Entwicklung von Biosensoren für die biotechnologische Praxis

Zur Verbesserung biotechnologischer Prozesse ist es notwendig, die wichtigsten Schlüsselkomponenten in den Kultivierungsmedien zu überwachen und zu regeln. Voraussetzung dafür ist die In-situ- und On-line-Messung dieser Größen. Dazu müssen die Analyseninstrumente an den Produktionsreaktor direkt angekoppelt werden. Wegen des hohen Preises dieser Instrumente würde die Ausstattung eines jeden Reaktors mit einem Analysensystem sehr aufwendig und teuer. Hier können die einfachen und preisgünstigen Biosensoren Abhilfe schaffen. Biosensoren bestehen aus einem chemisch-spezifischen Empfänger (Enzym, Antikörper, Zelle), der mit einem sog. Transducer verbunden ist. Der Transducer ist ein physikalischer Sensor, der die chemischen Änderungen in der Empfängerschicht in Licht- oder elektrische Signale umwandelt. Abhängig davon, welchen physikalischen Sensor man verwendet, unterscheidet man zwischen - potentiometrischen, amperometrischen, kalorimetrischen, optischen und mechanischen Sensoren. Im Institut für Technische Chemie (TCI) der Universität Hannover werden potentiometrische, kalorimetrische und optische Sensoren entwickelt und zur Überwachung und Regelung biotechnologischer Prozesse eingesetzt. Daher werden hier nur diese Sensoren behandelt

Concentration factors and biological half-lives for the dynamic modelling of radionuclide transfers to marine biota in the English Channel

International audienceThe biokinetics of radionuclide transfers to biota in the marine environment can be modelled using two parameters, specific to both each element/radionuclide and biota. The Concentration Factor (CF) reflects the ratio between the activity concentrations in the biota and the surrounding seawater in steady state. The biological half-life (tb1/2) characterizes depuration kinetics for the radionuclide from the biota. While recommended CF values can be found in the literature, no guidelines actually exist for tb1/2 values. We used available time-series activity concentration measurements in biota in the English Channel, where controlled amounts of liquid radioactive waste are discharged by the ORANO La Hague reprocessing plant. We calculated the corresponding time-series activity concentrations in seawater for each biota dataset using an extensively-validated hydrodynamic model. We derived the values of CF and tb1/2 from seawater and biota data, to model radionuclide transfers between the two compartments. To assess the performance of the model, we analyzed the residual between observed and calculated levels in the biota. Datasets for macroalgae, mollusks, crustaceans and fish yielded parameters (CF, tb1/2) for H3 (as body water and as organically bound tritium), C14, Sb125, Cs137, I129, Mn54, Co60, Zn65 and Ru106. After discussing the results and qualifying the model's reliability, we proposed recommendations for CF and tb1/2 for the purposes of the operational modelling of radionuclide transfers to biota in the marine environment

Iodine uptake in brown seaweed exposed to radioactive liquid discharges from the reprocessing plant of ORANO La Hague

International audienceIodine-129 is present in controlled liquid radioactive waste routinely released in seawater by the ORANO nuclear fuel reprocessing plant in La Hague (Normandy, France). Brown algae are known for their exceptional ability to concentrate iodine from seawater. They also potentially emit volatile iodine compounds in response to various stresses, such as during emersion at low tide. For these reasons, brown seaweed is routinely collected for radioactivity monitoring in the marine environment (Fucus serratus and Laminaria digitata). Despite the high concentration ratio, the exact mechanism of iodine uptake is still unclear. Chemical imaging by laser desorption/ionization mass spectrometry provided evidence that iodine is stored by kelps as I−. In this study we investigate in vivo iodine uptake in kelps (L. digitata) with an emphasis on seawater iodine chemical speciation. Our results showed that kelp plantlets were able to take up iodine in the forms of both IO3− and I−. We also observed transient net efflux of I− back to seawater but no IO3− efflux. Since the seaweed stores I− but takes up both IO3− and I−, IO3− was likely to be converted into I− at some point in the plantlet. One major outcome of our experiments was the direct observation of the kelp-based biogenic conversion of seawater IO3− into I−. On the basis of both IO3− and I− uptakes by the seaweed, we propose new steps in the possible iodine concentration mechanism used by brown algae

Dynamic modeling of radionuclide transfers in the marine Environment in the English Channel from discharges to biota

