open access

https://hdl.handle.net/2115/72256

Downward migration of Cs-137 within the humus layer under temperate coniferous stands in the Czech Republic

英語

Alkali metals

2018-01

Springer

Journal of Soils and Sediments

18(1)

276-286

This study examined the current distribution and downward migration of Cs-137 in the humus horizon under temperate coniferous stands in the Czech Republic. Depth distribution profiles of lithogenic alkali metals (K, Rb, and Cs) were also traced to find any indication regarding the Cs-137 dynamics within the humus horizon. Soil (bulk soil) samples were collected manually from the uppermost down to a depth of 20 cm at three points situated 10-20 m apart in three locations diversely affected by the Chernobyl accident in 1986. Humus samples (about 6 cm in thickness) were separately collected at three points adjacent to the bulk soil sampling. The humus samples were divided into three fractions (upper, middle, and lower) denoted to H-u, H-m, and H-l, respectively, depending on their depths. Activity concentration of Cs-137 and the amount of alkali metals (K, Rb, and Cs) in each humus fraction were determined with gamma spectrometry and ICP spectrometry, respectively. Some properties (pH, density, SOM, and identification of clay minerals), of both bulk soils and humus horizons were also investigated. The highest activity concentration of Cs-137 (Bq kg(-1)) appeared in the upper portion of the soil (mainly humus horizon) under three coniferous stands about 30 years after the Chernobyl accident. Increasing activity of Cs-137 (Bq) was found in the lower humus fraction (H-l, 4 similar to 6-cm depth range) with no appreciable amounts of clay minerals like illite and smectite in the investigated sites. The findings suggest that the fallout Cs-137 moves downward at a speed of 0.13 similar to 0.19 cm year(-1) with degrading organic matter within the humus horizon. Possible association of Cs-137 with alkali metals (K, Rb, and Cs) was suggested by depth distribution profiles of lithogenic alkali metals (K, Rb, and Cs) in humus. The humus horizon under temperate coniferous stands plays an important role in retaining fallout Cs-137 for a long time. Comparing the depth distributions of the fallout radionuclide Cs-137 with the depth distributions of lithogenic alkali metals (K, Rb, and Cs) gives valuable information for clarifying mechanism of Cs-137 movement in humus. Further investigation is needed to elucidate mechanism of Cs-137 migration within humus horizon by tracing Cs-137 speciation and decomposing soil organic matter simultaneously.

学術雑誌論文

Accepted Manuscript

"The final publication is available at link.springer.com".

1439-0108