Aromatic ketones concentrated from Baltic Sea water

Aromatic ketones were concentrated from filtered Baltic Sea water by liquid—solid adsorption. After wet-chemical separation from acidic and basic components, the neutral fraction was column chromatographed to yield sub-fractions of increasing polarity. A subfraction eluted from silica gel with cyclopentane/diethyl ether contained a number of compounds which were identified by GC and GC—MS techniques as fluorenone, anthraquinone, benzanthrone, and benzene derivatives carrying an oxo group in the α-position relative to the aromatic ring. Formation and abiotic chemical reactions of these compounds in seawater are discussed.     

Late‐glacial and Holocene record of vegetation and climate from Cynthia Bay,Lake St Clair,Tasmania

A Late‐glacial–Holocene pollen record was obtained from a 3.96 m sediment core taken from Lake St Clair, central Tasmania. Modern vegetation and pollen analyses formed the basis for interpretation of the vegetation and climate history. Following deglaciation and before ca. 18450 yr BP Podocarpus lawrencei coniferous heath and Astelia–Plantago wet alpine herbfield became established at Lake St Clair. A distinct Poaceae‐Plantago peak occurs between 18450 and 11210 yr BP and a mean annual temperature depression from ca. 6.2°C to 3°C below present is inferred for this period. The marked reduction in Podocarpus and strong increase of Poaceae suggests reduced precipitation levels during the period of widespread deglaciation (ca. 18.5–11 kyr BP). The local Late Pleistocene–Holocene non‐forest to forest biostratigraphical boundary is dated at 11.2 kyr BP. It is characterised by expansion of the subalpine taxa Athrotaxis/Diselma with Nothofagus gunnii, and by the establishment of Nothofagus cunninghamii with Eucalyptus spp. A ‘Phyllocladus bulge’ prior to the expansion of Nothofagus cunninghamii, reported at other Tasmanian sites, is not present at Lake St Clair. Nothofagus cunninghamii cool temperate rainforest peaked at 7800 yr BP, probably under wetter climatic conditions than present. The maximum development of rainforest in the early–middle Holocene may indicate that the temperature was slightly warmer than present, but the evidence is not definitive. The expansion of Eucalyptus spp. and Poaceae after 6000 yr BP may be partly a disclimax effect as a result of Aboriginal burning, but appears also to reflect reduced precipitation. The changes in vegetation and inferred climate can be explained by major changes in synoptic patterns of southern Australia and the adjacent southwest Pacific. Copyright © 2000 John Wiley & Sons, Ltd.     

Behaviour of rare earth elements in geothermal systems of New Zealand

Rare earth element (REE) patterns of hydrothermally altered rhyolite from geothermal systems located in the Taupo Volcanic Zone in the North Island of New Zealand provide evidence of REE mobility. REE trends of unaltered rhyolites are characterised by moderate LREE enrichment ((La/Lu)_cn = 3.84 to 5.62) and pronounced negative Eu anomalies. In contrast, REE patterns of hydrothermally altered rhyolites commonly exhibit different signatures and may be placed into four chemically and petrographically distinct categories. Rocks with clay + quartz + feldspar + calcite (±zeolites, epidote, sphene, chlorite, opaque minerals) assemblages typically display patterns subparallel to fresh rock, whereas, samples which contain quartz + chlorite, or quartz + clay + zeolite assemblages have flat patterns without Eu anomalies, and highly silicified samples are characterised by depleted, bowed REE trends. These patterns may be produced by interaction with alkaline or acid fluids. A fourth group of very intensely altered samples, affected by interaction with acid fluids, exhibits unusual REE trends with highly enriched HREE and depleted LREE, or depleted HREE.These results indicate that some of the REE released by the breakdown of primary phases during alteration are transported away in the fluid. In addition, the degree of depletion is positively correlated with alteration intensity and the fluid/rock ratio. The similarity of REE patterns resulting from alteration by alkaline and acid fluids suggests that the shape of the REE trends is controlled principally by fluid/rock ratios and secondarily by mineralogy. The REE are retained in rocks with a diverse alteration mineralogy, whereas in samples with only one dominant alteration phase (e.g. quartz) it is more probable that not all REE liberated during alteration can be accommodated in the altered rock. Eu commonly behaves differently from the other REE, possibly due to the dominance of Eu²⁺.