INVESTIGATION OF RADONEXHALATION RATECORRELATIONS WITH SOIL TEXTURAL PARAMETER SANDRADIUM CONCENTRATION

Abstract

ABSTRACT

Radon ('2'Rn) is a naturally occurring radioactive gas formed in the decay series of '*‘U. It poses significant health risks due to its carcinogenic nature when inhaled, particularly at high concentrations in an enclosed environment. Indoor radon levels and radon exlialation rate are influenced by the concentrations of radon and radium in the soil and other physical parameters. Establishingcorrelationsbetweenthesoilparametersandradonexhalationratefromthesoilis crucial for assessing the potential health risk of indoor radon. This study investigated the correlation between"'Rnexhalation ratesand2°6Raconcentration ofdifferent soil textural classes within theFederal University of Agriculture, Abeokuta (FUNAAB) inOdeda Local Government Area ofOgun State, Nigeria. Five locations having different soil textures wererandomly selected within FUNAAB. Two soil samplesof4 kgeachwerecollected 10 niapart ateach location using a soil auger for determinationof particle size distribution,"6Ra concentration, and"'Rn exhalation rates. Another setoftwosoilsamples werecollected perlocation using acoresampler to determine hydraulic conductivity, soil moisture retention, soil porosity, and bulk density.The texturalclassesofthesoilsamplesweredetermined usingthemechanical sievingmethodforthe particle size distribution test,while the hydraulic conductivity was determined using theconstant head method. The 222Rn surface and mass exhalation rates were measured using radon accumulationchambertechnique,and"Raactivityconcentrationwasdetermined usingNaI(TI) scintillationgamma-rayspectrometer. Theresultsoftheparticlesizedistributionclassified thesoil samples into four based ontheirrespective percentages ofsand,clayand silt:sandy(90.8, 5.2and 4.0),sandy loam (74.8-80.8, 13.2-17.2 and 6.0-8.0), loamy sand (82.8-86.8, 9.2 and 4.0-8.0) and sandy clay loam (60.4-60.8, 20.64-23.2 and 16-18.96). The loamy sand soils of fadama farm demonstrated the highest average hydraulic conductivity (0.02050 cm/s), while sandy clay loam soils presentedthelowest(0.00043cm/s)due to itsfinerparticlesize.Sandy clayloamwasfound iV

to have the highest average of 2'6Ra concentration (237.55z31.37 Bq/kg) while loamy sandy of fadamafarmhasthelowest(96.93z29.96Bq/kg),attributabletoitshighercationexchange capacity.The average '22Rn mass (0.1056 Bqkp*1/i*1)and surface (4.4776 Bqm 'h’) exhalation rates from sandyclay loam were higher thanall theothersoil textures.These indicated thatareas with sandy clay loam soil could be prone to higher radon exhalations. Generally, the correlation of "'Rn mass and surface exhalation rates were strongly positive with "Ra concentrations (r = 0.7369;p=0.1773),positive withsoilmoistureretention(r=0.6020;p=0.0882)andporosity(r =0.4018;p—0.1326),negativewithbulkdensity(r=-0.4018;p=0.0681),andnegativewith hydraulicconductivity(r=-0.2771; p=0.0521).Theresults revealed that"Raconcentrationand soil moisture retention were the most important factors that influenced soil "'Rnexlialation rates asexemplifiedbysandyclayloamsoil;inthestudyarea.