Jacques Navez

Barium and carbon fluxes in the Canadian Arctic Archipelago

The seasonal and spatial variability of dissolved Barium (Ba) in the Amundsen Gulf,southeastern Beaufort Sea, was monitored over a full year from September 2007 to September 2008. Dissolved Ba displays a nutrient・type behavior: the maximum water column concentration is located below the surface layer. The highest Ba concentrations are typically observed at river mouths, the lowest concentrations are found in water masses of Atlantic origin. Barium concentrations decrease eastward through the Canadian Arctic Archipelago. Barite (BaSO 4 ) saturation is reached at the maximum dissolved Ba concentrations in the subsurface layer, whereas the rest of the water column is undersaturated. A three end‐member mixing model comprising freshwater from sea・ice melt and rivers, as well as upper halocline water, is used to establish their relative contributions to the Ba concentrations in the upper water column of the Amundsen Gulf. Based on water column and riverine Ba contributions, we assess the depletion of dissolved Ba by formation and sinking of biologically bound Ba (bio・Ba), from which we derive an estimate of the carbon export production. In the upper 50 m of the water column of the Amundsen Gulf, riverine Ba accounts for up to 15% of the available dissolved Ba inventory, of which up to 20% is depleted by bio-Ba formation and export. Since riverine inputs and Ba export occur concurrently, the seasonal variability of dissolved Ba in the upper water column is moderate. Assuming a fixed organic carbon to bio・Ba flux ratio, carbon export out of the surface layer is estimated at 1.8 ・ 0.45 mol C m −2 yr −1 . Finally, we propose a climatological carbon budget for the Amundsen Gulf based on recent literature data and our findings, the latter bridging the surface and subsurface water carbon cycles.

Radium analysis by sector field ICP-MS in combination with the Diffusive Gradients in Thin Films (DGT) technique

A new and simple method to assess low radium concentrations in water and sediment pore water was developed. The 226Ra ions are trapped on a laboratory prepared MnO2 resin (3 other ones have also been tested) that is inserted in a DGT probe (diffusive gradients in thin films). The probe can be deployed for days to weeks sufficient to accumulate enough 226Ra to be quantified. Because the High Resolution ICP-MS was operated in low resolution mode to get the highest sensitivity, isobaric interference from the Sr88Ba138 molecular ion could not be avoided. However, the pre-concentration on the MnO2 resin favours 226Ra accumulation versus that of Ba and Sr. The instrumental repeatability on a standard of 2 ng L−1226Ra was 1.4% (n = 10), while the relative standard deviation on natural samples was 8% (average of 2.2 pg L−1226Ra, n = 3). A detection limit as low as 0.022 pg L−1226Ra (0.80 mBq L−1) was achieved for a 24 h DGT deployment.

Connectivity between migrating and landlocked populations of a diadromous fish species investigated using otolith microchemistry.

Smelt Osmerus eperlanus has two different life history strategies in the Netherlands. The migrating population inhabits the Wadden Sea and spawns in freshwater areas. After the closure of the Afsluitdijk in 1932, part of the smelt population became landlocked. The fresh water smelt population has been in severe decline since 1990, and has strongly negatively impacted the numbers of piscivorous water birds relying on smelt as their main prey. The lakes that were formed after the dike closure, IJsselmeer and Markermeer have been assigned as Natura 2000 sites, based on their importance for (among others) piscivorous water birds. Because of the declining fresh water smelt population, the question arose whether this population is still supported by the diadromous population. Opportunities for exchange between fresh water and the sea are however limited to discharge sluices. The relationship between the diadromous and landlocked smelt population was analysed by means of otolith microchemistry. Our interpretation of otolith strontium (88Sr) patterns from smelt specimens collected in the fresh water area of Lake IJsselmeer and Markermeer, compared to those collected in the nearby marine environment, is that there is currently no evidence for a substantial contribution from the diadromous population to the spawning stock of the landlocked population.

An improved multiple internal standard normalisation for drift in LA-ICP-MS measurementsPresented at the 2nd International Conference on High-resolution Sector Field ICP-MS, Vienna, Austria, September 12???15, 2001.

One of the primary factors limiting precision in LA-ICP-MS measurements is the instrument fluctuation. To overcome this limitation one usually employs a normalisation based on a single internal standard. This article reports a new approach for the normalisation of LA-ICP-MS measurements, based on multiple internal standards. The novelty of the approach is that it (i) takes into account the measurement uncertainties, (ii) generates uncertainty bounds on the normalized measurements and (iii) allows one to check and dismiss the mass dependency of the normalisation procedure. As a result, it is shown that the improvement in normalisation factor increases proportionally to the square root of the number of internal standards (e.g., the use of two internal standards leads to a decrease of the standard deviation by 30%, three to 42% and four up to 50% compared with the classical normalisation). This is illustrated on the NIST 610 standard with a 266 nm UV LA-ICP-MS. An extra advantage of the use of multiple internal standards is that it allows the detection of artifacts in the measurements (internal quality check).