Temporal evolution of ¹³7Cs⁺, K⁺ and Na⁺ in fruits of South American tropical species.

Concentrations of (137)Cs, K and Na in fruits of lemon (Citrus limon B.) and of K and Na in fruits of coconut (Cocos nucifera L.) trees were measured by both gamma spectrometry and neutron activation analysis, with the aim to understand the behaviour of monovalent inorganic cations in tropical plants as well as the plant ability to store these elements. Similar amounts of K(+) were incorporated by lemon and coconut trees during the growth and ripening processes of its fruits. The K concentration decreased exponentially during the growth of lemons and coconuts, ranging from 13 to 25 g kg(-1) dry weight. The incorporation of Na(+) differed considerably between the plant species studied. The Na concentration increased linearly during the lemon growth period (0.04 to 0.70 g kg(-1) d.w.) and decreased exponentially during the coconut growth period (1.4 to 0.5 g kg(-1) d.w.). Even though radiocaesium is not an essential element to plants, our results have shown that (137)Cs incorporation to vegetable tissues is positively correlated to K distribution within the studied tropical plant species, suggesting that the two elements might be assimilated in a similar way, going through the biological cycle together. A mathematical model was developed from the experimental data allowing simulating the incorporation process of monovalent inorganic cations by the fruits of such tropical species. The agreement between the theoretical approach and the experimental values is satisfactory along fruit development.

In vivo measurement technique of 40K as an indicator of the amount of skeletal muscle tissue in the human body.

Potassium is an essential element for human metabolism. It is present in all living cells, predominantly in the skeletal muscle tissue. The energy of the 40K photon and its uniform distribution within the human body allow its in vivo measurement. Subjects of both sexes were monitored at the whole-body counter of the IRD facility for the evaluation of 40K body burden, being divided into two groups: (1) subjects who do not exercise routinely, and (2) subjects who do exercise routinely. The average values found for potassium mass and potassium concentration in group 1 were 99 +/- 17 g of K and 1.3 +/- 0.2 g of K kg(-1) of body mass, respectively, and in group 2 the average values found for potassium mass and potassium concentration were 118 +/- 33 g of K and 1.6 +/- 0.2 g of K kg(-1) of body mass, respectively. The comparison between average values for potassium mass and concentration shows a significant statistical difference.

Assessment of the doses received by the Cuban population from 40K contained in the body: modelling based on a neural network.

Potassium-40 constitutes the main natural source of potassium present in the body, which influences the effective dose received by people. With the aim of assessing the contribution of this component to the doses received by the Cuban population, a study intended to assess the doses was developed. For this purpose, a representative sample of the Cuban population was selected according to age and sex. The measurements were made using the whole-body counter (WBC) of the Center for Radiation Protection and Hygiene (CPHR). For dose estimations, a uniform distribution of potassium for the whole body was assumed. The methodology used was the one recommended by the ICRP. The values of annual effective dose range between 93 and 209 microSv for females and between 123 and 212 microSv for males. The annual average effective dose for members of the public was estimated as 150 +/- 40 microSv, taking into account the experimental data and the specific features of the Cuban population. With the dose values obtained, it was possible to model dose estimates by means of a neural network, which was trained with the results obtained and using as starting data the sex, age, height and corporal weight of people studied. The modelobtained allows consideration of the anatomical features of each person in the estimation of doses.