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1.
Plant species that accumulate high levels of metals in proportion to the metal content in the soil are of considerable interest in biogeochemical and biogeobotanical prospecting. This study was aimed at investigating copper and nickel accumulation in the plants Helichrysum candolleanum and Blepharis diversispina, to assess their potential use as mineral indicators in biogeochemical prospecting. Soils and plants were collected from copper–nickel mineralised areas in Botswana. Analyses of the soils and the respective plant parts (roots, stem, leaves and flowers) were carried out using ultrasonic slurry sampling electrothermal atomic absorption spectrometry (ETAAS), which allowed rapid determination of copper and nickel in small amounts of the samples.The metal concentration in the soil was in the range ≈ 40 μg/g–4% (w/w) for Cu and ≈ 60 μg/g–0.3% (w/w) for Ni. The concentration ranges of the elements in the plant parts were ≈ 6 μg/g–0.2% Cu and ≈ 3–210 μg/g Ni. At high soil metal content (greater than 2.5% (w/w) Cu and 0.1% (w/w) Ni), high levels of both nickel and copper were found in the shoots (leaves and flowers) of H. candolleanum. Concentrations as high as 0.2% (w/w) Cu were found in the leaves and flowers of H. candolleanum, indicating hyperaccumulation for this plant. For B. diversispina, the metal concentrations did not exceed 100 μg/g for any plant part, for both metals. Both plant species tolerate high concentrations of metals and should therefore be categorized as metallophytes. In order to evaluate metal translocation from the soil to the shoots, metal leaf transfer coefficients (ratio of metal concentration in the leaf to metal concentration in the soil) were calculated. Our data suggest that the two plant species have different metal uptake and transport mechanisms, which needs to be investigated further. The present work also suggests that H. candolleanum may be used as a copper/nickel indicator plant in biogeochemical or biogeobotanical prospecting.  相似文献   

2.
A herbarium collection of plants from Obi Island (North Moluccas) was analyzed for nickel and other elements in order to identify new hyperaccumulators (> 1000 μg/g dry weight) which are indicative of ultrabasic substrates. Ultrabasic substrates are usually hosts for important economic minerals. Planchonella oxyedra Dubard and Trichospermum kjellbergii Burret were found to be hyperaccumulators of nickel and the work was therefore followed up by analysis of further specimens of these two species from localities throughout their range in Southeast Asia and Oceania. The data pinpointed previously known ultrabasic areas in Sulawesi (Celebes) and West Irian (Indonesian New Guinea) as well as one in Ambon (South Moluccas) which is not recorded on geological maps.  相似文献   

3.
The focal point of this report is a bibliography of 133 references and an associated topic index — both of which could be useful to geochemists attempting to locate new Au deposits. Fifty of these references originated in the Soviet Union, where most of the initial work on biogeochemical exploration for Au had been done. The 15 topics in the index range from agriculture (Au in crop plants) to silver.As an introduction to the bibliography, we have briefly described some examples of applications and difficulties in using plants. These examples are drawn from the literature and from field experience. Because of the generally low Au concentrations found in plants, the analysis of plant tissue is critical to the successful application of the biogeochemical method of prospecting. Neuron activation analysis is the most widely used method to detect Au in plants, due largely to its sensitivity; levels in the parts per billion range are easily attained. Two general types of sampling media are used in prospecting for Au: humus and living plants. Humus has been widely used in Canada, but the sampling of plants has increased there and elsewhere in recent years. Our use of douglas-fir (Pseudotsuga menziesii) at a Au-bearing stockwork in Idaho is a prime example. A maximum Au concentration of 14 μg/g (ppm) was detected in the wood ash of this coniferous tree, well above the normal concentration of ≈ 0.15 μg/g. Among shrubs that might be useful in Au prospecting, we recommend sagebrush or wormwood (genus Artemisia), because it is extremely responsive to concealed mineralization. It has been used extensively in the Soviet Union and could be used in areas of the western United States where disseminated Au occurrences might be located.Among the problems one may encounter in using plants for Au prospecting are: (1) physiological barriers, by which many plant species simply do not absorb Au at detectable levels; (2) misconceptions of soil-plant correlations; (3) localization of Au in plant tissue; and (4) the variation of Au concentrations due to season. Despite these limitations, biogeochemical techniques can complement or replace other geochemical methods currently used.  相似文献   

