共查询到20条相似文献，搜索用时 15 毫秒
1.
Priscu JC Adams EE Lyons WB Voytek MA Mogk DW Brown RL McKay CP Takacs CD Welch KA Wolf CF Kirshtein JD Avci R 《Science (New York, N.Y.)》1999,286(5447):2141-2144
Data from ice 3590 meters below Vostok Station indicate that the ice was accreted from liquid water associated with Lake Vostok. Microbes were observed at concentrations ranging from 2.8 x 10(3) to 3.6 x 10(4) cells per milliliter; no biological incorporation of selected organic substrates or bicarbonate was detected. Bacterial 16S ribosomal DNA genes revealed low diversity in the gene population. The phylotypes were closely related to extant members of the alpha- and beta-Proteobacteria and the Actinomycetes. Extrapolation of the data from accretion ice to Lake Vostok implies that Lake Vostok may support a microbial population, despite more than 10(6) years of isolation from the atmosphere. 相似文献
2.
Jouzel J Petit JR Souchez R Barkov NI Lipenkov VY Raynaud D Stievenard M Vassiliev NI Verbeke V Vimeux F 《Science (New York, N.Y.)》1999,286(5447):2138-2141
Isotope studies show that the Vostok ice core consists of ice refrozen from Lake Vostok water, from 3539 meters below the surface of the Antarctic ice sheet to its bottom at about 3750 meters. Additional evidence comes from the total gas content, crystal size, and electrical conductivity of the ice. The Vostok site is a likely place for water freezing at the lake-ice interface, because this interface occurs at a higher level here than anywhere else above the lake. Isotopic data suggest that subglacial Lake Vostok is an open system with an efficient circulation of water that was formed during periods that were slightly warmer than those of the past 420,000 years. Lake ice recovered by deep drilling is of interest for preliminary investigations of lake chemistry and bedrock properties and for the search for indigenous lake microorganisms. This latter aspect is of potential importance for the exploration of icy planets and moons. 相似文献
3.
The reactions of dinitrogen pentoxide (N(2)O(5)) with H(2)O and hydrochloric acid (HCl) were studied on ice surfaces in a Knudsen cell flow reactor. The N(2)O(5) reacted on ice at 185 K to form condensed-phase nitric acid (HNO(3)). This reaction may provide a sink for odd nitrogen (NO(x)) during the polar winter, a requirement in nearly all models of Antarctic ozone depletion. A lower limit to the sticking coefficient, gamma, for N(2)O(5) on ice is 1 x 10(-3). Moreover, N(2)O(5) reacted on HCl-ice surfaces at 185 K, with gamma greater than 3 x 10(-3). This reaction, which produced gaseous nitryl chloride (ClNO(2)) and condensed-phase HNO(3), proceeded until all of the HCl within the ice was depleted. The ClNO(2), which did not react or condense on ice at 185 K, can be readily photolyzed in the Antarctic spring to form atomic chlorine for catalytic ozone destruction cycles. The other photolysis product, gaseous nitrogen dioxide (NO(2)), may be important in the partitioning of NO(x) between gaseous and condensed phases in the Antarctic winter. 相似文献
4.
S Baumgartner J Beer J Masarik G Wagner L Meynadier H Synal 《Science (New York, N.Y.)》1998,279(5355):1330-1332
Geomagnetic field strength is expected to affect the production rate of cosmogenic isotopes such as beryllium-10, carbon-14, or chlorine-36. Chlorine-36 data from the Greenland Ice Core Project (GRIP) ice core agree well with a production rate calculation based on a paleomagnetic reconstruction for the past 100,000 years over both long- and short-term variations. A chlorine-36 peak at 38,000 years ago previously found in the beryllium-10 record from the Vostok ice core can be explained by a period of low geomagnetic field intensity. 相似文献
5.
Shackleton NJ 《Science (New York, N.Y.)》2000,289(5486):1897-1902
The deep-sea sediment oxygen isotopic composition (delta(18)O) record is dominated by a 100,000-year cyclicity that is universally interpreted as the main ice-age rhythm. Here, the ice volume component of this delta(18)O signal was extracted by using the record of delta(18)O in atmospheric oxygen trapped in Antarctic ice at Vostok, precisely orbitally tuned. The benthic marine delta(18)O record is heavily contaminated by the effect of deep-water temperature variability, but by using the Vostok record, the delta(18)O signals of ice volume, deep-water temperature, and additional processes affecting air delta(18)O (that is, a varying Dole effect) were separated. At the 100,000-year period, atmospheric carbon dioxide, Vostok air temperature, and deep-water temperature are in phase with orbital eccentricity, whereas ice volume lags these three variables. Hence, the 100,000-year cycle does not arise from ice sheet dynamics; instead, it is probably the response of the global carbon cycle that generates the eccentricity signal by causing changes in atmospheric carbon dioxide concentration. 相似文献
6.
