Caesium, potassium and ammonium distributions in different organs of tropical plants

In the present work the distribution of ions in aboveground plant parts was studied in order to establish the suitability of using radiocaesium as a tracer for the plant absorption of nutrients, such as potassium (K(+)) and ammonium (NH(4)(+)). We present the results for the distributions of (137)Cs, (40)K and NH(4)(+) from four tropical plant species: lemon (Citrus aurantifolia), orange (Citrus sinensis), guava (Psidium guajava) and chili pepper (Capsicum frutescens). Activity concentrations of (137)Cs and (40)K were measured by gamma spectrometry and concentrations of free NH(4)(+) ions by a colorimetric method. Similarly to potassium and ammonium, caesium showed a high mobility within the plants, exhibiting the highest values of concentration in the growing parts of the tree (fruits, new leaves, twigs, and barks). A significant correlation between activity concentrations of (137)Cs and (40)K was observed in these tropical plants. The K/Cs discrimination ratios were approximately equal to unity in different compartments of each individual plant, suggesting that caesium could be a good tracer for (40)K in tropical woody fruit species. Despite the similarity observed for the behaviour of caesium and ammonium in the newly grown plant compartments, (137)Cs was not well correlated with NH(4)(+). Significant temporal changes in the NH(4)(+) concentrations were observed during the development of fruits, while the (137)Cs activity concentration alterations were not of great importance, indicating, therefore, that Cs(+) and free NH(4)(+) ions could have distinct concentration ratios for each particular plant organ. (C) 2008 Elsevier B.V. All rights reserved.

Artificial and natural radioactivity in edible mushrooms from Sao Paulo, Brazil

Environmental biomonitoring has demonstrated that organisms such as crustaceans, fish and mushrooms are useful to evaluate and monitor both ecosystem contamination and quality. Particularly, some mushroom species have a high capacity to retain radionuclides and some toxic elements from the soil and the air. The potential of mushrooms to accumulate radionuclides in their fruit-bodies has been well documented. However, there are no studies that determine natural and artificial radionuclide composition in edible mushrooms, in Brazil. Artificial (Cs-137) and natural radioactivity (K-40. Ra-226. Ra-228) were determined in 17 mushroom samples from 3 commercialized edible mushroom species. The edible mushrooms collected were Agaricus sp., Pleurotus sp. and Lentinula sp. species. The activity measurements were carried out by gamma spectrometry. The levels of Cs-137 varied from 1.45 +/- 0.04 to 10.6 +/- 0.3 Bq kg(-1), K-40 levels varied from 461 +/- 2 to 1535 +/- 10 Bq kg(-1), Ra-226 levels varied from 14 +/- 3 to 66 +/- 12 Bq kg(-1) and Ra-228 levels varied from 6.2 +/- 0.2 to 54.2 +/- 1.7 Bq kg(-1). Cs-137 levels in Brazilian mushrooms are in accordance with the radioactive fallout in the Southern Hemisphere. The artificial and natural activities determined in this study were found to be below the maximum permissible levels as established by national legislation. Thus, these mushroom species can be normally consumed by the population without any apparent risks to human health.

137Cs in the meat of wild boars: a comparison of the impacts of Chernobyl and Fukushima

The impact of Chernobyl on the 137Cs activities found in wild boars in Europe, even in remote locations from the NPP, has been much greater than the impact of Fukushima on boars in Japan. Although there is great variability within the 137Cs concentrations throughout the wild boar populations, some boars in southern Germany in recent years exhibit higher activity concentrations (up to 10,000 Bq/kg and higher) than the highest 137Cs levels found in boars in the governmental food monitoring campaign (7900 Bq/kg) in Fukushima prefecture in Japan. The levels of radiocesium in boar appear to be more persistent than would be indicated by the constantly decreasing 137Cs inventory observed in the soil which points to a food source that is highly retentive to 137Cs contamination or to other radioecological anomalies that are not yet fully understood.

Fukushima-derived radionuclides in sediments of the Japanese Pacific Ocean coast and various Japanese water samples (seawater, tap water, and coolant water of Fukushima Daiichi reactor unit 5)

We investigated Ocean sediments and seawater from inside the Fukushima exclusion zone and found radiocesium (134Cs and 137Cs) up to 800 Bq kg-1 as well as 90Sr up to 5.6 Bq kg-1. This is one of the first reports on radiostrontium in sea sediments from the Fukushima exclusion zone. Seawater exhibited contamination levels up to 5.3 Bq kg-1 radiocesium. Tap water from Tokyo from weeks after the accident exhibited detectable but harmless activities of radiocesium (well below the regulatory limit). Analysis of the Unit 5 reactor coolant (finding only 3H and even low 129I) leads to the conclusion that the purification techniques for reactor coolant employed at Fukushima Daiichi are very effective.

Effective and ecological half-lives of 90Sr and 137Cs observed in wheat and rice in Japan

Published pre-Fukushima food monitoring data from 1963 to 1995 were used to study the long-term presence of 137Cs and 90Sr in rice and wheat. Effective half-lives (T eff) were calculated for rice (137Cs: 5.6 years; 90Sr: 6.7 years) and wheat (137Cs: 3.5 years; 90Sr: 6.2 years), respectively. In rice, 137Cs exhibits a longer T eff because putrefaction processes will lead to the formation of NH4 + ions that are efficient ion exchangers for mineral-adsorbed cesium ions, hence making it more readily available to the plant. Knowledge on the long-term behavior of radiocesium and radiostrontium will be important for Japanese food-safety campaigns after the Fukushima nuclear accident.