4.
The Okchon black shale in Korea provides a typical example of natural geological materials enriched with potentially toxic elements. The Chung-Joo, Duk-Pyung, Geum-Kwan, I-Won, Bo-Eun and Chu-Bu areas are underlain by these black shales and slates of the Guryongsan Formation or the Changri Formation, which are parts of the Okchon Group in the central part of the southern Korean Peninsula. In order to investigate the enrichment levels and dispersion patterns of potentially toxic elements in the rock–soil–plant system, environmental geochemical surveys were undertaken in the above six study areas in the Okchon Zone. After appropriate preparation, rock and soil samples were analyzed for potentially toxic elements by instrumental neutron activation analysis (INAA) and inductively coupled plasma atomic emission spectrometry (ICP-AES), and plant samples by atomic absorption spectrometry (AAS). In particular, Ba, Cd, Mo, V and U in Okchon black shales are highly enriched, and their mean concentrations are significantly higher than those in black slates. These elements are geochemically associated, and might be enriched simultaneously. The highest mean concentrations of 42.0 μg g−1 As, 2100 μg g−1 Ba, 10.9 μg g−1 Cd, 213 μg g−1 Mo, 83 μg g−1 U, 938 μg g−1 V and 394 μg g−1 Zn are found in black shales from the Duk-Pyung area. Mean concentrations of As, Mo and U in soils overlying black shales occurring in the Duk-Pyung area (30 μg g−1 As, 24 μg g−1 Mo and 50 μg g−1 U) and Chu-Bu area (39 μg g−1 As, 15 μg g−1 Mo and 27 μg g−1 U) are higher than the permissible level. Enrichment index values of the six study areas decrease in the order of Duk-Pyung > Chu-Bu > Bo-Eun > Chung-Joo > Geum-Kwan = I-Won areas. Relationships between trace element concentrations in soils and plants are significantly correlated, and the biological absorption coefficients (BAC) in plants are in the order of Cd > Zn = Cu > Pb, which suggests that Cd is more bioavailable to plants than the other elements. Cadmium concentrations in plant species decrease in the order of chinese cabbage > red pepper > soybean = sesame > rice stalk > corn > rice grain. From the result of sequential extraction analysis of soils, relatively high proportions of Cu, Pb and Zn are present as residual fractions, and that of Cd as non-residual fractions. Cadmium occurs predominantly as exchangeable/water-acid soluble phase in soils, and this is in agreement with the findings of high Cd concentrations in plants.  相似文献   

5.
This contribution is a short history of the Zambian copper flower, Becium homblei (recently renamed B. centraliafricanum that has attracted attention as a plant associated with Cu-rich soils. It has a peculiar discontinuous distribution in Central Africa which has been explained in terms of biotype depletion. A field investigation into the ecology of the species shows that it is able to tolerate soil Cu concentrations of up to 15,000 μg/g (ppm), and soil nickel concentrations of nearly 5000 μg/g. B. homblei is also found on areas where soil metals are in trace quantities, and where soil bases, particularly Ca, are low. In spite of its tolerance to a wide range of edaphic conditions, the distribution of the species is very restricted in Zimbabwe, and this is almost certainly due to severe interspecific competition with a closely related species, B. obovatum, which is common on soils not unusually enriched in heavy metals. Pioneering work on geobotanical prospecting by use of Becium homblei was carried out by the late G. Woodward and others in the 1950s and 1960s. This species was used successfully for geobotanical prospecting for Cu. This present report is a brief history of these pioneering studies  相似文献   

