Climate signals in sediment mineralogy of Lake Baikal and Lake Hovsgol during the LGM-Holocene transition and the 1-Ma carbonate record from the HDP-04 drill core

Modeling the bulk sediment XRD patterns allows insight into the environmental and depositional histories of two neighboring rift lake basins within the Baikal watershed. Parallel ¹⁴C-dated LGM-Holocene records in Lakes Baikal and Hovsgol are used to discuss the mineralogical signatures of regional climate change. In both basins, it is possible to distinguish ‘glacial’ and ‘interglacial’ mineral associations. Clay minerals comprise in excess of 50% of layered silicates in bulk sediment.The abundance of smectite (expandable) layers in mixed-layer illite–smectites and the total illite abundance are the main paleoclimatic indices in the clay mineral assemblage. Both indices exhibit coherent responses to the Bølling–Allerød and the Younger Dryas. The smectite layer index is not equivalent to the abundance of illite–smectite, because illite–smectite tends to transform into illite. Repeated wetting–drying cycles in soils and high abundance of expandable layers in illite–smectites (>42%) favor the process of illitization. This relationship is clearly shown in both Baikal and Hovsgol records for the first time. The opposite late Holocene trends in illite abundance in Lake Baikal and Lake Hovsgol records suggest that a sensitive optimal regime may exist for illite formation in the Baikal watershed with regard to warmth and effective moisture.The Lake Hovsgol sediments of the last glacial contain carbonates, suggesting a positive trend in the lake's water budget. A progressive change towards lower Mg content in carbonates indicates lowering mineralization of lake waters. This trend is consistent with the lithologic evidence for lake-level rise in the Hovsgol basin.The pattern of mineralogical changes during the past 20 ka is used to interpret bulk sediment and carbonate mineralogy of the long 81-m Lake Hovsgol drill core (HDP-04) with a basal age of 1 Ma. The interglacial-type silicate mineral associations are confined to several thin intervals; most of the sediment record is calcareous. Carbonates are represented by six main mineral phases: calcite, low-Mg calcite, intermediate/high-Mg calcite, dolomite, excess-Ca dolomite and metastable monohydrocalcite. These mineral phases tend to form stratigraphic successions indicative of progressive changes in lake water chemistry. Five sediment layers with abundant Mg-calcites in the HDP-04 section suggest deposition in a low standing lake with high mineralization (salinity) and high Mg/Ca ratios of lake waters. Lake Hovsgol sediments contain the oldest known monohydrocalcite, found tens of meters below lake bottom in sediments as old as 800 ka. This unusual find is likely due to the conditions favorable to preservation of this metastable carbonate.     

Acid catalysis of alkyl hydrogen exchange and configurational isomerisation reactions: acyclic isoprenoid acids

Acid-catalysed alkyl hydrogen exchange and configurational isomerisation has been studied in a series of acyclic isoprenoid acids when they were heated at 160°C in the presence of a montmorillonite. Hydrogen exchange occurred between the adsorbed water of the clay surface and the a position of the isoprenoid acids. In cases where this position was chiral, exchange was accompanied by configurational isomerisation. Configurational isomerisation occurred more slowly in experiments conducted without a clay matrix in the presence of water. These results have been rationalized in terms of a reaction mechanism involving protonation of the carbonyl oxygen causing enolization and consequent hydrogen exchange at the a position of the acids. This mechanism was used to account for the relatively fast rate of isomerisation of C-2 chiral centres in sedimentary acyclic isoprenoid acids during maturation.     

Magnetic field at the core boundary in the nearly symmetric hydromagnetic dynamo z

Summary The behaviour of the poloidal and toroidal magnetic field at the core-mantle boundary is analysed in more detail, assuming that the conductive layer in the lowest mantle is thin. We can conclude that, in the case of the Z-model of the nearly symmetric hydromagnetic dynamo, the poloidal field may be considered potential everywhere in the mantle and that the azimuthal field depends on the geostrophic azimuthal velocity in the same manner as derived in[1] and[3].

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aau ¶rt;-amu n¶rt;nuu m n¶rt; amuu aauum n¶rt;u nu¶rt;a u mu¶rt;a n. am ¶rt;, m Z-¶rt;u nmu umuu¶rt;aum ¶rt;ua aum nu¶rt;a n umam nmua ¶rt; amuu a n¶rt;u . ¶rt;m¶rt;am na [1] u [3] auum auma aum n m auma mu.

     

Trace metals in southern Californian mussels

The intertidal mussel Mytilus californianus is a useful indicator of anthropogenic inputs of several trace metals off southern California. Highest metal concentrations were measured in the digestive glands, and no significant differences attibutable to sex were found for this tissue. The distribution of lead appears to be dominated by diffuse inputs, while those of copper, chromium, and silver are most related to urban point sources. No distinct pattern was observed for nickel or zinc.     

