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1.
In 2007,the U.S.Geological Survey,the Geological Survey of Canada,and the Mexican Geological Survey initiated a low-density(1 site per 1600 km2,13323 sites) geochemical and mineralogical survey of North American soils(North American Soil Geochemical Landscapes Project).Sampling and analytical protocols were developed at a series of workshops in 2003-2004 and pilot studies were conducted from 2004-2007.The ideal sampling protocol at each site includes a sample from 0-5 cm depth,a composite of the soil A horizon,and a sample from the soil C horizon.The <2-mm fraction of each sample is analyzed for Al,Ca,Fe,K,Mg,Na,S,Ti,Ag,Ba,Be,Bi,Cd,Ce,Co,Cr,Cs,Cu,Ga,In,La,Li,Mn,Mo,Nb,Ni,P,Pb,Rb,Sb,Sc,Sn,Sr,Te,Th,Tl,U,V,W,Y,and Zn by inductively coupled plasma-mass spectrometry and inductively coupled plasma-atomic emission spectrometry following a near-total digestion in a mixture of HCl,HNO3,HClO4,and HF.Separate methods are used for As,Hg,Se,and total C on this same size fraction.The major mineralogical components are determined by a quantitative X-ray diffraction method.Sampling in the conterminous U.S.was completed in 2010(c.4800 sites) with chemical and mineralogical analysis currently underway.In Mexico,approximately 66% of the sampling(871 sites) had been done by the end of 2010 with completion expected in 2012.After completing sampling in the Maritime provinces and portions of other provinces(472 sites,7.6% of the total),Canada withdrew from the project in 2010.Preliminary results for a swath from the central U.S.to Florida clearly show the effects of soil parent material and climate on the chemical and mineralogical composition of soils.A sample archive will be established and made available for future investigations.  相似文献   

2.
地壳全元素探测——构建“化学地球”   总被引：17，自引：1，他引：16  
地壳物质探测是地壳探测工程的重要组成部分。化学元素是地球物质组成的最基本单位,被称为地球的基因。矿产资源是由化学元素组成的,环境是受化学元素行为制约的,因此,对地壳中所有元素精确含量和分布的探测,对解决人类所面临的资源和环境问题具有重大意义。地壳全元素探测项目拟发展4种地球化学探测技术,包括地壳中所有天然元素的精确分析技术,中下地壳物质成分识别技术,穿透性地球化学探测技术,海量地球化学数据和图形显示技术。建立1个覆盖全国的地球化学基准网,系统采集代表性岩石样品10000件,疏松物样品6000件,按标准化的方法分析其主量元素和微量元素含量(包含78种元素),建立中国大陆地球化学基准值,为研究化学元素的分布、演化和成矿物质背景提供基准参考数据。进行总长度3300km的3条地球化学走廊带的实验与示范,采集各类代表性岩石样品5000件,进行元素和同位素测定,构建走廊带地壳地球化学模型、跨越不同大地构造单元的元素空间变化和大型矿集区成矿物质背景。为开展全国地壳探测工程奠定基础,并为最终建立"化学地球"进行技术准备和先导性实验。  相似文献   

3.
《Applied Geochemistry》2004,19(2):257-260
Over the past 30 a, regional and national solid-phase geochemical surveys have been conducted by the United States Geological Survey and the Geological Survey of Canada. In the present paper the authors have examined the distribution of As in stream-sediment and soil samples of the US and Canada in terms of geologic and anthropogenic components. The results of the compilations indicate that the distribution of As in stream sediments, lake sediments, and soils in Canada and the US shows that most of the variability is controlled by the bed rock characteristics.  相似文献   

4.
Conventional stream sediment sampling in which sediments are taken from the active channels during reconnaissance regional geochemical surveys in gold exploration has over the years failed to delineate prospective target zones in northern Ghana, where the relict is flat. Whereas the technique has been successful in the south western Ghana, which is characterised by moderate to high relief, generally the savannah north is associated with low relief, commonly with flat topographies and generally decoupled stream channels. Geochemical comparison of active stream and overbank sediments in this study demonstrate that active stream channels may contain contaminated materials of recent origin, but overbank sediments, except for the uppermost horizons, represent alluvial regolith of earlier depositional cycles over time. Based on gold value repeatability, composite samples taken from the overbank sediment layers were relatively less erratic and are considered to be an appropriate geochemical medium in delineating potential regional gold targets for follow up. The results show that overbank sediment sampling can be used as a cost-effective method to define broad anomalous zones; and the technique must be considered useful during reconnaissance geochemical surveys in the savannah regions.  相似文献   

