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Sk. Md. Equeenuddin S. Tripathy P. K. Sahoo M. K. Panigrahi 《Environmental Earth Sciences》2010,60(4):723-731
The deposition of ochreous is common by a consequence of acid mine drainage (AMD). The ochreous precipitated from the AMD
sites around Tertiary coalfield of Assam, India were collected and characterized by X-ray diffractometry (XRD), Fe to S molar
ratio, ammonium oxalate acid (pH 3.0) extraction, fourier-transform infrared spectroscopy (FTIR), field emission scanning
electron microscopy (FESEM), scanning electron microscope (SEM) and transmission electron microscope (TEM). The ochreous mainly
consists of goethite, schwertmannite, ferrihydrite and jarosite. Mineralogy of ochreous was controlled by the pH whereas formation
of ferrihydrite was favored at high organic carbon content. Role of bacteria for the formation of secondary minerals was observed.
Mobility of metals was controlled by the ochreous, and they were also retained during the process of phase transformation
of poorly ordered iron-oxyhydroxysulfates into the stable forms. 相似文献
23.
Arsenic contamination of ground and pond water and water purification system using pond water in Bangladesh 总被引:1,自引:0,他引:1
H. Yokota K. Tanabe M. Sezaki Y. Akiyoshi T. Miyata K. Kawahara S. Tsushima H. Hironaka H. Takafuji M. Rahman Sk. A. Ahmad M. H. S. U. Sayed M. H. Faruquee 《Engineering Geology》2001,60(1-4):323-331
This paper, firstly, shows the distribution of arsenic-contaminated groundwater in Samta village. This village, which is in Jessore district in Bangladesh, was chosen as a model village for investigating the mechanism of groundwater contamination. 90% of the tube wells in this village had arsenic concentrations above the Bangladesh standard of 0.05 mg/l. Tube wells with arsenic concentrations of over 0.50 mg/l were distributed in the southern part of the village with a belt-like shape from east to west. Secondly, groundwater distribution is discussed with respect to its flow and the high arsenic zone (As≥0.50 mg/l) agrees well with the drifting zone of the groundwater. Furthermore, arsenic-free water supply systems suitable for a small area in the village have been developed. A pond sand filter (PSF) system which purifies pond water is discussed in this paper. Prior to the construction of the PSF, the water quality in ponds was examined for arsenic levels. The inflow of drainage from the tube wells was found to be the major cause of arsenic contamination of pond water. The PSF installed in Samta is working very well and produces a good quality of treated water. 相似文献
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Direct 40Ar/39Ar dating of Late Ordovician and Silurian brittle faulting in the southwestern Norwegian Caledonides
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Thomas Scheiber Giulio Viola Camilla Maya Wilkinson Morgan Ganerød Øyvind Skår Deta Gasser 《地学学报》2016,28(5):374-382
Structural data as well as U–Pb zircon and 40Ar/39Ar biotite and muscovite ages were collected from the Rolvsnes granodiorite in western Norway. The granodiorite intruded at c. 466 Ma, cooled quickly and escaped later viscous deformation. Brittle top‐to‐the‐NNW thrust faults (Set I) and WNW–ESE striking dextral strike‐slip faults (Set II) formed in a NNW–SSE transpressional regime. 40Ar/39Ar dating of synkinematic mica from both sets reveals a c. 450 Ma (Late Ordovician) age of faulting, which constrains early‐Caledonian brittle deformation. Set I and II faults are overprinted by a set of lower‐grade, variably oriented chlorite‐ and epidote‐coated faults (Set III) constraining WNW–ESE shortening. A lamprophyric dyke oriented compatibly with this stress field intruded at c. 435 Ma (Silurian), indicating that Set III formed at the onset of the Scandian Baltica–Laurentia collision. The preservation of Caledonian brittle structures indicates that the Rolvsnes granodiorite occupied a high tectonic level throughout the Caledonian orogeny. 相似文献
26.