RP Scherer A Aldahan S Tulaczyk G Possnert H Engelhardt B Kamb 《Science (New York, N.Y.)》1998,281(5373):82-85
Some glacial sediment samples recovered from beneath the West Antarctic ice sheet at ice stream B contain Quaternary diatoms and up to 10(8) atoms of beryllium-10 per gram. Other samples contain no Quaternary diatoms and only background levels of beryllium-10 (less than 10(6) atoms per gram). The occurrence of young diatoms and high concentrations of beryllium-10 beneath grounded ice indicates that the Ross Embayment was an open marine environment after a late Pleistocene collapse of the marine ice sheet. 相似文献
7.
Spahni R Chappellaz J Stocker TF Loulergue L Hausammann G Kawamura K Flückiger J Schwander J Raynaud D Masson-Delmotte V Jouzel J 《Science (New York, N.Y.)》2005,310(5752):1317-1321
The European Project for Ice Coring in Antarctica Dome C ice core enables us to extend existing records of atmospheric methane (CH4) and nitrous oxide (N2O) back to 650,000 years before the present. A combined record of CH4 measured along the Dome C and the Vostok ice cores demonstrates, within the resolution of our measurements, that preindustrial concentrations over Antarctica have not exceeded 773 +/- 15 ppbv (parts per billion by volume) during the past 650,000 years. Before 420,000 years ago, when interglacials were cooler, maximum CH4 concentrations were only about 600 ppbv, similar to lower Holocene values. In contrast, the N2O record shows maximum concentrations of 278 +/- 7 ppbv, slightly higher than early Holocene values. 相似文献
8.
冰封期湖泊水体及冰体内水质发生变化,直接影响水产健康养殖发展。基于2016年1月15日乌梁素海冰封期浮游植物及水质监测结果,分析冰封期湖泊浮游植物物种组成、密度及多样性指数空间动态,利用典范对应分析法(CCA)揭示浮游植物物种与环境因子关系。结果表明,冰下水体共鉴定出浮游植物7门32属37种,浮游植物群落组成呈硅藻—绿藻型;冰体中共检出7门34属60种,浮游植物群落组成以硅藻为主。冰体中Margalef丰富度指数(D)、Shannon-Wiener多样性指数(H)、Pielou均匀度指数(J)变化趋势一致。3种指数综合显示乌梁素海冰封期浮游植物群落结构相对稳定。水体共发现优势种10种,冰体中优势种共14种。CCA排序显示,TP为影响乌梁素海冰下水体浮游植物群落分布最重要环境因子。冰层中NH4+、TP、TN等环境因子复杂分布对浮游植物群落在冰层中分布影响较大。研究结果为开展寒旱区冰封期水体及冰体中水质与浮游植物群落特征关系方面研究奠定基础。 相似文献
9.
灰色聚类法评价淀山湖水质状况 总被引：1，自引：0，他引：1
2004年逐月在淀山湖6个站点进行水质参数测定。水质参数在各站点的月平均变化范围为DO7．210～9．943（mg／L）、BOD53．810～4．940（mg／L）、CODMn6．016～7．053（mg／L）、TP0．137～0．366（mg／L）、NH3．N2．176～3．362（mg／L）、Chl．a29．814～56．02（mg/m^3）。对各站点2004年水质参数的月平均测定结果应用灰色聚类方法进行富营养化程度和水环境质量等级评价，结果显示：调查的六个站点全部处于富营养化水平；六个站点的水质全部处于V类水等级。在灰色聚类法评价水质过程中，权系数最大的是氮、磷及叶绿素a。因此，在淀山湖人工栽植水草进行脱氮除磷、放养滤食性鱼类抑制藻类大量繁殖是改善淀山湖水质的有效途径。 相似文献
10.
