Loss on ignition as a method for estimating organic and carbonate content in sediments: reproducibility and comparability of results

Five test runs were performed to assess possible bias when performing the loss on ignition (LOI) method to estimate organic matter and carbonate content of lake sediments. An accurate and stable weight loss was achieved after 2 h of burning pure CaCO3 at 950 °C, whereas LOI of pure graphite at 530 °C showed a direct relation to sample size and exposure time, with only 40-70% of the possible weight loss reached after 2 h of exposure and smaller samples losing weight faster than larger ones. Experiments with a standardised lake sediment revealed a strong initial weight loss at 550 °C, but samples continued to lose weight at a slow rate at exposure of up to 64 h, which was likely the effect of loss of volatile salts, structural water of clay minerals or metal oxides, or of inorganic carbon after the initial burning of organic matter. A further test-run revealed that at 550 °C samples in the centre of the furnace lost more weight than marginal samples. At 950 °C this pattern was still apparent but the differences became negligible. Again, LOI was dependent on sample size. An analytical LOI quality control experiment including ten different laboratories was carried out using each laboratory's own LOI procedure as well as a standardised LOI procedure to analyse three different sediments. The range of LOI values between laboratories measured at 550 °C was generally larger when each laboratory used its own method than when using the standard method. This was similar for 950 °C, although the range of values tended to be smaller. The within-laboratory range of LOI measurements for a given sediment was generally small. Comparisons of the results of the individual and the standardised method suggest that there is a laboratory-specific pattern in the results, probably due to differences in laboratory equipment and/or handling that could not be eliminated by standardising the LOI procedure. Factors such as sample size, exposure time, position of samples in the furnace and the laboratory measuring affected LOI results, with LOI at 550 °C being more susceptible to these factors than LOI at 950 °C. We, therefore, recommend analysts to be consistent in the LOI method used in relation to the ignition temperatures, exposure times, and the sample size and to include information on these three parameters when referring to the method.

MeV ion beam lithography of biocompatible halogenated Parylenes using aperture masks

Parylenes are poly(p-xylylene) polymers that are widely used as moisture barriers and in biomedicine because of their good biocompatibility. We have investigated MeV ion beam lithography using 16O+ ions for writing defined patterns in Parylene-C, which is evaluated as a coating material for the Cochlear Implant (CI) electrode array, a neuroprosthesis to treat some forms of deafness. Parylene-C and -F on silicon and glass substrates as well as 50 μm thick PTFE were irradiated to different fluences (1×1013-1×10161×1013-1×1016 1 MeV 16O+ ions cm−2) through aperture masks under high vacuum and a low pressure (<10−3 mbar) oxygen atmosphere. Biocompatibility of the irradiated and unirradiated surfaces was tested by cell-counting to determine the proliferation of murine spiral ganglion cells. The results reveal that an oxygen ion beam can be used to pattern Parylene-C and -F without using a liquid solvent developer in a similar manner to PTFE but with a ∼25× smaller removal rate. Biocompatibility tests showed no difference in cell adhesion between irradiated and unirradiated areas or ion fluence dependence. Coating the Parylene surface with an adhesion-promoting protein mixture had a much greater effect on cell proliferation.

Optimizing Performance of Conductive Nanoparticle-filled Membranes

Conductive membranes were prepared by magnetic alignment of graphite-coated iron nanoparticles (GCINs) in a polyisobutylene (PIB) matrix, which was cast onto an interdigitated surface electrode. Toluene and tetrahydrofuran (THF) were used as solvents for the casting solution. Different molecular weights of PIB and solutions with concentrations ranging from 0.05- to 50-wt% were explored to optimize the mechanical and physical properties of the membrane. The amount of GCINs used in the membranes ranged from 0.1- to 2.5-wt%, and a sonicator was used to disperse the particles in the membrane. Sedimentation and surfactant studies were conducted to investigate the dispersion of GCINs in solutions. Progresses were made to find an optimal combination of various parameters in order to attain thin homogenous membranes for fast response.

Composition of sedimentary material from the bottom and the area surrounding the Lake Untersee, East Antarctica

This paper presents data on geographic and geologic conditions of modern sedimentation in the Lake Untersee, the largest lake in the East Antarctica. Geochemical and sedimentation data indicate that the leading mechanism supplying aluminosilicate sedimentary material to the surface layer of bottom sediments is seasonal melting of the Anuchin glacier and the mountain glacier on the southeastern part of the valley hosting the lake. Strongly reduced conditions in the lowermost 25 m of the water column in the smaller of two depressions of the lake bottom were favorable for enrichment of the bottom sediments in bacteriogenic organic matter, Mo, Au, and Pd. H2S-contaminated water results to significant enrichment of the sediments only in redox-sensitive elements that are able to migrate in anionic complexes and precipitate (co-precipitate) as sulfides.

Geochemistry of basement clasts from sediment core CRP-3 in the ross Sea, Antarctica

Distribution patterns and petrographical and mineral chemistry data are described for the most representative basement lithologies occuring as clast in the c. 824 m thick Tertiary sedimentary sequence at the CRP-3 drillsite. These are granule to bolder grain size clasts of igneous and metamorphic rocks. Within the basement clast assemblage, granitoid pebbles are the predominant lithology. They consist of dominant grey biotic-bearing monzogranite, pink biotite-hornblende monzogranite, and biotite-bearing leucomomonzgranite. Minor lithologies include: actinolite-bearing leucotonalite, microgranite, biotite-hornblende quartz-monzonitic porphyr, and foliated biotic leucomonzogranite. Metamorphic clasts include rocks of both granitic and sedimentary derivation. They include mylonitic biotic orthogneiss, with or without garnet, muscovite-bearing quartzite, sillimanite-biotite paragneiss, biotite meta-sandstone, biotite-spotted schist, biotite-clacite-clinoamphibole meta-feldspathic arenite, biotite-calcite-clinozoisite meta-siltstone, biotite±clinoamphibole meta-marl, and graphite-bearing marble. As in previous CRP drillcores, the ubiquitous occurence of biotite±hornblende monzogranite pebbles is indicative of a local provenance, closely mirroring the dominance of these lithologies in the on-shore basement, where the Cambro-Ordovician Granite Harbour Intrusive Complex forms the most extensively exposed rock unit.