Environmental Radionuclides in Surface Soils of Vietnam

Abstract

A database on U, Th, K, and Cs in surface soils was established to provide inputs for the assessment of the collective dose to the population of Vietnam and to support soil erosion studies using Cs as a tracer. A total of 292 soil samples was taken from undisturbed sites across the territory and the concentrations of radionuclides were determined by gamma spectrometry method. The multiple regression of Cs inventories against characteristics of sampling locations allowed us to establish the distribution of Cs deposition density and its relationship with latitude and annual rainfall. The Cs deposition density increases northward and varies from 178 Bq m to 1,920 Bq m. High rainfall areas in the northern and central parts of the country have received considerable Cs inputs exceeding 600 Bq m, which is the maximum value that can be expected for Vietnam from the UNSCEAR global pattern. The mean activity concentrations of naturally occurring radionuclides U, Th, and K are 45, 59, and 401 Bq kg, respectively, which entail an average absorbed dose rate in air of 62 nGy h, which is about 7% higher than the world average.

Natural radioactivity in farm soil and phosphate fertilizer and its environmental implications in Qena governorate, Upper Egypt

“…The estimated dose rate for farm soil and Nile island's soil are comparable with the results in China (Ziqiang et al, 1988), Vietnam (Hien et al, 2002), Yugoslavia (Bikit et al, 2005) and Brazil (Malanca et al, 1993).…”

Distribution of gamma radiation dose rate related with natural radionuclides in all of Vietnam and radiological risk assessment of the built-up environment

“…The contents of natural radionuclides in the soil are very important because these radionuclides contribute significantly to the collective dose of the general population 11 . Some researchers have measured activity concentrations of natural radionuclides in soil in Vietnam 12 – 14 . The most recent observations 13 for all of Vietnam showed that the average concentrations of 238 U, 232 Th and 40 K were 43 ± 18 Bq kg −1 , 60 ± 20 Bq kg −1 and 442 ± 230 Bq kg −1 , respectively, which are 1.2, 2.0 and 1.0 times higher than the worldwide averages 1 .…”