An early Little Ice Age brackish water invasion along the south coast of the Caspian Sea (sediment of Langarud wetland) and its wider impacts on environment and people

Caspian Sea level has undergone significant changes through time with major impacts not only on the surrounding coasts, but also offshore. This study reports a brackish water invasion on the southern coast of the Caspian Sea constructed from a multi-proxy analysis of sediment retrieved from the Langarud wetland. The ground surface level of wetland is >6 m higher than the current Caspian Sea level (at -27.41 m in 2014) and located >11 km far from the coast. A sequence covering the last millennium was dated by three radiocarbon dates. The results from this new study suggest that Caspian Sea level rose up to at least -21.44 m (i.e. >6 m above the present water level) during the early Little Ice Age. Although previous studies in the southern coast of the Caspian Sea have detected a high-stand during the Little Ice Age period, this study presents the first evidence that this high-stand reached so far inland and at such a high altitude. Moreover, it confirms one of the very few earlier estimates of a high-stand at -21 m for the second half of the 14th century. The effects of this large-scale brackish water invasion on soil properties would have caused severe disruption to regional agriculture, thereby destabilizing local dynasties and facilitating a rapid Turko-Mongol expansion of Tamerlane’s armies from the east.N Ghasemi (INIOAS), V Jahani (Gilan Province Cultural Heritage and Tourism Organisation) and A Naqinezhad (University of Mazandaran), INQUA QuickLakeH project (no. 1227) and to the European project Marie Curie, CLIMSEAS-PIRSES-GA-2009-24751

Utilization of lime for stabilizing soft clay soil of high organic content

This paper presents the results of geotechnical and mineralogical investigations on lime-treated soft clay soil from Idku City, Egypt, where high organic matters of about 14% exist. Lime was added in the order of 1, 3, 5 and 7% by weight and laboratory experiments after 7, 15, 30 and 60 days were conducted including the mineralogical and microstructural examinations, grain size analysis, plasticity limits, unconfined compressive tests, vane shear tests and oedometer tests. The results indicate that soft clay soil of high organic content of 14% can be stabilized satisfactorily with the addition of 7% lime. The results also demonstrate that the changes in the mineralogical contents and soil fabric of high organic lime-treated soft clay improve soil plasticity, strength and compressibility

Ballistic Spin Resonance

The phenomenon of spin resonance has had far reaching influence since its discovery nearly 70 years ago. Electron spin resonance (ESR) driven by high frequency magnetic fields has informed our understanding of quantum mechanics, and finds application in fields as diverse as medicine and quantum information. Spin resonance induced by high frequency electric fields, known as electric dipole spin resonance (EDSR), has also been demonstrated recently. EDSR is mediated by spin-orbit interaction (SOI), which couples the spin degree of freedom and the momentum vector. Here, we report the observation of a novel spin resonance due to SOI that does not require external driving fields. Ballistic spin resonance (BSR) is driven by an internal spin-orbit field that acts upon electrons bouncing at gigaHertz frequencies in narrow channels of ultra-clean two-dimensional electron gas (2DEG). BSR is manifested in electrical measurements of pure spin currents as a strong suppression of spin relaxation length when the motion of electrons is in resonance with spin precession. These findings point the way to gate-tunable coherent spin rotations in ballistic nanostructures without external a.c. fields.Comment: 24 pages, including supplementary material

Filterability of staphylococcal species through membrane filters following application of stressors

<p>Abstract</p> <p>Background</p> <p>Passage of bacterial cells through filter pores has been reported for a number of bacterial species. In this investigation, we tested the filterability of staphylococcal cultures that were exposed to several environmental stress conditions by passing them through 0.22 and 0.45 μm sterile filters, which are industry standards.</p> <p>Findings</p> <p>Results showed repeated passage of viable staphylococcal cells through both pore sizes, although more passage was seen through the 0.45 μm pore size. Of the three staphylococcal species, <it>S. lugdunensis </it>showed the best passage at relatively higher numbers regardless of the treatment, while both <it>S. aureus </it>and <it>S. epidermidis </it>showed limited passage or complete inhibition.</p> <p>Conclusion</p> <p>The data showed that staphylococcal bacteria were capable of passing through sterile filters in a viable state. There was better passage through 0.45 μm sterile filters than through the 0.22 μm sterile filters. Application of a stress condition did not appear to enhance filterability of these bacterial cultures.</p

Wanted dead or alive : high diversity of macroinvertebrates associated with living and ’dead’ Posidonia oceanica matte

The Mediterranean endemic seagrass Posidonia oceanica forms beds characterised by a dense leaf canopy and a thick root-rhizome ‘matte’. Death of P. oceanica shoots leads to exposure of the underlying matte, which can persist for many years, and is termed ‘dead’ matte. Traditionally, dead matte has been regarded as a degraded habitat. To test whether this assumption was true, the motile macroinvertebrates of adjacent living (with shoots) and dead (without shoots) matte of P. oceanica were sampled in four different plots located at the same depth (5–6 m) in Mellieha Bay, Malta (central Mediterranean). The total number of species and abundance were significantly higher (ANOVA; P<0.05 and P<0.01, respectively) in the dead matte than in living P. oceanica matte, despite the presence of the foliar canopy in the latter. Multivariate analysis (MDS) clearly showed two main groups of assemblages, corresponding to the two matte types. The amphipods Leptocheirus guttatus and Maera grossimana, and the polychaete Nereis rava contributed most to the dissimilarity between the two different matte types. Several unique properties of the dead matte contributing to the unexpected higher number of species and abundance of motile macroinvertebrates associated with this habitat are discussed. The findings have important implications for the conservation of bare P. oceanica matte, which has been generally viewed as a habitat of low ecological value.peer-reviewe

