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81.
Marina Ulyanova Vadim Sivkov Timur Kanapatskij Nikolay Pimenov 《Geo-Marine Letters》2014,34(2-3):231-240
Expected seasonal variations in methane concentrations and diffusive fluxes from surficial sediments into near-bottom waters were investigated in autumn 2012 and winter 2013 in the Curonian and Vistula lagoons of the Baltic Sea, expanding on earlier findings for summer 2011. Methane concentrations in bottom sediments (upper ca. 2 cm) generally ranged from ca. 1 to 1,000 μmol/dm3, and in near-bottom waters from ca. 0 to 1 μmol/l. Highest concentrations were found in the Curonian Lagoon, plausibly explained by the influence of freshwater conditions and finer-grained, organic-rich sediments. Vistula Lagoon methane concentrations and fluxes are dampened by periodic saline water inflow from the open sea, intensifying sulphate reduction. Calculated diffusive methane fluxes from the upper sediment layer (usually 0–5 cm, i.e. excluding any fluffy layer) into near-bottom waters were highest—2.48 mmol/(m2 day)—in clayey silts of the Curonian Lagoon in autumn (September) 2012, contrasting strongly with the minimum value of 0.002 mmol/(m2 day) observed there in February 2013 under ice-covered conditions. Seasonal and even weekly variations in methane dynamics can be largely explained by two main drivers, i.e. wind and temperature, operating at various spatiotemporal scales via, for example, wind wave-induced resuspension of bottom sediments, and involving regional weather patterns including autumnal low-pressure zones over the Gulf of Gdansk. 相似文献
82.
Ilya V VekslerAlexander M Dorfman Donald B Dingwell Nikolay Zotov 《Geochimica et cosmochimica acta》2002,66(14):2603-2614
The main objectives of this study were to investigate conditions for stable and metastable liquid immiscibility in dry borosilicate synthetic systems and to evaluate effects of temperature and bulk melt composition on two-liquid element partitioning and boron speciation. To distinguish between the stable immiscibility and quench heterogeneity, we used high-temperature centrifuge phase separation. For the case of stable liquid immiscibility, silica-rich (LS) and borate-rich (LB) conjugate liquids formed two distinct layers separated by a sharp meniscus. The liquids were quenched into glasses, which were analysed by electron microprobe. Some of the glasses were also studied by Raman spectroscopy. We used several synthetic mixtures along the danburite-anorthite (CaB2Si2O8-CaAl2Si2O8) and danburite-reedmergnerite (CaB2Si2O8-NaBSi3O8) joins. In addition, we studied four complex, six-component, Mg-bearing compositions with variable Na2O and Al2O3 contents. The experiments show that the width of the LS-LB miscibility gap decreases more rapidly with the B-Al substitution (in the danburite-anorthite join) than with the Ca-Na substitution, implying that interactions between network-forming elements have a greater effect on borate-silicate unmixing than the nature of network-modifying cations. Ca and Mg partition strongly to the depolymerised borate-rich liquid with LB-LS partition coefficients of ∼40 and higher. On the other hand, two-liquid partition coefficients of Na and Al in most cases are close to 1 and show complex variations with temperature and bulk melt composition. Raman spectra of LB glasses quenched at different temperatures suggest that the proportion of trigonal boron in bulk boron content decreases with decreasing temperature. The change in boron speciation appears to affect Al and Na two-liquid partitioning in such a way that at low temperatures, the latter element becomes more compatible with LS. 相似文献
83.
