Biokinetics of Tritium in Wheat Plants: Measurements and Model - PowerPoint PPT Presentation

Biokinetics of Tritium in Wheat Plants: Measurements and Model Calculations S. Strack, S. Diabaté, W. Raskob, __________________________________________________________________  Objectives: Development of a ‘process oriented’ model - general description of relevant mechanisms - risk assessments, based on predictions of expected concentrations in nutrients - Application in assessment codes like UFOTRI for decisions  calculations by application only of general available parameters: 1. air temperature 2. relative humidity 3. solar radiation

Experiments: 1993 and 1994 Laboratory chamber experiments with potted spring wheat   1995 winter wheat in a small experimental field for short-term exposure experiments during the grain-filling period. transparent plexi-glass box (30 x 30 cm, 100 cm height)   tritiated water (HTO) evaporated by constantly heating  homogeneous tritiated air humidity in the box with a fan  concentration of HTO in the air humidity: detection by a calibrated bubbler system (trapping in vials with a scintillation cocktail (for 5 minutes)  Further parameters:  Air temperature in °C  Relative air humidity in %  solar radiation inµE/m 2 s with a Quantum sensor (PPFD) 

OBT concentrations in grains at the time of harvest, given as 1.0% percentage of the TWT concentrations in leaves at the end of the exposure (2 h), chamber experiments 1993 0.9% 0.8% 0.7% % 0.6% in ra g 0.5% MEAN grain filling period = 0.62 % in T B O 0.4% 0.3% 0.2% night experiments 0.1% 0.0% 0 5 10 15 20 25 30 35 days after beginning of anthesis

Experiments: 1993 and 1994 Laboratory chamber experiments with potted spring wheat   1995 winter wheat in a small experimental field for short-term exposure experiments during the grain-filling period. transparent plexi-glass box (30 x 30 cm, 100 cm height)   tritiated water (HTO) evaporated by constantly heating  homogeneous tritiated air humidity in the box with a fan  concentration of HTO in the air humidity: detection by a calibrated bubbler system (trapping in vials with a scintillation cocktail (for 5 minutes)  Further parameters: Air temperature in °C Relative air humidity in % solar radiation in µE/m 2 s with a Quantum sensor (PPFD)

Experiments: 1993 and 1994 Laboratory chamber experiments with potted spring wheat   1995 winter wheat in a small experimental field for short-term exposure experiments during the grain-filling period. transparent plexi-glass box (30 x 30 cm, 100 cm height)   tritiated water (HTO) evaporated by constantly heating  homogeneous tritiated air humidity in the box with a fan  concentration of HTO in the air humidity: detection by a calibrated bubbler system (trapping in vials with a scintillation cocktail (for 5 minutes)  Further parameters:  Air temperature in °C  Relative air humidity in %  solar radiation in µE/m 2 s with a Quantum sensor (PPFD)

Outlets for: Monitor Bubbler Cuvette of gas exchange system Heating unit Fan Temperatur, rel. humidity Inlet for air flushing  tritiated water (HTO) evaporated by constantly heating  homogeneous tritiated air humidity in the box with a fan  concentration of HTO in the air humidity: detection by a calibrated bubbler system (trapping in vials with a scintillation cocktail (for 5 minutes) and a Beckman Monitor 

Experiments: 1993 and 1994 Laboratory chamber experiments with potted spring wheat   1995 winter wheat in a small experimental field for short-term exposure experiments during the grain-filling period. transparent plexi-glass box (30 x 30 cm, 100 cm height)   tritiated water (HTO) evaporated by constantly heating  homogeneous tritiated air humidity in the box with a fan  concentration of HTO in the air humidity: detection by a calibrated bubbler system (trapping in vials with a scintillation cocktail (for 5 minutes)  Further parameters:  Air temperature in °C  Relative air humidity in %  solar radiation in µE/m 2 s with a Quantum sensor (PPFD)

• TWT concentration after lyophilisation • removing all exchangeable Tritium in a tritium-free humid atmosphere • OBT concentration by combustion (Packard Oxidiser) • cultivation of residual wheat plants under normal field conditions until harvest • in certain intervals: samples from leaves and ears • 7 exposures at different time of day and during the night in 1995 (improvement of existing model) • 1996: 7 experiments for validation the plant-OBT model.

