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Optimal mapping of terrestrial gamma dose rates using geological parent material and aerogeophysical survey data.
MedLine Citation:
PMID:  23147566     Owner:  NLM     Status:  Publisher    
Regulatory authorities need ways to estimate natural terrestrial gamma radiation dose rates (nGy h(-1)) across the landscape accurately, to assess its potential deleterious health effects. The primary method for estimating outdoor dose rate is to use an in situ detector supported 1 m above the ground, but such measurements are costly and cannot capture the landscape-scale variation in dose rates which are associated with changes in soil and parent material mineralogy. We investigate the potential for improving estimates of terrestrial gamma dose rates across Northern Ireland (13 542 km(2)) using measurements from 168 sites and two sources of ancillary data: (i) a map based on a simplified classification of soil parent material, and (ii) dose estimates from a national-scale, airborne radiometric survey. We used the linear mixed modelling framework in which the two ancillary variables were included in separate models as fixed effects, plus a correlation structure which captures the spatially correlated variance component. We used a cross-validation procedure to determine the magnitude of the prediction errors for the different models. We removed a random subset of 10 terrestrial measurements and formed the model from the remainder (n = 158), and then used the model to predict values at the other 10 sites. We repeated this procedure 50 times. The measurements of terrestrial dose vary between 1 and 103 (nGy h(-1)). The median absolute model prediction errors (nGy h(-1)) for the three models declined in the following order: no ancillary data (10.8) > simple geological classification (8.3) > airborne radiometric dose (5.4) as a single fixed effect. Estimates of airborne radiometric gamma dose rate can significantly improve the spatial prediction of terrestrial dose rate.
B G Rawlins; C Scheib; A N Tyler; D Beamish
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Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2012-11-13
Journal Detail:
Title:  Journal of environmental monitoring : JEM     Volume:  -     ISSN:  1464-0333     ISO Abbreviation:  J Environ Monit     Publication Date:  2012 Nov 
Date Detail:
Created Date:  2012-11-13     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  100968688     Medline TA:  J Environ Monit     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
British Geological Survey, Keyworth, Nottingham NG12 5GG, UK.
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