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 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 (specifically the ICRP Reference Pine Tree trunk geometry as define in ICRP Publication 108). Therefore, the default tree reference organism within the ERICA Tool may not model this scenario very well especially with regard to external dose rates. 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 - although you may then need to consider how to interpret the results. RESRAD-BIOTA has a default geometry which is stated as appropriate for plant roots (default geometry 1 with dimensions 0.2x0.2x0.2 cm and allows any orgaism type to me modelled as in soil); the Environment Agency R&D128 spreadsheet model alos probably has a default geometry more analogous to plant roots. Note that the deafult CR values in both these models can be highly conservative - read the documention before using.

Answered by Nick Beresford 08/06/2010

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