Rare earth elements in Andaman Island surface water : geochemical tracers for the monsoon

The Asian summer monsoon affects the lives of billions of people. With the aim of identifying geochemical tracers for the monsoon related freshwater input from the major rivers draining into the Bay of Bengal and Andaman Sea we have taken surface seawater samples from various locations up and down the Andaman Islands during 2011. Importantly, in some locations samples have been taken in March, July and November, covering most of a seasonal cycle and different monsoon phases. Samples were collected from the side of small wooden boats or while swimming and were filtered within a few hours at 0.45 or 0.22 microns using the vacuum produced by a water jet or a hand operated peristaltic pump. Filtered and unfiltered samples were acidified to < pH 2 and analysed for Y and the REEs with an automated online preconcentration ICP-MS technique [1]. The local input of REEs from streams and sediment rich areas such as mangrove environments is clearly identified by middle REE enrichments in the shale normalised patterns of some samples. These middle REE bulges accompany large increases in dissolved REE concentrations at some locations, especially for the July samples obtained during the peak monsoon season with frequent storms. Y/Ho fractionation aslo occurs during the local input of dissolved REEs with affected samples having lower Y/Ho ratios. Conversly, some samples, in particular those taken after heavy rainfall in March, show strong REE scavenging accompanied by the prefferential removal of dissolved light REEs and higher Y/Ho ratios. The time series at a location away from local input sources shows remarkably similar REE patterns and concentraions in March and July. Then in October-November, following the peak in monsoon river discharge, the dissolved REE concentration increases by almost a factor of 2. The notable exception to this seasonal pattern is the Ce anomally which is around 0.3 in March and November but 0.6 in July, implying less oxidative removal of Ce(IV) during the peak summer monsoon rains. With the exception of elevated dissolved Ce concentrations, the North Pacific Deep Water normalised REE patterns are similar to those reported for offshore samples from the Bay of Bengal and Andaman Sea [2]. These seawater normalised patterns are distinctive having a middle REE enriched arc with similar light and heavy REE values suggesting the input from large rivers in the region is traceable using seawater REE chemistry. [1] Hathorne et al. (2012), Online preconcentration ICP-MS analysis of rare earth elements in seawater, Geochem. Geophys. Geosyst., 13, Q01020, doi:10.1029/2011GC003907. [2] Amakawa et al. (2000), Geochim. Cosmochim. Acta 64, 1715-1727

Extravehicular mobility unit subcritical liquid oxygen storage and supply system

The storage of life support oxygen in the Extravehicular Mobility Unit in the liquid state offers some advantages over the current method of storing the oxygen as a high pressure gas. Storage volume is reduced because of the increased density associated with liquid. The lower storage and operating pressures also reduce the potential for leakage or bursting of the storage tank. The potential for combustion resulting from adiabatic combustion of the gas within lines and components is substantially reduced. Design constraints on components are also relaxed due to the lower system pressures. A design study was performed to determine the requirements for a liquid storage system and prepare a conceptual design. The study involved four tasks. The first was to identify system operating requirements that influence or direct the design of the system. The second was to define candidate storage system concepts that could possibly satisfy the requirements. An evaluation and comparison of the candidate concepts was conducted in the third task. The fourth task was devoted to preparing a conceptual design of the recommended storage system and to evaluate concerns with integration of the concept into the EMU. The results are presented

