An assessment of soil-to-plant concentration ratios for some natural analogues of the transuranic elements.

A field study was conducted in an area of enhanced, natural radioactivity to assess the soil to edible vegetable concentration ratios (CR = concentration in dry vegetable/concentration in dry soil) of 232Th, 230Th, 226Ra, 228Ra, and the light rare earth elements (REE's) La, Ce and Nd. Twenty-nine soil and 42 vegetable samples consisting of relatively equal numbers of seven varieties were obtained from 11 farms on the Pocos de Caldas Plateau in the state of Minas Gerais, Brazil. This region is the site of a major natural analogue study to assess the mobilization and retardation processes affecting Th and the REE's at the Morro do Ferro ore body and U series radionuclides at a nearby open pit U mine. Thorium (IV) serves as a chemical analogue for quadrivalent Pu and the light REE's (III) as chemical analogues for trivalent Am and Cm. The geometric mean CR's (all times 10(-4] decreased as 228Ra (148) greater than 226Ra (76) greater than La (5.4) greater than Nd (3.0) = Ce (2.6) greater than 232Th (0.6), or simply as M (II) greater than M (III) greater than M (IV). These differences may reflect the relative availability of these metals for plant uptake. Significant differences were found in the CR's (for any given analyte) among many of the vegetables sampled. The CR's for the different analytes were also highly correlated. The reasons for the correlations in CR's seen among elements with such diverse chemistries as Ra-REE or Ra-Th are not clear but are apparently related to the essential mineral requirements or mineral status of the different vegetables sampled. This conclusion is based on the significant correlations obtained between the Ca content of the dried vegetables and the CR's for all of the elements studied.

Marcacao de caramujos Biomphalaria glabrata por radionuclideos para trabalhos em campos. / Radionuclide labeling of Biomphalaria glabrata snails for fiel studies

Os autores marcam caramujos Biomphalaria glabrata com 75Se, 75Fe, 89Sr e 90Sr atraves das curvas de captacao, decaimento e distribuicao dos radionuclideos na concha/partes moles do caramujo, concluem que o radioestroncio pode ser utilizado em experiencias em campo sobre dispersao e dinamica de populacao de caramujos

Padronizacao da tecnica de marcacao de caramujos Biomphalaria glabrata com radioestroncio. / Standardization of the technic of labeling Biomphalaria glabrata snails with radiostrontium

Caramujos Biomphalaria glabrata vetor da esquistossomose mansonica, utilizados em experiencias de campo, nas quais se faz necessario sua identificacao e/ou localizacao, devem ser marcados com radioestroncio 85, 89 ou 90.Sua marcacao em laboratorio deve ser procedida em aquarios de vidro sem fundo de areia, temperatura de 26,5 +/- 1 grau C, pH ajustado ao valor encontrado no "habitat", aeracao artificial,alimentacao diaria com pequenas porcoes de alface fresca e 25 ml de agua desionizada por caramujo. O nivel de atividade no caramujo pode ser estimado sabendo-se que para o tempo de marcacao de 5 dias e atividades iniciais de 0,036 a 0,362 microCi/ml, a captacao global para grupos de 10 caramujos esta en torno de 84 +/- 2% e que a marcacao em agua contendo calcio, praticamente nao se altera ate concentracoes de 50 ppm. A sobrevida ao longo de nove semanas nao foi influenciada pela presenca de radioestroncio no caramujo