The carbohydrates in relation to mineralogic and granulometric composition of surface sediments in the karst estuary (River Krka estuary,Yugoslavia)

The investigation of mineral, granulometric and chemical composition of sediments of the River Krka estuary (Yugoslavia) were performed in order to elucidate the origin of the sediments and the pattern of sedimentation. Estuarine surface sediments were found to be fine-grained with a bimodal distribution. Environmental conditions in estuarine sediments favour conservation of the organic matter (anoxic conditions). The carbohydrates in the sediments were investigated to determine whether they are of terrigenous or authigenous origin. Glucose, galactose, mannose, xylose, rhamnose, glucosamine and glucuronic acid were detected in the sediments. Their mutual relationship indicates a preferentially terrigenous source of sedimented organic material in estuarine sediments.     

Trapped Xe and I-Xe ages in aqueously altered CV3 meteorites

Twenty-two dark inclusions (DIs) from Allende (18), Leoville (2), Vigarano (1) and Efremovka (1) were studied by the I-Xe method. All except two of these DIs (Vigarano 2226 and Leoville LV2) produce well-defined isochrons, and precise I-Xe ages. The Allende DIs formed a tight group about 1.6 Ma older than Shallowater (4.566 ± 0.002 Ga), about 5 Ma older than four previously studied Allende CAIs. Most of the dark inclusions require trapped Xe with less ¹²⁹Xe (or more ¹²⁸Xe) than conventional planetary Xe (well restricted in composition by Q-Xe or OC-Xe). Studies of an irradiated/unirradiated DI pair from Allende demonstrate that the ¹²⁸Xe/¹³²Xe ratio in trapped is normal planetary, so that a ¹²⁹Xe/¹³²Xe ratio below planetary seems to be required. Yet, this is not possible given constraints on ¹²⁹Xe evolution in the early solar system. Trends among all of the Allende DIs suggest that an intimate mixture of partially decayed iodine and Xe formed a pseudo trapped Xe component enriched in both ¹²⁹Xe and ¹²⁷I, and subsequently in ¹²⁸Xe after n-capture during reactor irradiation. Enrichment in radiogenic ¹²⁹Xe, but with a ¹²⁹Xe/¹²⁷I ratio less than that observed in the iodine host phase, places closure of this trapped mixture ≥13 Ma after precipitation of the major iodine-bearing phase. Because the I-Xe isochron is a mixing line between iodine-derived and trapped Xe (pseudo or not), I-Xe ages, given by the slope of this mixing line, are not compromised by the presence of pseudo trapped Xe, and the precision of the I-Xe ages is given by the statistics of the line fit.     

Aqueous uptake of uranium onto pyrite surfaces; reactivity of fresh versus weathered material

In order to better understand the interaction between aqueous uranium and pyrite (FeS₂) the uptake of uranium onto the surfaces of both weathered and freshly generated pyrite surfaces was examined using batch sorption experiments. Analysis was performed using X-ray photoelectron spectroscopy (XPS). The results clearly indicate that freshly polished pyrite surfaces are efficient scavengers of uranium from solution, while weathered surfaces exhibit only limited uptake. Results also indicate partial reduction of uranium at the pyrite surfaces, with a heterogeneous distribution of U(IV) and U(VI) species.     

The Maribo CM2 meteorite fall—Survival of weak material at high entry speed

High entry speed (>25 km s^?1) and low density (<2500 kg m^?3) are the two factors that lower the chance of a meteoroid to drop meteorites. The 26 g carbonaceous (CM2) meteorite Maribo recovered in Denmark in 2009 was delivered by a bright bolide observed by several instruments across northern and central Europe. By reanalyzing the available data, we confirmed the previously reported high entry speed of (28.3 ± 0.3) km s^?1 and trajectory with slope of 31° to the horizontal. In order to understand how such a fragile material survived, we applied three different models of meteoroid atmospheric fragmentation to the detailed bolide light curve obtained by radiometers located in Czech Republic. The Maribo meteoroid was found to be quite inhomogeneous with different parts fragmenting at different dynamic pressures. While 30–40% of the (2000 ± 1000) kg entry mass was destroyed already at 0.02 MPa, another 25–40%, according to different models, survived without fragmentation up to the relatively large dynamic pressures of 3–5 MPa. These pressures are only slightly lower than the measured tensile strengths of hydrated carbonaceous chondrite (CC) meteorites and are comparable with usual atmospheric fragmentation pressures of ordinary chondritic (OC) meteoroids. While internal cracks weaken OC meteoroids in comparison with meteorites, this effect seems to be absent in CC, enabling meteorite delivery even at high speeds, though in the form of only small fragments.     

Estimating masses of selected stars in the Pulkovo program by means of astrometry methods

Stars in the Pulkovo Observatory program are observed with a 65-cm refractor during many years to study their positions and movements. We present examples of two visual binary stars, for which orbits and masses of components were determined, and two astrometric stars, for which masses of their unseen companions were estimated. The first two stars are ADS 14636(61 Cygni) and ADS 7251,and the others are Gliese 623 and ADS 8035(Alpha UMa). Direct astrometric methods are used for estimation of mass-ratio and masses.     