灰色聚类法评价淀山湖水质状况 总被引：9，自引：2，他引：9
2004年逐月在淀山湖6个站点进行水质参数测定。水质参数在各站点的月平均变化范围为DO7．210～9．943（mg／L）、BOD53．810～4．940（mg／L）、CODMn6．016～7．053（mg／L）、TP0．137～0．366（mg／L）、NH3．N2．176～3．362（mg／L）、Chl．a29．814～56．02（mg/m^3）。对各站点2004年水质参数的月平均测定结果应用灰色聚类方法进行富营养化程度和水环境质量等级评价，结果显示：调查的六个站点全部处于富营养化水平；六个站点的水质全部处于V类水等级。在灰色聚类法评价水质过程中，权系数最大的是氮、磷及叶绿素a。因此，在淀山湖人工栽植水草进行脱氮除磷、放养滤食性鱼类抑制藻类大量繁殖是改善淀山湖水质的有效途径。 相似文献
11.
The oxygen-18/oxygen-16 ratio of molecular oxygen trapped in ice cores provides a time-stratigraphic marker for transferring the absolute chronology for the Greenland Ice Sheet Project (GISP) II ice core to the Vostok and Byrd ice cores in Antarctica. Comparison of the climate records from these cores suggests that, near the beginning of the last deglaciation, warming in Antarctica began approximately 3000 years before the onset of the warm B?lling period in Greenland. Atmospheric carbon dioxide and methane concentrations began to rise 2000 to 3000 years before the warming began in Greenland and must have contributed to deglaciation and warming of temperate and boreal regions in the Northern Hemisphere. 相似文献
12.
以内蒙古乌梁素海为研究对象,对其在冰封过程中富营养化指标在冰体和水体中的浓度及分布特征及其在乌梁素海的空间变异性进行分析,得出冰封期乌梁素海富营养化状况。其中,乌梁素海水体中的富营养化指标含量均大于对应的冰体中的含量,主要指标COD、总氮、总磷在水体中的含量均值分别是冰体中含量均值的1.65、1.61和1.78倍;水体中的营养盐变异性明显小于冰体中的。说明低温冷冻过程对水体中污染物有一定浓缩效应,并对此进行了解释,以期为乌梁素海富营养化治理提出研究方向。 相似文献
13.
Esposito LW Colwell JE Larsen K McClintock WE Stewart AI Hallett JT Shemansky DE Ajello JM Hansen CJ Hendrix AR West RA Keller HU Korth A Pryor WR Reulke R Yung YL 《Science (New York, N.Y.)》2005,307(5713):1251-1255
Neutral oxygen in the saturnian system shows variability, and the total number of oxygen atoms peaks at 4 x 10(34). Saturn's aurora brightens in response to solar-wind forcing, and the auroral spectrum resembles Jupiter's. Phoebe's surface shows variable water-ice content, and the data indicate it originated in the outer solar system. Saturn's rings also show variable water abundance, with the purest ice in the outermost A ring. This radial variation is consistent with initially pure water ice bombarded by meteors, but smaller radial structures may indicate collisional transport and recent renewal events in the past 10(7) to 10(8) years. 相似文献
14.
Activities of beryllium-10 and aluminum-26 dissolved in 200-year-old Greenland ice were found to be 18.4 (+ 8.4, - 4.8) x 10(-6) and 3.2 +/- 0.9 x 10(-7) disintegration per minute per liter, respectively. From these values and the precipitation rate (30 milliliters of water per square centimeter per year), the production rates of these isotopes are calculated to be 3.6 (+ 1.6, - 0.9) x 10(-2) and 1.7 +/- 0.5 x 10(-4) atom per second * square centimeter. These rates agree with the rates calculated for the production of these isotopes by cosmic rays in the atmosphere. Probably all the Al(26) in the ice is accounted for by such atmospheric production; however, an upper limit for the influx of cosmic dust bearing aluminum-26 is calculated at 3.2 x 10(5) tons per year for Earth. Only upper limits could be found for Al(26) and Be(10) in the undissolved particulate matter in the ice; their addition to the activities in the dissolved material leaves our conclusions unchanged. 相似文献
15.
Price PB 《Science (New York, N.Y.)》1995,267(5205):1802-1804
The depth dependence of bubble concentration at pressures above the transition to the air hydrate phase and the optical scattering length due to bubbles in deep ice at the South Pole are modeled with diffusion-growth data from the laboratory, taking into account the dependence of age and temperature on depth in the ice. The model fits the available data on bubbles in cores from Vostok and Byrd and on scattering length in deep ice at the South Pole. It explains why bubbles and air hydrate crystals coexist in deep ice over a range of depths as great as 800 meters and predicts that at depths below approximately 1400 meters the AMANDA neutrino observatory at the South Pole will operate unimpaired by light scattering from bubbles. 相似文献
16.
