Geological Society of America The Geological Society of America bulletin Melville, NY : American Institute of Physics, 1890 129(2017), 7/8, Seite 820-836 Online-Ressource
von P. D. Clift ; Hongbo Zheng ; Andy Carter ; Philipp Böning ; Tara N. Jonell ; Hannah Schorr ; Xin Shan ; Katharina Pahnke ; Xiaochun Wei ; Tammy Rittenour
"Despite its toxicity and versatile geochemistry, not much is known on the distribution, speciation and behaviour of Thallium (Tl) in the marine coastal environment, notably in estuaries. We here contribute to the discussion by presenting dissolved (<0.45 μm) and particulate data of Tl, Fe, Mn, as well as dissolved organic carbon (DOC) and dissolved Si for two transects through the Weser estuary during summer (July 2013) and winter (early March 2014). The results show that both, dissolved Tl (70130 pM) and DOC (1001000 μM) are elevated against average river concentrations, show the same distinct seasonality, decrease with increasing salinity and positively deviate from conservative mixing. Compared to that, dissolved Si displays almost conservative mixing with seawater while dissolved Fe and Mn are quickly removed in the estuarine turbidity maximum (ETM) classically located in the low salinity region of the estuary. The data further suggest that both, dissolved Tl and DOC exhibit only little loss at the ETM, and that Tl does not seem to cycle with Fe and Mn as was suggested for other estuaries. Moreover, reactive particulate Tl (as calculated from excess Tl enriched versus the lithogenic background) on the particles amount to only 2050% of the dissolved Tl concentrations. This is in agreement with earlier studies underlining the low particle reactivity of Tl. However, the strong correlation between dissolved Tl and DOC is new and suggests a combined cycling through the estuary. Albeit being indirect, our observations support earlier suggestions of a possible association of Tl with organic ligands, and that Tl tends to remain in the dissolved phase when entering the ocean." (Abstract)
Estuarine, coastal and shelf science London : Academic Press, 1981 187(2017) vom: 5. März, Seite 146-151 Online-Ressource
Neodymisotope (Nd) und Seltene Erdelemente (REE) wurden in nordpazifischem Meerwasser analysiert (nahe Hawaii), um Elementeintrag in den Ozean zu untersuchen. Weiterhin wurden Nd-Isotope in Sedimentarchiven des Südpazifiks analysiert, um Zirkulationsänderungen während der letzten 30.000 und 140.000 Jahre zu untersuchen. REE und Nd isotope nahe Hawaii zeigen den signifikanten Einfluss von lokalen (Hawaii) und entfernten (Asiatischer Staub) Quellen auf ihre Budgets im zentralen Nordpazifik und Saisonalität des Elementeintrages. Nd-Isotope aus Sedimentarchiven des Südpazifiks zeigen Änderungen der Tiefenwasserzirkulation seit des letzten und vorletzten Hochglazials. Sie deuten auf eine Kontrolle des südhemisphärischen Klimas auf früh-deglaziale Entstratifizierung im Tiefenwasser hin, zusätzlich zum generellen variablen Einfluss von nordatlantischem und nordpazifischem Tiefenwasser auf die Tiefenwassermischung im Südpazifik. Ein methodischer Ansatz zeigt, dass fossile Tiefenwasser-Nd-Isotopensignale nicht mittels üblicher Extraktionsprotokolle aus Eisen-Mangan-Oxiden des tiefen Südpazifiks gewonnen werden können. <dt.>
Neodymium (Nd) isotopes and rare earth elements (REE) were analysed in North Pacific seawater (near Hawaii) to investigate lithogenic input to the ocean. Further, Nd isotopes measured in South Pacific sedimentary archives were used to study changes in deep ocean circulation during the last 30,000 and 140,000 years. REE and Nd isotopes in seawater near Hawaii suggest a significant contribution of local (Hawaiian) and distal (Asian dust) sources to their budgets in the central North Pacific and seasonality of element supply. South Pacific sedimentary Nd isotope compositions reflect the changing deep water circulation and water mass mixing since the last and penultimate Glacial Maximum. They suggest a Southern Hemisphere climate control on early deglacial deep destratification in addition to the more general influence of varying fractions of North Atlantic and North Pacific deep waters on the deep water mixture in the South Pacific. A methodological approach shows the failure of common leaching protocols for the extraction of paleo-bottom water Nd isotope signals from deep South Pacific sedimentary ferromanganese oxides. <engl.>
von Torben Struve ; Tina van de Flierdt ; Laura F. Robinson ; Louisa I. Bradtmiller ; Sophia K. Hines ; Jess F. Adkins ; Myriam Lambelet ; Kirsty C. Crocket ; Katharina Kreissig ; Barry Coles ; Maureen E. Auro