Improved predictive mapping of indoor radon concentrations using ensemble regression trees based on automatic clustering of geological units

A comprehensive study was carried out to measure indoor radon/thoron concentrations in 78 dwellings and soil-gas radon in the city of Mashhad, Iran during two seasons, using two common radon monitoring devices (NRPB and RADUET). In the winter, indoor radon concentrations measured between 75 ± 11 to 376 ± 24 Bq·m−3 (mean: 150 ± 19 Bq m−3), whereas indoor thoron concentrations ranged from below the Lower Limit of Detection (LLD) to 166 ± 10 Bq·m−3 (mean: 66 ± 8 Bq m−3), while radon and thoron concentrations in summer fell between 50 ± 11 and 305 ± 24 Bq·m−3 (mean 115 ± 18 Bq m−3) and from below the LLD to 122 ± 10 Bq m−3 (mean 48 ± 6 Bq·m−3), respectively. The annual average effective dose was estimated to be 3.7 ± 0.5 mSv yr−1. The soil-gas radon concentrations fell within the range from 1.07 ± 0.28 to 8.02 ± 0.65 kBq·m−3 (mean 3.07 ± 1.09 kBq·m−3). Finally, indoor radon maps were generated by ArcGIS software over a grid of 1 × 1 km2 using three different interpolation techniques. In grid cells where no data was observed, the arithmetic mean was used to predict a mean indoor radon concentration. Accordingly, inverse distance weighting (IDW) was proven to be more suitable for predicting mean indoor radon concentrations due to the lower mean absolute error (MAE) and root mean square error (RMSE). Meanwhile, the radiation health risk due to the residential exposure to radon and indoor gamma radiation exposure was also assessed.

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THE RESULTS OF MEASURING AND MODELLING SOIL-INDOORS RADON TRANSPORTATION / RADONO PERNAŠOS IŠ DIRVOŽEMIO Į PATALPAS MATAVIMO IR MODELIAVIMO REZULTATAI

Mokslas - Lietuvos ateitis ◽

10.3846/mla.2013.62 ◽

2013 ◽

Vol 5 (4) ◽

pp. 388-396 ◽

Cited By ~ 1

Author(s):

Erika Streckytė ◽

Donatas Butkus

Keyword(s):

Moisture Content ◽

Indoor Radon ◽

Ambient Air ◽

Summer Season ◽

Monitoring Device ◽

Volumetric Activity ◽

Indoor Temperature ◽

Radon Gas ◽

Radon Monitoring ◽

Radon Concentrations

The article presents the entry of radon gas into premises and introduces the parameters accelerating and slowing this process. The paper determines the dependence of radon gas entering the premises on ambient temperature and humidity changes. It is noted that a growth in differences under ambient and indoor temperature increases indoor radon concentrations in the air due to an increase in the intensity of radon exhalation from soil. Also, an increase in the moisture content indoors decreases the volumetric activity of radon in the air. The simulated values of radon volumetric activity in ambient air were similar to those measured using radon monitoring device RTM2200. Radon concentration in the air of the first floor was higher than that in the second floor. Indoor radon concentrations were highest in the winter and lowest in summer season. Article in Lithuanian. Santrauka Nagrinėjama radono dujų patekimo į patalpas procesas, šį procesą spartinantys ir lėtinantys parametrai. Nustatoma radono dujų patekimo į patalpas priklausomybė nuo aplinkos temperatūros bei drėgnio kitimo. Pastebėta, kad, didėjant aplinkos ir patalpos temperatūrų skirtumui, didėja ir radono tūrinis aktyvumas patalpos ore (vasarą radono tūrinis aktyvumas siekė 45,0±3,0 Bq/m3, kai temperatūrų skirtumas buvo 3,1 °C, o rudenį – 62,0±5,0 Bq/m3, esant temperatūrų skirtumui 3,9 °C), didėja radono ekshaliacijos iš dirvožemio intensyvumas, o didėjant drėgmės kiekiui patalpose radono tūrinis aktyvumas ore mažėja. Sumodeliuotos radono tūrinio aktyvumo patalpos ore reikšmės buvo panašios kaip ir išmatuotos naudojant radono monitorių RTM2200. Pirmajame aukšte radono tūrinis aktyvumas ore buvo didesnis nei antrajame. Žiemos sezonu jo vertė buvo didžiausia (47,0±10,5 Bq/m3), o vasaros sezonu – mažiausia (15±1,8 Bq/m3).

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