Impact Of Snow Drift On The Antarctic Ice Sheet Surface Mass Balance: Possible Sensitivity To Snow-Surface Properties

A mesoscale atmospheric numerical model is coupled with a physically based snow-pack model and with a snow-drift model. The snow model is verified for the French Alps by comparing its simulations to observations performed at the Col de Porte in the Chartreuse Massif. The snow erosion threshold depends on snow-pack properties such as density, dendricity, sphericity and particle size. The atmospheric turbulence scheme is modified in order to take into account stabilization effects due to airborne blown snow particles. In particular, vertically integrated stability functions for the stable boundary layer are completed by including the threshold friction velocity for snow erosion. The snow-drift model is calibrated by simulating the conditions observed during the Byrd snow project, held in West Antarctica in 1962. Finally, sensitivity experiments to the snow-surface properties show the importance of their accurate representation when modelling the contribution of deflation to the Antarctic surface mass balance.     

Lacustrine and palustrine carbonate petrography: an overview

Lacustrine limestones were formerly identified by their faunistic (limnea, planorbis) and floristic (Charophytes) content. For 30 years, indications of pedogenesis have been found in many lacustrine deposits, and consequently the concept of palustrine limestone was defined.Lacustrine fabrics are not that numerous: varved, laminated, homogeneous, peloidal, brecciated, gravelly, bioturbated (burrows), bioclastic, algal, and stromatolitic. Detrital beds are sometimes present and are interpreted as bottomset deposits. Palustrine fabrics result from exposure and pedogenesis of lacustrine mud. The main processes involved in this evolution are: cracking, with planar, curved, craze and skew planes, colonization by plants resulting in root traces, marmorization (redistribution of iron due to water table fluctuation), and redistribution of carbonates (needles, subspherical or cylindrical vertical nodules, carbonate coatings, early and late diagenetic crystals, Microcodium). Carbonate palustrine features can be associated with other minerals: palygorskite, gypsum, or silica. Alternation of lacustrine sedimentation and exposure/pedogenesis leads to the pseudo-microkarst facies resulting from enlargement of the complex network of root traces and horizontal cracks. The voids in the pseudo-microkarst facies are infilled with a polyphased internal sediment composed of carbonate and vadose silt and phreatic and vadose cements. Traces of exposure and pedogenesis are less in evidence in lacustrine bioclastic sands and algal-stromatolitic limestones. Finally, under certain conditions, the surficial laminar horizon and its associated perlitic crust (ooids) develops on palustrine muds and form a desert stromatolite.     

1988 COMPILATION OF ELEMENTAL CONCENTRATION DATA FOR USGS AGV-1, GSP-1 AND G-2

Concentration data on up to 90 individual constituents in USGS AGV-1, GSP-1, and G-2 have been collected from 1270 journal articles and technical reports. These data are summarized in consensus (mean) values with uncertainties expressed as +/- one standard deviation. Mean values are also calculated as a function of analytical procedure and all raw data are given in the tables. Recommended values are proposed based upon data criteria used by NIST (National Institute of Standards and Technology, formerly the National Bureau of Standards or NBS).     

Instrumental neutron activation in geoanalysis

Theoretical aspects of instrumental neutron activation analysis (INAA) are discussed. Various applications of INAA to exploration geochemistry are described demonstrating its capabilities and its limitations.Cost, turnaround time, high sensitivity for certain elements, the non-destructive nature of analysis and its precision and accuracy have combined to make INAA an indispensible method for multielement determination on virtually all geological matrices. Humus, vegetation, heavy minerals, lake bottom sediments as well as rocks and soils comprise the major sample types analyzed by INAA. As many as 50 elements can be determined routinely and easily by INAA.     

Trace metals in sediments from the inner continental shelf of the western Beaufort Sea

Increased development and changing climate have enhanced global interest in the Arctic Ocean and adjacent seas. Using a large, 3-yr data base, we have determined the distribution of trace metals in sediments from the inner shelf of the western Beaufort Sea. Metal concentrations in these sediments reflect pristine conditions, consistent with those for most coastal areas in the Arctic and with predictions based on average continental crust. Geographic variations in metal values are primarily related to sediment grainsize distribution. However, grain-size patterns are a complex function of several variables including source areas, ice and water movement, as well as physical and chemical weathering. Future identification of any metal contamination in Beaufort Sea sediments will be simplified by understanding the predictable natural patterns.     

Application of new thermodynamic data to grossular phase relations

Recent low temperature, adiabatic calorimetric heat capacity measurements for grossular have been combined with DSC measurements to give entropies up to 1000 K. In conjunction with enthalpy of solution values for grossular, these data have yielded H _f ^o (298.15K) and G _f ^o (298.15K) values of –1583.2 ± 3.5 and –1496.74 ± 3.7 kcal mol^–1 respectively. For 15 reactions in the CaO-Al₂O₃-SiO₂-H₂O system, thermodynamically calculated P-T curves have been compared with experimental reversals and have shown good agreement in most cases. Calculations indicate that gehlenite is probably totally disordered. Estimates of zoisite and lawsonite entropies are consistent with the phase equilibrium and grossular data, but estimates of the entropies of pyrope and andradite show large discrepancies when compared with experimental reversals.Contribution no. 600 from the Mineralogical Laboratory, The Department of Geology and Mineralogy, The University of Michigan, Ann Arbor, Michigan 48109, USA     

Distribution of viral and bacterial pathogens in a coastal canal community

Significant concentrations of human enteric viruses and bacteria were found to be present in the water and sediment of a coastal canal community into which secondarily treated sewage was being discharged.