Kristen M. Reifel Scott C. Johnson Paul M. DiGiacomo Michael J. Mengel Nikolay P. Nezlin Jonathan A. Warrick Burton H. Jones 《Continental Shelf Research》2009,29(15):1821-1835
The effects from two winter rain storms on the coastal ocean of the Southern California Bight were examined as part of the Bight ‘03 program during February 2004 and February–March 2005. The impacts of stormwater from fecal indicator bacteria, water column toxicity, and nutrients were evaluated for five major river discharges: the Santa Clara River, Ballona Creek, the San Pedro Shelf (including the Los Angeles, San Gabriel, and Santa Ana Rivers), the San Diego River, and the Tijuana River. Exceedances of bacterial standards were observed in most of the systems. However, the areas of impact were generally spatially limited, and contaminant concentrations decreased below California Ocean Plan standards typically within 2–3 days. The largest bacterial concentrations occurred in the Tijuana River system where exceedances of fecal indicator bacteria were noted well away from the river mouth. Maximum nitrate concentrations (~40 μM) occurred in the San Pedro Shelf region near the mouth of the Los Angeles River. Based on the results of general linear models, individual sources of stormwater differ in both nutrient concentrations and the concentration and composition of fecal indicator bacteria. While nutrients appeared to decrease in plume waters due to simple mixing and dilution, the concentration of fecal indicator bacteria in plumes depends on more than loading and dilution rates. The relationships between contaminants (nutrients and fecal indicator bacteria) and plume indicators (salinity and total suspended solids) were not strong indicating the presence of other potentially important sources and/or sinks of both nutrients and fecal indicator bacteria. California Ocean Plan standards were often exceeded in waters containing greater than 10% stormwater (<28–30 salinity range). The median concentration dropped below the standard in the 32–33 salinity range (1–4% stormwater) for total coliforms and Enterococcus spp. and in the 28–30 salinity range (10–16% stormwater) for fecal coliforms. Nutrients showed a similar pattern with the highest median concentrations in water with greater than 10% stormwater. Relationships between colored dissolved organic matter (CDOM) and salinity and between total suspended solids and beam attenuation indicate that readily measurable, optically active variables can be used as proxies to provide at least a qualitative, if not quantitative, evaluation of the distribution of the dissolved, as well as the particulate, components of stormwater plumes. In this context, both CDOM absorption and the beam attenuation coefficient can be derived from satellite ocean color measurements of inherent optical properties suggesting that remote sensing of ocean color should be useful in mapping the spatial areas and durations of impacts from these contaminants. 相似文献
84.
A. Yu. Guzhikov M. V. Pimenov S. Yu. Malenkina A. G. Manikin S. V. Astarkin 《Stratigraphy and Geological Correlation》2010,18(1):42-62
The Bathonian—Callovian boundary section located near the Prosek Settlement (Nizhni Novgorod region) is described with the
characteristic of its grain-size composition and terrigenous—mineralogical, petromagnetic, and paleomagnetic properties. Based
on lithological—mineralogical and petromagnetic data, the section is subdivided into four members corresponding to the most
significant sedimentation rhythms. No sharp changes in the composition of sediments are noted through the section, which indicates
its relative continuity. Despite the significant re magnetization of these sediments during the Quaternary, the characteristic
component (ChRM) is definable by the method of the intersection of large circles. The similarity between coordinates of the
calculated virtual geomagnetic pole (VGMP) and the positions of standard virtual geomagnetic poles in the stable European
continent during corresponding periods serves as an important argument in favor of the primary nature of the ChRM. The compiled
magnetostratigraphic section is well consistent with the paleomagnetic zonation, established in the coeval sediments of “West
Europe. As compared with the Bathonian—Callovian boundary section in the Albstadt—Pfeffingen of Germany, which claims to the
GSSP role, the Prosek section represents a more favorable object for paleomagnetic studies. Combined with the lack of large-scale
gaps in the sedimentary record and, with other conditions being equal, this makes this section a more preferable candidate
for the Callovian GSSP standard. 相似文献
85.
We have recently announced that the General Catalogue of Variable Stars enters the stage of its fifth, purely electronic edition(GCVS 5.1). We have included 1408 variable stars in the constellation Centaurus in this new version, GCVS 5.1. Working on this revision, we applied current possibilities from data mining, suggested new variability types for many variable stars and found new light elements for a large number of periodic variables. This paper describes the work completed during the preparation of GCVS 5.1 for Centaurus and discusses in detail a number of the most astrophysically significant cases. 相似文献
86.
Bondarenko N. A. Rusanov I. I. Chernitsyna S. M. Shubenkova O. V. Zaharenko A. S. Pogodaeva T. V. Pimenov N. V. Zemskaya T. I. 《Water Resources》2022,49(1):98-108
Water Resources - A study of the structure and production parameters of phytoplankton (biomass, photosynthesis rate, chlorophyll a content, and assimilation numbers) in the coastal and pelagic... 相似文献
87.