International audienceRadionuclide transfer parameters between water and biota recommended in the literature are generally limited to the concentration factor values (CF). So a steady state must be assumed when using them for modeling. But in the event of an accident or in the close vicinity of a regular input source where concentrations are maximal, sharp changes in seawater concentration are likely to occur and the assumption of a steady state is usually not met. Dynamic modeling requires taking into account the kinetics of the transfer, usually characterized by the radionuclide biological half-life (tb1/2), but recommendations for tb1/2 values are still scarce. The nuclear reprocessing plant of ORANO La Hague (France, Normandy) is the major source of liquid radioactive discharges to the marine environment in the English Channel. A hydrodynamic model has been extensively validated by matching several thousands of calculated and locally observed concentrations in seawater. It is now available to reliably predict the dispersion of radioactive discharges in this area. It is also possible to calculate the corresponding seawater radionuclide concentrations in locations where long time-series measurement in biota are available. Using the calculated signal in seawater and the observed signal in biota, it is possible to derive dynamic transfer parameters (CF, tb1/2) to model radionuclide transfers between seawater and the biota. This data processing was performed with radionuclides data including Cs-137, Co-60, I-129, monitored in algae, mollusks, crustacean and fish, around La Hague Cape. In addition, a distribution analysis of the residual between the calculated and observed values was carried out. On the basis of this data processing, recommendations for dynamic transfer parameters (CF, tb1/2) values are proposed for these radionuclides and these recommendations are supported by documenting the reliability of the modeling from the discharges down to the biota

Transfer of radiocarbon liquid releases from the AREVA La Hague spent fuel reprocessing plant in the English Channel

International audienceThe recent risk assessment by the North-Cotentin Radioecology Group (http://www.irsn.org/nord-cotentin/, 1999) outlined that 14 C has become one of the major sources of the low dose to man through seafood consumption. It was recommended that more data should be collected about 14 C in the local marine environment. The present study aims to respond to this recommendation. The estimation of 14 C activity in marine species is based on concentration factor values. The values reported here ranged from 1 Â 10 3 to 5 Â 10 3 Bq kg À1 ww/Bq L À1. A comparison was made between the observed and predicted values. The accuracy of 14 C activity calculations was estimated between underestimation by a factor of 2 and over-estimation by 50% (95% confidence interval). However, the use of the concentration factor parameter is based on the biological and seawater compartments being in steady state. This assumption may not be met at short distances from the point of release of discharges, where rapid changes in seawater concentration may be smoothed out in living organisms due to transfer kinetics. The data processing technique, previously published by Fiévet and Plet (2003. Estimating biological half-lives of radionuclides in marine compartments from environmental time-series measurements. Journal of Environmental Radioactivity 65, * Corresponding author. Tel.: þ33 2 33 01 41 01; fax: þ33 2 33 01 41 30. Journal of Environmental Radioactivity 90 (2006) 173e196 www.elsevier.com/locate/jenvrad 91e107), was used to deal with 14 C transfer kinetics, and carbon half-lives between seawater and a few biological compartments were thus estimated

Alderney Race, general hydrodynamic and particular features

(IF 4.23; Q1)International audienceThis work presents an overview of the main hydrodynamic features of the Alderney Race issued from in-situ measurements and hydrodynamic model simulations. This area encompasses a large range of tidal properties (tidal amplitude, tidal wave propagation) and particularly strong currents exceeding 5 m.s-1 with associated counter currents and gyres. Variations of depth, sea bottom roughness, coastal topography and current orientation around the La Hague Cape give access to a large variety of original hydrodynamic phenomena. Some are pointed out as places with a 0.3 m lower mean sea level associated to nearly constant average tidal currents. A resonance effect linked with the strong offshore currents is also observed close to the coasts. The "St Martin whistle" occurs in a bay whose gyre center oscillates with a reversal of the measured current every 5 – 7 minutes. The Alderney Race represents a workshop area for coastal hydrodynamic studies. The available in-situ measurement datasets are rich with recordings of: sea levels; ADCP current profiles; surface radar currents; waves; dye experiments; surface and in depth dissolved tracer surveys. Associated with 3D hydrodynamic models it allow understanding the complexity of this area and refine the knowledge of hydrodynamic process and forcing parameters that could be applied in other coastal area

Dissolved Radiotracers and Numerical Modeling in North European Continental Shelf Dispersion Studies (1982–2016): Databases, Methods and Applications

Significant amounts of anthropogenic radionuclides were introduced in ocean waters following nuclear atmospheric tests and development of the nuclear industry. Dispersion of artificial dissolved radionuclides has been extensively measured for decades over the North-European continental shelf. In this area, the radionuclide measurement and release fluxes databases provided here between 1982 and 2016 represent an exceptional opportunity to validate dispersion hydrodynamic models. This work gives accessibility to these data in a comprehensive database. The MARS hydrodynamic model has been applied at different scales to reproduce the measured dispersion in realistic conditions. Specific methods have been developed to obtain qualitative and quantitative results and perform model/measurement comparisons. Model validation concerns short to large scales with dedicated surveys following the dispersion: it was performed within a two- and three-dimensional framework and from minutes and hours following a release up to several years. Results are presented concerning the dispersion of radionuclides in marine systems deduced from standalone measurements, or according to model comparisons. It allows characterizing dispersion over the continental shelf, pathways, transit times, budgets and source terms. This review presents the main approaches developed and types of information derived from studies of artificial radiotracers using observations, hydrodynamic models or a combination of the two, based primarily on the new featured datasets

