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281.
Speciation and colloid transport of arsenic from mine tailings 总被引:2,自引:0,他引:2
In addition to affecting biogeochemical transformations, the speciation of As also influences its transport from tailings at inoperative mines. The speciation of As in tailings from the Sulfur Bank Mercury Mine site in Clear Lake, California (USA) (a hot-spring Hg deposit) and particles mobilized from these tailings have been examined during laboratory-column experiments. Solutions containing two common, plant-derived organic acids (oxalic and citric acid) were pumped at 13 pore volumes d−1 through 25 by 500 mm columns of calcined Hg ore, analogous to the pedogenesis of tailings. Chemical analysis of column effluent indicated that all of the As mobilized was particulate (1.5 mg, or 6% of the total As in the column through 255 pore volumes of leaching). Arsenic speciation was evaluated using X-ray absorption spectroscopy (XAS), indicating the dominance of arsenate [As(V)] sorbed to poorly crystalline Fe(III)-(hydr)oxides and coprecipitated with jarosite [KFe3(SO4, AsO4)2(OH)6] with no detectable primary or secondary minerals in the tailings and mobilized particles. Sequential chemical extractions (SCE) of <45 μm mine tailings fractions also suggest that As occurs adsorbed to Fe (hydr)oxides (35%) and coprecipitated within poorly crystalline phases (45%). In addition, SCEs suggest that As is associated with 1 N acid-soluble phases such as carbonate minerals (20%) and within crystalline Fe-(hydr)oxides (10%). The finding that As is transported from these mine tailings dominantly as As(V) adsorbed to Fe (hydr)oxides or coprecipitated within hydroxysulfates such as jarosite suggests that As release from soils and sediments contaminated with tailings will be controlled by either organic acid-promoted dissolution or reductive dissolution of host phases. 相似文献
282.
Katy R. Wiest Diane I. Doser Aaron A. Velasco James Zollweg 《Pure and Applied Geophysics》2007,164(10):1905-1919
Over the past ~65 years intraslab earthquakes have caused the most significant damage in the western Washington region. This
study examines regional and teleseismic seismograms for four historic, suspected intraslab events of M > 5.5 occurring within
the Cascadia Subduction zone in 1939 (South Seattle), 1946 (Puget Sound), 1949 (Olympia) and 1965 (Sea-Tac) to better determine
the source locations, mechanisms and rupture histories of these events. Our study is aided by digital seismograms of post-1990
intraslab events with well-determined focal depths and focal mechanisms that were recorded in the same locations as the historic
events. Thus the recent events were used as empirical Greens functions to study the historic events. Our results suggest that
the 1946 earthquake is not an intraslab event, that the 1939 event closely resembles the 1965 event, and that the 1949 event
is similar to the 2001 Nisqually earthquake, although the 1949 event appears to have ruptured toward the south, causing significantly
more damage than the Nisqually event. These results suggest that earthquakes periodically rupture along the same or similarly
oriented faults within the subducting slab. 相似文献
283.
