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.
Other useful Q&A sources:
Entering data into the wildlife transfer database.
Technical issues related to the ERICA Tool (on Facilia website)
Posted: 18/11/2010
Non-human biota, environment or wildlife?
From:
Marko Černe
Jožef Stefan Institute
Slovenia
Question:
What is more appropriate term for non-human organisms: radiological risk to biota or environmental risk from ionising radiation to biota? The opinion of many radiologist is, that the term radiological relates to humans only? The biota dosimetry is relatively young science, so this is probably the reason of many disagreements.
Answer:
Answered by Nick Beresford 18/11/2010
Posted: 20/10/2010
Wildlife transfer
From:
Marko Černe
Jožef Stefan Institute
Slovenia
Question:
1) If I have only the tissue concentration, than the whole body:tissue ratios are used for the calculation of wholebody activity concentrations as repoted by Yankovich et al. (2010)?
2) If I have activity concentration for muscles and bones together, what should I do?
3) If CR values are in the range from 61 to 493 for one fish for Ra, what should I do? Should I use average or maximum? N of samples is 15.
Answer:
1. Yes Yankovich et al. 2010 presents the most up to date compilation of tissue:wholebody activity concentration ratios you can use these to convert tissue specific activity concentrations to wholebody values. Note the Yankovich et al. paper has been published today (26/10/10) in an issue of Radiation and Environmental Biopyhsics see http://www.springerlink.com/content/0301-634x/49/4/. Given the uncertainty around the collated values Yankovich et al. recommend that ratios of between 0.75 and 1.5 should not be applied and that a value of 1.0 should be assumed instead; in the tables available for these webpages values between 0.75 and 1.5 have been replaced with a value of 1.0 for ease of use.
2. Might depend upon the radionuclide: you may want to convert both bone and muscle data and take average for radionuclides which do not accumulate in either of these tissues; for other radionuclides which accumulate in one of the two tissues you may have more confidence in the data for the accumulating tissue (e.g. Sr, Pu, Am and Ra accumulate in bone and have comparatively low transfers to muscle).
3. Depends upon the purpose of your assessment. If conservative then assume the maximum value, if more realistic then use an average value. Remember that in both RESRAD BIOTA and the ERICA Tool you can use a pdf to conduct a probabilistic assessment if appropriate for your purposes.
Answered by Nick Beresford 26/10/2010
Back to topPosted: 12/10/2010
Predicting future biota and media concentrations
From:
Chutarat Saengkulž
Burapha University
THAILAND
Question:
I would like to predict of radiocesium activity in fish and water in the future using the ERICA Tool. How can I do this?
Answer:
You cannot use the ERICA Tool (or other packages such as RESRAD BIOTA) to make future predictions of water and fish activity concentrations.
How you can address this depends upon the nature of your assessment and available information:
1. If you have discharge data you could use the dis[ersion model available within the ERICA Tool to predict water concentrations (although I suspect from your previous question that this will not be the case).
2. You have data over the period 1962-2006 - consider analysing these data for time trends and making predictions for water and fish in the future outside of the ERICA Tool. Then input your results into the ERICA Tool to obtain dose rate estimates.
3. I am unsure if you are considering a freshwater or marine ecosystem? If marine then consider if you can make use of the Marine dynamic model.
Answered by Nick Beresford 26/10/2010
Back to topPosted: 30/09/2010
Time series data
From:
Chutarat Saengkulž
Burapha University
THAILAND
Question:
I have a problem about putting data into the ERICA Tool - I have many data for cesium-137 concentrations in water and fish from 1962-2006 but I cannot put all data in ERICA Tool. Now I can input one data point from one year to calculate the absorbed dose rate. Please advise me about how to input such data into Tier 2 of the ERICA Tool.
Answer:
Currently, you cannot input time series data, or data for more than one location, into the ERICA Tool to model in a single run. This functionality is something which has been requested previously by users and it MAY be provided in future Tool versions.