Transfer of Tritium Released into the Marine Environment by French Nuclear Facilities Bordering the English Channel

International audienceControlled amounts of liquid tritium are discharged as tritiated water (HTO) by the nuclear industry into the English Channel. Because the isotopic discrimination between 3H and H is small, organically bound tritium (OBT) and HTO should show the same T/H ratio under steady-state conditions. We report data collected from the environment in the English Channel. Tritium concentrations measured in seawater HTO, as well as in biota HTO and OBT, confirm that tritium transfers from HTO to OBT result in conservation of the T/H ratio (ca. 1 × 10 −16). The kinetics of the turnover of tritium between seawater HTO, biota HTO, and OBT was investigated. HTO in two algae and a mollusk is shown to exchange rapidly with seawater HTO. However, the overall tritium turnover between HTO and the whole-organism OBT is a slow process with a tritium biological half-life on the order of months. Nonsteady-state conditions exist where there are sharp changes in seawater HTO. As a consequence, for kinetic reasons, the T/H ratio in OBT may deviate transiently from that observed in HTO of samples from the marine ecosystem. Dynamic modeling is thus more realistic for predicting tritium transfers to biota OBT under nonsteady-state conditions

A comprehensive assessment of radioactivity monitoring in the Channel Islands

International audienceThe Channel Islands are located in the Normand-Breton Gulf (NBG), in the mid-part of the English Channel (France, Normandy). In the northern part, off Cap La Hague, controlled amounts of radioactive liquid waste are discharged by the ORANO La Hague nuclear fuel reprocessing plant (RP). Radionuclides were monitored in the NBG to assess the dispersion of radioactive discharges from the RP in the marine environment. The temporal and spatial distribution of the data are consistent with the history of the discharges, with most gamma emitter radionuclide environmental levels being close to or below the current limits of detection. A clear fingerprint of H-3, C-14 and I-129 radionuclides discharged from the RP is measured. The hydrodynamics in the NBG do not yield a simple gradient with linear distance from the outfall of the RP. Modelling tools were used to understand how radioactive discharges spread from the source of input. Dispersion patterns clearly illustrate the different behaviours of soluble and non-soluble radionuclides. The study indicated that the footprint of radioactive liquid discharges by French nuclear facilities was still measurable in species collected from the NBG for the mostly dissolved radionuclides. The less conservative ones, with a high affinity for suspended matter, are potentially influenced by old releases. These pathways could be investigated by dedicated hydrodynamic dispersion models. Overall, in the Channel Islands the levels are low and consistent with the general decrease in liquid radionuclide discharges by the RP since the 1990s

Inventory and distribution of tritium in the oceans in 2016

International audienceTritium concentrations in oceans were compiled from the literature, online databases and original measurements in order to determine the global distribution of tritium concentrations according to latitude and depth in all oceans. The total inventory of tritium decay corrected in 2016 has been estimated using evaluation of the natural and artificial contributions in 23 spatial subdivisions of the total ocean. It is determined equal to 26.8 ± 14 kg including 3.8 kg of cosmogenic tritium. That is in agreement with the total atmospheric input of tritium from nuclear bomb tests and the natural inventory at steady-state estimated from natural production rates in the literature (25.6 – 28 kg in the Earth). A global increase in tritium concentration was observed according to latitude in the Northern hemisphere with a maximum in the Arctic Ocean. The minimum tritium concentrations observed in the Southern Ocean were close to steady-state with known natural tritium deposition. We focused on the temporal evolution of surface (0 to 500 m) tritium concentrations in a selected area of the North Atlantic Ocean (30°N - 60°N) where we found the 2016 concentration to be 0.60 ± 0.05 TU (1σ). Results showed that in that area, between 1988 and 2013, tritium concentrations: i) decreased faster than the sole radioactive decay, due to a mixing with lower and lateral less concentrated waters, and ii) decreased towards an apparent steady state concentration. The half-time mixing rate of surface waters and the steady state concentration were respectively calculated to be 23 ± 5 years (1σ) and 0.38 ± 0.07 TU (1σ). This apparent steady-state concentration in the North Atlantic Ocean implies a mean tritium deposition of 1870 ± 345 Bq.m-2 (1σ), five folds higher than the known inputs (natural, nuclear tests fallout and industrial releases, ~367 Bq.m-2) in this area. Keywords: Radionuclide, Tracer, Database, Background concentration