Distribution and Characteristics of 137cs in Surface Soil in the Middle of Laos

This paper presents the assessment of the distribution and characteristics of 137Cs activity in surface soil in the middle of Laos. Measurement has been conducted for 212 soil samples distributed evenly in the middle of Laos using low background gamma spectrometers. It is found that the activity concentrations of 137Cs vary in the range of 0.50–7.97 Bq kg−1 with the average value of 1.46 ± 0.21 Bq kg−1. The values agree well with those reported for neighboring regions and are significantly lower than the world average value. Higher activity concentrations of 137Cs were observed in geological formations with claystone, siltstone, and mud. Foothills were found with higher concentrations of 137Cs, while lower 137Cs concentrations were observed in low-altitude plains. No significant variation of the 137Cs activity concentration with terrain elevation was found.