Chuanlun L. Zhang Bruce W. Fouke Aaron D. Peacock Yongsong Huang 《Geochimica et cosmochimica acta》2004,68(15):3157-3169
Lipid biomarkers and 13C fractionation patterns were used to understand the dynamics of carbon cycling during microbial metabolisms in different environments of travertine precipitation (called facies) at Spring AT-1 on Angel Terrace in the Mammoth Hot Springs complex of Yellowstone National Park, USA. Microbial mats that encrust travertine deposits were collected for analyses of lipid biomarkers and carbon isotopes along the continuous drainage outflow system of Spring AT-1. The spring water exhibits a continuous temperature drop from 71°C in the vent at top to 24°C in the distal slope at bottom. Phospholipid fatty acids (PLFA) and glycolipid fatty acids (GLFA) exhibit distinctly different compositions in each of the facies, which are consistent with partitioning of the bacterial 16S rRNA gene sequences in the Spring AT-1 travertine facies (Fouke et al., 2003).The δ13C composition of total biomass within the microbial mats decreases from −16.1‰ in the vent to −23.5‰ in the distal slope. However, lower values occur in the pond (−26.0‰) and the proximal slope (−28.0‰) between the vent and the distal slope. Isotopic compositions of PLFA and GLFA have variations similar to those of total biomass. The average δ13C values of PLFA are −12.4 ± 5.2‰ (n = 10 individual fatty acids, same below) in the vent, −33.0 ± 3.1‰ (n = 11) in the pond, −33.7 ± 3.8‰ (n = 16) in the proximal slope, and −22.4 ± 3.4‰ (n = 10) in the distal slope; the average δ13C values of GLFA are −19.6 ± 3.0‰ (n = 3) in the vent, −30.4 ± 4.7‰ (n = 8) in the pond, −36.9 ± 2.8‰ (n = 12) in the proximal slope, and −27.9 ± 3.1‰ (n = 13) in the distal slope. In particular, fatty acids in the vent are enriched in 13C relative to the total biomass, which is consistent with the notion that the biosynthetic pathways of the extant microbial community in the vent may be dominated by Aquificales using the reversed tricarboxylic acid cycle. Fractionations between fatty acids and total biomass in the pond, the proximal slope and the distal slope suggest the involvement of other biosynthetic pathways for CO2 fixation by extant microbial populations. The results indicate that lipid biomarkers provide valuable information on the changing diversity and activity of microbial communities in different depositional environments. Carbon-isotope fractionations, on the other hand, can provide insight into the operating biosynthetic pathways associated with different organisms in the changing environment. This integrated approach may serve as a powerful tool for identifying functional metabolism within a community and identify shifts in microbial community structure in modern hot-spring systems. 相似文献
284.
J. W. Hannigan M. T. Coffey William G. Mankin Aaron Goldman 《Journal of Atmospheric Chemistry》1998,30(1):103-118
As part of the Second European Stratospheric Arctic and Mid-latitude Experiment (SESAME) field campaign, observations were made during the period from October 1994 to April 1995 at Søndre Strømfjord, Greenland (67°N, 53°W). Using a Fourier transform spectrometer, high resolution (0.06 cm-1) infrared spectra were recorded with the sun as a radiation source. Column amounts of trace gases including HCl, HF, HNO3, N2O and O3 are shown for five time periods during the course of the 1994-95 Arctic winter. Results are compared with lower stratospheric potential vorticity fields to describe variations in trace gas column amounts. 相似文献
285.
Aaron S. Evans 《Astrophysics and Space Science》1999,266(1-2):73-78
HST NICMOS observations of a sample of 24 luminous (LIGs: L
IR[8-1000 m] = 1011.0-11.99 L) and ultraluminous (ULIGs:L
IR 1012.0 L) infrared galaxies are presented.The observations provide, for the first time, high resolution HST imagingof the imbedded 1.1 - 2.2 m nuclear regions of these mergers. Allbut one of the ULIGs are observed to have at least one compact (50-200 pc)nucleus, and more than half contain what appear to be blue star clusters.The warm infrared galaxies (i.e., the transition sources) are observed tohave bright nuclei which account for most of the light of the galaxy.This, combined with the tendency for the light of ULIGs to become morecentrally concentrated as a function of increasing wavelength, impliesthat most of their energy is generated within a region 50-200 pcacross. 相似文献
286.
287.
The three-dimensional geometry of spiral inclusion trails from the Canton Schist were measured to determine whether the spirals were a product of porphyroblast rotation within a shear zone, or porphyroblast growth during a series of overprinting fold events. The spiral inclusion trails are composed of three separate, sub-planar inclusion trail surfaces occupying texturally distinct parts of the porphyroblasts. These surfaces are correlated across a >10 km2 area using textural criteria and relative timing. Measured patterns of inclusion trail orientation and asymmetry suggest they did not form by porphyroblast rotation within a non-coaxial shear zone. Rather, the porphyroblasts grew during three successive overprinting fold events (F2–F4), and the spiral inclusion trails represent the accumulated curvature associated with folding of successive axial plane foliations. The data show that spiral garnets are not peculiar to shear zones, and can form by overprinting crenulations and folds. This is consistent with the common occurrence of spiral garnets in multiply-deformed, regionally metamorphosed fold belts. 相似文献
288.