Classroom contexts: Connections between class size and within class grouping

Background. There has been a vigorous debate for many years about the educational effects of class size differences, but even if differences have an impact on pupils' academic progress this still leaves unanswered important questions about what mediates the effect. Aims. This paper is informed by a classroom contextual perspective, and examines associations between class size and within class groupings (in terms of size and number of groups, adult presence in groups, and type of interaction between grouping members). Age differences in these relationships are also explored. Samples. The quantitative study is based on analysis of 3157 groupings, from 672 Reception, Year 2 and Year 5 classes in 331 schools. The qualitative study was based on 12 classes in 8 case study schools, and questionnaire responses completed by over 100 class teachers. Methods. Links between size of class and within class groupings were examined on the basis of a 'grouping mapping survey', in which teachers at a given time in the school day provided information on group size and number, adult presence, and type of interaction between pupils, and complementary qualitative analyses of data from teacher-completed questionnaires, and interviews. Results. The number of groups in a class increased with the size of the class. Over all three year groups, small classes had on average just over three groups, while large classes approached six groups. The size of groups in the class decreased with size of class. In class sizes over 25, pupils were more likely to be in a large group of 7-10, while in classes under 25 they were more likely to be in whole class groupings. Qualitative analyses showed that teachers felt that groups of 7-10 pupils had negative educational effects, for example, in terms of the quality and quantity of teaching and children's concentration and contribution in groups. Conclusions. Results suggest that the effects of class size can be best seen as through the size and number of groups, which will then have implications for learning experiences. So while debate about size of class has often been in terms of reduced size of class resulting in pupil academic gains, it is also important educationally to consider within class grouping size and number, and their effects.link_to_subscribed_fulltex

Past changes in riverine input and ocean circulation in the Gulf of Guinea

Large river systems draining the West African Monsoon area deliver sediments and dissolved trace elements into the Gulf of Guinea (GoG) in the easternmost equatorial Atlantic. The different catchment areas of these river systems are characterized by different geological ages and rock types releasing distinct radiogenic neodymium isotope compositions during weathering which are supplied to the GoG. The main rivers discharging into the GoG are the Niger, the Sanaga, the Nyong and the Ntem with present day εNd signatures of -10.5 [1], -12.3, -12.5 and -28.1 [2], respectively. These riverine inputs mix with the tropical Atlantic surface waters. At intermediate water depths Antarctic Intermediate Water (AAIW) prevails whereas the deep basin at this location is mainly filled with NADW. We focus on a marine sediment core that was recovered off the Sanaga and Ntem Rivers and we reconstruct changes in riverine inputs and in mixing of surface and deep water masses over the past 140,000 years. Changes in riverine inputs most likely reflecting latitudinal shifts of the rainfall zones across the different catchment areas were obtained from the Nd isotope signatures of the residual detrital fraction of the sediment. Sediment leachates of several GoG core top samples reflect the riverine input from nearby rivers indicating transport of particles coated in the rivers. Both the sediment leachates and the residual detrital fraction show similar patterns, with shifts towards radiogenic values during the interglacials and least radiogenic values during glacial periods. This shift in εNd values may be attributed to the migration of the rainfall zones towards the north during interglacial times and thus implies the increased influence of the northern rivers, the Sanaga and Nyong. The oxidatively-reductively cleaned planktonic foraminiferal calcite of the core top samples in the GoG reflects surface seawater signatures. Non-reductively cleaned planktonic foraminiferal tests and cleaned shallow endo-benthic and epi-benthic foraminiferal tests were used to acquire information about past bottom waters. Difficulties in cleaning down core foraminiferal samples were experienced and these samples appear to be contaminated by secondary manganese and iron bearing phases, even after cleaning. Those phases may have overprinted the original surface water Nd isotope composition in the planktonic foraminiferal tests. As the planktonic and benthic foraminiferal values are overall similar to the sediment leachates, the foraminiferal isotope signatures are most likely overprinted by isotopic signals originating from the rivers due to remobilization processes in the sediments and formation of secondary phases such as Mn-carbonates, which are attached to the foraminiferal calcites. References: [1] Goldstein et al. (1984) Earth and Planetary Science Letter 70, 221-236. [2] Weldeab et al. (2011) Geophysical Research Letter 38, pp. 5

Using a Flow Through device to reconstruct the thermal gradient in the water column based on G. inflata Mg/Ca

