) and winter (May–June) of 1998 at Tussen die Riviere Nature Reserve in the Karoo, to determine temporal and spatial variations in the availability of potential prey species of the aardvark (Orycteropus afer). Pitfall trapping, dig sampling and quadrat sampling were used to ensure as complete a sampling effort as possible. Forty-five ant species of five sub-families and 17 genera were recorded. The grassland habitat yielded the highest abundance and diversity, followed by the steep slope and riverine areas. Ant abundance and diversity were higher during summer than winter in all three habitats. Anoplolepis custodiens was the most abundant species in summer, whilst Monomorium albopilosum was the most abundant species in winter. Pitfall trapping was responsible for recording more species than dig sampling or quadrat sampling. No method recorded all of the species present.     

Monthly botanical composition of the diet of cattle in the rangelands of Mendoza plain, Argentina

Monthly botanical composition of cattle diet was determined for the period July 1994 to June 1995 in faecal samples by microhistological analysis. Principal components and cluster analyses were used to evaluate diet homogeneity among months. November through March diets were mainly composed of grasses and forbs (50 to 73%). During the April–September period, shrubs represented 36 to 57% of the overall diet. In October more than half the diet came from two species, one shrub (32%) and one grass (25%) making this month very different from the rest. The composition of cattle diets was significantly correlated with temperature and/or rainfall.     

流动注射在线萃取-火焰原子吸收光谱法测定地质试样中痕量银

研究了在线萃取系统流程中最佳参数,提出一个流动注射在线萃取-火焰原子吸收光谱法测定地质试样中痕量Ag的分析方法。检出限为0.54ng/ml,对于含Ag 20ng/ml试样测定10次,精密度(RSD)为1.64％,分析速度可达20～30N/h,经地质标样分析验证结果可靠。     

偏最小二乘－分光光度法测定地质样品中铈组稀土元素的研究

采用偏最小二乘回归（ＰＬＳＲ）算法，对均三溴偶氮胂显色体系光度法同时测定地质样品中铈组稀土元素的结果进行数据处理，取得满意结果。讨论了消除样品中的钇组稀土元素干扰、校准样品群的建立以及最佳因子数的确定等问题。用所拟定方法对国家级ＧＳＤ、ＧＳＲ系列地质标样进行测定，其结果与推荐值相符。对地质样品ＮＢ３６７平行９次测定，铈组各稀土元素的ＲＳＤ在２．２％～１０．Ｏ％范围。     

地质样品中超痕量铂族元素的中子活化分析

文章概述了中子活化分析的基本原理和地质样品中超痕量铂族元素的中子活化分析方法。其中除介绍了样品的制备方法、照射和测量条件之外，还对地质样品中铂族元素放射化学分离方法进行了说细的讨论和评述。引用文献２４篇。     

Trends in Analytical Developments and Earth Science Applications in LA-ICP-MS and LA-MC-ICP-MS for 2004 and 2005

This review of laser ablation-inductively coupled plasma-mass spectrometry includes research that employed quadrupole instruments, and single-collector and multicollector magnetic sector field instruments. The most important trend in 2004–2005 was the growing appreciation that small matrix effects in LA-(MC)-ICP-MS need to be addressed in order to produce highly precise and accurate data by the method. The issue is most acute for isotope ratio measurements that require standard-sample-standard bracketing but can also be important for certain elemental analysis. Matrix-dependent elemental and isotopic fractionations were studied from the standpoint of laser-sample interactions and the behaviour of laser-generated particles in the ablation cell, transfer tubing and ICP torch. Innovations in LA-(MC)-ICP-MS involved signal smoothing, in torch laser ablation, on-line isotope dilution and molecular oxide monitoring. Other important research was carried out on the calibration and homogeneity of various reference materials; and the exploration of mature ( in situ U-Pb geochronology) and emerging (apatite fission-track chronometry, U-Th/He thermochronology, boron/strontium/uranium-series isotopic microanalysis) applications in the Earth sciences.     

New Applications of the Model of de Wijs in Regional Geochemistry

This paper is concerned with the lognormal, and its logbinomial approximation, in connection with a three-parameter version of the model of de Wijs. The three parameters are: overall average element concentration value (ξ), dispersion index (d), and apparent number of subdivisions of the environment (N). Multifractal theory produces new methods for estimating the parameters of this model. In practical applications, the frequency distribution of element concentration values for small rock samples is related to self-similar spatial variability patterns of the element in large regions or segments of the Earth's crust. The approach is illustrated by application to spatial variability of gold and arsenic in glacial till samples from southern Saskatchewan. It is shown that for these two elements the model of de Wijs is satisfied on a regional scale but degree of dispersion decreases rapidly toward the local, sample-size scale. Thus the apparent number of subdivisions (N) is considerably less than would be expected if degree of dispersion were to extend from regional to local scale. A random-cut variant of the model of de Wijs produces an empirical frequency distribution of relative element concentration values that can be related to random dispersion index     

大管回流消解ICP-MS测定植物样品中的Hg及其他痕量元素

针对易挥发元素Hg提出了大试管和红外加热的多孔控温消解炉的简单装置消解植物样品的大管回流法。该方法结合ICP-MS测定Hg,指出在0.18%L-半胱氨酸加入内标做清洗液消除汞的记忆效应,校准曲线有一个更好的相关系数r=0.9993,Hg的测定限可达0.012μg/g(10σ,DF=100);并比较了原子荧光测定Hg的测定限0.0013μg/g(10σ,DF=100)和测定结果。该方法经标准物质GSV-3、GSV-4、GSB-1、GSB-6、GSB-10和GSB-4验证,测定值与标准值基本吻合。实验结果表明,该消解方法中Hg基本没有损失,而且ICP-MS的测定Hg的同时可以测定Li、B、Cr、Mn、Co、Ni、Cu、Zn、As、Sr、Mo、Cd、Ba和Pb等痕量元素。     

电感藕合等离子体原子发射光谱法快速测定地质样品中的钒

炭质页岩中钼、镍、钒、磷等元素的含量相对较高;作者采用充氩电荷注入检测器(CID)-电感藕合等离子体全谱直读原子发射光谱仪,建立了适应于地质样品中钒的快速测定的方法。方法的特点是:线性范围宽、快速、准确、稳定性好且能同时测试多种元素;该方法也可同时用于:Mn、Cu、Pb、Zn、Co、N i、P等杂质元素的快速测定。通过对实际样品的检测,取得良好结果,与化学法测定结果基本吻合。     

Preliminary ESR dating results on loess samples from the loess–paleosol sequence at Luochuan, Central Loess Plateau, China

The quartz Al centre has been used in pioneering studies for ESR dating of sediments. Acceptable age estimates could be obtained for a range of deposits using this centre after estimating the residual level. To inspect the feasibility and reliability of ESR dating of windblown sediments, six loess samples from the loess–paleosol sequences of Luochuan profile on central Loess Plateau, China, were dated by ESR with regeneration method using the quartz Al centre measured at 115 K. The samples were exposed to sunlight for 430 h. Only about 25% signal intensity was bleached. According to our preliminary results, ESR age estimates increased with the depth along the loess profile, however, the ESR age of each sample is only about a half of the reference age of the corresponding strata. For example, the ESR age of a sample from the top of L₈ loess near B/M boundary (a known age of 780 ka) yields an age of only 385 ka. It seems that ESR dating using quartz Al centre with dose regeneration protocol may have the potential for dating of loess and other aeolian deposits, but the studies on the nature of the quartz Al centre and experiment protocols have to be studied further.