排序方式： 共有15条查询结果，搜索用时 31 毫秒
1.
Heavy metal retention in secondary precipitates from a mine rock dump and underlying soil, Dalarna, Sweden 总被引：7，自引：2，他引：7
This study investigates the retention of heavy metals in secondary precipitates from a sulfidic mine rock dump and underlying
podzolic soils by means of mineralogical and chemical extraction methods. The rock dump, which is at least 50 years old, consists
of a 5–10-cm-thick leached zone and an underlying 110–115-cm-thick accumulation zone. Optical microscopy and electron microprobe
analyses confirm that pyrrhotite weathering has proceeded much further in the leached horizon relative to the accumulation
horizon. The weathering of sulfides in the leached zone has resulted in the migration of most heavy metals to the accumulation
zone or underlying soils, where they are retained in more stable phases such as secondary ferric minerals, including goethite
and jarosite. Some metals are temporarily retained in hydrated ferrous sulfates (e.g., melanterite, rozenite).
Received: 28 October 1996 · Accepted: 24 February 1997 相似文献
2.
Je-Hun Jang Ryan Mathur Laura J. Liermann Shane Ruebush Susan L. Brantley 《Chemical Geology》2008,250(1-4):40-48
We measured the Fe isotope fractionation during the reactions of Fe(II) with goethite in the presence and absence of a strong Fe(III) chelator (desferrioxamine mesylate, DFAM). All experiments were completed in an O2-free glove box. The concentrations of aqueous Fe(II) ([Fe(II)aq]) decreased below the initial total dissolved Fe concentrations ([Fe(II)total], 2.15 mM) due to fast adsorption within 0.2 day. The concentration of adsorbed Fe(II) ([Fe(II)ads]) was determined as the difference between [Fe(II)aq] and the concentration of extracted Fe(II) in 0.5 M HCl ([Fe(II)extr]) (i.e., [Fe(II)ads] = [Fe(II)extr] − [Fe(II)aq]). [Fe(II)ads] also decreased with time in experiments with and without DFAM, documenting that fast adsorption was accompanied by a second, slower reaction. Interestingly, [Fe(II)extr] was always smaller than [Fe(II)total], indicating that some Fe(II) was sequestered into a pool that is not HCl-extractable. The difference was attributed to Fe(II) incorporated into goethite structure (i.e., [Fe(II)inc] = [Fe(II)total] −[Fe(II)extr]). More Fe(II) was incorporated in the presence of DFAM than in its absence at all time steps. Regardless of the presence of DFAM, both aqueous and extracted Fe(II) (δ56/54Fe(II)aq and δ56/54Fe(II)extr) became isotopically lighter than or similar to goethite (− 0.27‰) at day 7, implying that the isotope exchange occurred between bulk goethite and aqueous Fe. Consistently, the mass balance indicated that the incorporated Fe is isotopically heavier than extracted Fe. These observations suggested that (i) co-adsorption of Fe(II) with DFAM resulted in more pervasive electron transfer, (ii) the electron transfer from heavy Fe(II) in the adsorbed Fe(II) to light Fe(III) in goethite results in the fixation of heavy adsorbed Fe(III) on the surface and accumulation of Fe(II) within the goethite, and (iii) desorption of the reduced, light Fe from goethite does not necessarily occur at the same surface sites where adsorption occurred. 相似文献
3.
A study of the pattern of dissolution of synthetic and natural Fe oxides in 6 M HCl indicates that the rate of element release from synthetic Fe oxides is strongly influenced by mineralogy and the level of element incorporation. Synthetic maghemite (γ-Fe2O3) samples are subject to much more rapid dissolution than goethite (FeOOH) and hematite (α-Fe2O3). In samples dominated by hematite and maghemite, Cu, Zn and particularly Pb, in comparison to Fe, are preferentially released during the early stages of dissolution. Similar patterns are apparent from the dissolution of hematite- and maghemite-dominated samples derived from natural gossan. Comparison of XRD scans with data from the dissolution of natural gossan samples transformed by incremental heating to hematite- and maghemite-dominated assemblages suggests that the degree of crystallinity may also be a significant factor in the release of elements incorporated in the Fe oxides. Ferruginous materials made up of varying proportions of goethite, hematite, maghemite, kaolinite and quartz are important sampling materials in a range of regolith environments. These are products of complex chemical and mechanical mobilization over long periods of geological time. If the patterns of Fe oxide dissolution in 6 M HCl and the release of incorporated metals reflect stability in such weathering regimes, knowledge of the retention characteristics of incorporated metals in different Fe oxide phases, as indicated by this study, will be useful in the planning and interpretation of geochemical surveys in such regions. 相似文献
4.
Impact of AMD on water quality in critical watershed in the Hudson River drainage basin: Phillips Mine,Hudson Highlands,New York 总被引：1，自引：0，他引：1
Sivajini Gilchrist Alexander Gates Zoltan Szabo Paul J. Lamothe 《Environmental Geology》2009,57(2):397-409
A sulfur and trace element enriched U–Th-laced tailings pile at the abandoned Phillips Mine in Garrison, New York, releases
acid mine drainage (AMD, generally pH < 3, minimum pH 1.78) into the first-order Copper Mine Brook (CMB) that drains into
the Hudson River. The pyrrhotite-rich Phillips Mine is located in the Highlands region, a critical water source for the New
York metro area. A conceptual model for derivation/dissolution, sequestration, transport and dilution of contaminants is proposed.
