Stable (Cu, Mg) and radiogenic (Sr, Nd) isotope fractionation in colloids of boreal organic-rich waters

• Published in: Chemical Geology
• Main Authors: Ilina, Svetlana, Viers, Jérôme, Lapitsky, Sergey, Mialle, Sebastian, Mavromatis, Vasileios, Chmeleff, Jérôme, Brunet, Pierre, Alekhin, Yuriy, Isnard, Hélène, Pokrovsky, Oleg
• Other Authors: Géosciences Environnement Toulouse (GET), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales Toulouse (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales Toulouse (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France-Centre National de la Recherche Scientifique (CNRS), Moscow MV Lomonosov State Univ, Fac Geog, European Commission - Joint Research Centre Geel (JRC), Département de Physico-Chimie (DPC), CEA-Direction des Energies (ex-Direction de l'Energie Nucléaire) (CEA-DES (ex-DEN)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay, Service d'Etudes du Comportement des Radionucléides (SECR), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-CEA-Direction des Energies (ex-Direction de l'Energie Nucléaire) (CEA-DES (ex-DEN)), Laboratoire de développement Analytique Nucléaire Isotopique et Elémentaire (LANIE), Service d'études analytiques et de réactivité des surfaces (SEARS), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Département de Physico-Chimie (DPC), UroRAS
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2013
• Subjects: [CHIM.ANAL]Chemical Sciences/Analytical chemistry; Subarctic
• Online Access: https://hal.science/hal-04453556; https://doi.org/10.1016/j.chemgeo.2013.01.019

International audience Stable (Cu and Mg) and radiogenic (Sr and Nd) isotopic compositions in filtrates and ultrafiltrates of various size fractions have been measured in waters of subarctic watersheds (NW Russia) and in temperate rivers and lakes of the south boreal zone. A large volume of samples were filtered in the field using cascade filtration and ultrafiltration employing progressively decreasing pore sizes (100, 20, 10, 5, 0.8, 0.4, 0.22, and 0.1 mu m; 100, 10 and 1 kDa) followed by element isotopic analysis using thermal ionization mass spectrometers and a Neptune multicollector ICP-MS. In the boreal watershed underlain by Archean and Proterozoic rocks, the Sr-87/Sr-86 ratio decreased in the 1-100 kDa ultrafiltrates and dialysates by 0.0001-0.0004 units compared to the 0.45 mu m filtrates. Despite the dominance of colloids in the Nd speciation in surface waters, the isotopic value of Nd in the filtrates and ultrafiltrates remained constant within the uncertainty of the measurements. We hypothesize the absence of an atmospheric input of silicate dust for Nd but the presence of marine aerosols for Sr. It follows that the Sr in the investigated surface waters has a short residence time compared to the time required for achieving isotopic equilibrium between the colloidal (1 kDa-022 mu m) and truly dissolved (<1 kDa) pools. For Nd, the residence time is long enough to achieve this equilibrium. The stable isotope composition of Cu in the streams remained constant within +/- 0.1 parts per thousand during filtration through 100 pm to I kDa membranes, despite the fact that 40-60% of Cu was colloidal. This result suggests that the homogeneity of the Cu isotopic composition within the colloidal and truly dissolved pools is likely associated with the similarity of the structure and stability of Cu(II) complexes with fulvic adds of different molecular weights. The stable isotope composition of dissolved Mg in soil solution and bog surface water demonstrates similar, within the analytical uncertainty, isotopic ...