How you can best proceed depends upon what you want to do to some extent. Here are two suggestions:
1. As you are only considering Cs-137 you could extract the DCC values and if required Kd and CR values from the Tool and use them in an Excel spreadsheet. If you do this then make sure you check calculations by running one or two through the Tool as well as your spreadsheet
2. If you have multiple entries for a single year you could use Tier 3 to input mean values with an associated pdf.
On a different note, it looks like you have access to a large and potentially useful dataset, please consider making this available to the IAEA working group who are collating transfer parameter values for wildlife.
Answered by Nick Beresford 30/09/2010
Back to topPosted: 12/08/2010
Plant geometries
From:
Marko Černe
Jožef Stefan Institute
Slovenia
Question:
I am trying to apply the ERICA Tool to plants. If a plant, such as the Marsh Marigold, has a large leave on top of the stem - what dimensions should be used?
Answer:
To be honest perhaps the plant geometries have not been well thought out to date - they do not really represent whole-organisms as perhaps implied by documentation accompanying the ERICA Tool. The grass geometry in the ERICA Tool is taken from the ICRP Wild Grass RAP and is a 'grass spike'; no in soil dose rates are estimated only above ground. If you are concerned that the default plant may not adequately represent the species you want to assess then have a play with the create organism function of Tier 2 or 3: create an organism to represent your marigold leaf and compare DCC values to the default grass. We'd be interested to hear what you find.
Answered by Nick Beresford 26/09/2010
Back to topPosted: 23/09/2010
Are dose conversion coefficient formula in ERICA consistent?
From:
Marko Černe
Jožef Stefan Institute
Slovenia
Question:
In the ERICA Tool are the all of the DCC values estimated using the same methodology or is Monte-Carlo simulation used on for terrestrial organisms?
Answer:
The key factor in the estimation of DCC is the absorbed fraction, and this is always calculated by Monte Carlo simulation using a phantom geometry. The only difference is that, historically, in FASSET, the aquatic and terrestrial formulas were calculated by two different Monte Carlo methods, but for ERICA the Ulanovsky and Proehl sphericity method (see ERICA papers) was adopted for everything, after having checked that, for aquatic organisms, both methods gave very similar results.
Answered by Jordi Vives i Batlle 23/09/2010
But note for terrestrial animals a shielding factor due to fur/feathers/skin is applied in the estimation of external dose rate. This is not used for aquatic animals.
Added by Nick Beresford 24/09/2010
Back to topPosted: 09/08/2010
Question on aquatic ecosystem 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).
<span style="color: #ff0000"><strong>Answer:</strong></span>
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 (from Marko Černe) below re how occupancies are (not) used in estimatation of internal dose rate.
Answered by Nick Beresford 09/08/2010
Back to topPosted: 05/08/2010
Question about dose rate to flying animals
From:
Susan Schneider
Serco
UK
Question:
Please can you clarify about contaminated air.
Box 4.1 in The D-ERICA :Integrated Approach report, mentions chronic atmospheric releases of H, C, P and S, and in the report R+D 128, Sec 5.6, dose rates for these are calculated from concentrations in air.
Has this dependence on air concentration been removed in this more recent version of ERICA (I had previously used the prototype version, in Dec 2006)? Is the chronic atmospheric release only relevant when using the transport models?
Answer:
For H, C, S and P air concentrations are the input rather than soil concentrations. ERICA uses a specific activity approach to then estimate biota concentrations of C&H (there's an article by Galeriu et al describing this). This is in-line with approaches taken for human assessment (e.g. see IAEA 2010 TRS472). Honest answer to S and P is that ERICA adopted parameters from R&D128.
Note that the air concentrations are used to estimate activity concentrations in biota they are not used to estimate external dose rates from air. External dose rates for H, C, S and P are assumed to be zero in the ERICA Tool anyway (most models assume zero or very low external dose rates - see Vives i Batlle et al 2007.)
Answered by Nick Beresford 05/08/2010
Back to topPosted: 05/08/2010
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
Back to topPosted: 28/07/2010
Use of the 'IAEA SRS-19 estuarine dispersion model' within the ERICA Tool
From:
Corynne McGuire
University of Strathclyde
UK
Question:
When using the estuarine model should I be using the estuary width and depth at the point of discharge or should it be the maximum width and maximum depth?