Rel.OBT leaf 1,2,4h,1d,harv. 1.8 leaf OBTr meas-1h leaf OBTr meas-2h 1.6 leaf OBTr meas-4h leaf OBTr meas-1d 1.4 seed OBTr meas-harv 1.2 1.0 % 0.8 0.6 0.4 0.2 0.0 7 7 8 9 10 11 11 14 15 15 20 20 23 23 F3 F14 F 7 F 2 F 4 F 10 F 15 F 1 F9 F 13 F 5 F 11 F6 F 12 leaf OBTr meas-1h 0.84 0.50 0.56 1.39 0.87 0.60 1.56 1.45 1.49 1.42 0.50 0.42 0.44 0.33 leaf OBTr meas-2h 0.80 0.68 0.62 1.01 0.98 0.66 1.23 1.16 1.29 1.48 0.64 0.48 0.39 0.33 leaf OBTr meas-4h 0.62 0.53 0.85 0.69 0.73 0.71 1.39 0.85 1.27 0.46 0.39 0.33 leaf OBTr meas-1d 0.20 0.11 0.28 0.28 0.41 0.34 0.39 0.35 0.42 0.22 0.36 0.16 seed OBTr meas-harv 0.23 0.14 0.30 0.19 0.29 0.19 0.23 0.20 0.23 0.28 0.35 0.25 0.34 0.20

Plant-OBT Model ear 30% leave 60% OBT leaf 1.part net-photosynthesis, basic metabolism and respiration respiration translokation atmos OBT grain phere TRANS 1 rapid TRANS 2 slow photo- 2.Teil respiration Nettophotosynth. gross- photosynth. Basic metabolism TWT grain TWT leaf stem 10%

Relative OBT-concentrations in the grains at harvest 1,0 0,9 Korn OBTgemessen relative OBT concentrations, % 0,8 Korn OBT modelliert Polynom 2.Ordn. 0,7 0,6 0,5 0,4 0,3 0,2 median 0,23 % 0,1 0,0 6 8 10 12 14 16 18 20 22 24 time of the day (h) at the beginning of the exposure ______________________________________________________________ Forschungszentrum Karlsruhe, Technik und Umwelt

OBT grain at harvest, related to time integrated TWT integ. in leaves and ears 400 350 300 OBT in grains at harvest, Bq/ml 250 200 F 15, July 3 150 100 TWT integ. leaf + 0.5 (TWT integ ear during day) 50 - and during night (f=0.2) 0 0 100 200 300 400 500 600 700 800 TWT integ (kBq * h/ml) Forschungszentrum Karlsruhe, Technik und Umwelt

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F15 3,50 ear OBTmeas 3,00 earOBTmod 2,50 leaf OBTmeas 2,00 leaf OBTmod 1,50 1,00 0,50 0,00 1 10 100 1000

#F14 0,80 0,70 ear OBTmeas rel-meas earOBTmod rel-mod 0,60 leaf OBTmeas rel-meas leaf OBTmod rel-mod 0,50 0,40 0,30 0,20 0,10 0,00 1 10 100 1000

Die wichtigsten Prozesse im Pflanzenmodell: „ plant-OBT“ mit allgem.verfügb.meteorolog.Daten: Luft-Temperatur, rel.Feuchte, Licht Wachstum Aufnahme in Blatt, Ähre, Stengel (TWT) Bildung von OBT : Photosynthese, Photorespiration Grundumsatz, Respiration Translokation und Speicherung In 1995 and 1996 we switched to field experiments: opportunity to use winter wheat exposure more exactly for one hour (Plexiglas box) Uptake of HTO through Stomata: TWT

Die wichtigsten Prozesse im Pflanzenmodell: „ plant-OBT“ mit allgem.verfügb.meteorolog.Daten: Luft-Temperatur, rel.Feuchte, Licht Wachstum Aufnahme in Blatt, Ähre, Stengel (TWT) Bildung von OBT : Photosynthese, Photorespiration Grundumsatz, Respiration Translokation und Speicherung In 1995 and 1996 we switched to field experiments: opportunity to use winter wheat exposure more exactly for one hour (Plexiglas box) Uptake of HTO through Stomata: TWT