Determination of the distribution of size of irregularly shaped particles from laser diffractometer measurements

The formal stereological transformation equation for particle sieve size distribution from measurements in lower dimensional spaces is applied to laser diffractometer measurements. The transformation function for iron ore particles is measured experimentally, and modeled. The solution is tested against the measured transformation function data as well as synthetic composite distributions of the original sample. The natural size distribution of a sample taken from a grinding circuit stream was measured by a combination of standard sieving and cyclosizer, and the result is compared to the transformed size distribution calculated from laser diffractometer measurements. The stereological transformation technique performed well in all cases.     

黄土颗粒结构特征及其对剪切行为的影响

微结构控制着黄土的宏观力学行为,进而影响着工程土体稳定性.本文通过X射线CT试验研究了陕西泾阳Q2黄土试样的三维颗粒结构特征,结合三轴剪切试验建立了黄土的颗粒流离散元数值计算模型,探讨了颗粒尺寸、形态和排列等结构特征对黄土剪切行为的影响.结果表明黄土试样颗粒的等效直径分布满足Weibull概率分布,球度分布符合Gamm...     

堆石料缩尺方法的分形特性及缩尺效应研究

采用6种不同缩尺方法将同一条现场级配曲线缩制成不同的数值模拟级配曲线,建立以不同粒径范围内颗粒数为测量数的分形模型,研究了颗粒级配分布的分形特性;基于颗粒流方法,生成与级配曲线相对应的6组数值试样进行双轴压缩试验,研究了缩尺方法对数值试样宏观力学特性及细观力学响应的影响;并讨论了颗粒级配分布的分形特性与数值试样力学特性之间的关系。结果表明：采用不同方法缩尺后数值试样的颗粒级配分布具有分形特性,分维数D为1.463～1.783;随着缩尺方法相似比尺M的增大,数值试样中细颗粒数量增多,粗细颗粒的充填关系得到改善,力学特性逐步提高;颗粒级配分布分维数D与数值试样力学特性指标之间存在较好的线性关系。     

Groundwater contamination with arsenic and other trace elements in an area of the pampa,province of Córdoba,Argentina

A geochemical study of groundwater of the pampa in the province of Córdoba, Argentina, was performed; the area covered approximately 10,000 km².Physical-chemical parameters, dissolved solids, and seven trace elements were determined in 60 selected water samples. Systematic and accurate measurements of arsenic, flourine, and vanadium were performed for the first time. Three trace element contaminants not reported earlier were found: an important one, selenium, and two others of less known effects, uranium and molybdenum.Eighty-four percent of the water analyzed showed arsenic contents over 0.05 mg/L, maximum contaminant level established by the U.S. Environmental Protection Agency (1982). The frequency distribution of trace elements was analyzed, and its fit to the lognormal distribution was proved by means of the Pearson and Kolmogorov-Smirnov test; the geographic distribution of the seven trace elements was mapped and its correlation with the anion-cation composition of the water was studied.The maximum arsenic, fluorine, vanadium, and uranium contents were found in the western part of the area under study, in waters containing dominant alkali metals in the cation composition. Maximum selenium and antimony contents were found in the eastern part of the area, while molybdenum distribution does not show any relationship with the other two groups. In addition, the geographic distribution of the trace elements seems to be related to the subsurface structure, which has been inferred using interactive digital analysis of Landsat imagery. The movements of the subsoil have disturbed surface and subsurface drainage influencing the water salinity and trace element contents.In order to investigate the origin of the contamination, 54 loess samples were collected in wells at depths ranging from the surface down to the water table. This loess, which has a high proportion of volcanic components, mainly rhyolitic glass, exhibits a chemical composition corresponding to that of a dacite.The loess and the volcanic glass show anomalous contents of all contaminant trace elements, mainly arsenic and selenium. For this reason loess is considered the most important contamination source in the groundwater under study.     