5.
The continental area of Portugal is now entirely covered by a soil geochemical survey (1 site/135 km2), taking as the sampling media topsoils (upper mineral horizons, A) and organic horizons (humus, O). Standard methods for sampling, sample preparation and analysis were used in order to achieve high quality and consistent data. Each sample was analyzed for 32 chemical elements, pH, electrical conductivity and organic matter content.The main purpose of the survey was to obtain baseline levels for various chemical elements. The compilation of all data (nearly 45,000 individual data) in an organised way, led to the production of the first Soil Geochemical Atlas of Portugal. In this Atlas it is possible to find for each chemical element a set of information statistics (basic statistical parameters, boxplots, cumulative frequency curves, etc.), maps of spatial distribution, among other information of geochemical and environmental interest. This paper gives an overview of the Soil Atlas and examples of application. The data were used to calculate reference values for 9 elements of environmental importance and to obtain empirical formulae allowing the estimation of elements in the coarse fraction of soils (< 2.00 mm) from known concentration in a finer fraction (< 0.18 mm).  相似文献   

6.
In 2004, the US Geological Survey (USGS) and the Geological Survey of Canada (GSC) initiated a pilot study that involved collection of more than 1500 soil samples from 221 sites along two continental transects across Canada and the United States. The pilot study was designed to test and refine protocols for a soil geochemical survey of North America. The two transects crossed a wide array of soil parent materials, soil ages, climatic conditions, landforms, land covers and land uses. Sample sites were selected randomly at approximately 40-km intervals from a population defined as all soils of the continent. At each site, soils representing 0 to 5 cm depth, and the O, A, and C horizons, if present, were collected and analyzed for their near-total content of over 40 major and trace elements. Soils from 0–5 cm depth were also collected for analysis of organic compounds. Results from the transects confirm that soil samples collected at a 40-km spacing reveal coherent, continental- to subcontinental-scale geochemical and mineralogical patterns that can be correlated to aspects of underlying soil parent material, soil age and climate influence. The geochemical data also demonstrate that at the continental-scale the dominance of any of these major factors that control soil geochemistry can change across the landscape. Along both transects, soil mineralogy and geochemistry change abruptly with changes in soil parent materials. However, the chemical influence of a soil’s parent material can be obscured by changing climatic conditions. For the transects, increasing precipitation from west to east and increasing temperature from north to south affect both soil mineralogy and geochemistry because of climate effects on soil weathering and leaching, and plant productivity. Regional anomalous metal concentrations can be linked to natural variations in soil parent materials, such as high Ni and Cr in soils developed on ultramafic rocks in California or high P in soils formed on weathered Ordovician limestones in central Kentucky. On local scales, anomalous metal concentrations recognized in soil profiles, such as high P in soils from animal confinement sites, are consistent with local anthropogenic disturbances. At a larger scale, the distribution of Hg across the west to east transect demonstrates that it can be difficult to distinguish between natural or anthropogenic contributions and that many factors can contribute to an element’s spatial distribution.Only three samples in a subset of seventy-three 0–5 cm depth soil samples from the north to south transect had organochlorine pesticides values above the method detection limit, apparently related to historic usage of the pesticides DDT and dieldrin.  相似文献   

7.
The 42 element, 1190 sample Mobile Metal Ion subset of the National Geochemical Survey of Australia database was used to develop and illustrate the concept of Degree of Geochemical Similarity of soil samples. Element concentrations were unified to parts per million units and log(10)-transformed. The degree of similarity of pairs of samples of known provenance in the Yilgarn Craton was obtained using least-squares linear regression analysis and demonstrated that the method successfully assessed the degree of similarity of soils related to granitoid and greenstone lithologies. Exploratory Data Analysis symbol maps of all remaining samples in the database against various reference samples were used to obtain correlation maps not only for granitoid- and greenstone-related soil types but also to distinguish between, for example, samples derived from marine vs regolith carbonate. Likewise, the distribution of soil samples having a geochemical fingerprint similar to mineralised provinces (e.g. Mount Isa) can be mapped, and this can be used as a first-order prospection tool.  相似文献   