Early solar system aqueous activity: K isotope evidence from Allende

The alkali element K is moderately volatile and fluid mobile; thus, it can be influenced by both primary processes (evaporation and recondensation) in the solar nebula and secondary processes (thermal and aqueous alteration) in the parent body. Since these primary and secondary processes would induce different isotopic fractionations, K isotopes could become a potential tracer to distinguish them. Using recently developed methods with improved precision (0.05‰, 95% confidence interval), we systematically measured the K isotopic compositions and major/trace elemental compositions of chondritic components (18 chondrules, 3 CAIs, 2 matrices, and 5 bulks) in the carbonaceous chondrite fall Allende. Among all the components analyzed in this study, CAIs, which formed initially under high‐temperature conditions in the solar nebula and were dominated by nominally K‐free refractory minerals, have the highest K₂O content (average 0.53 wt%) and have K isotope compositions most enriched in heavy isotopes (δ⁴¹K: ?0.30 to ?0.25‰). Such an observation is consistent with previous petrologic studies that show CAIs in Allende have undergone alkali enrichment during metasomatism. In contrast, chondrules contain lower K₂O content (0.003–0.17 wt%) and generally lighter K isotope compositions (δ⁴¹K: ?0.87‰ to ?0.24‰). The matrix and bulks are nearly identical in K₂O content and K isotope compositions (0.02–0.05 wt%; δ⁴¹K: ?0.62 to ? 0.46‰), which are, as expected, right in the middle of CAIs and chondrules. This strongly indicates that most of the chondritic components of Allende suffered aqueous alteration and their K isotopic compositions are the ramification of Allende parent‐body processing instead of primary nebular signatures. Nevertheless, we propose the small K isotope fractionations observed (< 1‰) among Allende components are likely similar to the overall range of K isotopic fractionation that occurred in nebular environment. Furthermore, the K isotope compositions seen in the components of Allende in this study are consistent with MC‐ICP‐MS analyses of the components in ordinary chondrites, which also show an absence of large (10‰) isotope fractionations. This is not expected as evaporation experiments in nebular conditions suggest there should be large K isotopic fractionations. Nevertheless, possible nebular processes such as chondrules back exchanging with ambient gas when they formed could explain this lack of large K isotopic variation.     

Present rate of uplift in Fennoscandia from GRACE and absolute gravimetry

Fennoscandia is a key region for studying effects of glacial isostatic adjustment. The associated mass variations can be detected by the Gravity Recovery and Climate Experiment (GRACE) satellite mission, which observes the Earth's gravity field since April 2002, as well as by absolute gravimetry field campaigns. Since 2003, annual absolute gravity (AG) measurements have been performed in Fennoscandia by the Institut für Erdmessung (IfE, Institute of Geodesy) of the Leibniz Universität Hannover, Germany, within a multi-national cooperation. This offers a unique opportunity for validation and evaluation of the GRACE results. In this preliminary study, the GRACE results are compared to secular gravity changes based on the surveys from 2004 to 2007 with the FG5-220 gravimeter of the IfE.The results from GRACE monthly solutions provided by different analysis centres show temporal gravity variations in Fennoscandia. The included secular variations are in good agreement with former studies. The uplift centre is located west of the Bothnian Bay, the whole uplift area comprises Northern Europe. Nevertheless, the differences between the GRACE solutions are larger than expected and the different centre-specific processing techniques have a very strong effect on possible interpretations of GRACE results. The comparison of GRACE to the AG measurements reveals that the determined trends fit well with results from GRACE at selected stations, especially for the solution provided by the GFZ. Variations of land hydrology clearly influence results from GRACE and the AG measurements.     

Late Pleistocene and Holocene small- and large-mammal faunas from the Northern Urals

Data from the mammal fauna of the North Urals during the Late Pleistocene and Holocene are synthesised. Analysis of differentiation the degree of small- and large-mammal faunas during this time has been undertaken. Only differences of mammal species composition were significant between the Late Pleistocene and Holocene complexes, and within these complexes, the distinction between faunas was insignificant. The transition from the Late Pleistocene to the Holocene complex small-mammal faunas occurred in the Middle Late Valdai due to expansion of the forest species. In large-mammal faunas, the process was recorded later (in Dryas 3-Early Holocene) because of the extinction of some species and others that changed their areas of occupation.     

The droughts of 1997 and 2005 in Amazonia: floodplain hydrology and its potential ecological and human impacts

It is well known that most of the severe droughts in Amazonia, such as that of 1997, are El Niño-related. However, in 2005, the Amazon was affected by a severe drought that was not El Niño-related, as most of the rainfall anomalies that have happened in southwestern Amazonia are driven by sea surface temperature anomalies in the tropical North Atlantic. Earlier studies have analyzed both droughts in terms of their meteorological causes and impacts in terra firme (non-flooded) forests. This study compares the hydrological effects of both droughts on the Amazonian floodplain and discusses their potential ecological and human impacts based on an extensive literature review. The results revealed that the effects of the 2005 drought were exacerbated because rainfall was lower and evaporation rates were higher at the peak of the dry season compared to the 1997 drought. This induced a more acute depletion of water levels in floodplain lakes and was most likely associated with higher fish mortality rates. Based on the fact that the stem growth of many floodplain species is related to the length of the non-flooded period, it is hypothesized that the 1997 drought had more positive effects on floodplain forest growth than the 2005 drought. The fishing community of Silves in central Amazonia considered both droughts to have been equally severe. However, the 2005 drought was widely broadcasted by the press; therefore, the governmental mitigation efforts were more comprehensive. It is suggested that the availability of new communication technology and greater public awareness regarding environmental issues, combined with the new legal framework for assessing the severity of calamities in Brazil, are among the primary factors that explain the difference in societal response between the two droughts.