The acidic water interacts with the tailings, leaching and dissolving the trace metals. AMD evaporation during dry periods
concentrates solid phase trace metals and sulfate, forming melanterite (FeSO4·7H2O) on sulfide-rich tailings surfaces. Wet periods dissolve these concentrates/precipitates, releasing stored acidity and trace
metals into the CMB. Sediments along CMB are enriched in iron hydroxides which act as sinks for metals, indicating progressive
sequestration that correlates with dilution and sharp rise in pH when mine water mixes with tributaries. Seasonal variations
in metal concentrations were partly attributable to dissolution of the efflorescent salts with their sorbed metals and additional
metals from surging acidic seepage induced by precipitation. 相似文献
5.
T. S. Berquó R. A. L. Imbernon A. Blot D. R. Franco M. C. M. Toledo C. S. M. Partiti 《Physics and Chemistry of Minerals》2007,34(5):287-294
In this work a magnetic characterization was made of natural goethite from Burkina Faso, Africa, by using low temperature magnetization curves, hysteresis loops, Mössbauer spectroscopy at room temperature and 4.2 K, and AC susceptibility from 10 to 400 K. The samples are from two distinct geological sites that underwent different weathering processes. All measurements point to the occurrence of typical high coercivity goethite. Through Mössbauer spectroscopy sample BL44, from Gangaol, northeast Burkina Faso showed relaxation effects due to a wide distribution of grain size, including superparamagnetism threshold. AC susceptibility also supports this interpretation. The sample BL50 from Bonga in Burkina Faso is associated with lateritic Ni and in addition to goethite this sample also contained magnetite, as determined by Verwey transition in low temperature measurements as well as a small content of hematite identified by Mössbauer spectroscopy. 相似文献
6.
7.
8.
The yield stress and zeta potential (ζ) of slurries prepared from as-received goethite were evaluated as a function of pH, solids concentration, cationic polyethylenimine (PEI) concentration and molecular weight (Mw). The goethite slurries displayed a maximum yield stress at the isoelectric point (pI). These slurries do not have a low pH dispersed region. The yield stress obeyed the yield stress–DLVO force model. The maximum yield stress displayed a dependence on the solids volume fraction to a power of 3.8.PEI adsorbed and changed both the surface chemistry and rheological yield stress of the slurries. At most additive concentration ranging from 0.1 to 0.4dwb% for PEI of Mw 600, 1800 and 70,000, the maximum yield stress of the slurries is larger than that with no adsorbed additives. At low PEI concentration of 0.1dwb%, the same maximum yield stress of 30 Pa was obtained for three Mws; 600, 1800 and 70,000 representing a 1.5-fold increase. The increased attraction between particles was attributed to charge patch attraction at low surface coverages and hydrogen bonding at high coverages. Adsorbed PEI decreased the yield stress at low pH. However complete dispersion was observed only for 0.4dwb% PEI with Mw 70,000, at pH below 7. Complete dispersion was not observed at high pH for the same polymer at all concentrations. 相似文献
9.
Bolar earths deposits from Mt Amiata (Central Italy) consist of nanosized pseudo-spherical goethite, with average crystal
size of 10–15 nm (as determined by X-ray powder diffraction and transmission electron microscopy observations), possibly associated
to amorphous silica and minor sheet silicates, quartz and feldspars. Chemical analyses revealed high As contents (up to 7.4 wt%
As2O5), thus indicating the occurrence of a potentially dangerous contaminant. Arsenic doesn’t occur as a specific As phase, but
it is strictly associated with goethite nanocrystals. Eh and pH measurements suggest that As occurs as arsenate anions (H2AsO4− and HAsO42−), which are easily and strongly adsorbed to goethite surfaces. The high specific surface area, resulting from goethite nanosize,
and the absence of competitive anions explain the extremely efficient adsorption of arsenate and the anomalously high As content
in bolar earths. Overall physical/chemical data suggest stable arsenate adsorption, with very limited risk for As release
to the environment. 相似文献
10.
Oxygen isotopes of goethite from ferricrete deposits were measured from both northern and southern Rocky Mountain localities to assess geographic variability in regional Holocene paleoclimate change. A ∼3.7‰ increase in oxygen isotope values of 14C-dated goethites in the northern Rocky Mountains suggests a regional-scale relative increase in amounts of isotopically heavy summer precipitation since the early Holocene. In contrast, oxygen isotope values from the southern Rocky Mountains increase abruptly ∼2.1‰ at ∼6200 14C yr B.P., then decrease ∼2.4‰ between ∼2000 14C yr B.P. and the present. We interpret this period of relatively high δ18O values as evidence for a middle Holocene warm period combined with a relatively strong summer monsoon. These variable climate records suggest that the Rocky Mountains of the western United States have had a spatially heterogeneous Holocene climate history. 相似文献