8.
The United States and other nations use the term natural conditions or reference conditions in legislation providing for the protection of aquatic ecosystems. Natural or reference conditions are generally used to describe environmental conditions in an aquatic resource before any human introduced pollution. The natural or reference conditions are used in establishing water quality criteria for protection of aquatic resources, helping classify aquatic resources within a regulatory category, and for assessing effectiveness of aquatic resource restoration actions. Regional scale geochemical mapping of stream sediments is available for many countries that when combined with exploratory data analysis and geospatial data can be used to establish screening level natural conditions for trace metals in stream sediments. This approach is applied to the Cook Inlet watershed in Alaska using the US Geological Survey National Geochemical Survey stream sediment trace metals data. Upper concentration limits are developed for As, Cr, Cu, Pb, Hg, Ni, and Zn in the Cook Inlet watershed to aid in screening sediments for potential anthropogenic contamination.  相似文献   

9.
The geochemical baselines of nickel and chromium were studied from the data produced by the Barents Ecogeochemistry project, a large international regional geochemical mapping exercise. The project surveyed major and trace element distributions in stream water, organic and mineralogically-modified soil horizons, and terrestrial moss in the northwestern part of Russia and in Finland. Other materials were collected during the pilot phase and later from thirty special sites. The results on respective materials by XRF, ICP-MS and ICP-AES showed that both geological and anthropogenic factors have an influence on the geochemical baseline concentrations of Ni and Cr in organic soil and stream water. The main explanation of the observed distribution patterns in terrestrial moss is human activity, but geological factors can also affect the baselines. The variation of geochemical baselines in the mineral-rich soil horizon depends only on variations in bedrock. The mineralogy of samples mainly controls the leachability properties of soil samples.  相似文献   

10.
《Applied Geochemistry》1996,11(5):621-IN1
The stream water hydrogeochemical database, produced by the Geochemical Baseline Survey (GBASE) of the British Geological Survey, has recently been enhanced in the light of experimental pilot studies in North Wales, to meet a wider range of economic and environmental objectives which require modern, integrated and strategic geochemical surveys for their implementation. Hydrogeochemical data are therefore now collected, in conjunction with geochemical data for stream sediments, soil samples and mineral concentrates. The density of sampling, based on the collection of stream water at near-baseflow conditions during the late summer period each year, has been increased to one site per 1.75 km2 and a broader spectrum of geochemical determinants introduced. Provisional regional datasets are being prepared for an extensive region covering Wales, the Welsh Borders, and part of the West Midlands representing over 17 000 sample sites. Bedrock geology and base metal sulphide mineralisation are particularly well reflected in the stream water chemistry at the regional scale. The influence of secondary factors, such as geomorphology, atmospheric controls, and anthropogenic contamination due to agriculture, urban, industrial and military developments, can also be readily distinguished.The data obtained by systematic high resolution sampling of first and second order streams, vary in concentration over three or four orders of magnitude for many of the analytes studied here. This compares with a range of only one or two orders of magnitude for many of the analytes in stream sediment samples. The extended range in values for stream water is an important factor in the gridding, plotting and production of relatively stable maps. They are relatively unaffected either by short temporal changes in stream water flow, which are attributable either to storm events noted during the sampling campaign, or by annual differences between wet and dry summers in different years. This has enabled a series of robust surface hydrogeochemical maps to be prepared for analytical data collected during the summer sampling campaigns conducted annually from 1989 to 1994. These maps provide a unique source of synoptic baseline information for a wide range of economic and environmental applications especially, when combined with other geoscience datasets in a GIS environment.  相似文献   

11.
Reference samples of soils from the Institute of Applied Physics, Irkutsk (RIAP), the Institute of Geochemistry, Irkutsk (IGI) and the United States Geological Survey, Reston (USGS) were analysed with the aim of determining Ag, B, Ge, Mo, Sn, Tl and W abundances by an atomic emission method with air-stabilised D.C. arc excitation. Two series of reference samples of soils and bottom sediments, GSS-1-8 and GSD-1-12 (IGGE), were used to ensure the traceability link for the analytical results. Traceability was also demonstrated through the comparison of measured results by AES and ICP-MS methods. It is shown that the reference samples GSS-1-8 and GSD-1-12 satisfied the "fitness-for-purpose" criterion (uncertainty U of the certified value should be one-third to one-tenth the magnitude of routine laboratory data uncertainty S (S/U > 3-10)) and can be applied for calibrating AES techniques.  相似文献   

