排序方式: 共有9条查询结果,搜索用时 15 毫秒
1
1.
E. G. Drozhko Y. U. Glagolenko Y. G. Mokrov G. A. Postovalova L. M. Samsonova A. V. Glagolev S. A. Ter-Saakian M. L. Glinsky N. A. Vasil'kova A. V. Skokov H. A. Wollenberg C.-F. Tsang W. Frangos R. D. Solbau K. A. Stevenson W. M. Lowder M. G. Foley 《Environmental Geology》1997,29(3-4):216-227
In September 1994, a Russian-American team conducted hydrogeological, geochemical, geophysical, and radiometric measurements
in the territory of the Mayak Production Association, Russia. The primary purpose of these operations was to examine the frontal
area of a radioelement- and nitrate-laden groundwater plume moving from the disposal site, Lake Karachai, toward the Mishelyak
River. Activities encompassed (1) isolation of hydrologic intervals in two wells and production of water from these intervals,
to compare isolated versus open-well sampling methods and to determine hydraulic transmissivities of the aquifer(s); (2) surface
and soil-water sampling, accompanying radiometric measurements and subsequent chemical analyses; and (3) electrical resistivity
profiling in areas of expected contrasting resistivity.
Preliminary results indicate that (1) 60Co, 137Cs, and 90Sr are present in small concentrations (∼0.1% of permissible levels) in water of the Mishelyak River; (2) analyses of water
samples collected by a downhole sampler and of water produced from packed-off intervals agree within limits of laboratory
accuracy, attesting to the efficacy of the sampling methods presently used by the Russian workers; (3) considerable differences
in contaminant concentrations exist between nearby wells, supporting the concept that the plume from Lake Karachai toward
the Mishelyak River is controlled by steeply dipping fractures and shear zones; and (4) strong contrasts occur between the
electrical resistivities of soil and bedrock.
Further collaborative work is strongly recommended and should include more detailed isolation of intervals in wells by multi-packer
installations, to better determine the geochemical and hydrological characteristics of the Karachai-Mishelyak system; deployment
of a broader soil water and soil sampling array; a more detailed examination of the distribution and concentration of radionuclides
by high-resolution field gamma spectrometry; and a detailing of the area's electrical resistivity setting, using a mobile
electromagnetic measurement system.
Received: 22 January 1996 · Accepted: 1 April 1996 相似文献
2.
3.
4.
Cornelia MEYER Jörg FRITZ Martin MISGAISKI Dieter STÖFFLER Natalia A. ARTEMIEVA Ulrich HORNEMANN Ralf MOELLER Jean‐Pierre
De VERA Charles COCKELL Gerda HORNECK Sieglinde OTT Elke RABBOW 《Meteoritics & planetary science》2011,46(5):701-718
Abstract– Shock recovery experiments were performed with an explosive set‐up in which three types of microorganisms embedded in various types of host rocks were exposed to strong shock waves with pressure pulse lengths of lower than 0.5 μs: spores of the bacterium Bacillus subtilis, Xanthoria elegans lichens, and cells of the cyanobacterium Chroococcidiopsis sp. 029. In these experiments, three fundamental parameters were systematically varied (1) shock pressures ranging from 5 to 50 GPa, (2) preshock ambient temperature of 293, 233 and 193 K, and (3) the type of host rock, including nonporous igneous rocks (gabbro and dunite as analogs for the Martian shergottites and chassignites, respectively), porous sandstone, rock salt (halite), and a clay‐rich mineral mixture as porous analogs for dry and water‐saturated Martian regolith. The results show that the three parameters have a strong influence on the survival rates of the microorganisms. The most favorable conditions for the impact ejection from Mars for microorganisms would be (1) low porosity host rocks, (2) pressures <10–20 GPa, and (3) low ambient temperature of target rocks during impact. All tested microorganisms were capable of surviving to a certain extent impact ejection in different geological materials under distinct conditions. 相似文献
5.
