The FIRST large-scale mapping of radon concentration in soil gas and water in Romania
Graphical abstract
Introduction
On the basis of Articles 35–36 of the Euratom Treaty, the most important objective of the EU Members States is to monitor and report environmental radioactivity (Euratom, 2010). It has been acknowledged that natural radioactivity is the main source of human exposure to ionizing radiation (Euroatom, 2014; HG nr. 526/2018). Radon (222Rn), found ubiquitous in soil, rocks and water represents the main source of indoor radon. With a significant contribution to the contamination of indoor air in Romania (Todea et al., 2013) and worldwide, radon is listed by the World Health Organization (WHO, 2009) as the second leading cause of lung cancer after cigarette smoking. Areal variation of radon levels in houses primarily depends on the geological features of the investigated area (Ciotoli et al., 2017), secondly on the environmental parameters and ultimately on the building characteristics and occupational patterns (Matei, 2012). Through the latter can be mentioned the radon from tap water utilized by the household. Since radon is soluble in water, its degassing is added to the indoor exposure (Kendall and Smith, 2002; Todorovic et al., 2012). Special attention is needed when groundwater is used for supplying drinking water, as radon can become a risk factor for users if the radon concentration in the aquifer is high (NRC, 1999). Most of the cancer risks from radon in drinking water arise from the transfer of radon into indoor air, and the exposure through inhalation (WHO, 2009). A significant part of the Romanian population, from both rural and urban areas is still using raw water for drinking and household. In the present study, 73% of the analyzed water samples were collected from wells and springs, as those were pointed out as household water sources. In 2015 the Romanian government has adopted Law no. 301, implementing Directive 2013/51/Euratom (Euroatom, 2013), establishing a radon reference level of 100 Bq l−1 for drinking waters.
The measurements of the radon concentration in soil, has often been used as an indicator and a predictive method to evaluate the elevated indoor radon concentrations of on area (Åkerblom, 1987; Demoury et al., 2013; Cosma et al., 2013; Borgoni et al., 2014; Al-Khateeb et al., 2017; Chen and Ford, 2017; Timkova et al., 2017). The distribution of radon gas in soil can be strongly influenced by local parameters such as chemical and mineralogical composition, physical properties, climatic and geological factors. Another approach in identifying radon risk areas is to assess the geogenic radon potential (GRP), a quantity directly connected to the local geology. High GRP indicates a high probability of radon entering indoors due to geogenic reasons, such as radium content of the bedrock and rock permeability (Ciotoli et al., 2017).
The aim of this work is to assess whether risk areas could be identified based on screening measurements of radon concentration in soil gas and drinking water which will ultimately help prioritize indoor radon surveys.
Section snippets
Design of survey
The investigated territory covers 16 counties, with an area of 99,837 km2, in central and western Romania, representing ~42% of the Romanian territory. Several measurements campaigns were carried out between the years 2012 and 2018 in inhabited 10 × 10 km grid cells. The sampling points were selected near dwellings and densely populated areas. The median of the number of measurements per cell, for both radon measurements in soil and water samples was 3, with a minimum/maximum of 1/17. Water
Results and Discussions
The study area, spanning over 16 counties, was divided into 1111 polygons according to the internationally suggested 10 × 10 km grid for the European indoor radon map (Tollefsen et al., 2014). Approximately 12% of cells correspond to rocky mountain terrain, significant number of dwellings, which led to 977 cells being susceptible to radon measurements in soil and water, but also indoors (data on indoor radon is under review elsewhere). From a map-level integration perspective, 2564 measurements
Conclusions
The present study represents one of the first attempts to identify and map radon priority area according to the radon activity concentration in soil gas and drinking water in Romania. The map of radon in water indicates that there is no significant radiological problem from the perspective of inhaled/ingested radon due to water, except for 2 cells out of 694 cells investigated. Moreover, a radon concentration in water ranging from 0.3 to 352 Bq l−1 would insignificantly influence the indoor
Acknowledgements
This work was supported by the Romanian National Authority for Scientific Research and Innovation, CNCS-UEFISCDI, by the project “Radon map (residential, geogenic, water) for center, west and north-west regions from Romania (RAMARO)”, PN-II-PCCA-PT-73/2012 and by the project ID P_37_229, Contract No. 22/01.09.2016, with the title “Smart Systems for Public Safety through Control and Mitigation of Residential Radon linked with Energy Efficiency Optimization of Buildings in Romanian Major Urban
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