Exchange Velocity Approach and the Role of Photosynthesis for Tritium Transfer from Atmosphere to Plants

Uncertainty of current understanding regarding OBT formation in plants

“…-CEA (Commissariat of Atomic Energy, France) (with CERES model), a simple model with a constant exchange velocity for day or night and with OBT production depending on the integrated leaf HTO concentration (Patryl and Armand, 2005;2007); -IFIN ("Horia Hulubei" National Institute for Physics and Nuclear Engineering, Romania) (with FDMH+ model), a research grade and operational model of moderate complexity (Galeriu et al, 2000a;2000b;Melintescu et al, 2002;Melintescu and Galeriu, 2005), with an intermediate upgraded version (Galeriu et al, 2009b;Melintescu and Galeriu, 2011); -KIT (Karlsruhe Institute of Technology, Germany) (with UFOTRI model), a research grade and operational model of moderate complexity (Raskob, 1993), with an intermediate upgraded version (PLANT-OBT) (Raskob et al, 1996;Raskob, 2011).…”

“…UFOTRI was successfully tested for other crops as rice and soybean (Raskob, 2007). The IFIN model (Galeriu et al, 2009b;Melintescu and Galeriu, 2011) The present study analyses the experimental results regarding NE-OBT but in many cases, the measurements consider total OBT. Considering the field conditions at Perch Lake plot garden of Atomic Energy of Canada Limited (AECL) (Kim and Korolevych, 2013), the ratio between NE-OBT and total OBT of various vegetables (cabbage, lettuce, tomato, radish, and beet) varies between 0.46 and 0.74.…”

Modeling and validating tritium transfer in a grassland ecosystem in response to 3H release

“…The model was previously developed and tested on an hourly time-step basis for 14 C transfer to pasture [3,4] and is under development for tritium to take into account acute variations in 3 H releases and meteorology. It has the following main characteristics and assumptions:  The model is based on an hourly time-step;  It is driven by monthly (and every two-days) atmospheric concentrations of tritiated water vapour (HTO) above the canopy and hourly weather input data for radiation, temperature, relative humidity, wind speed, and precipitation;  The model integrates the day / night cycle of plant physiological behavior (photosynthetic uptake, respiratory loss, water and nutrient status, plant aboveground and below-ground dry matter production) derived from a simplified version of the PASIM (Pasture SImulation Model) process-based pasture model [6];  The net photosynthetic production of OBT in plant parts is linked to the tissue free water tritium (TFWT) concentration in leaves, ignoring the OBT production during the night time [7]. It is a function of leaf CO2 assimilation rate (net of respiration) derived from the biochemical Farquhar model [8] while the leaf area index (LAI) and the radiation scheme have been estimated in a quite simple manner [4];  A physiological approach is used to integrate LAI and resistances in the calculations of exchange velocities at the leaf/air and soil/air interfaces;  The model uses the same conceptual and mathematical modelling approaches as defined in SYMBIOSE [1]: the conceptual framework is based on the interaction matrix formalism (cf.…”