6.
An orientation survey was conducted over the Quartz Mountain, Oregon, hot-spring type disseminated gold deposit to address three questions critical to successful exploration of the area: What is the relationship between bedrock geology and the trace-element content of trees and soils; do these relationships change seasonally; are these relationships similar in the two tree species which discontinuously blanket the area?Twig, needle and wood samples were collected four times during the year from both ponderosa pine (Pinus ponderosa) and white fir (Abies concolor). Soils were collected once. All samples were analyzed for Au and As and the wood samples were analyzed also for Sb.Arsenic was the best pathfinder element, having little analytical, spatial, or seasonal variation in the twig and needle samples. Anomalous levels were 150 μg/g (ppm) As in pine and 30 μg/g in fir. Gold showed analytical variation of 20–30%, sample duplicate variation up to 90%, spatial changes, and seasonal variation ranging from winter-summer background [10–20 ng/g (ppb) Au] to anomalies of 300–400 ng/g (ppb) Au in pine and 100 μg/g (ppb) Au in fir in the spring and fall. Antimony could not be completely evaluated as a pathfinder element because it was only determined in wood samples.Needles and twigs from both species proved to be viable sample media for exploration of the area. Wood was not a suitable medium because of low, erratic values, perhaps due in part to analytical technique. Needles had 2 to 20 times higher As concentrations than did twigs. Twigs had a slightly higher Au content [25 ng/g (ppb)] than did needles. The pine samples were higher in both elements than were the fir samples. The data, normalized by species, could be treated as one homogeneous data base.The soil Au and As data outlined the mineralization clearly with a central Au anomaly [100 ng/g (ppb) and greater] surrounded by As anomalies [100 μg/g (ppm) and greater] over a distance of 594 m. Neither spring nor fall tree Au anomalies were coincident with the soil Au anomaly. Consistent throughout the year, tree As anomalies coincided with the soil As anomalies, but covered a smaller area. Both the Au and As anomalies in trees appeared to be related to bedrock contact zones rather than to the soil the trees were growing in.  相似文献   

7.
The triterpenol geochemistry of the Santa Monica Basin from the Southern California Borderland, off the U.S.A., is described from the study of two sets of trap deployments, five box cores (≈30 cm) and a hydroplastic core (≈1 m). The biogenic sources and diagenetic stability of the triterpenols are discussed.The 17β(H), 21β(H)-hopanols (22R isomer) occur in the carbon number range from 30 to 32 and their abundance is nearly uniform in the shallow sediment sections. However, the three hopanols follow the order of abundance, C32 > C31 C30, in deeper sections. Their concentrations spans from trace levels to 156 μg/g organic carbon (<15 ng to 7 μg/g dry sediment). Tetrahymanol (gammaceran-3β-ol) has been identified in all the samples except in one set of trap particles collected at 100 m water depth, from trace level (<1 μg) to 215 μg/g organic carbon (<20 ng to 9 μg/g dry sediment). Diplopterol is also detected in trace amounts in some samples. The triterpenols in the trap material generally increase with the water column depth and decrease with the subbottom depth in the sediment cores.The extended hopanols are either degradation products of polyhydroxybacteriohopanes or are biosynthesized by bacteria. Tetrahymanol is probably the only suggested biological precursor of gammacerane (the reduced counterpart of tetrahymanol), which has been recognized in numerous crude oils and lithified sediments. Although it has been reported earlier from Green River Shale and from a residual Pleistocene lake sediment, tetrahymanol has so far been positively identified from recent marine sediments only in two recent studies. The decreasing content of tetrahymanol in sedimentary depth profiles in the Santa Monica Basin would favor an origin for this compound in the water column or at the sediment surface. The ubiquitous occurrence of this compound throughout the study area suggests that this triterpenol most probably originates from primitive organisms (protozoa, bacteria?), hitherto not identified or, more likely, not yet analyzed for their lipid composition.  相似文献   

8.
Data are presented on rare-earth elements (REE) in prefiltered (<450 nm) near-surface and deeper groundwaters and in corresponding particulate matter (>450 nm) from the Osamu Utsumi uranium mine and the Morro do Ferro thorium-REE-deposit. Groundwaters from both sites typically contain between 1–50 μg/l of total REE, but can reach values of up to 160 μg/l in the deepest borehole F4 (U-Mine: 150–415 m). Even higher REE concentrations of up to 29 mg/l were measured in acidic, sulfate-rich near-surface waters of the same site. The chondrite-normalized REE patterns in deeper, more reducing groundwaters and in their corresponding suspended particle fractions are similar to those observed in the bedrock (phonolites), indicating that bedrock leaching and secondary mineral sorption occurred without significant fractionation between these elements, in accordance with the only small variations in the stability constants of the expected REE-sulfate complexes in these waters. Groundwaters from the unsaturated zone of both sites show a very characteristic cerium depletion (less pronounced than that observed in the corresponding suspended particulate fractions), which is most probably related to the oxidation of Ce (III) under the prevailing Eh-conditions of these waters (600 to 800 mV), and to sorption/precipitation reactions of the much less soluble Ce(IV) species. Coarse particulate matter (>450 nm), composed mainly of amorphous ferric hydrous oxides, has a strong capacity for sorption of REE. This is shown by its very high REE concentrations, in some boreholes > 8,000 μg/g (total REE), and by the calculated association ratios Ra (ml/g), which are in the order of 105 to 106. The implications of these findings for the migration behavior of REE in both environments are discussed.  相似文献   

