Temporal variations of accumulated cesium in natural soils after an uncharacteristic external exposure

Abstract

The accumulation behaviors and solid phase partitioning patterns of stable cesium, which have been recognized as an indicator of the long-term movement of radioactive cesium ( 137 Cs or 134 Cs) in ecosystems, were studied in typical and natural soils of Japanese origin, namely, red clay, leaf-mold and andosol soils. The retention and migration of soil-phase cesium have been explained relative to various factors, such as soil organic matter contents, competitive cation concentrations and the adsorption ratio of Cs to the solid phase. Cesium was adsorbed nearly quantitatively in the leaf-mold type soil, and the rate of Cs absorption increased as the particle size decreased in the red clay and andosol soils. The distributions of Cs within the soil solid phases were defined using the selective sequential extraction scheme and were used to explain its relative incorporation in the soil fractions. Solid phase fractionation indicated that nearly half of the total cesium concentrations in the soils were in the 'residual' fraction (representing the metal that was incorporated within the crystalline lattice of the soil and was difficult to extract). These findings are expected to provide information regarding suitable conditions for remediation, immobilization or the recovery of cesium from contaminated soils with excess cesium concentrations. KeywordsCesium; Accidental exposure; Soil contamination; Solid-phase distribution; Sequential fractionation; Temporal variation 2 Microchemical Journal, 118: 158-165, 2015 The original publication is available at: http://dx.doi.org/10.1016/j.microc.2014.09.006 IntroductionWaste disposal operations or accidental releases due to nuclear-technology-related activities have resulted in the release of large amounts of radionuclides into the environment. Among the radioactive materials, the dispersion of radiocesium at elevated concentrations evokes concern due to its extended solubility characteristics as an alkaline metal ion, its comparatively longer half-life, and its easy incorporation into living beings [8][9][10] The objective of this study is to investigate the cesium distribution in the operationally defined physico-chemical and particle size fractions of soils to understand the temporal variations of cesium after being released at an uncharacteristic rate. Experimental InstrumentsThe atomic absorption spectroscopy (AAS) technique was used to determine the stable cesium concentration in solution. An AAnalyst 600 (PerkinElmer, Waltham, MA) was used that was equipped with a transverse heated graphite atomizer with an integrated, pyrolytic graphite coated platform and a longitudinal Zeeman-effect background corrector. The light source was an electrodeless discharge lamp (EDL) that was powered by an EDL System II that was operated at 18 mA. The wavelength was set at the 852.1 nm resonance line and the monochromator spectral bandpass was set at 0.7 nm. In addition, a baseline offset correction time at 2.0 s was used with a read delay of 0.0 s. Argon was used as the purg...

Adsorption characteristics of atrazine on different soils in the presence of Cd(II)

“…Then 2 g of soils were mixed with 10 ml of atrazine in a centrifugal tube. The HCl and NaOH of 1 mol/l were used to adjust the pH value of atrazine solution to 3.0, 5.0, 7.0, 9.0, and 11.0, respectively (Sawai et al., 2015). The centrifuge tube was placed in a 298 K water bath vibrating screen and oscillated for 24 h. The rest were referred to the isothermal adsorption experiment.…”

Bioleaching and removal of radiocesium in anaerobic digestion of biomass crops: Effect of crop type on partitioning of cesium

“…Anaerobic degradability varies widely among crops [14] , so the amount of RCs released might also depend on crop type. Researchers have measured RCs distribution coefficients (particulate/dissolved forms) in river, soil, and sediment samples [15] , [16] , but that of plants decomposed in a bioreactor is not yet understood. Therefore, phase partitioning of RCs between bulk solution and suspended solids in AD needs to be examined in detail.…”