Siriporn Angkunrat, Triphop Bhongsuwan, Thawat Chittrakarn, and Darunee Bhongsuwan

pp. 1439 - 1455

Abstract

Specific activity of radium-226 in 13 types of vegetables grown in Namom district, Songkhla province, were analyzed using a low background gamma-ray spectrometer. The analyzed vegetables included Ivy Gourd, Yellow Cassia, White Popinac, Yard Long Bean, Rice, Peanut, Egg Plant, Spineless Amaranth, Swamp Cabbage, Mustart, Chinese Cabbage, Collards and Cucumbers. The control vegetables were taken from Bangklum district, 40 km south of Namom district. The samples were weighed, dried in an oven and finally burnt to ash in a furnace before being analyzed for a gamma ray of 186.2 keV emitted from Radium-226. The results showed that the geometrical means of specific activity of radium-226 of vegetables grown in Pijit, Namom, Klongrang and Thungkamin sub-district and over the Namom district were 1082, 1220, 1457, 1253 and 1250 mBq/kg, respectively. The highest and lowest values were 7882 and 26 mBq/kg, found in Ivy Gourd
and Yard Long Bean, respectively. The high specific activities of radium-226 in vegetables were found to be distributed uniformly in the area. This probably indicated the source of radium-226 was also distributed
uniformly in the shallow granitic bedrock throughout the area. We concluded that the radium-226 contents in vegetables grown in Namom district depended on the absorbability of alkaline earth metals in vegetables
themselves, geographic features and radium content in natural water in the area. The estimated annual effective dose averaged over Namom district was 21 µSv. Consumption of Ivy Gourd may receive the maximum annual effective dose of 132 µSv.