9.
In the Pine Creek Geosyncline, fast moving, annually recharged, low-salinity ground waters dissolve uranium- and magnesium-enriched gangue minerals from mineralized aquifer rocks. The level of dissolved uranium depends on prevailing pH, Eh, salinity and degree of adsorption, which limits its effectiveness as an exploration indicator. Near each known deposit, leaching of magnesium-enriched gangue minerals produces ground waters with very similar major-element concentration plots, the shape of which constitutes a mineralized aquifer “signature”. Gangue minerals also supply high levels of Mg2+ (expressed as NMg = [Mg2+]/[Ca2+ + Mg2+ + Na+ + K+] in milliequivalents per litre) to contained ground waters, NMg > 0.8 being common in ground waters from mineralized aquifers at each Pine Creek Geosyncline deposit. Data from Ranger One No. 3 ore body illustrates how progressive mixing of waters from mineralized and unmineralized aquifers causes graded reductions in NMg, which, when plotted onto a ground plan, delineate a hydrogeochemical aureole.High NMg (> 0.8) coincides with high uranium concentration (> 20 μg/l of U) in ground waters near Nabarlek and Ranger. Because pH-Eh conditions in aquifers at Jabiluka depress uranium solution, < 10 μg/l of U is present, although NMg values are generally > 0.8. To date NMg has always been < 0.8 in nonmineralized aquifer waters, whereas uranium may be > 50 μg/l in ground waters from felsic igneous aquifers, which can be identified as uneconomic by low (< 0.4) NMg, and by a fixed relationship between uranium and co-leached species such as F- and soluble salts.Measurements of pH, Eh, salinity, Fe(II), Ca, Mg, Na, K, Cl, SO4, total carbonate, phosphate, F-, Cu, Pb, Zn and U in waters from 48 percussion holes in and near the Koongarra ore bodies have been related to mineralogy recorded in drill logs. The composition of waters from 20 holes near and along strike from known mineralization, fitted the mineralized aquifer “signature”, had NMg > 0.8 and uranium up to 4100 μ/l. These data confirm the use in this region of NMg as a hydrogeochemical indicator of uranium mineralization; they also indicate additional zones of possible mineralization.  相似文献   

10.
Summary of biogeochemical prospecting for mercury mineralization in the Pinchi Fault is given. One thousand two hundred and eight plant samples were collected and analyzed for mercury. In mineralized areas the typical mercury content of dried plants was not less than 0.2 and 0.4 μg/g and even concentrations between 0.6 and 1.6 μg/g were observed. In nonmineralized zones at least 90% of the plants contained no more than 0.15 μg/g of mercury. Analytical and sampling procedures are described.  相似文献   

11.
Arkosic sandstones and conglomerates of Tertiary age beneath the Challis Volcanics of Eocene age at Basin Creek, 10 km northeast of Stanley, Idaho, contain uranium-bearing vitrainized carbon fragments. The economic potential of these sandstones and conglomerates is currently being assessed. Springs abound at the contacts of rock units, and water from these springs supports abundant growths of bryophytes (mosses and liverworts). Water from 22 springs and associated bryophytes were sampled; two springs were found to contain apparently anomalous concentrations (normalized) of uranium — as much as 6.5 μg/L (ppb) in water and 1800 μg/g (ppm) in ash of mosses. Moss samples from both springs also contained anomalous concentrations of arsenic, and one contained highly anomalous amounts of beryllium. Water from a third spring contained slightly anomalous amounts of uranium, and two species of mosses at the spring contained anomalous uranium (400 and 700 μg/g) and high levels of both cadmium and lead. Water from a fourth spring was normal for uranium (0.18 μg/L), but the moss from the water contained a moderate uranium level and highly anomalous concentrations of lead, germanium, and thallium.These results suggest that, in the Basin Creek area, moss sampling at springs may give a more reliable indication of uranium occurrence than would water sampling. The reason for this may be the ability of mosses to concentrate uranium and its associated pathfinder elements and to integrate uranium fluctuations that occur in the spring water over any period of time.  相似文献   