Answer:
Good question ... we may have added - should it be the assessment site or should it be the average values for the estuary between the point of discharge and the assessment site to your options. We would probably not suggest using the maximum values for the estuary although the minimum values should result in a conservative assessment if that is your aim. Unfortunately there appears to be no guidance on this in the IAEA SRS-19 document (http:www-pub.iaea.org/MTCD/publications/PDF/Pub1103_scr.pdf).
For flow rate the SRS-19 text on the estuarine model (see Section 4.2.2) states that the flow rate for the river upstream of tidal limit should be used.
Answered by Nick Beresford with input from Justin Brown (Norwegian Radiation Protection Authority) 05/08/2010
Back to topPosted: 28/07/2010
Choice of analogue radionuclides to represent radionuclides that are not included in the ERICA Tool
From:
Corynne McGuire
University of Strathclyde
UK
Question:
I was wondering if you can offer advice on what to do when chosing analogues to represent radionuclides that are not included in the ERICA Tool or when the radionuclide is unknown and in a vague category such as other non-alpha radionuclide? I have attached an excel document with the list of radionuclides and vague categories that I will need to assess with suggested analogues.
Answer:
To represent radionuclides not included within the Tool as defaults you assuming Pu-239 for all alpha-emitters and Tc-99 for all other categories you have to assess which is as suggested by the England and Wales Environment Agency (EA) . You could argue this approach on the grounds of consistency. However, it depends upon the purpose of your assessment - do you want to be conservative?. If yes then the analogues suggested by EA may not always be the most conservative choices. However, the ERICA Tool allows you to explore alternatives as it has more fuctionality than the EA approach:
(a) You could add some of the missing radionuclides to the ERICA Tool and generate your own EMCLs. Some of the elements (e.g.) Ce already have transfer parameters. This would involve using Tier 3 and you would then have to compare the resultant Environmental Medial Concentration Limits (EMCLs) to your media concentrations outside of the Tool as the user cannot add EMCLs (see Brown et al. 2008 for details of how to estimate EMCLs);
(b) look at the available EMCL values and pick the most conservative (i.e. lowest) available dependent upon emitter type. You can view the Tools EMCL value by selecting Database and then Parameter Database from any screen within the Tool.
There is not a definitive 'correct' answer to this question - but you need to justify your choice.
Answered by Nick Beresford 05/08/2010
Back to topPosted: 07/06/2010
Modelling exposure to Acacia trees growing on a waste burial trench
From:
Marko Černe
Jožef Stefan Institute
Slovenia
Question:
Acacia has it's roots 0-2m deep in the waste (part in Zone 1 and part in Zone 2) and has also aboveground part. How to use occupancy factors in this case? The major part of the tree is above the soils, so in that case we will use on soil, but the dose from ionising radiation here is a consequence of underground direct contact and aboveground part, but according to permitted occupancies for tree reference organisms (ERICA help) we could use occupancy factor just on soil? Does this approach include also the roots? How to deal with such cases?
Answer:
This question is in regard to one of the IAEA EMRAS II programme Biota Modelling Group (WG4) scenarios - Little Forest Burial Ground, Australia. 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 (specifically the ICRP Reference Pine Tree trunk geometry as defined 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 organism type to me modelled as in soil); the Environment Agency R&D128 spreadsheet model also probably has a default geometry more analogous to plant roots. Note that the default CR values in both these models can be highly conservative - read the documentation before using.
Answered by Nick Beresford 08/06/2010
Back to topPosted: 25/05/2010
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 influence the CR value?
Answer:
There is no transformation of CRs according to geometry or occupancy factors - these are used by the ERICA Tool to determine dose rates 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 (and wholebody activity concentration) would be the same (as if the animal spend 100 % of time in the ecosystem).Note that the Area Factor (AF) parameter in RESRAD-BIOTA is used in the estimation of internal dose rate (although the reported tissue activity concentration appears to stay the same regardless of the value of AF).
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
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