Avacir Casanova Andrello

Brazil nuts: determination of natural elements and aflatoxin

Um estudo foi realizado para avaliar a associacao dos niveis de radioatividade, selenio e aflatoxinas em castanha-do-Brasil descascada, que foram classificadas em diferentes tamanhos, para exportacao. As determinacoes de selenio foram realizadas por espectrometria de emissao optica com plasma indutivamente acoplado (LOQ=3,0 µg kg-1) e aflatoxinas foram detectadas por LC-MSMS (LOQ=0,85 µg kg-1), as taxas de recuperacao ficaram entre 92 e 100%. A radioatividade foi medida por espectrometria gama de alta resolucao. A concentracao media de selenio foi de (22,7 ± 7,4) µg g-1. (n = 30). A atividade media determinada para os radioisotopos foram: 15,77 Bq kg-1 para o 224Ra, 104,8 Bq kg-1 para 226Ra e 99,48 Bq kg-1 para 228Ra. Para 226Ra, os niveis nao variaram significativamente com o tamanho das nozes, embora tais diferencas foram observadas para 224Ra e 228Ra. Nao houve associacao estatisticamente significativa entre o nivel de selenio e a atividade de radionuclideos, no entanto, houve correlacao entre os radionuclideos. Nao foi encontrado aflatoxinas acima do limite de quantifcacao.A study was carried out to evaluate the association of levels of radioactivity, selenium and aflatoxin in shelled Brazil nuts, which were classified in different sizes, for export. The selenium determinations were performed by inductively coupled plasma optical emission spectrometry (LOQ = 3.0 µg g-1), and aflatoxins were detected by Liquid chromatography-mass spectrometry (LOQ = 0.85 µg kg-1), recovery rates were between 92 and 100%. Radioactivity was measured by high-resolution gamma spectrometry. The selenium mean concentration was (22.7 ± 7.4) µg g-1. (n = 30). Mean activities determined for the following radium isotopes were: 15.77 Bq kg-1 for 224Ra, 104.8 Bq kg-1 for 226Ra and 99.48 Bq kg-1 for 228Ra. For 226Ra, the levels did not vary significantly with nut sizes, although such differences were observed for 224Ra and 228Ra. There was no statistically significant association between the level of selenium and the activity of radionuclides, however, there was correlation between the radionuclides. Aflatoxins above the quantification limit were not found.

Use of cesium-137 methodology in the evaluation of superficial erosive processes

Superficial erosion is one of the main soil degradation agents and erosion rates estimations for different edaphicclimate conditions for the conventional models, as USLE and RUSLE, are expensive and time-consuming. The use of cesium-137 antrophogenic radionuclide is a new methodology that has been much studied and its application in the erosion soil evaluation has grown in countries as USA, UK, Australia and others. A brief narration of this methodology is being presented, as the development of the equations utilized for the erosion rates quantification through the cesium-137 measurements. Two watersheds studied in Brazil have shown that the cesium-137 methodology was practicable and coherent with the survey in field for applications in erosion studies.

Soil erosion determination in a watershed from northern Paraná (Brazil) using 137Cs

The objective of this work was study the soil losses or gains in a watershed in the municipal district of Cambe, Parana using 137Cs as marker for the determination of soil redistributions. A transect sampling was used to evaluate the influence of different tillage on soil erosion. One point, located in a forest area was sampled and analyzed to determine the reference inventory of cesium-137 deposited by fallout. The average value of the reference inventory was 292 Bq m-2. The cesium-137 inventory of the transect samples varied from 80 Bq m-2 to 403 Bq m-2. The sampling points in pasture presented soil losses. The sampling points in coffee plantation did not present losses or gains. The sampling points in soybean cultivated areas presented soil losses.

Measurements of the fallout flux of beryllium-7 and its variability in the soil

Berilio-7 e um radionuclideo cosmogenico, com meia-vida de 53 dias, produzido pelo processo de espalacao de atomos de oxigenio e nitrogenio dentro da troposfera e estratosfera. Apos sua producao, este e transportado ate a superficie terrestre pela deposicao umida e seca. A precipitacao seca contribui somente com 3-8% do inventario total. Medidas de berilio-7 no solo podem serem usadas para indicar movimento de solo da camada superficial e este estudo objetiva examinar o comportamento de berilio-7 no solo. Variabilidade natural do inventario de berilio-7 e em torno de 23% (desvio padrao relativo). A distribuicao em profundidade de berilio-7 pode ser aproximada por uma funcao exponencial no solo nu, com uma profundidade media de distribuicao no solo em torno de 1 cm. O berilio-7 nao foi encontrado abaixo da profundidade de 2 cm para o tipo de solo estudado, o que confirma sua utilizacao para avaliar processo de erosao superficial como um tracador de solo superficial. A concentracao maxima de berilio-7 no periodo analisado e em torno de 40 Bq.kg-1.

A preliminary survey of soil erosion in a small basin in the Paraná State by using 137Cs methodology

Abstract The 137 Cs methodology was used in a small basin in Parana State, Brazil for a preliminary verification of the soil erosion quantification. Six transects at the cultivated areas in the basin were sampling for soil erosion and deposition estimation and one site in a forest area was sampling for the 137 Cs input determination in the region. Three published equations were used for the soil losses or gain determination at the sampling sites in transects. The results showed that a precaution must be taken in the use of these equations.

Uncertainties of the 137Cs technique for validation of soil redistribution modelling in a semiarid meso-scale watershed

Scarcity of long-term series of sediment-related variables has led watershed managers to apply mathematical models to simulate sediment fluxes. Due to the high efforts for installation and maintenance of sedimentological gauges, tracers have been pointed out as an alternative to validate soil redistribution modelling. In this study, the 137Cs technique was used to assess the WASA-SED model performance at the Bengue watershed (933 km²), in the Brazilian semiarid. Qualitatively, good agreement was found among the 137Cs technique and the WASA-SED model results. Nonetheless, quantitatively great differences, up to two orders of magnitude, were found between the two methods. Among the uncertainties inherent to the 137Cs technique, definition of the reference inventory seems to be a major source of imprecision. In addition, estimations of water and sediment fluxes with mathematical models usually also present high uncertainty, contributing to the quantitative differences of the soil redistribution estimates with the two methods.

Assesment of soil erosion by 137Cs technique in native forests in Londrina City, Parana, Brazil

The aim of this work was to assess the soil erosion process in native forest by the 137Cs methodology. The mass balance model was applied to assess the rates of soil loss in three native forests around of Londrina city, Parana, Brazil. 137Cs distribution depth was of exponential type for the three forests and 137Cs inventory was 241 Bq m-2 for Mata 1, 338 Bq m-2 for Mata 2 and 325 Bq m-2 for Mata UEL. The soil loss value calculated for three native forests was: 6,684 kg ha-1 yr-1 for Mata 1, 1,788 kg ha-1 yr-1 for Mata 2 and 4,524 kg ha-1 yr-1 for Mata UEL.