12.
The Cr and Ni contents are high in the Eocene lignite of the Shenbei coalfield, which is a small intracontinental basin located in Liaoning Province, China. In this paper, we studied the distribution, origin and occurrence of Cr, Ni and other hazardous trace elements in the Shenbei lignite on the basis of coal petrology, and geochemistry of the lignite and combustion products. The following conclusions on the Shenbei lignite can be drawn: (1) The dominant maceral group in the Shenbei coal is huminite (humodetrinite), accounting for 96%–99% of the total maceral. Inertinite content is less than 1%. Liptinite content (sporinite and cutinite) is 0.2–1.6%. Common minerals in the Shenbei lignite include clay minerals (kaolinite), pyrite and quartz, and calcite and siderite. Chromite is not present in the lignite. (2) Potentially hazardous trace elements such as Co (22 μg/g), Cr (79 μg/g), Cu (63 μg/g), Zn (93 μg/g), V (88 μg/g) and Ni (75 μg/g) are strongly enriched in the Shenbei lignite compared with average concentration of trace elements in the Chinese coal and worldwide lignite. These elements are mainly associated with fulvic acid (FA) and/or coal organic macromolecular compounds in most of the studied lignite samples, indicating an organic association and enrichment of these elements in the Shenbei lignite. (3) Unusually high trace elements contents in the Shenbei lignite are derived mainly from the olivine basalt (country rock of coal basin) that consists of 52.7% plagioclase, 17.8% pyroxene, 14% olivine and 15.5% Ti–Fe oxide minerals. These olivine basalts have higher Cr, Ni, Pb and Zn contents than other types of rock and worldwide basalts do. (4) Fly ash of the Shenbei lignite, with 90% 1–50 μm amorphous particles and 8% 1–10 μm cenosphere, has high contents of Zn (23,707 μg/g), Be (12 μg/g), Sr (1574 μg/g), Pb (486 μg/g) and Cr (349 μg/g). In particular, the ferruginous micro-cenoshperes contain 1–12.79% Zn. Fine bottom ash (<0.031mm) of the Shenbei lignite has higher contents for most of the elements with the exception of Mo, Sn and Zn. Therefore, the potentially environmental and health impact of the fly ash and fine bottom ash should constitute a major concern.  相似文献   

13.
This paper discusses the mineralogy and geochemistry of the No. 6 Coal (Pennsylvanian) in the Junger Coalfield, Ordos Basin, China. The results show that the vitrinite reflectance (0.58%) is lowest and the proportions of inertinite and liptinite (37.4% and 7.1%, respectively) in the No. 6 Coal of the Junger Coalfield are highest among all of the Late Paleozoic coals in the Ordos Basin. The No. 6 Coal may be divided vertically into four sections based on their mineral compositions and elemental concentrations. A high boehmite content (mean 6.1%) was identified in the No. 6 Coal. The minerals associated with the boehmite in the coal include goyazite, rutile, zircon, and Pb-bearing minerals (galena, clausthalite, and selenio-galena). The boehmite is derived from weathered and oxidized bauxite in the weathered crust of the underlying Benxi Formation (Pennsylvanian). A high Pb-bearing mineral content of samples ZG6-2 and ZG6-3 is likely of hydrothermal origin. The No. 6 coal is enriched in Ga (44.8 μg/g), Se (8.2 μg/g), Sr (423 μg/g), Zr (234 μg/g), REEs (193.3 μg/g), Hg (0.35 μg/g), Pb (35.7 μg/g), and Th (17.8 μg/g). Gallium and Th in the No. 6 Coal mainly occur in boehmite, and the Pb-bearing selenide and sulfide minerals contribute not only to Se and Pb contents in the coal, but also probably to Hg content. A high Zr content is attributed to the presence of zircon, and Sr is related to goyazite. The REEs in the coal are supplied from the sediment-source region, and the REEs leached from the adjacent partings by groundwater.  相似文献   