Particle-size dependence on metal(loid) distributions in mine wastes: Implications for water contamination and human exposure

The mining and processing of metal-bearing ores has resulted in contamination issues where waste materials from abandoned mines remain in piles of untreated and unconsolidated material, posing the potential for waterborne and airborne transport of toxic elements. This study presents a systematic method of particle size separation, mass distribution, and bulk chemical analysis for mine tailings and adjacent background soil samples from the Rand historic mining district, California, in order to assess particle size distribution and related trends in metal(loid) concentration as a function of particle size. Mine tailings produced through stamp milling and leaching processes were found to have both a narrower and finer particle size distribution than background samples, with significant fractions of particles available in a size range (?250 μm) that could be incidentally ingested. In both tailings and background samples, the majority of trace metal(loid)s display an inverse relationship between concentration and particle size, resulting in higher proportions of As, Cr, Cu, Pb and Zn in finer-sized fractions which are more susceptible to both water- and wind-borne transport as well as ingestion and/or inhalation. Established regulatory screening levels for such elements may, therefore, significantly underestimate potential exposure risk if relying solely on bulk sample concentrations to guide remediation decisions. Correlations in elemental concentration trends (such as between As and Fe) indicate relationships between elements that may be relevant to their chemical speciation.     

华能南京电厂不同粒径粉煤灰中微量元素分布及其富集规律

华能南京电厂不同粒径粉煤灰的化学成分和矿物相组成基本相同，煤粉所含矿物质在高温燃烧过程中的挥发－凝聚作用，导致微量元素趋向细粒径粒煤灰中富集，其富集的程度则与粉煤灰的平均粒径和元素的地球化学性质密切相关，粉煤灰排放的环境效应表明，尤以细粒径灰粒的影响最大。     

Inorganic geochemistry of roadway dust from the metropolitan area of Palermo,Italy

Inorganic matter from roadway dust collected in the urban area of Palermo, Italy, was analysed to identify the chemical elements introduced into the environment as a result of human activities. Metals of environmental concern exhibit very high enrichment factors, which in some cases exceed 100. Metal size distribution indicates that Pd, Pt, Au, Sb, Zn, S, Ni, V, Mo and Cr substantially accumulate in the finest particles, whereas Pb, Br, As, Cu, Ag and Ba are almost independent of the size fraction. SEM/EDS analyses revealed that some individual particles contain clusters of foreign particles (<10 wm) made up of Fe-Ni, Cr-Ni or Fe alone, typical of the abrasion of stainless steel. Others are aggregates of smaller Pb-Br-Cl particles. Lead isotope composition indicates that Pb pollution is mainly due to automobile exhausts and industrial sources. Pt and Pd concentrations reveal the increasing release of these elements into the environment from catalytic converters. Data indicate that monitoring Total Solid Particles, as generally done by the municipal agencies for the environment, is inadequate from a sanitary point of view, while there is a need for more attention to the presence of trace elements in airborne particulate matter and their distribution as a function of particle size.     

Composition Characteristic and Surface Charge Simulation of Atmospheric Dust Fall in Tianshui City

In order to know the particle size distribution and mineral compositions of dust in Maiji town, Tianshui City, Gansu Province, size distribution and physical compositions of atmosphere natural dropping dust have been analyzed. Based on the natural dropping dust ζ potential and the mass percentage of main mineral compositions in dust fall, we present two models (calculation method and hybrid method) for the zeta potential of atmospheric dust fall in pure water. The results illustrated that the natural dropping dust in Maiji town belongs to inhalable particles. The main mineral compositions and contents of the dust are quartz (57.08%), calcite (27.79%), albite (10.29%), muscovite (4.84%). Atmospheric dust fall in pure water is electronegativity and ζ potential decreased with increasing pH. There are some differences exist in the two modeling ways, but have a similar tendency. The zeta potential differences between natural dropping dust and modeling dust reflects the zeta potential contribution rate of main mineral particles in dust and the effect of trace polarity organic pollutants or other minerals.     

