Bruno Lansard

Evidence of the radioactive fallout in France due to the Fukushima nuclear accident

Radioactive fallout due to the Fukushima reactor explosion in Japan was detected in environmental samples collected in France. The presence of (131)I in aerosols (200±6 μBq m(-3)) collected at the Pic du Midi observatory, located at 2877 m altitude in the French Pyrénées, indicated that the Japanese radioactive cloud reached France between 22 and 29 March, i.e. less than two weeks after the initial emissions, as suggested by a (137)Cs/(134)Cs ratio of 1.4. Cesium radioisotopes ((134)Cs and (137)Cs) were not detected in this sample but they were present in the aerosol sample collected the next week, i.e. between 29 March and 05 April (about 10 μBq m(-3)). We also report (131)I activities measured in grass (1.1-11 Bq kg(-1); fresh weight) and soil samples (0.4 Bq kg(-1)) collected in the Seine River basin between 30 March and 10 April. The (134)Cs from the damaged Fukushima power plant was also detected in grass collected in the Seine River basin between 31 March and 10 April (0.2-1.6 Bq kg(-1) fresh weight, with a (137)Cs/(134)Cs ratio close to 1, which is consistent with Fukushima radioactive release). Despite the installation of a network of nested stations to collect suspended matter in the upstream part of the Seine River basin, (131)I was only detected in suspended matter (4.5-60 Bq kg(-1)) collected at the most upstream stations between 30 March and 12 April. Neither (131)I nor (134)Cs has been detected in environmental samples since the end of April 2011, because of the rapid decay of (131)I and the very low activities of (134)Cs (about 400 times lower than after Chernobyl accident).

Study of the phytoplankton plume dynamics off the Crozet Islands (Southern Ocean): A geochemical‐physical coupled approach

The Crozet Archipelago, in the Indian sector of the Southern Ocean, constitutes one of the few physical barriers to the Antarctic Circumpolar Current. Interaction of the currents with the sediments deposited on the margins of these islands contributes to the supply of chemical elements--including iron and other micro-nutrients--to offshore high-nutrient, low-chlorophyll (HNLC) waters. This natural fertilization sustains a phytoplankton bloom that was studied in the framework of the KEOPS-2 project. In this work, we investigated the time scales of the surface water transport between the Crozet Island shelves and the offshore waters, a transport that contributes iron to the phytoplankton bloom. We report shelf-water contact ages determined using geochemical tracers (radium isotopes) and physical data based on in situ drifter data and outputs of a model based on altimetric Lagrangian surface currents. The apparent ages of surface waters determined using the three independent methods are in relatively good agreement with each other. Our results provide constraints on the time scales of the transport between the shelf and offshore waters near the Crozet Islands and highlight the key role played by horizontal transport in natural iron fertilization and in defining the extension of the chlorophyll plume in this HNLC region of the Southern Ocean.

Preface to Bjørn Sundby’s Special Issue of Aquatic Geochemistry

This special issue of Aquatic Geochemistry is dedicated to the career of Bjorn Sundby (Fig. 1), Professor of Oceanography at the ‘‘Institut des Sciences de la Mer de Rimouski,’’ Canada. Bjorn earned his PhD in physical organic chemistry from the University of Bergen (Norway) in 1966. He started his professional career as an organic chemist for the ColgatePalmolive Company, where he worked to develop novel phosphate-free detergents in the face of the looming eutrophication crisis. Exploring his diverse interests while at Colgate, Bjorn enrolled in oceanography classes at Rutgers University and fell in love with the subject. In pursuit of a career in Oceanography, he then moved to Dalhousie University in Halifax to take on a postdoctoral position with Doug Loring. During this time, he met his wife Daniele Godbout. Ultimately, Bjorn took up a position as an oceanography research associate at the Universite du Quebec a Rimouski from 1974 to 1980, before becoming Professor of Oceanography from 1980 to 1984. He then returned to Europe to head the Department of Chemical Oceanography and Marine Pollution at the Netherlands Institute for Sea Research from 1984 to 1987, before coming back to Canada as Director of the Physical and Chemical Oceanography Branch at the Maurice Lamontagne Institute, Department of Fisheries and Oceans, Canada. With a mass of scientific achievements under his belt, Bjorn earned a prestigious Dr. Philos. Degree in aquatic geochemistry from the University of Bergen in 1987. From 1992 to his retirement in 2010, he was Professor of Oceanography at the Institut des Sciences de la Mer de Rimouski, QC. For nearly three decades, Bjorn has continued to challenge and change our view of sediment diagenesis, from the early models of a 1-dimensional steady-state system to our current picture of a 3D dynamic mosaic of biogeochemical reactions. One of his first major contributions was his work on manganese in the St. Lawrence Estuary. He was one of the