12.
The National Institute for Standards and Technology (NIST) has recently released three soil standard reference materials that are uncontaminated (SRM 2709), moderately contaminated (SRM 2711), and highly contaminated (SRM 2710) with metals. The SRMs were analyzed at the U.S. Geological Survey (USGS) for thirty two major, minor and trace elements using a combination of wavelength dispersive X-ray fluorescence spectroscopy (WDXRF) and inductively coupled plasma atomic emission spectroscopy (ICP-AES). Good agreement is observed between NIST certified values and USGS results. The wide concentration ranges for most transition metals should make these SRMs useful in assessing the accuracy of methods used in geochemical exploration and environmental studies.  相似文献   

13.
In 2004, the US Geological Survey (USGS) and the Geological Survey of Canada sampled and chemically analyzed soils along two transects across Canada and the USA in preparation for a planned soil geochemical survey of North America. This effort was a pilot study to test and refine sampling protocols, analytical methods, quality control protocols, and field logistics for the continental survey. A total of 220 sample sites were selected at approximately 40-km intervals along the two transects. The ideal sampling protocol at each site called for a sample from a depth of 0–5 cm and a composite of each of the O, A, and C horizons. The <2-mm fraction of each sample was analyzed for Al, Ca, Fe, K, Mg, Na, S, Ti, Ag, As, Ba, Be, Bi, Cd, Ce, Co, Cr, Cs, Cu, Ga, In, La, Li, Mn, Mo, Nb, Ni, P, Pb, Rb, Sb, Sc, Sn, Sr, Te, Th, Tl, U, V, W, Y, and Zn by inductively coupled plasma-mass spectrometry and inductively coupled plasma-atomic emission spectrometry following a near-total digestion in a mixture of HCl, HNO3, HClO4, and HF. Separate methods were used for Hg, Se, total C, and carbonate-C on this same size fraction. Only Ag, In, and Te had a large percentage of concentrations below the detection limit. Quality control (QC) of the analyses was monitored at three levels: the laboratory performing the analysis, the USGS QC officer, and the principal investigator for the study. This level of review resulted in an average of one QC sample for every 20 field samples, which proved to be minimally adequate for such a large-scale survey. Additional QC samples should be added to monitor within-batch quality to the extent that no more than 10 samples are analyzed between a QC sample. Only Cr (77%), Y (82%), and Sb (80%) fell outside the acceptable limits of accuracy (% recovery between 85 and 115%) because of likely residence in mineral phases resistant to the acid digestion.A separate sample of 0–5-cm material was collected at each site for determination of organic compounds. A subset of 73 of these samples was analyzed for a suite of 19 organochlorine pesticides by gas chromatography. Only three of these samples had detectable pesticide concentrations. A separate sample of A-horizon soil was collected for microbial characterization by phospholipid fatty acid analysis (PLFA), soil enzyme assays, and determination of selected human and agricultural pathogens. Collection, preservation and analysis of samples for both organic compounds and microbial characterization add a great degree of complication to the sampling and preservation protocols and a significant increase to the cost for a continental-scale survey. Both these issues must be considered carefully prior to adopting these parameters as part of the soil geochemical survey of North America.  相似文献   

