Development of radon transport model in different types of dwellings to assess indoor activity concentration

https://doi.org/10.1016/j.jenvrad.2020.106501Get rights and content

Highlights

  • Evaluation of Radon indoor at different dwelling floors through transport models.

  • Radon indoor is simulated by varying soils characteristics and building materials.

  • Finite differences method (FDM) is used to solve the transport models equations.

  • The position of lower floor of dwellings plays a significant role.

  • Radon activity concentrations increase using yellow tuff.

Abstract

The influence of different building types on the activity concentration of Radon indoor is studied through transport models in soil and building materials. The numerical solutions of the relevant transport equations are solved by the finite differences method (FDM) and used to evaluate the indoor Radon activity concentration. Several boundary conditions are introduced to simulate the Radon entry into the buildings from soils and to assess the Radon activity concentration at the different floors. The types of dwelling investigated differ in the position of the lower floor respect to the ground. Comparisons are made to modeling assessments obtained considering different soil characteristics underneath the building and building materials to simulate indoor Radon activity concentration. These investigations lead to the conclusion that, in addition to the nature of the soil and building materials, the position of lower floor of dwellings plays a significant role in determining the amount of radon entry into residential buildings. This work is effective to assess the health hazards coming from the Radon accumulation in living environments.

Introduction

The healthiness of indoor environments is increasingly evaluated to try to safeguard the health of occupants both in the home and in the workplace. Radon is a natural radioactive gas and has been classified as a major natural pollutant in buildings and must be included in any assessment aimed at estimating indoor air quality (US EPA, 1988; ICRP, 1993; European Commission, 2013). Radon is present in all terrestrial environments in varying quantities in three isotopes; the most abundant is the 222Rn having a decay half-life of 3.823 days. This isotope, produced by 226Ra, belongs to the natural decay chains of 238U, which is one of the main elements constituent the Earth's crust (Ambrosino et al., 2020e; Malanca et al., 1991). The 222Rn (later called Radon) has been studied extensively over the past few decades for (i) its use as an environmental tracer (see for example more recent papers Ambrosino et al., 2018a, 2019a, 2020b; Sabbarese et al., 2017b, 2020), and (ii) the hazards associated with its indoor concentration in human living environment (Ambrosino et al., 2018b; Bochicchio et al., 2009; Kumar and Chauhan, 2014; Sabbarese et al., 2017a). In a built environment, Radon originates mainly from soil through cracks in the ground and building substructure by diffusion and advection and, secondly, from building material and in small quantity from the air and water used in the home (Ambrosino et al., 2020d; Szajerski and Zimny, 2020). The Radon contribution exhaled from building materials can be even higher, when NORM (Naturally Occurring Radioactive Materials) are used for production of dwellings (Leonardi et al., 2018). Radon emission from soil, and in general from a medium, is influenced by several factors: porosity, granulometry, permeability, relative humidity and temperature (De Martino et al., 1997, 1998; Monnin and Seidel 1997; Morawska and Philips, 1993; Semkov and Parekh, 1990; Thu et al., 2020). Understanding the characteristics of soil and building material enables estimation of the indoor Radon concentration in dwellings and associated human health risks (Ajayi et al., 2018). Radon is well-known to be the main cause of lung cancer just after cigarette smoking (Frutos et al., 2019). The residential exposure risk due to the Radon in dwellings can considerably increase for indoor workers or people with sedentary activity (Ambrosino et al., 2020f; Müller et al., 2016). The recent updates of EU Basic Safety Standards in 2013/59/EURATOM directive, established the risk related to Radon inside buildings and radioactivity of building materials: the reference levels for Radon indoor air has been established in 300 Bq/m3 (European Commission, 2013; Frutos et al., 2019). Nowadays it is more and more common practice to require appropriate certificates confirming safe Radon levels in buildings (Szajerski and Zimny, 2020). The continuously growing awareness of Radon risk among scientists and general population results in elaboration of new active systems for reduction of Radon activity concentration in buildings (Ambrosino et al., 2020c; Hung et al., 2018).

In this framework, the goal of the present work is the assessment of the Radon activity concentration in different types of dwelling studying the soil gas entry rates into buildings. Most of the papers in literature show a lot of measurements performed with this aim (Guo et al., 2004; Kumar and Chauhan, 2014; La Verde et al., 2018b; Righi and Bruzzi, 2006; Stanley et al., 2019). The importance of the present work is being able to carry out evaluations of indoor Radon before making extensive measurements, also to make a possible assessment of areas and/or buildings with significative risk of presenting high levels of Radon. This goal is poorly treated in literature, and only very few works deal partially with it, studying only selected problem connected with the simulation of Radon flux from fractured rocks, specific soils composition, insulation materials (Ajayi et al., 2018; Riley et al., 1999; Savović et al., 2011a, b; Skubacz et al., 2019; Szajerski and Zimny, 2020). There is absence of papers that compare different types of buildings to evaluate a relative Radon risk index depending on the soil type and building materials. The modeling technique implemented to simulate the Radon entry rates into buildings is the finite difference method (FDM) (Nikezić et al., 2008; Savović et al., 2011a) for predicting Radon flux considering the mechanisms responsible for gas-phase contaminant transport. The studied model does not concers any air exchange physics within the building or between indoors and outdoors but only considers diffusion/advection between floor materials and the ground in order to obtain a reference maximum level of possible activity concentration. With mechanism for air exchange between indoors and the outdoors, indoor radon concentrations can be reduced effectively up to ~40–50% (Syuryavin et al., 2020).

