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A soil and vegetation survey was undertaken in NW Euboea Island, Greece. The objectives of the study were to establish the geochemical baseline of soil and identify the impact of local geology on threshold values of potentially harmful elements. The studied area is characterized by complex geology comprising metamorphic and ultramafic rocks as well as active hot springs. A total of 117 soil samples were collected from 89 sites at depths of 0–25 cm and 25–50 cm. Eighteen vegetation samples were also collected representing prevalent indigenous perennial species in the region. Soil samples from the present study were enriched in As, Ca, Cu, Mg, Ni with concentrations reaching 233 mg/kg, 38%, 336 mg/kg, 10.8%, 1560 mg/kg respectively. Factor analysis revealed three main factors controlling the chemical composition of soil reflecting the influence of ultramafic rocks (Cr, Ca, Mg, Ni), hot spring deposits (Ca, S, Sr, As) and paedogenesis processes (Fe, Co, V, Mn, Al). The first two of these factors showed significant spatial correlation with the geological features within the study area. Subsequently, baseline concentrations based on statistical and spatial data were estimated within sub-areas reflecting the influence of local geology in soil composition. Concentrations of potentially harmful elements in the plant tissues of indigenous perennial vegetation species showed a wide range of variation from below the detection limit up to 1700 mg/kg for Ni in the hyperaccumulator Alyssum chalcidicum demonstrating that plant species have adapted to the stressful conditions caused by high elemental concentrations in soil. The results of this study can be utilized in future studies at areas of similar geology by providing an objective basis for setting realistic threshold values for pollution assessment and remediation. 相似文献
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Michael H. Ramsey Grace Solomon‐Wisdom Ariadne Argyraki 《Geostandards and Geoanalytical Research》2013,37(4):379-391
A general method for the evaluation of in situ heterogeneity of geochemical materials is described and the significance of the results discussed, by using three case studies and earlier data sets. The heterogeneity of Pb in soil (expressed as RSD due to sampling, RSDsamp) varies from < 5 to > 100% between different sites, in a way that relates to the mode of deposition of the element. The heterogeneity of an element also varies systematically as a function of the distance scale at some sites. This variation can be modelled using linear regression, accounting for over 90% of the experimental variance, at seven scales over three orders of magnitude. Variation in heterogeneity between elements at the same site, seems to be somewhat diagnostic of the origin of the element, lithogenic being less than anthropogenic, although the later is also being modified by the mode of deposition. Where the heterogeneity is large (RSD > 30%), it is proposed that it can be expressed more accurately as a heterogeneity factor (10GSDsamp), to reflect its frequency distribution, which is positively skewed towards higher concentration values. 相似文献
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The Lavrion carbonate-hosted Pb-Ag-Zn deposit in southeast Attica, Greece, consisted of significant non-sulfide ore bodies. The polymetallic sulfide mineralization was subjected to supergene oxidation, giving rise to gossan. The principal non-sulfide minerals of past economic importance were smithsonite, goethite and hematite. The supergene mineral assemblages occupy secondary open spaces and occur as replacement pods within marble. Calamine and iron ore mainly filled open fractures. X-ray diffraction and scanning electron microscopy of samples of oxidized ore indicate complex gossan mineralogy depending on the hypogene mineralogy, the degree of oxidation and leaching of elements, and the local hydrologic conditions. Bulk chemical analysis of the samples indicated high ore-grade variability of the supergene mineralization. On multivariate cluster analysis of geochemical data the elements were classified into groups providing evidence for their differential mobilization during dissolution, transport and re-precipitation. The mode of occurrence, textures, mineralogy and geochemistry of the non-sulfide mineralization confirm that it is undoubtedly of supergene origin: the product of influx into open fractures in the country rock of highly acidic, metal-rich water resulting from the oxidation of pyrite-rich sulfide protore. Dissolution of carbonates led to opening of the fractures. Mineral deposition in the supergene ore took place under near-neutral to mildly acidic conditions. The supergene dissolution and re-precipitation of Fe and Zn in the host marble increased metal grades and separated iron and zinc from lead, thereby producing economically attractive deposits; it further contributed to minimization of pollution impact on both soil and ground water. 相似文献
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