The effect of organic amendment on potential mobility and bioavailability of 137Cs and 60Co in tropical soils

Anthropogenic accumulation based on chemometrics of the radionuclide K-40 in tropical soils in the northeast Brazil

The continuous use of fertilizers can increase the radionuclides levels in soils, and their accumulation and concentration are related to their characteristics and the various processes of use and soil occupation. Analyzing data from radiometric and pedological measurements often demands the use of more robust tools for better integration of results. This work presents the results of a study to evaluate the accumulation of ⁴⁰K, in an area of the Zona da Mata region in Pernambuco, Northeastern Brazil, due to the contribution of natural or artificial sources. ⁴⁰K activity concentration was measured by high resolution gamma spectrometry in 108 soil samples, as well the organic matter content and particle size distribution. Results showed the ⁴⁰K activity ranged from 103 to 1843 Bq.Kg^-1, with the arable soils showing levels above the world average value (420 Bq.Kg^-1). A higher prevalence of ⁴⁰K was observed on arable soils, regardless of soil type, organic matter content, depth or texture. Agricultural activities increased of ⁴⁰K levels in different degrees, depending on the type of crop used, with an accumulation factor of up to 4 times greater compared to soils not impacted by agricultural activities. The radiochemometric diagnosis maded it possible to draw up a strategic management plan to improve the management practices of family farming in order to maximize production efficiency, and promote the conservation of natural resources and environmental preservation.

Technologies for the cobalt-contaminated soil remediation: A review

The cobalt-contaminated soil has exposed potential toxicity to humans, plants, and animals. Industrial activities like ore smelting, alloy manufacture, and electric and electronic devices production have induced the increased cobalt content in soil resulting in higher ecosystem risk in diverse environmental media. However, knowledge gaps in cobalt transfer in soil and the limited understanding of remediation techniques make it challenging to estimate their potential application scenarios. Thus, keeping in view the above facts, this paper summarizes the natural and anthropogenic sources arousing the increase of cobalt in soil and reviews the cobalt species in soil and factors that influence the mobilization of cobalt. Moreover, the status of the remediation technologies is critically evaluated, including phytoremediation, immobilization, and separation technologies (soil washing and electroremediation) with a focus on the application and mechanism of phytoremediation and immobilization. Based on the actual application, further improvements and prospects of all techniques are proposed. This comprehensive review might serve to guide technique selection and inspire more scientific exploration on the remediation of cobalt-contaminated soil.

Growth and (137)Cs uptake of four Brassica species influenced by inoculation with a plant growth-promoting rhizobacterium Bacillus pumilus in three contaminated farmlands in Fukushima prefecture, Japan

The effectiveness of the plant growth-promoting rhizobacterium Bacillus pumilus regarding growth promotion and radiocesium ((137)Cs) uptake was evaluated in four Brassica species grown on different (137)Cs contaminated farmlands at Fukushima prefecture in Japan from June to August 2012. B. pumilus inoculation did not enhance growth in any of the plants, although it resulted in a significant increase of (137)Cs concentration and higher (137)Cs transfer from the soil to plants. The Brassica species exhibited different (137)Cs uptake abilities in the order Komatsuna>turnip>mustard>radish. TF values of (137)Cs ranged from 0.018 to 0.069 for all vegetables. Komatsuna possessed the largest root surface area and root volume, and showed a higher (137)Cs concentration in plant tissue and higher (137)Cs TF values (0.060) than the other vegetables. Higher (137)Cs transfer to plants was prominent in soil with a high amount of organic matter and an Al-vermiculite clay mineral type.

Transfer of radiocesium to four cruciferous vegetables as influenced by organic amendment under different field conditions in Fukushima Prefecture

Soil-to-plant transfer of radiocesium ((137)Cs) in four cruciferous vegetables as influenced by cattle manure-based compost amendment was investigated. Komatsuna, mustard, radish and turnip were cultivated in three different (137)Cs-contaminated fields at Nihonmatsu City in Fukushima Prefecture from June to August 2012. Results revealed that organic compost amendments stimulated plant biomass production and tended to induce higher (137)Cs concentration in the cruciferous vegetables in most cases. Among the studied sites, Takanishi soil possessing low exchangeable potassium (0.10 cmolc kg(-1)) was associated with an increased concentration of (137)Cs in plants. Radiocesium transfer factor (TF) values of the vegetables ranged from 0.025 to 0.119. The increase in (137)Cs TFs was dependent on larger plant biomass production, high organic matter content, and high sand content in the studied soils. Average (137)Cs TF values for all study sites and compost treatments were higher in Komatsuna (0.072) and radish (0.059), which exhibited a higher biomass production compared to mustard and turnip. The transferability of (137)Cs to vegetables from soils was in the order Komatsuna > radish > mustard > turnip. The highest (137)Cs TF value (0.071) of all vegetables was recorded for a field where the soil had high organic matter content and a high clay proportion of 470 g kg(-1) consisting of Al-vermiculite clay mineral.

Soil to plant transfer of 137Cs and 60Co in Ferralsol, Nitisol and Acrisol

In this study, soil to plant transfer factor values were determined for 137Cs and 60Co in radish (Raphanus sativus), maize (Zea mays L.) and cabbage (Brassica oleracea L. var. capitata) growing in gibbsite-, kaolinite- and iron-oxide-rich soils. After 3 years of experiment in lysimeters it was possible to identify the main soil properties able to modify the soil to plant transfer processes, e.g. exchangeable K and pH, for 137Cs, and organic matter for 60Co. Results of sequential chemical extraction were coherent with root uptake and allowed the recognition of the role of iron oxides on 137Cs behaviour and of Mn oxides on 60Co behaviour. This information should provide support for adequate choices of countermeasures to be applied on tropical soils in case of accident or for remediation purposes.