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Radioactivity determination of ¹³⁷Cs, ²²⁶Ra, and ²³²Th in beach she-oak (Casuarina equisetifolia) bark samples collected from Thailand's coastal regions

Murnee Daoh^a,b, Komrit Wattanavatee^a,*, Sawasdee Yordkayhun^a, Prakrit Noppradit^c

 
ABSTRACT:     Tree bark can serve as a biological indicator for the contamination of radioactive materials through atmosphericabsorption. Thekeyobjectiveofthisstudyistoevaluatetheactivityconcentrationofradioactivesubstances in beach she-oak bark as abiomonitor for radioactive contamination. The bark samples in 19 provinces along Thailand?s coast werecollectedandanalyzedusingahigh-puritygermaniumdetectorandgammaspectrometrysystem. Theresults show that the bark sample contained no detectable levels of 137Cs radioactivity, implying no contamination of artificial radiation from historical nuclear power plant accident or man-made sources. The activity concentration of 226Ra varied in the range of 1.30?0.30 to 8.5?0.8 Bq/kg, with an arithmetic mean of 3.8?0.5 Bq/kg, while the concentration is in the range of 2.6?0.6 to 15.1?1.9 Bq/kg, with an arithmetic mean of 7.8?1.4 Bq/kg, for 232Th. The variation of activities observed in the higher (>9? N) and lower latitude (<9? N) regions could be influenced by the weather and rainfall amounts, which would lead to the accumulation of these nuclides. Notably, the highest 226Ra and 232Th concentration values were observed in the samples from Phuket and Phang Nga Province, respectively. We believe that the higher activity concentrations of natural radionuclides in these provinces would be partly associated with granitic rocks exposed in the regions. Although the hazard index of activities in beach she-oak bark have not been reported, this study served as the background radioactivity levels which is useful in terms of monitoring the region for human health.

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* Corresponding author, E-mail: komrit.w@psu.ac.th

Received 14 Nov 2024, Accepted 0 0000