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On this page we try to provide answers to the questions you have asked (to ask a question select the Ask a question form). Also feel free to use the form to comment on the questions or answers provided.

Posted: 05/08/2010

Topic:

Question about terrestrial occupancies in ERICA

From:
Susan Schneider
Serco
UK

Question:

My question is about terrestrial occupancies in ERICA, which I would like to clarify for a report I am writing. In the database, terrestrial DCCs are provided for three habitats, in-air, in-soil and  on-soil. However in the ERICA Help, only two terrestrial habitats are defined in Figure 5. Habitat 6 must be In-soil, but is habitat 5 On-soil or In-air?  Is it assumed that air-borne contamination is insignificant?  (I am using media concentrations, not the transport models provided in ERICA).  Surely the In-air habitat would
need to be included for eg birds and flying insects?

Answer:

You are correct in saying that Figure 5 shows only two habitats for terrestrial ecosystems - Habitat 5 is 'on-soil'. However, you are able to consider flying organisms and a fraction of time in-air can be defined in Tiers 2 and 3 for some organism types - 'Occupancy Factors and Radiation Weighting Factors' screen. There are some limitations on sizes of organisms for which in air dose conversion coefficients can be calcuculated using the create organism wizard (see Table 10 of the Help file).  Note the dose rate estimated to a flying animals is that from contaminated soil and not contaminated air. There is no consideration of external dose rates from contaminated air in the ERICA Tool (nor is it considered in either R&D128 (exception being noble gases) or RESRAD-BIOTA).
The in-air habitat is not shown on Figure 5 as this presents the habitats consider during the estimation of the Environmental Media Concentration Limits used in Tier 1; these only consider the scenarios likely to give the highest dose rate.

Answered by Nick Beresford 05/08/2010

Posted: 28/07/2010

Topic:
Use of the 'IAEA SRS-19 estuarine dispersion model' within the ERICA Tool

...

Answered by Nick Beresford 07/06/2010

If you want to model an organism as spending only a proportion of time in a contaminated environment using the ERICA Tool then perhaps the simplest approach is to use an occupancy factor of 1.0 and multiply the resultant dose rate by the fraction of time spent in the assessment area.

Added 09/08/2010