ALBERT

Description: Visceral afferent pathways influence on vasopressin secretion, ADH levels and urinary excretory patterns of dogs during surgical stress

Description: The first isotopic compositions of dissolved hafnium in seawater from across the Arctic Ocean are reported. Most samples from the four sub-basins of the Arctic Ocean have values within error of an average of epsilon(Hf) = +0.8. Combined Hf-Nd isotope compositions do not fall on the well-established positive correlation for mantle and crustal rocks. Instead, Arctic waters have Hf that is more radiogenic than that typically found in rocks with similar Nd isotope compositions, a feature previously found in ferromanganese crusts and waters from the Pacific Ocean. Arctic seawater samples generally fall on the lower part of the ferromanganese crust array, reflecting influences of inputs from Arctic rivers and interactions of shelf waters with underlying sediments. Arctic rivers have much higher Hf concentrations (7-30 pM) than Arctic seawater (0.36-4.2 pM). Water from the Mackenzie River has the least radiogenic Hf, with epsilon(Hf) = -7.1 +/- 1.7, and plots furthest away from the ferromanganese crust array, while waters from the Ob, Yenisey, and Lena Rivers have values that are indistinguishable from most Arctic waters. In the Amundsen, Makarov, and Canada basins, Hf concentrations are highest at the surface and lowest in the deeper waters, reflecting the influences of riverine inputs and of waters that have flowed over the extensive Siberian continental shelves and have Nd and Hf characteristics that reflect water-sediment interactions. This is in contrast to the relatively low near surface Hf concentrations reported for locations elsewhere. The Pacific water layer in the Canada Basin exhibits the highest value of epsilon(Hf) = +6.8 +/- 1.8, reflecting the Hf isotopic composition of waters entering the Arctic from the Pacific Ocean. Mixing relationships indicate that a substantial fraction of the Hf in the Mackenzie River is lost during estuarine mixing; the behaviour of Hf from other rivers is less constrained. (C) 2009 Elsevier Ltd. All rights reserved.

Description: The first Hf isotope data for seawater are reported for a series of stations in the Northwestern Pacific and define a range from epsilon(Hf) = 3.5 +/- 1.4 to 8.6 +/- 1.6. Most samples have values within error of the average of epsilon(Hf) = 5.9, but significant variations are found in intermediate waters at a depth of 600 m, as well as in deep waters. The Nd and Hf isotope compositions of the deep waters fall within the range of values found for surfaces of hydrogenetic ferromanganese crusts in the region, confirming that Hf in the Fe-Mn crusts has been derived from the overlying water column, which thus provide an archive of past seawater compositions. Although the seawater samples are generally close to the global epsilon(Nd)-epsilon(Hf) correlation obtained from ferromanganese crusts, there are significant deviations from this correlation indicating that there is some additional decoupling between Nd and Hf isotope signals, most likely caused by local water mass mixing and differences in residence times. This is not resolved in the crust samples, which integrate seawater signals over 10(4) years. The combined use of these two isotope systems in seawater therefore provides an additional dimension for tracing water masses in the oceans. Studies of the distribution of oceanic Hf isotope compositions that have been confined to deep water and boundary waters, as recorded in seafloor ferromanganese crusts, can now be extended and aimed at characterising the entire present-day water column. Average Hf concentrations measured in this study are somewhat lower than previously reported, suggesting a shorter residence time for Hf in the global oceans, although the uncertainty in the extent of Hf removal from the water column during estuarine mixing as well as a lack of data on hydrothermal and dust inputs remains a limit on how well the residence time can be defined. (C) 2008 Elsevier Ltd. All rights reserved.