Maximum likelihood estimation of joint size from trace length measurements

Summary Usually, rock joints are observed in outcrops and excavation walls only as traces. Under some assumptions about the shapes of the joints and the nature of their size distributions, the underlying joint size distribution can be estimated from trace length measurements. However, the interpretation of trace length distributions from line mapping data should be approached with caution. The data are always length-biased and furthermore, the semi-trace length, the trace length, and the underlying joint size may have different distributional forms. Semi-trace length distributions are monotonic decreasing functions not sensitive to changes in the real trace length distributions. Experimental full trace length distributions are shown to have lognormal distributions and to be insensitive to major changes in the underlying joint size distributions. Under the assumptions of joint convexity and circularity a parametric model for the three-dimensional distribution of joint sizes is developed. A maximum likelihood estimation of the distribution of joint diameters, which best reflects the observed joint trace data, and corrects simultaneously for joint censoring, truncation and size bias, is developed. The theory is illustrated with numerical examples using data collected from five field sites.     

新场气田地表微量元素异常分布特征及其成因探讨

油气田上方地表微量元素的分布与油气田的分布有一定的关系,即在气田上方形成环状和顶端异常。通过微量元素与渗漏烃分析,发现新场气田的Cd不仅与烃类相关,而且与Mn聚为一类。利用中子活化分析和原子力显微镜观察不仅发现了天然气中含有微量元素,而且还证明其以钠米微粒的形式被上升气流运载迁移到地表,在气田地表形成微量元素分布异常。     

铂矿化探:取子样误差与控制方法

通过对颗粒铂分布与取子样误差关系的讨论 ,发现在铂矿地球化学勘查中 ,铂分析的取子样误差主要出现在铂异常的查证和异常源追踪阶段 ,导致误差的主要因素是随着与矿床或矿体的不断接近 ,样品中铂含量迅速增高 ,可能出现铂的颗粒效应。为了使铂分析的误差控制在 5 0 %之内 ,建议在铂矿地球化学勘查的不同阶段 ,采取不同的子样量分析铂。在区域化探阶段 ,大多数样品仍可采用取 1 0 g子样分析铂 ;而在异常追踪和查证阶段 ,由于样品中的铂含量往往大于 1 0ng/ g ,土壤、水系沉积物样品中颗粒铂粒径通常为 5～ 2 0 μm ,故建议取 2 0 g子样分析可保证大多数样品的分析误差控制在 5 0 %之内。文献中报道的取 5g、1 g样品获得的铂分析数据 ,使用时应慎重     

HELOS/BF型激光粒度仪湿法测试条件的优化

激光粒度仪以测试速度快、操作方便、重复性好等优点得到越来越广泛的应用,但仪器技术参数和测试条件不同对样品粒度测试结果有着显著影响。本文通过实验得到了HELOS/BF型激光粒度仪的优化测试条件,结果表明:对于比重小或粒径小的样品,采用低搅拌速率、高超声强度和较长超声时间;对于粒径大或比重大的样品,应采用高搅拌速率、低超声强度和较短超声时间。分散剂能加快样品颗粒的分散,且对于粒径小的样品分散效果更好。测试时进样浓度(遮光度)过低,样品中的颗粒数过少,检测不到足够的信号,使样品不具有代表性,样品粒径测定结果偏高;进样浓度过高,出现多重散射而使粒度分布范围较宽,样品粒径测定结果偏低。研究认为,HELOS/BF型激光粒度仪的合适进样浓度为10%～25%。     

青藏高原典型地区沉积物地球化学特征与矿物组成的粒度效应

地表松散沉积物中不同粒级的颗粒蕴含着不同的信息,这种差异与其物质来源、搬运和沉积过程中的分选作用以及沉积后的风化作用等有关。因此,可根据沉积物中不同粒级颗粒地球化学特征与矿物组成的差异,进行沉积物物源追踪或沉积环境重建。选择青藏高原在气候和地貌方面具有典型意义的柴达木盆地、错那湖、雅鲁藏布江流域作为研究区,分别采集了这几个地区的沙丘沙、黄土、湖积物、冲积物、洪积物、残坡积物等地表松散沉积物样品,用干筛法将沉积物样品分为两个部分,粗颗粒部分粒径范围为≥75~500 μm,细颗粒部分粒径<75 μm。对上述粗、细颗粒分别进行稀土与微量元素、Sr-Nd同位素、轻矿物组成的实验室分析测试,并对沉积物中粗、细颗粒的测试结果采用古典多维尺度方法进行相似性分析。结果表明：青藏高原松散沉积物中粗、细颗粒在轻矿物组成、微量和稀土元素含量、稀土特征、元素参数等方面存在差异;细颗粒部分蕴含了更多的环境信息,富含容易受化学风化影响的黏土矿物以及硬度较小、容易被磨蚀的方解石等矿物。在物源示踪中不同气候区的沉积物细颗粒不宜进行直接比较,应根据样品的粒度分布情况优先选择合适的粗颗粒组分进行物源示踪。     

