Role of lipid/water partitioning and membrane composition in the uptake of organochlorine pesticides into a freshwater mussel

The aim of this investigation is to understand the factors influencing uptake of persistent organochlorine pesticides into a freshwater mussel (Sphaerium corneum). Previous work has shown that although a substantial proportion of dieldrin is bound to particulates in the river system, uptake is from the dieldrin in solution. This suggests partitioning of the hydrophobic xenobiotics into membranes as the major route of entry. Membrane composition was established using lipid fractionation into neutral lipids and phospholipids followed by derivatisation to fatty acid methyl esters and estimation using GC/FID. Membrane composition varied with acclimation temperature over the range 5–20°C. Dieldrin concentrations in the mussel at equilibrium with 2000 ng dieldrin/litre water burden were studied at one temperature under laboratory conditions using animals acclimated to different temperatures. Any differences may be explicable in terms of effects of membrane composition on partitioning or other physiological adaptations. To establish which of these factors is most significant a membrane fragment partition system has been analysed in vitro. Preliminary results indicate that although water/lipid partitioning may be important in entry (and exit) of non-polar xenobiotics, significant differences could not be found using current methods. The role of membrane composition and therefore temperature history of the organism may still be significant. The implications of this for attempted correlations between bioaccumulation factors and simple octanol/water partition coefficients are discussed.     

Age and pyrite Pb-isotopic composition of the giant Sukhoi Log sediment-hosted gold deposit, Russia

Sukhoi Log is one of the largest gold deposits in Russia (1100 t Au at 2.45 g/t). Like many other sediment-hosted gold deposits throughout the world, Sukhoi Log preserves textural, structural and geochemical evidence for multiple generations of Au enrichment and pyrite growth.The deposit is located in the Lena gold province of Siberia, on the edge of the Siberian Craton and occurs in the core of a recumbent anticline in a Neoproterozoic black shale and quartz-rich siltstone-sandstone turbidite succession. Temporal constraints on pyrite paragenesis at the deposit have been determined using laser ablation inductively coupled mass spectrometry (LA-ICPMS) measurements of U, Th and Pb isotopes in pyrite, monazite and zircon. LA-ICPMS age determinations on detrital zircons indicate the host rocks were deposited after 600 ± 10 Ma and derived from a mixture of Palaeoproterozoic and Neoproterozoic sources. The U, Th and Pb isotopic systematics indicate the cores of large monazite crystals, which predate obvious tectonic fabric development in the host rocks, began growing at 573 ± 12 Ma. The rims of the same monazite crystals formed at 516 ± 10 Ma, during peak metamorphism and deformation. Small monazite crystals also grew in the sedimentary rocks during the Devonian (374 ± 20 Ma) and the Carboniferous or Early Permian (288 ± 22 Ma), possibly in response to fluid movements triggered by synchronous granite intrusion in the area. Multi-collector and quadrupole LA-ICPMS Pb isotopic determination on pyrite, combined with overprinting criteria, show that the earliest (stratiform) Pb and Au-bearing pyrite formed prior to metamorphism—possibly during sedimentation or early diagenesis (575-600 Ma). Small Au-rich pyrite nodules preserved as cores to folded bedding-parallel pyrite-quartz veins probably grew during late diagenesis or early metamorphism. Large pyrite euhedra, which overgrow the strong axial planar cleavage in the host rocks, have more radiogenic Pb-isotopic compositions and formed either late during or after deformation. Framboidal pyrite that is overgrown by both the late diagenetic-early metamorphic and syn- to post-metamorphic pyrite has the most radiogenic Pb-isotopic composition suggesting exchange with radiogenic Pb in the matrix may have continued until late in the history of the deposit.The dating and Pb isotopes support a multistage origin for the gold deposit with Au first introduced during or prior to growth of the earliest stratiform pyrite and progressively re-concentrated (with or without addition of further gold) during later metamorphic events.     

Isotope Ratio Determination in the Earth and Environmental Sciences: Developments and Applications in 2006–2007

This review documents developments and applications in the field of isotope ratio determination, as reflected in the literature for the Earth and Environmental Sciences for the years 2006 and 2007. The emphasis is predominantly on applications, reflecting the enormous diversity of problems to which isotopic analysis can now be applied, but viewed in the context of rapid uptake of new analytical technologies and significant new drivers of research output.     

GGR Critical Review of Analytical Developments in 2006–2007

In 2005 the Geostandards and Geoanalytical Research editorial team, in the true spirit of scientific endeavour, embarked on an experiment of our own. We decided to trial a new kind of review, somewhat different from those more typically observed in journals, and one that would provide readers with a summary of analytical developments across a broad range of topics appropriate to the Earth sciences. The first contribution of this kind appeared in 2005, and reported on developments in 2003 (Hergt et al. 2005). The second, this time a biennial review, was published in 2006 and reported on highlights of the 2004 and 2005 literature (Hergt et al. 2006). Based on reprint requests, positive remarks at conferences and strong citations we consider the experiment a resounding success and proudly present here the third in this series. This comprises six individual review sections that cover the main analytical technologies and topical application fields in geoanalysis and geochemistry, including geological and environmental reference materials, ICP‐thermal and secondary ionisation‐mass spectrometry, as well as neutron activation analysis, X‐ray fluorescence and atomic absorption spectrometry.     

THE TROUBLE WITH ANTITHESES: THE CASE OF G. K. GILBERT,GEOGRAPHER AND EDUCATOR

Accounts of the paradigmatic history of twentieth century American geomorphology traditionally describe Gilbert and Davis in anthithetical terms. That characterization partially misrepresents Gilbert, who was a geographer and an educator as well as a geologist and an investigator. Viewing the Gilbertian paradigm as the antithesis of the outmoded Davisian paradigm may have facilitated the acceptance of Gilbert's approach, but extending the dichotomous generalization to other aspects of Gilbert and Davis impedes full appreciation of Gilbert's contributions.     

Selected topics in arctic atmosphere and climate

This paper summarizes the main elements of four IPY projects that examine the Arctic Atmosphere. All four projects focus on present conditions with a view to anticipating possible climate change. All four investigate the Arctic atmosphere, ocean, ice, and land interfacial surfaces. One project uses computer models to simulate the dynamics of the Arctic atmosphere, storms, and their interactions with the ocean and ice interface. Another project uses statistical methods to infer transports of pollutants as simulated in large-scale global atmospheric and oceanic models verifying results with available observations. A third project focuses on measurements of pollutants at the ice-ocean?Catmosphere interface, with reference to model estimates. The fourth project is concerned with multiple, high accuracy measurements at Eureka in the Canadian Archipelago. While these projects are distinctly different, led by different teams and interdisciplinary collaborators, with different technical approaches and methodologies, and differing objectives, they all strive to understand the processes of the Arctic atmosphere and climate, and to lay the basis for projections of future changes. Key findings include: ? Decreased sea ice leads to more intense storms, higher winds, reduced surface albedo, increased surface air temperature, and enhanced vertical mixing in the upper ocean. ? Arctic warming may affect toxic chemicals by remobilizing persistent organic pollutants and augmenting mercury deposition/retention in the environment. ? Changes in sea ice can dramatically change processes in and at the ice surface related to ozone, mercury and bromine oxide and related chemical/physical properties. ? Structure and properties of the Arctic atmospheric??troposphere to stratosphere??and tracking of transport of pollution and smoke plumes from mid-latitudes to the poles.