Siegenthaler U Stocker TF Monnin E Lüthi D Schwander J Stauffer B Raynaud D Barnola JM Fischer H Masson-Delmotte V Jouzel J 《Science (New York, N.Y.)》2005,310(5752):1313-1317
A record of atmospheric carbon dioxide (CO2) concentrations measured on the EPICA (European Project for Ice Coring in Antarctica) Dome Concordia ice core extends the Vostok CO2 record back to 650,000 years before the present (yr B.P.). Before 430,000 yr B.P., partial pressure of atmospheric CO2 lies within the range of 260 and 180 parts per million by volume. This range is almost 30% smaller than that of the last four glacial cycles; however, the apparent sensitivity between deuterium and CO2 remains stable throughout the six glacial cycles, suggesting that the relationship between CO2 and Antarctic climate remained rather constant over this interval. 相似文献
17.
A continuous record of oxygen-18 (delta(18)O) variations in the continental hydrosphere during the middle-to-late Pleistocene has been obtained from a uranium-series dated calcitic vein in the southern Great Basin. The vein was deposited from ground water that moved through Devils Hole-an open fault zone at Ash Meadows, Nevada-between 50 and 310 ka (thousand years ago). The configuration of the delta(18)O versus time curve closely resembles the marine and Antarctic ice core (Vostok) delta(18)O curves; however, the U-Th dates indicate that the last interglacial stage (marine oxygen isotope stage 5) began before 147 +/- 3 ka, at least 17,000 years earlier than indicated by the marine delta(18)O record and 7,000 years earlier than indicated by the less well dated Antarctic delta(18)O record. This discrepancy and other differences in the timing of key climatic events suggest that the indirectly dated marine delta(18)O chronology may need revision and that orbital forcing may not be the principal cause of the Pleistocene ice ages. 相似文献
18.
The terrestrial ages of three Allan Hills meteorites are between 3 x 10(4) and 3 x 10(5) years and one is (1.54(-0.28)(+0.14)) x 10(6) years old. The Antarctic ice sheet is therefore older than (1.54(-0.28)(+0.14)) x 10(6) years and the meteorite accumulation process at Allan Hills probably began between 3 x 10(4) and 3 x 10(5)years ago. 相似文献
19.
滇池水体氮的时空变化与藻类生长的关系 总被引：4，自引：0，他引：4
水体氮的时空变化及其与藻类生长的关系对研究水体富营养化具有十分重要的作用。采用GPS定位,对滇池海埂、斗南、罗家村、新街、昆阳5个代表性位点断面水体总氮、铵态氮、硝态氮及叶绿素a含量进行了为期1a的监测和动态研究,全面分析了不同区域、不同层次、不同时期滇池水体各形态氮的时空变化特征及其对藻类生长的影响。结果表明,全湖各采样点水体总氮、铵态氮、硝态氮的平均浓度分别是2.14、0.11、0.20mg·L-1,全年分别在0.66～6.44mg·L-1、0～0.74mg·L-1、0～0.94mg·L-1之间变化。各区域水体总氮的浓度以海埂和斗南最高,铵态氮和硝态氮的变化幅度较大。全湖水体总氮和铵态氮与叶绿素a呈显著正相关,硝态氮与叶绿素a呈负相关趋势;滇池不同区域水体总氮与叶绿素a呈显著正相关,海埂和罗家村位点水体铵态氮与叶绿素a呈显著正相关,海埂位点水体硝态氮与叶绿素a呈显著负相关,其他区域则无显著相关性;水体总氮、铵态氮、硝态氮对藻类生长的影响呈现显著的区域性和水层差异。 相似文献
20.
Anderson JD Johnson TV Schubert G Asmar S Jacobson RA Johnston D Lau EL Lewis G Moore WB Taylor A Thomas PC Weinwurm G 《Science (New York, N.Y.)》2005,308(5726):1291-1293
Radio Doppler data from the Galileo spacecraft's encounter with Amalthea, one of Jupiter's small inner moons, on 5 November 2002 yield a mass of (2.08 +/- 0.15) x 10(18) kilograms. Images of Amalthea from two Voyager spacecraft in 1979 and Galileo imaging between November 1996 and June 1997 yield a volume of (2.43 +/- 0.22) x 10(6) cubic kilometers. The satellite thus has a density of 857 +/- 99 kilograms per cubic meter. We suggest that Amalthea is porous and composed of water ice, as well as rocky material, and thus formed in a cold region of the solar system, possibly not at its present location near Jupiter. 相似文献