The Zoning of Semi-Enclosed Bodies of Water According to the Sediment Pollution: The Bay of Algeciras as a Case Example

This paper reports a study of the occurrence and levels of polycyclic aromatic hydrocarbons (PAHs) in a bay characterised by a chronic persistent impact. A total of 55 sediment samples were taken at different depths up to 111 m in two sampling campaigns. Chemical analyses were carried out by gas chromatography-mass spectroscopy. The results indicate that: (1) significant spatial variations exist, (2) levels of PAHs are related more strongly to the spatial distribution of sediments than to mineralogy/granulometry, (3) the sediments are slightly-to-moderately contaminated by PAHs, and (4) these PAHs derive from pyrolytic and petrogenic sources. Through use of an innovative data classification system (proposed according to depth and spatial location of sampling points), and using factorial and cluster techniques, five zones have been differentiated depending on the contamination level and source

Benthic pH gradients across a range of shelf sea sediment types linked to sediment characteristics and seasonal variability

This study used microelectrodes to record pH profiles in fresh shelf sea sediment cores collected across a range of different sediment types within the Celtic Sea. Spatial and temporal variability was captured during repeated measurements in 2014 and 2015. Concurrently recorded oxygen microelectrode profiles and other sedimentary parameters provide a detailed context for interpretation of the pH data. Clear differences in profiles were observed between sediment type, location and season. Notably, very steep pH gradients exist within the surface sediments (10–20 mm), where decreases greater than 0.5 pH units were observed. Steep gradients were particularly apparent in fine cohesive sediments, less so in permeable sandier matrices. We hypothesise that the gradients are likely caused by aerobic organic matter respiration close to the sediment–water interface or oxidation of reduced species at the base of the oxic zone (NH4+, Mn2+, Fe2+, S−). Statistical analysis suggests the variability in the depth of the pH minima is controlled spatially by the oxygen penetration depth, and seasonally by the input and remineralisation of deposited organic phytodetritus. Below the pH minima the observed pH remained consistently low to maximum electrode penetration (ca. 60 mm), indicating an absence of sub-oxic processes generating H+ or balanced removal processes within this layer. Thus, a climatology of sediment surface porewater pH is provided against which to examine biogeochemical processes. This enhances our understanding of benthic pH processes, particularly in the context of human impacts, seabed integrity, and future climate changes, providing vital information for modelling benthic response under future climate scenarios

Climate variability of southern Chile since the Last Glacial Maximum : a continuous sedimentological record from Lago Puyehue (40°S)

Author Posting. © Springer, 2007. This is the author's version of the work. It is posted here by permission of Springer for personal use, not for redistribution. The definitive version was published in Journal of Paleolimnology 39 (2008): 179-195, doi:10.1007/s10933-007-9117-y.This paper presents a multi-proxy climate record of an 11 m long core collected in Lago Puyehue (southern Chile, 40°S) and extending back to 18,000 cal yr BP. The multi-proxy analyses include sedimentology, mineralogy, grain size, geochemistry, loss-on-ignition, magnetic susceptibility and radiocarbon datings. Results demonstrate that sediment grain size is positively correlated with the biogenic sediment content and can be used as a proxy for lake paleoproductivity. On the other hand, the magnetic susceptibility signal is correlated with the aluminium and titanium concentrations and can be used as a proxy for the terrigenous supply. Temporal variations of sediment composition evidence that, since the last glacial maximum, the Chilean Lake District was characterized by 3 abrupt climate changes superimposed on a long-term climate evolution. These rapid climate changes are: (1) an abrupt warming at the end of the last glacial maximum at 17,300 cal yr BP; (2) a 13,100-12,300 cal yr BP cold event, ending rapidly and interpreted as the local counter part of the Younger Dryas cold period, and (3) a 3400-2900 cal yr BP climatic instability synchronous with a period of low solar activity. The timing of the 13,100-12,300 cold event is compared with similar records in both hemispheres and demonstrates that this southern hemisphere climate change lags behind the northern hemisphere Younger Dryas cold period by 500 to 1000 years.This research is supported by the Belgian OSTC project EV/12/10B "A continuous Holocene record of ENSO variability in southern Chile"

New physical characterization of the Fontana Lapilli basaltic Plinian eruption, Nicaragua

The Fontana Lapilli deposit was erupted in the late Pleistocene from a vent, or multiple vents, located near Masaya volcano (Nicaragua) and is the product of one of the largest basaltic Plinian eruptions studied so far. This eruption evolved from an initial sequence of fluctuating fountain-like events and moderately explosive pulses to a sustained Plinian episode depositing fall beds of highly vesicular basaltic-andesite scoria (SiO2 > 53 wt%). Samples show unimodal grain size distribution and a moderate sorting that are uniform in time. The juvenile component predominates (> 96 wt%) and consists of vesicular clasts with both sub-angular and fluidal, elongated shapes. We obtain a maximum plume height of 32 km and an associated mass eruption rate of 1.4 × 108 kg s−1 for the Plinian phase. Estimates of erupted volume are strongly sensitive to the technique used for the calculation and to the distribution of field data. Our best estimate for the erupted volume of the majority of the climactic Plinian phase is between 2.9 and 3.8 km3 and was obtained by applying a power-law fitting technique with different integration limits. The estimated eruption duration varies between 4 and 6 h. Marine-core data confirm that the tephra thinning is better fitted by a power-law than by an exponential trend