Test of a model for trace element partition during closed-system solidification of a silicate liquid

Distributions of trace elements during solidification of a basalt are adequately described by the model of Helmkeet al. (1972) for crystallization as a closed system. A hypidiomorphic granular basalt was coarsely crushed to particles < 2 mm in size, was sieved, and materials from nine size fractions were analyzed by neutron activation for REE, Co, Cr, Fe, Hf, Na, Sc, and Ta. Mineral separates from one of the size fractions were also analyzed.Trace-element concentrations of analyzed samples containing statistically significant numbers of mineral grains were matched very well by a mixing model whose end-member components were the analyzed major minerals and mesostasis. Highly accurate modal analyses of the analyzed materials were obtained from the mixing model. Differences in proportions of mesostasis (range 0.57–2%) were shown to be responsible for large differences in trace element concentrations among 0.25–1 g chips from a single hand-specimen of the basalt. Ilmenite in the basalt is badly contaminated with mesostasis.The closed-system model for crystallization yields values for temperature- and composition-averaged distribution coefficients for incompatible elements that are accurate to ? 15 to + 30%, and relative to each other are accurate to a few percent. The model demonstrates why some current practices for estimating values of distribution coefficients or of parent liquid compositions lead to errors of factors of several times.     

Geochemistry of Cu, Co, Ni, Zn, Cd and Cr in the surficial sediments of a tropical estuary, southwest coast of India: a granulometric approach

 Geochemical characteristics of six trace metals – Cu, Co, Ni, Zn, Cd and Cr – in the bulk sediment and sand, silt and clay fractions of a tropical estuary on the southwest coast of India have been studied and discussed. In bulk sediment, the trace metal concentration is controlled mainly by the textural composition of the sample. Mud, sandy mud and sandy silt register higher concentrations of trace metals than that in sand-dominant sediments. The granulometric partitioning studies also re-affirmed the role of particle size in enriching the trace metals. The silt and clay fractions exhibit 7–8 times the enrichment of Cu and Cd compared to that in sand. The enrichment factors of Zn, Cr, Ni and Co in the silt and clay fractions, compared to that in sand, are 5–6, 4–5, 2–5 and 2–3 times, respectively. The trace metals in the sand fraction, particularly Ni and Cr, exhibit strong positive correlation with the heavy mineral content of the samples. It clearly indicates a heavy mineral pathway to the trace metals in the sand fraction. Cu and Co in silt and clay fractions exhibit a marked decrease towards the high saline zones of the estuary. This is attributed to the desorption of Cu and Co from particulate phases during estuarine mixing. Contrary to Cu and Co, the content of Zn in the clay fraction shows a marginal increase towards the estuarine mouth. This could be explained by the influx of Zn-rich contaminant discharges from Zn-smelting industries located slightly north of the estuarine mouth. The released Zn will effectively be held in the lattices of the clay mineral montmorillonite, which also exhibits a marked increase towards the estuarine mouth. The anomalously high values of Cd in some places of the Central Vembanad estuary is attributed to the local pollution. Received: 10 July 1995 · Accepted: 3 June 1996     

Particle transport within water-saturated porous media: Effect of pore size on retention kinetics and size selection

The transport and filtration behaviour of fine particles (silt) in columns packed with sand was investigated under saturated conditions by using step-input injections. Three samples of different particle size distributions (coarse medium, fine medium and a mixture of both) were used in order to highlight the influence of the pore size distribution on particle retention and size selection of recovered particles. The main parameters of particle transport and deposition were derived from the adjustment of the experimental breakthrough curves by an analytical model. The higher particle retention occurs in the mixture medium, owing to its large pore size distribution, and the filtration coefficient decreases with increasing flow velocity. Particle size distribution of recovered particles shows a thorough size selection: (i) the first recovered particles are the coarser ones; (ii) the size of the recovered particles increases with increasing flow velocity and enlarger pore distribution of the medium.     