Planetary-type rare gases in an upper mantle-derived amphibole

All twenty-three stable rare gas isotopes have been measured in a mantle-derived amphibole, kaersutite. The elemental abundance pattern of the rare gases is similar to the “planetary” rare gas pattern as defined by carbonaceous chondrites. The³He/⁴He ratio, (4.9 ± 0.6) × 10^?5, is suggestive of primordial He degassing from the mantle. Excess²¹Ne is present. The measured⁴⁰Ar/³⁶Ar ratio,400 ± 5, may represent a mantle⁴⁰Ar/³⁶Ar ratio <240 when corrected for radiogenic⁴⁰Ar. The heavy isotopes of Kr and t0he Xe isotopes are within error of the atmosphere values.     

Using and Improving Neural Network Models for Ground Settlement Prediction

Earth-fill structures such as embankments, which are constructed for the preservation of land and infrastructure, show significant amount of settlement during and after construction in lowland areas with soft grounds. Settlements are often still predicted with large uncertainty and frequently observational methods are applied using settlement monitoring results in the early stage after construction to predict the long term settlement. Most of these methods require a significant amount of measurements to enable accurate predictions. In this paper, an artificial neural network model for settlement prediction is evaluated and improved using measurement records from a test embankment in The Netherlands. Based on a learning pattern that focuses on convergence of the settlement rate, the basic model predicted settlements which were in good agreement with the measurements, when the amount of measured data used as teach data for the model exceeded a degree of consolidation of 69 %. For lower amounts of teach data the accuracy of settlement prediction was limited. To improve the accuracy of settlement prediction, it is proposed to add short-term predicted values that satisfy predefined statistical criteria of low coefficient of variance or low standard deviation to the teach data, after which the model is allowed to relearn and repredict the settlement. This procedure is repeated until all predicted values satisfy the criterion. Using the improved network model resulted in significantly better predictions. Predicted settlements were in good agreement with the measurements, even when only the measurements up to a consolidation stage of 35 % were used as initial teach data.     

Rethinking geopolitics in an era of climate change

This article examines the disconnect between predictions about climate change and dominant geopolitical framings of the future. To begin, we introduce four popular geopolitical models of the world. We then show how climate change is a critical variable when considering the future of international politics. Focusing on the specific issues of water availability, agricultural productivity, coastal impacts, and shipping routes, we discuss the implications of predicted changes in the wake of climate change for the assumptions on which these scenarios are built. We show that work linking climate change and geopolitics has clear implications for the ways in which the future geopolitical (dis)order is conceptualized, and we argue that the failure to incorporate this work into geopolitical scenario-planning represents a significant limitation to their utility. We offer some direction for a re-conceptualization of the future based on a more dynamic and flexible approach to geopolitics that recognizes the disruptions posed by climatic and other environmental changes.     

Alternative climate data sources for distributed hydrological modelling on a daily time step

Two major criteria in choosing climate data for use in hydrological modelling are the period of record of the data set and the proximity of the collection platform(s) to the basin under study. Conventional data sets are derived from weather stations; however, in many cases there are no weather stations sufficiently close to a basin to be representative of climate conditions in that basin. In addition, it is often the case either that the period of record for the weather station(s) does not cover the period of the proposed simulation or that there are gaps in the data. Therefore, the objectives of this study are to investigate alternative climate data sources for use in hydrological modelling and to develop a protocol for creating hydrological data sets that are spatially and temporally harmonized. The methods we used for constructing daily, spatially distributed, climatic data sets of precipitation, maximum and minimum temperature, wind speed, solar radiation, potential evapotranspiration, and relative humidity are described. The model used in this study was the Soil and Water Assessment Tool implemented on the Mimbres River Basin located in southwestern New Mexico, USA, for the period 2003–2006. Our hydrological simulations showed that two events in January and February 2005 were missed, while an event in August 2006 was well simulated. We have also investigated the usefulness of several other precipitation data sets and compared the simulation results. Copyright © 2010 John Wiley & Sons, Ltd.     

The State of knowledge about wetlands and their future under aspects of global climate change: the situation in Russia

About two-thirds of Russia’s land area are flat lands, which contributes to the development of conditions favouring wetland formation. Wetlands cover vast areas, especially in the north. Wetlands in the former Soviet Union were not recognized as separate or distinct ecosystems and this is still the situation in Russia today. Bogs are one of the most abundant and typical wetlands and were treated as worthless wastelands. Beginning in the 17th century and continuing under the Soviet government there was an enforced policy to drain wetlands and reclaim the land, mainly for farming. After the collapse of the USSR, this practice was discontinued along with the Soviet model of agriculture and an end to the forced and unnecessary use of pesticides and fertilizers with the result that the toxic load on Russian aquatic systems decreased drastically. Industrial production was also greatly curtailed. While it is now recovering, many of these are turning to environmentally-friendly technologies. The intensity of land-use related impacts upon Russian wetlands is negligible compared to that in more densely populated countries and therefore the environmental conservation of wetlands in Russia may not currently be an urgent problem. There is currently no consensus on what the overall direct and indirect impacts of climate change on the number of Russian wetlands will be—in some areas they may increase but decrease in others. In Russia, the most urgent issue is not the preservation of wetlands but the development of proper wetland management practices. For effective plans, data and information on wetland status, trends and characteristics are required that are not currently available.