Jan Valenta Milan Brož Jiří Málek Bedřich Mlčoch Vladislav Rapprich Zuzana Skácelová the Doupov Working Group 《Acta Geophysica》2011,59(3):597-617
The Doupovské Hory Volcanic Complex (DHVC) is the best-preserved large volcanic suite of the Cenozoic intraplate volcanism
in the Bohemian Massif. However, many uncertainties remain in the geological setting of its basement. In summer 2008, two
seismic refraction profiles ran across this area to reveal the depth of the volcanic rocks and the underlying geological structure. 相似文献
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Sudhir Kumar Singh Prosper Basommi Laari Sk. Mustak Prashant K. Srivastava Szilárd Szabó 《国际地球制图》2013,28(11):1202-1222
AbstractAn integrated Markov Chain and Cellular Automata modelling (CA MARKOV), multicriteria evaluation techniques have been applied to produce transition probability. The unsupervised method was employed to classify the satellite images of year 1985, 1995, 2005 and 2015 to meet the magnitude of LULC change. Results showing the spatial pattern of the sub-basin is largely influenced by the biophysical and socio-economic drivers leading to growth of agricultural lands and built-up area in the basin. Simulated plausible future LULC changes for 2025 which is based on a CA MARKOV that integrates Markovian transition probabilities computed from satellite-derived LULC maps and a CA contiguity spatial filter (5 × 5). Further, the fragmentation analysis was performed to check the fragmentation scenario in the year 2025. The result for year 2025 with reasonably good accuracy will be useful to the planners, policy- and decision-makers. 相似文献
29.
Miroslav Novotný Zuzana Skácelová Jan Mrlina Bedřich Mlčoch Bohuslav Růžek 《Surveys in Geophysics》2009,30(6):561-600
The refraction data from the SUDETES 2003 experiment were used for high-resolution tomography along the profile S01. The S01
profile crosses the zone Erbendorf-Vohenstrauss (ZEV) near the KTB site, then follows the SW–NE oriented Eger Rift in the
middle part and continues toward the NE across the Elbe zone and the Sudetic structures as far as the Trans-European Suture
Zone. To get the best resolution in the velocity image only the first arrivals of Pg waves with minimum picking errors were
used. The previous depth-recursive tomographic method, based on Claerbout’s imaging principle, has been adapted to perform
the linearized inversions in iterative mode. This innovative DRTG method (Depth-Recursive Tomography on Grid) uses a regular
system of refraction rays covering uniformly the mapped domain. The DRTG iterations yielded a fine-grid velocity model with
a required level of RMS travel-time fit and the model roughness. The travel-time residuals, assessed at single depth levels,
were used to derive the statistical lateral resolution of “lens-shaped” velocity anomalies. Thus, for the 95% confidence level
and 5% anomalies, one can resolve their lateral sizes from 15 to 40 km at the depths from 0 to 20 km. The DRTG tomography
succeeded in resolving a significant low-velocity zone (LVZ) bound to the Franconian lineament nearby the KTB site. It is
shown that the next optimization of the model best updated during the DRTG iterations tends to a minimum-feature model with
sweeping out any LVZs. The velocities derived by the depth-recursive tomography relate to the horizontal directions of wave
propagation rather than to the vertical. This was proved at the KTB site where pronounced anisotropic behavior of a steeply
tilted metamorphic rock complex of the ZEV unit has been previously determined. Involving a ~7% anisotropy observed for the
“slow” axis of symmetry oriented coincidentally in the horizontal SW–NE direction of the S01 profile, the DRTG velocity model
agrees fairly well with the log velocities at the KTB site. Comparison with the reflectivity map obtained on the reflection
seismic profile KTB8502 confirmed the validity of DRTG velocity model at maximum depths of ~16 km. The DRTG tomography enabled
us to follow the relationship of major geological units of Bohemian Massif as they manifested in the obtained P-wave velocity
image down to 15 km. Although the contact of Saxothuringian and the Teplá-Barrandian Unit (TBU) is collateral with the S01
profile direction, several major tectonic zones are rather perpendicular to the Variscan strike and so fairly imaged in the
S01 cross-section. They exhibit a weak velocity gradient of sub-horizontal directions within the middle crust. In particular,
the Moldanubian and TBU contact beneath the Western Krušné hory/Erzgebirge Pluton, the buried contact of the Lusatia unit
and the TBU within the Elbe fault zone were identified. The maxima on the 6,100 ms−1 isovelocity in the middle crust delimitated the known ultrabasic Erbendorf complex and implied also two next ultrabasic massifs
beneath the Doupovské hory and the České středohoří volcanic complexes. The intermediate mid-crustal P-wave velocity lows
are interpreted as granitic bodies. The presented geological model is suggested in agreement with available gravity, aeromagnetic
and petrophysical data. 相似文献
30.