Assessment of NO<Subscript>3</Subscript><Superscript>−</Superscript> contamination in a karstic aquifer,with the use of geochemical data and spatial analysis

Kopaida plain is a cultivated region of Eastern Greece, with specific characteristic related with the paleogeographic evolution and the changes in land use. The present article examines the contamination that derives from nitrates, in terms of contaminant levels, definition of sources and spatial distribution of contaminant plume. For this purpose, 50 water samples were collected from the karstic aquifer and analyzed for 15 parameters including major ions, trace elements, physicochemical parameters, and stable isotopes. The assessment of the above parameter values along with the notes derived by the statistical process revealed the existence of nitrate contamination which has been spatial defined with the aid of spatial interpolation techniques. The correlation of NO₃ ⁻ concentrations with the stable isotope values, defined the infiltration conditions and showed contaminant transport. Nitrate values revealed the potential environmental threat for local people, as 10% of the samples exceeded the parametric value of 50 ppm and 54% of them are above 25 ppm, indicating no optimal quality conditions. The origin of nitrate contamination seems to derive exclusively from the application of N-fertilizers, since the rest of potential sources were not verified by analytical data and field works.     

黑龙江镜泊湖地区蛤蟆塘火山空落堆积物形成机制研究

火山碎屑物的粒度、粒形和分布特征蕴含着其形成机制和喷发的环境信息。基于镜泊湖地区蛤蟆塘火山的一个空落堆积剖面的野外地质和岩相学,以粒度分析和分形理论定量研究了火山碎屑物的粒度分布、粒形几何及其分形特征。蛤蟆塘火山空落碎屑粒度分布均为单峰式,由岩浆爆炸形成的空落浮岩粒度峰值较小,而由射气岩浆喷发形成的含细花岗岩碎屑夹层的碎屑粒度峰值较大。空落浮岩颗粒的类球度、长宽比和凸度都小于含细花岗岩碎屑夹层的数值,表明空落浮岩颗粒相对不规则的特点。利用多段幂律方法拟合了蛤蟆塘火山空落碎屑颗粒分布规律,发现空落浮岩颗粒存在四个幂律分布段（即对应四个分形维数）,这是由于岩浆初始破碎、火山通道内的二次破碎以及风力筛选作用等造成的;含细花岗岩碎屑夹层的碎屑分布有两个幂律分布段（对应两个明显不同的分形维数）,即浮岩和花岗岩碎屑的形成是因不同破碎机制造成的。     

地球化学异常提取的自适应衬值滤波法

地球化学数据分布,特别是微量元素的频率分布,是正向偏斜的,其异常下限的计算也是基于对数正态分布。当定性分析元素的分布状态时,大部分样本分布状态的结果是可以接受的,但是当定量计算异常下限时,一定要结合具体样本的实际分布情况。引入g-h分布函数对样本数据进行拟合,根据所得到的参数确定异常下限,将异常下限与标准离差分割开来。结合子区中位数衬值滤波法,对个旧及其外围成矿区的化探数据进行处理,同时自适应的调节滤波窗口大小,提取化探异常,从而对预测靶区进行圈定。     

颗粒分析试验研究

颗粒分析试验是测定干土中各种粒组所占该土总质量的百分数的方法,借以明了颗粒大小分布情况,供土的分类及粗略判断土的工程性质及建筑材料选料之用,其中的密度计法用于测定小于0.075 mm以下的颗粒大小及分布情况,测量的准确度直接关系到土中黏粒和胶粒的多少,在试验的角度分析了密度计法试验结果误差的原因,指出现行规范中温度校正的不合理性,提出了空白试验方法,供工程技术人员和土工试验人员参考并验证.