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Posted: 09/08/2010

Topic:

Question on aqueous occupancies

From:
Susan Schneider
Serco
UK

Question:

In the aqueous (ie marine and freshwater) environments, I can see how the dose rates relate to fractions of time spent in-sediment and in-water, and to water and sediment concentrations (using the distribution coefficient Kd).

Looking at Tables 14 and 15 in the ERICA Help (which I realise correspond to Tier 1 assessments, and therefore have default occupancies which maximise the exposure), it looks as though time spent on the sediment surface counts as 0.5 x in-sediment and 0.5 x in-water.  And at the water surface, it counts as all in-water.

Please can you clarify in Tier 2 how ERICA uses the input occupancies (of which there are four, in-sediment, sediment-surface, in water and water-surface).

Answer:

_In Tier 2 you can select the occupancy factors to be what you want - these are  used to determine the external exposure only. The dose rate at water surface will be  50 % of that in water column. The DCCs for sediment and water are the same. For  sediment-water interface the dose rate is  (\[0.5*DCC_external*sediment activity  concentration\]+\[0.5*DCC_external*water activity concentration\])._ _The DCCs for sediment and water are the same._ _See response  posted to question on website Q&A re how occupancies are (not) used in  estimatation of internal dose rate._

Answered by Nick Beresford 09/08/2010

Posted: 05/08/2010

Topic:

Question about dose rate to flying animals

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