14.
In order to study the first steps of incorporation of lipids in recent organic-rich sediments into free and bound fractions, we have selected the Santa Barbara Basin, off California. This basin with a maximum of 590 m water depth is characterized by high phytoplankton production in surface waters and a low oxygen content in bottom waters. Sediments show the following features: high sedimentation rate ≈ 4 mm/yr, no bioturbation, and development of a bacterial mat community at the surface with predominance of sulphur-oxidizing bacteria trapping particles, thus preventing re-distribution of sediment, which permit a unique observations of organic sedimentation on a new few years basis.A sediment core has been divided into 2 cm thick slices corresponding to a time resolution of ≈5 years, from 1835 up to 1987. Samples have been analyzed using a multi-parameter approach, such as for plankton species identification, carbon stable isotope ratios and, as reported here, for lipid organic tracers. Organic tracers have been analyzed in the sterol and fatty series for both free and bound compounds by gas chromatography and gas chromatography/mass spectrometry.The incorporation processes of sterols with depth appear different for free and bound compounds. Total free sterol concentrations show high values in surface sediments (≈ 100 μg/g dry sediment), rapidly decrease up to ≈ 10 cm depth and remain at a constant value of 30–40 μg/g. Total bound sterol concentrations show low values in surface sediment (13.6 μg/g), and vary irregularly with depth up to a value of 55 μg/g at 7.3 m, and then remain constant at 25–26 μg/g.Profiles of evolution with depth of free C27, C28 sterols show a regular decrease, whereas C29 sterols show an irregular decrease with anomalies at 7.3 cm (approximately age: 1977–1978) and at 14.1 cm (1962–1964). Profiles of bound compounds are rather different, very regular for C28 sterols, irregular with oscillations for C27 and C29 sterols at 7.3, 12.2 and 18.0 cm (1954–1956), suggesting a different mode of incorporation and probably different inputs for C27, C29 and C28 sterols.The study of the kinetics of degradation of sterols between surface (1987) and 10.5 cm (1968–1972) shows that C27 compounds are degraded at a slight higher rate (0.53 μg/μg of initial C27 concentration/ year) than are C28 and C29 compounds (0.047 μg/μg of initial concentration/year). An intermediate value is found for brassicasterol: 0.049 μg/μg/year.  相似文献   

15.
This paper describes the influence of siliceous and iron-rich calcic low-temperature hydrothermal fluids (LTHF) on the mineralogy and geochemistry of the Late Permian No. 11 Coal (anthracitic, Rr=2.85%) in the Dafang Coalfield in northwestern Guizhou Province, China. The No. 11 Coal has high contents of vein ankerite (10.2 vol.%) and vein quartz (11.4 vol.%), with formation temperatures of 85 and 180 °C, respectively, indicating that vein ankerite and vein quartz were derived from low-temperature calcic and siliceous hydrothermal fluids in two epigenetic episodes. The vein quartz appears to have formed earlier than vein ankerite did, and at least three distinct stages of ankerite formation with different Ca/Sr and Fe/Mn ratios were observed.The two types of mineral veins are sources of different suites of major and trace metals. Scanning electron microscope and sequential extraction studies show that, in addition to Fe, Mg, and Ca, vein ankerite is the dominant source of Mn, Cu, Ni, Pb, and Zn in the coal, and the contents of these five elements are as high as 0.09% and 74.0, 33.6, 185, and 289 μg/g, respectively. In contrast, vein quartz is the main carrier mineral for platinum-group elements (PGEs) Pd, Pt, and Ir in the coal, and the contents of Pd, Pt, and Ir are 1.57, 0.15, and 0.007 μg/g, respectively. Sequential extraction showed a high PGE content in the silicate fraction, up to 10.4 μg/g Pd, 1.23 μg/g Pt, and 0.05 μg/g Ir, respectively. It is concluded that the formation of ankerite and quartz and the anomalous enrichment of trace elements in the No. 11 Coal in the Dafang Coalfield, Guizhou, result from the influx of calcic and siliceous low-temperature hydrothermal fluids.  相似文献   