14.
The Mexican Geological Survey (SGM), the National Institute of Statistics, Geography and Informatics (INEGI) and the Autonomous University of San Luis Potosi (UASLP) have established a multidisciplinary team with the objective of creating a national program of geochemical mapping of soils in Mexico. This is being done as part of the North American Soil Geochemical Landscapes Project in partnership with the US Geological Survey and the Geological Survey of Canada. As the first step, a pilot study was conducted over a transect that extends from the Mexico–US border near Ciudad Juarez in the north to the Pacific Ocean in the south. This pilot transect was conducted in two phases, and this paper presents results from the first phase, which sampled soils at about a 40-km spacing along a 730-km transect beginning in Central Mexico and ending at the Pacific Coast. Samples were collected from the A and C horizons at each site and 60 elements were analyzed. This pilot study demonstrates that geochemical mapping based on a 40-km spacing is adequate to identify broad-scale geochemical patterns. Geologic influence (i.e., soil parent material) was the most important factor influencing the distribution of elements along the transect, followed by the influence of regional mineralization. The study also showed that influence by human activities over the transect is minimal except possibly in large mining districts. A comparison of element abundance in the A horizon with the environmental soil guidelines in Mexico showed that the natural concentrations of the studied soils were lower than the established threshold for soil restoration with the exception of V and As. The former had a median value (75 mg/kg) approximately equal to the value established in Mexico for soil restoration in agricultural and residential lands (78 mg/kg), and the latter had three values higher than the 22 mg/kg threshold for soil restoration in agricultural and residential lands. These cases demonstrate the importance of knowing the national- and regional-scale geochemistry of Mexican soils as a support for the decision-making process, particularly for the proper formulation and application of soil guidelines designed to protect human and ecosystem health.  相似文献   

15.
The Forum of European Geological Surveys (FOREGS) includes representatives from 33 European countries and is responsible for co-ordinating Geological Survey activities in Europe. The FOREGS Geochemistry Task Group was established in 1994 to develop a strategy for the preparation of European geochemical maps following the recommendations of the International Geological Correlation Programme (IGCP) Project 259 ‘International Geochemical Mapping’ (now the International Union of Geological Sciences (IUGS) /International Association of Geochemistry and Cosmochemistry (IAGC) Working Group on Global Geochemical Baselines).The FOREGS geochemistry programme is aimed at preparing a standardised European geochemical baseline to IGCP-259 standards. The principal aims of this dataset will be for environmental purposes, as a baseline for the assessment of the extent and distribution of contaminated land in the context of variations in the natural geochemical background, but it will also have applications in resource assessment and for the development of policy for the sustainable management of metalliferous mineral and other resources.The first phase of the programme was the compilation of an inventory of geochemical data based on the results of a questionnaire completed by Geological Surveys and related organisations throughout the FOREGS community. The results show that the sample types which have been used most extensively are stream sediment (26% coverage), surface water (19% coverage) and soil (11% coverage). Stream sediments have been collected using a narrow range of mesh sizes (< 150–< 200 μm), but soil samples have been collected according to two different conventions: some surveys used a similar mesh size range to that used for stream sediments while others employed the < 1000 or < 2000 μm fractions traditionally used by soil surveys. Sample densities range from 1 sample per 0.5 km2 to 1 per 3500 km2. Various analytical methods have been used, but most of the available data have been calibrated using international reference materials, and data for the most important of the potentially harmful elements (PHEs) are available for most datasets. Systematic radiometric data are available for only a small proportion of Europe, a situation which compares very unfavourably with that in Australia, North America, the former Soviet Union and many developing countries.Recommendations are made for increasing the compatibility of geochemical methods between national geochemical surveys as a basis for the preparation of a series of European geochemical maps. The next stage of the FOREGS Geochemistry Task Group will be the collection of the Global Reference Network of samples against which to standardise national datasets according to the methods recommended in the final report of the IGCP 259 programme.  相似文献   

16.
The Task Group on Global Geochemical Baselines,operating under the auspices of both the International Union of Geological Sciences(IUGS) and the International Association of Geochemistry(IAGC),has the long-term goal of establishing a global geochemical database to document the concentration and distribution of chemical elements in the Earth's surface or near-surface environment.The database and accompanying element distribution maps represent a geochemical baseline against which future human-induced or natural changes to the chemistry of the land surface may be recognized and quantified.In order to accomplish this long-term goal,the activities of the Task Group include:(1) developing partnerships with countries conducting broad-scale geochemical mapping studies;(2) providing consultation and training in the form of workshops and short courses;(3) organizing periodic international symposia to foster communication among the geochemical mapping community;(4) developing criteria for certifying those projects whose data are acceptable in a global geochemical database;(5) acting as a repository for data collected by those projects meeting the criteria for standardization;(6) preparing complete metadata for the certified projects;and(7) preparing,ultimately,a global geochemical database.This paper summarizes the history and accomplishments of the Task Group since its first predecessor project was established in 1988.  相似文献   

