Plant OBT Model Wolfgang Raskob Karlsruher Institut fr Technologie - - PowerPoint PPT Presentation

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Plant OBT Model

Wolfgang Raskob Karlsruher Institut für Technologie (KIT)

Tritium modelling overview

Karlsruhe Institute of Technology (KIT-IKET)

25.01.2011 2

Objectives of Plant OBT

A physically based approach, considering all the necessary transport and transformation processes Improvement of the present plant sub-model of the assessment code UFOTRI Pre- and recalculation of experimental work to get a better understanding and to identify areas of model and experimental design improvements Treat day and night releases correctly

high air concentrations at night, rather low at daytime uptake at night might be important (rate of tritium intake into the plant is only by a factor of about 4-5 lower compared to daytime values, results from wheat exposure experiments performed at FZK)

Tritium modelling overview

Karlsruhe Institute of Technology (KIT-IKET)

25.01.2011 3

Flow chart Plant OBT

ear OBT ear TWT HTO atmosphere ear TRANS leaf OBT grain OBT leaf TWT leaf TRANS stem OBT stem TWT stem TRANS grain TWT

Tritium modelling overview

Karlsruhe Institute of Technology (KIT-IKET)

25.01.2011 4

Regulatory requirements for a model

Processes important for the OBT formation:

• 1. light dependent:

photosynthesis photorespiration

• 2. light independent

maintenance respiration basic metabolism

Subdivision of the wheat plant into three parts:

stem leaves ears (+ grains)

Contribution of the individual organs to the total process:

stem: 10% leaves: 60% ears: 30%

Tritium modelling overview

Karlsruhe Institute of Technology (KIT-IKET)

25.01.2011 5

OBT production (non-exchangeable)

where: COBTspec specific OBT concentration in Bq/g dry matter COBT0 initial specific OBT concentration in Bq/g dry matter CTWTspec specific TWT concentration in Bq/g water Pact net photosynthesis rate B basic metabolism rate Red reduction factors such as isotopic effect, H2 content and exchangeable / non exchangeable fraction Wd dry matter content in g

 

 

 

COBT COBT d P B CTWT W

spec act spec d

    Re /

Tritium modelling overview

Karlsruhe Institute of Technology (KIT-IKET)

25.01.2011 6

Respiration rate, expressed in CO2 equivalents

R = photorespiration + maintenance respiration where: C1p Pc photorespiration, dependent on the photosynthesis rate C2m Wd maintenance respiration, dependent on the plant weight C1p C2m constants

R C P C W

p c m d

    1 2

Tritium modelling overview

Karlsruhe Institute of Technology (KIT-IKET)

25.01.2011 7

BIOMOVS test of wheat exposure at day-time

TRIMOVS (2) TRIMOVS (1) TRICAROM ETMOD UFOTRI-AECL UFOTRI STAR H-3 (2) STAR H-3 (1) Plant-OBT

• 4
• 3
• 2
• 1

deviation from observation TRIMOVS (2) TRIMOVS (1) TRICAROM ETMOD UFOTRI-AECL UFOTRI STAR H-3 (2) STAR H-3 (1) Plant-OBT 'Day' exposure: TWT and OBT TWT OBT 2 3

4 1 2 3 4

models excluding OBT formation during the night

lower higher 2.1

• 1.9
• 2.9
• 2.6
• 2.6
• 2.8
• 2.7
• 1.4
• 5.3
• 1.1

1.7 1.1 1.2 1.1 1.1 1.1 1.1

• 1.2

5

TWT in leaves after exposure, OBT at harvest

Tritium modelling overview

Karlsruhe Institute of Technology (KIT-IKET)

25.01.2011 8

BIOMOVS test of wheat exposure at night-time

TRIMOVS (2) TRIMOVS (1) TRICAROM ETMOD UFOTRI-AECL UFOTRI STAR H-3 (2) STAR H-3 (1) Plant-OBT

• 4
• 3
• 2
• 1

deviation from observation TRIMOVS (2) TRIMOVS (1) TRICAROM ETMOD UFOTRI-AECL UFOTRI STAR H-3 (2) STAR H-3 (1) Plant-OBT 'Night' exposure: TWT and OBT TWT OBT

models excluding OBT formation during the night

1 2 3 4 5 2 3 4 higher lower

• 2.1
• 3.1
• 2.5
• 3.1
• 2.4
• 2.4

>-100

• 21
• 9.1
• 3.6
• 4.0
• 54
• 4.0
• 7.5
• 1.2
• 1.1

1.4 1.0

TWT in leaves after exposure, OBT at harvest

Tritium modelling overview

Karlsruhe Institute of Technology (KIT-IKET)

25.01.2011 9

OBT-FORMATION: rel. OBTgrain at harvest, related toTWT in leaves at the end of exposure (Plant OBT)

0,0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 1,0 6 8 10 12 14 16 18 20 22 24

Time of day (h) at the beginning of exposure %

grain OBTmes grain OBT mod polynomial fit

mean 0.23 %

Tritium modelling overview

Karlsruhe Institute of Technology (KIT-IKET)

25.01.2011 10

Conclusion

Yes, there is a need of a physical based tritium OBT model approach Before developing models, it is necessary to carry out a sensitivity analysis about the importance of the processes Sub-models for assessment codes should be as simple as possible, but physically based The ‘PLANT-OBT’ model considers the relevant processes (light dependent and independent), even if the parameterisation is sometimes still too simple (basic metabolism) Non tritium part (growth) of the ‘PLANT-OBT’ model was successfully tested Parameterisation of the photosynthesis process is still under discussion for the OBT formation (specific tritium activity in the photosynthetic cell organs)