16.
Concentrations of Au, Ag, As, Cd and Sb in aquatic bryophytes collected from the Dolgellau Mineral Belt, North Wales, U.K. are reported. One aquatic liverwort, Scapania undulata (L) Dum. and two mosses, Fontinalis squamosa Hedw. and Racomitrium aciculare (Hedw.) Brid. were collected from sites upstream and downstream of the recently reopened Gwynfyndd Au mine. There was little inter-species variation in metal contents for these three bryophytes, but Scapania undulata appeared the most sensitive to changes in water concentrations of Ag, As and Sb. Gold concentrations varied little between the contaminated and control sites. Concentrations in the range < 4–18 ng Aug g−1 D.W. were typical background levels, while bryophytes collected immediately below the mine contained 6–45 ng Au g−1. Silver and Sb both showed more pronounced ( 5–10 fold) elevations above control concentrations in samples collected downstream of the mine. Background concentrations for these elements were 5–85 ng Ag g−1 and 0.15–1.3 μg Sb g−1.Arsenic concentrations downstream of the mine (160–1080 μg g−1) greatly exceeded the background range of 9–32 μg g−1. It is suggested, therefore, that As may be an ideal ‘pathfinder’ element when prospecting for auriferous deposits using aquatic bryophytes.  相似文献   

17.
The amount of Cu and Fe associated with humic acids was estimated in five sediment cores from a tropical coastal lagoon (Piratininga Lagoon, Rio de Janeiro, Brazil). Core samples were analysed for humic acid contents, total Fe and Cu content. Fe and Cu associated with humic acids were also measured. Results show amounts of humic acids ranging from 0.7 to 21.7% of the dry weight of sediment (average 4.6%, standard deviation 4.4%). Concentrations of Fe and Cu ranged from 0.3 to 6.0% (average 2.2%, S.D. 1.2%) and from <1.0 to 65.0 μg g−1 (average 28.6 μg g−1, S.D. 16.4 μg g−1), respectively. The results of strongly bound metals show that while humic acids are the main carrier for Cu, Fe does not seems to be significantly associated with this organic matter.  相似文献   

18.
High groundwater As concentrations in oxidizing systems are generally associated with As adsorption onto hydrous metal (Al, Fe or Mn) oxides and mobilization with increased pH. The objective of this study was to evaluate the distribution, sources and mobilization mechanisms of As in the Southern High Plains (SHP) aquifer, Texas, relative to those in other semiarid, oxidizing systems. Elevated groundwater As levels are widespread in the southern part of the SHP (SHP-S) aquifer, with 47% of wells exceeding the current EPA maximum contaminant level (MCL) of 10 μg/L (range 0.3–164 μg/L), whereas As levels are much lower in the north (SHP-N: 9%  As MCL of 10 μg/L; range 0.2–43 μg/L). The sharp contrast in As levels between the north and south coincides with a change in total dissolved solids (TDS) from 395 mg/L (median north) to 885 mg/L (median south). Arsenic is present as arsenate (As V) in this oxidizing system and is correlated with groundwater TDS (Spearman’s ρ = 0.57). The most likely current source of As is sorbed As onto hydrous metal oxides based on correlations between As and other oxyanion-forming elements (V, ρ = 0.88; Se, ρ = 0.54; B, ρ = 0.51 and Mo, ρ = 0.46). This source is similar to that in other oxidizing systems and constitutes a secondary source; the most likely primary source being volcanic ashes in the SHP aquifer or original source rocks in the Rockies, based on co-occurrence of As and F (ρ = 0.56), oxyanion-forming elements and SiO2 (ρ = 0.41), which are found in volcanic ashes. High groundwater As concentrations in some semiarid oxidizing systems are related to high evaporation. Although correlation of As with TDS in the SHP aquifer may suggest evaporative concentration, unenriched stable isotopes (δ2H: −65 to −27; δ18O: −9.1 to −4.2) in the SHP aquifer do not support evaporation. High TDS in the SHP aquifer is most likely related to upward movement of saline water from the underlying Triassic Dockum aquifer. Mobilization of As in other semiarid oxidizing systems is caused by increased pH; however, pH in the SHP aquifer is near neutral (10–90 percentiles, 7.0–7.6). Although many processes, such as competitive desorption with SiO2, VO4, or PO4, could be responsible for local mobilization of As in the SHP aquifer, the most plausible explanation for the regional As distribution and correlation with TDS is the counterion effect caused by a change from Ca- to Na-rich, water as shown by the high correlation between As and Na/(Ca)0.5 ratios (ρ = 0.57). This change in chemistry is related to mixing with saline water that moves upward from the underlying Dockum aquifer. This counterion effect may mobilize other anions and oxyanion-forming elements that are correlated with As (F, V, Se, B, Mo and SiO2). Competition among the oxyanions for sorption sites may enhance As mobilization. The SHP case study has similar As sources to those of other semiarid, oxidizing systems (original volcanic ash source followed by sorption onto hydrous metal oxides) but contrasts with these systems by showing lack of evaporative concentration and pH mobilization of As but counterion mobilization of As instead in the SHP-S aquifer.  相似文献   

