# INST2019 (International Nuclear Science and Technology Conference)

4-6 February 2019
Asia/Bangkok timezone
Deadline for full paper revision: 21 May 2019.

## Long-Term Cyling of Radiocaesium in Pine Forest at Wat Chan Thailand

5 Feb 2019, 14:40
1h 10m

#### Centara Grand at Central Ladprao

Chatuchak, Bangkok 10900, Thailand
Poster Environment

### Speaker

Dr Thawatchai Itthipoonthanakorn (Office of Atoms for Peace)

### Description

This study focused on the long-term cycling of radiocaesium in pine forests at Wat Chan in northern Thailand. Systematic studies were made of stable and radiocaesium, potassium and rubidium in soil horizons, tree stems and needles. Measurements of total concentrations were complemented with determinations of exchangeable fractions as well as the isotopic exchangeability of radio- and stable caesium. Wat Chan in Thailand is a native tropical forest of Pinus kesiya (or Three-needled pine) which received chronic distribution of atmospheric fallout from nuclear weapons tests in the 1960s. Samples were taken from this site in late February 2016 at six randomly located co-ordinates. The forest soil is typical of similar forest soils in the tropical zone. The organic matter, even at the surface, is much less abundant than in temperate forest soils while the mineral soil is composed almost entirely of quartz with no identifiable clay minerals. About 84% of nuclear weapons fallout $^{137}$Cs is distributed within the upper 3 cm and the maximal distribution is 37.6% at 2 cm depth. These inventories were decay corrected to 1963 and summed to provide a total soil profile inventory of 643 Bq m$^{-2}$. Even though the organic matter content in the upper 2 – 3 cm of the soil profile is low it probably still plays an important role in the vertical distribution of $^{137}$Cs. The variation of soil pH throughout the upper 13 cm of the soil profile is less than 1 pH unit and thus is unlikely to influence the vertical distributions of $^{137}$Cs and $^{133}$Cs in the soil. K and Rb are strong competitors of Cs during cycling within the forest ecosystems at Wat Chan. K is present in the exchangeable fraction in soil at much higher concentration than Rb and especially Cs. The overall degree of translocation from soil to pine needles is in the order of $^{39}$K > $^{85}$Rb > $^{133}$Cs.

### Primary authors

Dr Thawatchai Itthipoonthanakorn (Office of Atoms for Peace) Prof. George Shaw (University of Nottingham UK)

### Presentation Materials

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