We present Mg/Ca analyses performed via a Flow Through sequential dissolution device connected to an ICP-OES on the planktonic foraminifer Globorotalia inflata. The aim of the study is to explore the possibility to reconstruct the thermal gradient in the water column by separating non-crusted and crusted calcite phases in the tests of G. inflata using the difference between their Mg/Ca ratios as a measure of the thermal gradient. An important assumption is that the non-crusted part of the tests is calcified in shallow, warmer water than the crusted part. For analyses a range of different preparation steps were used to determine the ideal way of separating the phases. Foraminifer tests were (not) cleaned, (not) crushed, and (not) pulverized before online analysis with the FT device. To analyze samples with a FT device the foraminifer tests are placed on a filter with a mesh of 0.45 μm preventing clay minerals to wash through. A sequential dissolution protocol first rinses the samples with buffered Seralpur water before QD HNO3 is added in small steps to create a ramp of increasing acid strength. As acid is kept constant at each concentration for several minutes, dissolution of a specific calcite phase can take place. Initial results show that it is most effective to slightly crush the tests without applying standard cleaning procedures, but rather analyze them without cleaning. Samples were selected from the South Atlantic (core tops and specific downcore samples) and the Mediteterranean (plankton tows). All samples were chosen based on previous work on them to provide comparison with routinely analysed Mg/Ca ratios. The South Atlantic samples have been analyzed extensively as bulk samples separated in difference size fractions and crusted vs. non-crusted (Groeneveld and Chiessi). The Mediterranean samples were not only analyzed as bulk samples but also by Laser Ablation ICP-MS (von Raden et al.). Results show that bulk analyses are reliably reproduced by the FT method, especially for samples which are dominated by crusted calcite. Samples which were uncrusted often gave much higher Mg/Ca ratios than the bulk analyses. These higher Mg/Ca ratios mainly occur in the plankton tow samples and were also identified with Laser Ablation ICP-MS. A possible reason for this could be the presence of a high Mg amorphous calcite layer on the outside of foraminifer tests which have not completed their calcification yet as was recently also pointed out in several other studies. Identification of the crusted and uncrusted phases, and therewith a thermal gradient, seems to give the expected differences but a more rigorous statistical treatment is needed to pinpoint singular dissolution phases

Effect of Deforestation by the Douglas-Fir Tussock Moth on the Quality of Streamflow and Stream Productivity Parameters

The purpose of this study was to determine if deforestation by a recent outbreak of Douglas-fir tussock moth and logging of such deforested timber has had any effect on stream water quality. To determine this, seven different watersheds of three types were examined. The three types were: undamaged watersheds as controls, watersheds with deforestation and watersheds with deforestation where the timber was subsequently logged. Twenty-four variables were used to determine water quality. Included were seven biological and seventeen chemical variables. In general, the results indicate only seasonal fluctuations and differences between watersheds due to inherent properties of individual watersheds. Increased turbidity levels were detected on logged watersheds which could be correlated with the logging activities

Social Ecology State of the Art and Future Prospects

The book ‘Social Ecology. State of the Art and Future Prospects’ is published by ISOE – Institute for Social-Ecological Research, Frankfurt am Main and the Vienna Institute of Social Ecology (SEC). Both institutes have made defining contributions to the field of social ecology. How the complex relations between society and nature can be theoretically captured, empirically investigated and sustainably shaped is a focal question for both institutes. This book provides an overview of the current state of social-ecological research. It contains 11 contributions from 29 scientists, edited by Johanna Kramm and Martin Zimmermann (ISOE) and Melanie Pichler and Anke Schaffartzik (SEC). Topics range from the conceptional and theoretical foundations of social ecology to empirical case studies and research frontiers. The peer-reviewed essays highlight the role of social ecology as a critical, transdisciplinary science, discussing the current challenges for social-ecological transformations. Key concepts for sustainability research like ecosystem services, societal metabolism, risk, or extractive economies are applied and advanced