Irene Schimmelpfennig Joerg M. Schaefer Brent M. Goehring Nathaniel Lifton Aaron E. Putnam David J. A. Barrell 《第四纪科学杂志》2012,27(7):671-674
In situ cosmogenic 14C (in situ 14C) analysis from quartz‐bearing rocks is a novel isotopic tool useful for quantifying recent surface exposure histories (up to ~25 ka). It is particularly powerful when combined with longer‐lived cosmogenic isotopes such as 10Be. Recent advances in the extraction of in situ 14C from quartz now permit the routine application of this method. However, only a few experiments to calibrate the production rate of in situ 14C in quartz have been published to date. Here, we present a new in situ 14C production rate estimate derived from a well‐dated debris flow deposit in the Southern Alps, New Zealand, previously used to calibrate 10Be production rates. For example, based on a geomagnetic implementation of the Lal/Stone scaling scheme we derive a spallogenic production rate of 11.4 ± 0.9 atoms 14C (g quartz)?1 a?1 and a 14C/10Be spallogenic production rate ratio of 3.0 ± 0.2. The results are comparable with production rates from previous calibrations in the northern hemisphere. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
289.
Nancy W. Hinman J. Michelle Kotler Beizhan Yan Aaron Tenesch Richard V. Morris Andrew Tveter Daphne L. Stoner Jill R. Scott 《Applied Geochemistry》2009
The purposes of this study were to (i) document chemical and mineralogical compositions in two naturally acidic drainages over a 1 m soil profile, (ii) document organic and inorganic signatures representative of past chemical or biological processes in the soils, and (iii) determine whether mineralogical and chemical differences are a consequence of differences in original composition, depositional conditions, or diagenesis. Two sites were studied: Paymaster Creek in the Heddleston Mining District near Lincoln, Montana and the New World Mining District near Cooke City, Montana. The oldest deposits at both naturally acidic sites pre-date human mining activity by several thousand years, although there is recent human activity at both sites. Both sites have streams with high dissolved Fe and moderately low pH and actively accumulate schwertmannite on streambeds. Soil deposits away from the streambed at Paymaster Creek contained goethite with adsorbed sulfate, but no schwertmannite, suggesting either that the original conditions precluded schwertmannite precipitation or that diagenesis occurred rapidly converting the schwertmannite to goethite. The New World Mining District site showed the expected profile, which is a gradual transition from schwertmannite- and goethite-bearing soils to goethite-only soils. Concentrations of Cr, As and other trace elements shown to retard diagenesis were higher at the New World site than at the Paymaster site. 相似文献
290.
Jamaica Bay, NY, is a highly urbanized estuary within the boroughs of New York City conspicuously lacking published information
on dissolved trace metal concentrations. The current study examines the distribution and cycling of trace metals in that embayment
with data gathered during cruises in November 2004, April 2005, and June 2006. Most of the metal distributions (Fe, Zn, Co,
Ag, Cu, Pb, Ni) in the water column are explained by the input of substantial volumes of treated wastewater effluent. However,
several lines of evidence suggest that submarine groundwater discharge (SGD) is also an important source of dissolved Fe,
Zn, Co, Ni, and isotopically distinct stable Pb ratios (206Pb, 207Pb, 208Pb) in the Bay. Conversely, the recirculated seawater component of SGD is an apparent sink for dissolved Mo. This study provides
the first measurements of dissolved trace metals in the Jamaica Bay water column and subterranean estuary and provides evidence
for trace metal input due to SGD. 相似文献