Younger Dryas in southern South America? 总被引:3,自引:0,他引:3
Two high resolution pollen records, Caunahue from mid-latitudes and Harberton from high latitudes, illustrate the issues in defining the Younger Dryas episode in records from southern South America. At mid-latitudes in the Chilean lake region, previous claims for the existence of a substantially cooler and wetter episode between 11,000 and 10,000 BP can no longer be supported by new pollen records with high temporal and paleoenvironmental resolution, such as Caunahue. The transition from glacial to interglacial conditions occurred in several steps, one shortly after 13,000 BP, when open Nothofagus woodland was replaced by cool-temperate North Patagonian forest, and one at 9,500 BP, when warmtemperate Validivian forest elements replaced the North Patagonian elements. At high latitudes, on the other hand, high resolution records do show marked short-term changes during the late-glacial, inclding the 11,000 to 10,000 BP Interval. However, neither the exact timing nor the duration of these changes is synchronous for specific taxa, neither within one record nor between different records. One of the two intervals of low pollen influx that has been singled out as evidence for a cooler episode is consistently dated between 11,000 and 12,000 BP, while the other interval dates between 10,800 and 9,000 BP. Based on all this information I believe that there is no evidence of Younger Dryas episode for the midlatitudes. For the high latitudes, on the other hand, the overall high paleoenvironmental variability in the records offers multiple choices for a Younger Dryas-type interval if specific taxa are selected without considering the overall context. However, the lack of synchroneity between short-term changes of specific taxa between different records suggests primarily a response to local disturbances, rather than a response to a global forcing. 相似文献
6.
SERBAN Mihaela LI Guo-yu SERBAN Raul-David WANG Fei FEDOROV Alexander VERA Samsonova CAO Ya-peng CHEN Peng-chao WANG Wei 《山地科学学报》2021,(2):323-337
Active layer is a key component for permafrost environment studies as many subsurface biological,biogeochemical,ecological,and pedogenic activities prevail in this layer.This study focuses on active layer temperature monitoring in an area with sporadic permafrost at two adjacent sites along China-Russia Crude Oil Pipeline(CRCOP),NorthEast China.Site T1 is located in disturbed ground on the right-of-way(on-ROW)2 m away from the center of the oil pipeline.T2 is located in a natural and undisturbed site,around 16.6 m off-ROW.Our objective was to study seasonal variability of the active layer depth and thermal regime from October 2017 to September 2018.The monitoring sites consist of soil temperature probes arranged in a vertical array at different depths at both sites.The following parameters were computed:number of isothermal days(ID),freezing days(FD),thawing days(TD),freezing degree days(FDD),thawing degree days(TDD),number of freeze-thaw days(FTD).The mean air temperature in the monitoring period reached-3.2℃.The temperature profile indicates that the maximum active layer thickness observed during the study period was 10 m at T1 and 2 m at T2.The majority of the soil temperatures were above or close to 0℃,resulting in great values of TDD,especially in the first 4 m depth.TDD for T1 were predominant and ranged between 600-1160℃·days(0-4 m depth)reflecting the influence of oil temperature from the pipeline.In T2 borehole FDD were predominant for all the soil layer depths resulting in less permafrost degradation.This comparison emphasizes the significant influence of vegetation removal and the dispersed heat from the pipeline on the active layer thickness. 相似文献
7.
Scott A. SANDFORD Saša BAJT Simon J. CLEMETT George D. CODY George COOPER Bradley T. DEGREGORIO Vanessa
De VERA Jason P. DWORKIN Jamie E. ELSILA George J. FLYNN Daniel P. GLAVIN Antonio LANZIROTTI Thomas LIMERO Mildred P. MARTIN Christopher J. SNEAD Maegan K. SPENCER Thomas STEPHAN Andrew WESTPHAL Sue WIRICK Richard N. ZARE Michael E. ZOLENSKY 《Meteoritics & planetary science》2010,45(3):406-433
Abstract– Numerous potential sources of organic contaminants could have greatly complicated the interpretation of the organic portions of the samples returned from comet 81P/Wild 2 by the Stardust spacecraft. Measures were taken to control and assess potential organic (and other) contaminants during the design, construction, and flight of the spacecraft, and during and after recovery of the sample return capsule. Studies of controls and the returned samples suggest that many of these potential sources did not contribute any significant material to the collectors. In particular, contamination from soils at the recovery site and materials associated with the ablation of the heatshield do not appear to be significant problems. The largest source of concern is associated with the C present in the original aerogel. The relative abundance of this carbon can vary between aerogel tiles and even within individual tiles. This C was fortunately not distributed among a complex mixture of organics, but was instead largely present in a few simple forms (mostly as Si‐CH3 groups). In most cases, the signature of returned cometary organics can be readily distinguished from contaminants through their different compositions, nonterrestrial isotopic ratios, and/or association with other cometary materials. However, some conversion of the carbon indigenous to the flight aerogel appears to have happened during particle impact, and some open issues remain regarding how this C may be processed into new forms during the hypervelocity impact collection of the comet dust. 相似文献
8.
9.
1