A COMPARATIVE STUDY OF SOIL RADON AND THORON EXHALATION FROM FOUR VILLAGES OF KOLLAM, KERALAM. MIDHUN, R.S. REJITH, SHILPA MARIAM SAMUEL, SAMUEL MATHEW, P.J. JOJO AND B.K. SAHOO
Exhalation rates of Radon and Thoron from surface soil were measured at four selected villages of Kollam district in Kerala, India, using a continuous radon monitor coupled to an accumulator system. Two villages (Chavara and Neendakara) in the coastal high background radiation area and the other two (Panmana and Ayanivelikulangara) were from interior normal background region. Environmental gamma dose, radon and thoron gas concentrations in the outdoors and exhalation of radon and thoron from surface soil were measured. Locations for measurement were selected on the basis of prevailing environmental gamma level. Measured rates of radon exhalation from surface soilin Chavarawere found to vary from 11Bqm-2h-1 to 301Bqm-2h-1 and those from Neendakara were from 17 Bqm-2h-1 to 317 Bqm-2h-1. Exhalation rates of Thoron were found to have a wide variation from 0.187 KBqm-2h-1 to 26.6 KBqm-2h-1 in Chavara village and that in Neendakara village were found to vary from 0.218 KBqm-2h-1 to 144.3 KBqm-2h-1. Environmental gamma dose levelswere found vary from 0.17Î¼Svh-1 to 4.75Î¼Svh-1 in Chavara and from 0.31Î¼Svh-1 to 7.63Î¼Svh-1in Neendakara. Radon exhalation rates from Panmana village varied from 12 Bqm-2h-1 to 151 Bqm- 2h-1 and thoron exhalation rates varied from 0.35 KBqm-2h-1 to 22.76 KBqm-2h-1. Exhalation rates of radon in Ayanivelikulangara village varied from 56Bqm-2h-1to 189 Bqm-2h-1 and thoron exhalation rates varied from 6.57 KBqm-2h-1 to 24.66 KBqm-2h-1. Gamma dose levelsin Panmana village were found to vary from 0.04 to 0.83 Î¼Svh-1 and that in Ayanivelikulangara village was from 0.10Î¼Svh-1 to 1.23Î¼Svh-1. The observations of exhalation rates and gamma dose levels were found to have no correlation with each other. Radon exhalation rates from soil with the atmospheric radon (outdoor) were found to have a very weak correlation while for thoron, there were no correlation observed.