88.
Research Note: First results of a low‐altitude unmanned aircraft system gamma survey by comparison with the terrestrial and aerial gamma survey data 下载免费PDF全文
Alexander Parshin Nikolay Grebenkin Vladimir Morozov Fedor Shikаlenko 《Geophysical Prospecting》2018,66(7):1433-1438
In order to increase the efficiency of geological survey in difficult landscape‐morphological conditions, the authors have developed low‐altitude gamma technology surveys based on a multi‐rotor unmanned aircraft system, also known informally as Drones. These results have been compared against those from standard terrestrial and aerial gamma surveys. The successful results obtained at the reference site show that the developed methodology enables compilation of high‐quality data in difficult landscape conditions. These results yield the same level of information content as standard terrestrial gamma surveys. The exact unmanned aircraft system altitude over the earth must be maintained for carrying out high‐quality surveys. It was found that a CsI(Tl) detector with sizes 80 × 80 mm (vol. 0.4 dm3) enables obtaining of high‐quality radiometric data at altitudes of up to 70 m, at a speed of at least 20 km/h. The authors believe that low altitude ‘quasi‐terrestrial’ gamma surveys with a terrain drape may in the future replace terrestrial gamma surveys since they can offer better effectiveness at a lower cost. 相似文献
89.
Nikolay G. Granin Natalia A. Radziminovich Liba Z. Granina Vadim V. Blinov Ruslan Y. Gnatovskiy 《Geo-Marine Letters》2012,32(5-6):453-464
In September 2008, freshening of near-bottom water and an increase in concentration of suspended particles were observed in the western part of southern Lake Baikal. The reduction in the content of total dissolved solids was about 0.4–0.7?mg/kg (0.7?%), and average suspended particle concentration increased strongly to 6–9?mg/l, the background value being 0.2?mg/l. The spatial distribution of these waters was virtually identical to the focal area of the Mw6.2 Kultuk earthquake that occurred on 27 August 2008. It is suggested that there was a causal relationship between these two phenomena. Freshening of a significant amount (about 20?km3) of near-bottom waters was plausibly caused by an input of poorly mineralized pore waters from bottom sediments as a result of dissociation of methane gas hydrates suspected to occur in the area. The energy radiated by the earthquake source was four orders of magnitude smaller than that needed to explain the observed freshening of near-bottom waters. This points to other mechanisms leading to seismic-induced sediment failure and possible subsequent hydrate dissociation in the case of the Kultuk earthquake. 相似文献
90.
Multispectral polarimetry as a tool to investigate texture and chemistry of lunar regolith particles
Yuriy Shkuratov Nikolay Opanasenko Yevgen Grynko Viktor Korokhin Gorden Videen Urs Mall 《Icarus》2007,187(2):406-416
We report results of telescope polarimetric imaging of the Moon with a CCD LineScan Camera at large phase angles, near 88°. This allows measurements of the polarization degree with an absolute accuracy better than 0.3% and detection of features with polarization contrast as small as 0.1%. The measurements are carried out in two spectral bands centered near 0.65 and 0.42 μm. We suggest characterizing the lunar regolith with the parameter a(Pmax)A, where Pmax,A, and a are the degree of maximum polarization, albedo, and the parameter describing the linear regression of the correlation Pmax-A. The parameter bears significant information on the particle characteristic size and packing density of the lunar regolith. We also suggest characterizing the lunar regolith with color-ratio images obtained with a polarization filter at large phase angles. We here consider the color-ratios C||(0.65/0.42 μm) and C⊥(0.65/0.42 μm). Using light scattering model calculations we show that the color-ratio images obtained with a polarization filter at large phase angles suggest a new tool to study the lunar surface. In particular, it turns out that the color-ratios C||(0.65/0.42 μm) and C⊥(0.65/0.42 μm) are sensitive to somewhat different thicknesses of the surfaces of regolith particles. We consider the applicability of the Hubble Space Telescope, the Very Large Telescope (ESO), and a spacecraft on a lunar polar orbit for polarimetric observations of the lunar surface. 相似文献