Jarae Wutthisasna, Thawat Chittrakarn, Darunee Bhongsuwan, and Tripob Bhongsuwan

pp. 201 - 215

Abstract

Altogether 150 water samples were collected from shallow wells widely distributed in Namom district, Songkhla province. Co-precipitation technique was used to absorb radium into co-precipitate Ra-BaSO₄, which was measured for Ra-226 using a low background alpha spectrometer. The results showed that the Ra-226 concentration in well water in Namom district ranged 3.51-292.1 mBq/l, with a geometric mean 50.7 mBq/l. Ra-226 concentration in thirty one water samples or 29.31% exceeded 111 mBq/l, which was the maximum contaminant level of the US Environmental Protection Agency. Six villages having an arithmetic mean of Ra-226 concentration in well water exceeding the 111 mBq/l level included Ban Koktang Moo 2, Pijit sub-district; Ban Tungkho Moo 2, Namom sub-district; Ban Lancai Moo 2, Ban Tungpho Moo 3, Tung kamin sub-district; Ban Meapia Moo 3, Ban Tonpling Moo 5, Klongrang sub-district. Ban Tonpling Moo 5 had the highest concentration at 177.8 mBq/l. The high Ra-226 contaminated water wells are generally located in granitic basement with associated fault/fracture zones. The estimated annual dose averaged over
Namom district was 15.3 µSv while people living in Ban Tonpling Moo 5 met the highest estimated annual dose of 36.3 µSv. However, the ratios between the number of water wells with and without associated oral and esophagus cancer cases in the area where the estimated dose is over and below 8 µSv did not differ
significantly.