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On this page we try to provide answers to the questions you have asked. Feel free to use the Ask a Question form to comment on the questions or answers provided.

Posted: 25/05/2010

Topic:
Effect of occupancy factors on estimated wholebody activity concentrations

From:
Marko Černe
Jožef Stefan Institute
Slovenia

Question:

How does the geometry or occupancy factor within the ERICA Tool influnce the CR value?

Answer:

There is no transformation of CRs according to geometry or occupancy factors - these are used in determination of dose only. Occupancy factors influence external dose estimates only. However, perhaps the guidance within the ERICA Help is to some extent misleading as it suggests the user can use the occupancy factors to model organims which do not spend 100 % of their time in a given ecosystem. However, if for example an occupancy factor of 0.4 is used the external dose rate would be reduced to 40 % of that if the organism was assumed to spend 100 % of its time in the ecosystem under consideration whereas the internal dose estimation would not be estimated to be the same.

Answered by Nick Beresford 07/06/2010

Posted: 07/06/2010

Topic:
Modelling exposure to Acacia trees (EMRAS II Little Forest Burial Ground Scenario)

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The Zone 1 referred to in the question is contamination at >1 m depth into which it is assumed the Acacia roots. An interesting question as you are correct in that the ERICA Tool considers plants to be on the soil surface and in the case of trees the assumed geometry is the trunk. Therefore, the default tree reference organism within the ERICA Tool will not model this scenario very well. It would be a fair criticism of the currently available models to say that perhaps the dosimetry for plants requires some further thought. However, scenarios such as this are proposed to make you think and identify problems and (hopefully) solutions. It's not the purpose of the exercise to tell participants what to do - but there are (probably) ways you could try to get around the limitations of the ERICA Tool (e.g. could you create an organism that is representative of roots?) although you would may then need to consider how to interpret the results.

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