Section snippets

Background

The basic concept in measuring Radon concentration involves observations of Radon through the porous medium being studied (Fournier et al., 2005). This medium separates two chambers that have different Radon concentrations. In such configurations, Radon moves from one chamber to another, primarily in one direction only (Gauthier et al., 1999; Sasaki et al., 2006). The problem of Radon transport can be treated using a plane sheet model (Savović et al., 2011a, b). In such conditions, the Radon

Research approach

The aim of the present study is to simulate the increase in activity concentration of indoor Radon in different types of dwelling, following the equation governing the Radon production and transport into the soil and its entry into buildings (§2.1). Fig. 1a shows the different types of buildings analyzed, coming from Italian campaigns of Radon monitoring carried out in the ‘80-‘90s (Sciocchetti et al., 1985), and, then, highlighted in the ‘National Radon Plan’ by Italian public institution for

Results and discussion

The Radon activity concentration at each floor of the different types of dwelling (0, I, II, III, IV) is computed. The solutions of the system composed by equations (2), (4) and the boundary conditions (8) are of the type of equations (5), (6), with different parameters D, ε, k, μ and S according to the medium that Radon passes through. For brevity, they are not reported. The numerical solutions are reported. A constant 222Rn activity concentration at the input side, from 6 m depth of ground

Conclusions

The present work aims to evaluate the Radon activity concentration within the different floors of a building. The growing awareness of the impact of Radon on human health has increased the demand to know the amount of radon with which one lives in a confined environment. Support for a pre-assessment is provided on the basis of the type of building, the underlying soil and building materials. Radon gas, naturally produced in the Earth's crust, migrates within the rock mass by diffusion and/or

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgments

The authors are grateful to the University of Campania “Luigi Vanvitelli” for the financial support provided through the VALERE PLUS 2018 PROGRAM.

References (68)

  • F. Girault et al.

    Estimating the importance of factors influencing the radon-222 flux from building walls

    Sci. Total Environ.

    (2012)
  • L.C. Hung et al.

    Characterisation of specified granular fill materials for radon mitigation by soil depressurisation systems

    Construct. Build. Mater.

    (2018)
  • A. Kumar et al.

    Measurement of indoor radon–thoron concentration and radon soil gas in some North Indian dwellings

    J. Geochem. Explor.

    (2014)
  • F. Leonardi et al.

    A study on natural radioactivity and radon exhalation rate in building materials containing norm residues: preliminary results

    Construct. Build. Mater.

    (2018)
  • A. Malanca et al.

    Influence of tuff on the radon concentration in dwellings

    J. Environ. Radioact.

    (1991)
  • B. Milenković et al.

    Numerical solving of the track wall equation in LR115 detectors etched in direct and reverse directions

    Radiat. Meas.

    (2009)
  • M.M. Monnin et al.

    Physical models related to radon emission in connection with dynamic manifestations in the upper terrestrial crust: a review

    Radiat. Meas.

    (1997)
  • L. Morawska et al.

    Determination of the Radon surface emanation rate from laboratory emanation data

    Sci. Total Environ.

    (1991)
  • L. Morawska et al.

    Dependence of the Radon emanation coefficient on radium distribution and internal structure of the material

    Geochem. Cosmochim. Acta

    (1993)
  • R. Mosley et al.

    The influences of diffusion and advective flow on the distribution of radon activity within USEPA's soil chamber

    Environ. Int.

    (1996)
  • E. Muñoz et al.

    A finite element model development for simulation of the impact of slab thickness, joints, and membranes on indoor radon concentration

    J. Environ. Radioact.

    (2017)
  • R. Nazir

    Taylor series expansion based repetitive controllers for power converters, subject to fractional delays

    Contr. Eng. Pract.

    (2017)
  • S. Righi et al.

    Natural radioactivity and radon exhalation in building materials used in Italian dwellings

    J. Environ. Radioact.

    (2006)
  • W.J. Riley et al.

    Effects of variable wind speed and direction on radon transport from soil into buildings: model development and exploratory results

    Atmos. Environ.

    (1999)
  • M.D. Rowberry et al.

    Calculating flux to predict future cave radon concentrations

    J. Environ. Radioact.

    (2016)
  • N.K. Ryzhakova

    Parameters of modeling radon transfer through soil and methods of their determination

    J. Appl. Geophys.

    (2012)
  • C. Sabbarese et al.

    Analysis of alpha particles spectra of the Radon and Thoron progenies generated by an electrostatic collection detector using new software

    Appl. Radiat. Isot.

    (2017)
  • S. Savović et al.

    Numerical solution of the diffusion equation describing the flow of radon through concrete

    Appl. Radiat. Isot.

    (2008)
  • S. Savović et al.

    Radon diffusion in an anhydrous andesitic melt: a finite difference solution

    J. Environ. Radioact.

    (2011)
  • S. Savović et al.

    Explicit finite difference solution of the diffusion equation describing the flow of radon through soil

    Appl. Radiat. Isot.

    (2011)
  • G. Sciocchetti et al.

    The Italian national survey of indoor radon exposure

    Sci. Total Environ.

    (1985)
  • K. Skubacz et al.

    Modelling of radon hazards in underground mine workings

    Sci. Total Environ.

    (2019)
  • P. Szajerski et al.

    Numerical analysis and modeling of two-loop experimental setup for measurements of radon diffusion rate through building and insulation materials

    Environ. Pollut.

    (2020)
  • F. Ureña et al.

    Solving the telegraph equation in 2-D and 3-D using generalized finite difference method (GFDM)

    Eng. Anal. Bound. Elem.

    (2020)
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