19.
The potential for using groundwater helium surveys in exploration has been evaluated by conducting local and regional surveys in several mineralized and background areas in Australia. Dissolved helium contents decrease markedly upwards, particularly in the top 10–15m, due to degassing in attaining dynamic equilibrium with the atmosphere. Gradients of depth profiles are not uniform but because total concentration variations to 50m or more are commonly less than 10, whereas regional variations are 103–105, samples from the greatest constant depth possible below water-table are adequate for survey purposes. Helium concentrations in excess of the atmosphere equilibrium value of 0.044 μl He/l H2O were found to be associated with uranium mineralization at Honeymoon (6.9–44.4 μl/l), Manyingee (0.08–1.68 μl/l), Bennett Well (9.9–29.5 μ/l) and the Stuart Shelf—Roxby Downs (910–2495 μl/l), with a carbonatite at Mt. Weld (0.18–13.6 μl/l), and with kimberlites at Wandagee (0.2–3.25 μl/l). No anomaly was associated with the shallow calcrete uranium deposit at Yeelirrie. However, equivalent or higher concentrations were found in groundwaters from unmineralized areas around these deposits, e.g. up to 85 μl/l at Manyingee—Bennett Well, to 215 μl/l at Yeelirrie and to 1525 μl/l, Stuart Shelf—Mt. Gunson. Similarly, helium in waters from stock wells near Mt. Weld appears to indicate the presence of the carbonatite but in a survey of a geologically similar area near Malcolm, equivalent anomalies were not related to carbonatite.Although the uranium (and thorium) mineralization is a significant source, high helium concentrations can arise by accumulation in groundwaters with long residence times and by leakage from deep sources, particularly granitoid basement. The concentration reached is also a function of the porosity and configuration of the aquifer and the permeability of the aquiclude to helium. These factors are more important in determining dissolved helium concentrations than the uranium and thorium contents of the rocks. However, the effects are not readily quantifiable, particularly in exploration areas where geology and hydrology are relatively unknown, hence helium groundwater data can be difficult if not impossible to interpret.  相似文献   

20.
This paper describes the influence of volcanic ash on the concentrations and occurrences of associated elements in coal in the Zhijin Coalfield in western Guizhou Province, China. Our studies reveal that the No. 9 coal seam in the Zhijin Coalfield has very high content of Fe (4.34%), Cu (369.90 μg/g), U (49.6 μg/g), Mo (63.10 μg/g), Zn (33.97 μg/g), and Zr (841.80 μg/g). The studies have also found that elements, such as Fe and Cu, do not occur as sulfides in this coal seam, in sharp contrast to many other coal seams in China. The geochemical and mineralogical anomalies of the coal seam are attributed to synsedimentary volcanic ash. In addition to normal macerals and minerals in coal, a volcanic-influenced material (VIM) derived from volcanic ash, detrital material of terrigenous origin and organic matter was identified under polarized-light reflectance microscopy and scanning electron microscopy equipped with energy-dispersive X-ray (EDX) analyzer. The volcanic-influenced material is the main carrier of the above elements in this coal. Six types of the volcanic-influenced material (VIM-1, VIM-2, VIM-3, VIM-4, VIM-5, and VIM-6) are further distinguished on the basis of their structures and compositions. To the best of our knowledge, this is the first report that presents a detailed classification of coal components with a high content of volcanic ash.  相似文献   

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