17.
Although the term ‘geochemical baseline’ appears in the international geochemical mapping programmes IGCP 259 and 360, it has never been well defined. Several considerations relevant to such a definition are discussed. A geochemical baseline for an element refers to its natural variations in concentration in the surficial environment. Geochemical baselines were studied in Finland by comparing results from regional geochemical mapping programmes based on samples of till, clay and organic stream sediment. The geochemical background changes regionally with the basic geology and locally with the type and genesis of the overburden. Baseline concentrations depend on sample material collected, grain size and extraction method. In Finland, concentrations of potentially harmful elements tend to be higher in fine-grained marine and lacustrine sediments than in glacial till. Concentrations are also systematically higher in the < 0.06 mm fraction than in the < 2 mm size fraction of till samples. Only small proportions of the total heavy metal concentrations in Finnish marine clays are bioavailable. Geochemical baselines are needed for environmental legislation and political decision-making, especially in the assessment of contaminated soil. In many areas of Finland, natural concentrations of several heavy metals exceed the guide or limit values designated for contaminated soils. Thus baselines must always be verified in any assessment of sites for contamination.  相似文献   

18.
《Applied Geochemistry》2005,20(10):1857-1874
The authors investigated statistical distributions for concentrations of chemical elements from the National Geochemical Survey (NGS) database of the U.S. Geological Survey. At the time of this study, the NGS data set encompasses 48,544 stream sediment and soil samples from the conterminous United States analyzed by ICP-AES following a 4-acid near-total digestion. This report includes 27 elements: Al, Ca, Fe, K, Mg, Na, P, Ti, Ba, Ce, Co, Cr, Cu, Ga, La, Li, Mn, Nb, Nd, Ni, Pb, Sc, Sr, Th, V, Y and Zn. The goal and challenge for the statistical overview was to delineate chemical distributions in a complex, heterogeneous data set spanning a large geographic range (the conterminous United States), and many different geological provinces and rock types. After declustering to create a uniform spatial sample distribution with 16,511 samples, histograms and quantile–quantile (Q–Q) plots were employed to delineate subpopulations that have coherent chemical and mineral affinities.Probability groupings are discerned by changes in slope (kinks) on the plots. Major rock-forming elements, e.g., Al, Ca, K and Na, tend to display linear segments on normal Q–Q plots. These segments can commonly be linked to petrologic or mineralogical associations. For example, linear segments on K and Na plots reflect dilution of clay minerals by quartz sand (low in K and Na). Minor and trace element relationships are best displayed on lognormal Q–Q plots. These sensitively reflect discrete relationships in subpopulations within the wide range of the data. For example, small but distinctly log-linear subpopulations for Pb, Cu, Zn and Ag are interpreted to represent ore-grade enrichment of naturally occurring minerals such as sulfides.None of the 27 chemical elements could pass the test for either normal or lognormal distribution on the declustered data set. Part of the reasons relate to the presence of mixtures of subpopulations and outliers. Random samples of the data set with successively smaller numbers of data points showed that few elements passed standard statistical tests for normality or log-normality until sample size decreased to a few hundred data points. Large sample size enhances the power of statistical tests, and leads to rejection of most statistical hypotheses for real data sets. For large sample sizes (e.g., n > 1000), graphical methods such as histogram, stem-and-leaf, and probability plots are recommended for rough judgement of probability distribution if needed.  相似文献   

19.
During 1984 and 1985, the Geological Survey of Finland carried out regional geochemical mapping of till, at a scale of 1:2,000,000, as part of a programme to produce data for the first Geochemical Atlas of Finland. The Atlas is designed to give comprehensive background information on the distribution of elements in rocks, soils, and the surficial environment.  相似文献   

20.
美国矿床环境研究动态及建议   总被引：7，自引：0，他引：7  
通过收集美国地质调查局近几年公开出版物及其网站上发布的资料,总结了美国在环境矿床学研究方面的最新成果,内容涉及32种矿床的地质—环境模型、矿床的环境地球化学背景或基准值、流域性矿床—环境综合研究和特殊矿床的环境效应等方面。结合美国的研究成果和我国国情,建议我国地质调查局现阶段在该领域研究首先集中在矿床的地质—环境模型和用于战略性资源评价中的矿床环境评价指标等战略性研究上。  相似文献   

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