Solos formados a partir de sedimentos do Grupo Barreiras apresentam, em geral, baixos teores de ferro, mineralogia caulinítica, elevadas quantidades de quartzo na fração areia e pequena quantidade de carbono orgânico. Determinaram-se os teores de Cd, Co, Cr, Ni e Zn extraídos com água régia, em bloco digestor, em Argissolos Amarelos e Latossolos Amarelos sob vegetação natural do Pará e Amapá. Regressão linear múltipla foi utilizada para correlacionar os parâmetros de solo e os teores desses metais. Melhores correlações foram obtidas entre Fe, Mn, argila, silte e Cd, Co, Cu, Zn, Cr, Ni. Não foi encontrada correlação entre o pH e os teores de metais. Argila e areia apresentaram correlação inversa com os metais, porém de mesma magnitude, sendo necessária a exclusão de uma delas no modelo de regressão. Em geral, os teores dos elementos estudados foram inferiores aos encontrados em solos formados a partir de outros materiais de origem. O Mn foi incluído no modelo de regressão linear múltipla do Cd e Co, em função de sua associação com esses metais. O silte foi significativo nas equações para Cr e Co, o que pode ser devido à presença de minerais de argila e óxidos de Fe e Mn em agregados ferruginosos e argilosos de tamanho silte. Estas equações podem ser úteis quando se deseja conhecer, em termos gerais, quais as quantidades que determinada amostra teria se o solo em questão não estivesse contaminado ou sujeito a uso antrópico, podendo ser utilizadas na avaliação da contaminação do solo por estes metais.

Soils formed from the Barreiras Group sediments, located mainly along the coast of Brazil Northern and Northeastern regions, generally present low concentrations of iron oxides and total organic carbon, high quantities of quartz in the sand fraction, and kaolinitic clay mineralogy. The objective of the present study was to quantify the pseudo total concentrations of Cd, Co, Cu, Cr, Mn, Ni, Zn and Fe in Xhantic Udox and Xhantic Udult soils derived from these sediments. The reference sites were covered by native vegetation and located in the States of Pará and Amapá, Brazil. Multiple linear regression analysis was applied to determine correlations between soil parameters and the levels of these metals. The best correlation was obtained between Fe, Mn, clay, and silt contents, and Cd, Co, Cu, Zn, Cr, Ni. A correlation between pH and these metal levels was not found. Clay and sand contents showed a negative inverse correlation with the metal levels,of same magnitude but with a different sign; this was the reason for excluding one of the parameters in the regression model. In general, the contents of the elements were lower than those found in soils formed from other parent materials. The Mn content was included in the model of multiple linear regression for Cd and Co, due to its association with these last metals. Silt level showed to have a significant influence in the equations for Cr and Co, which is attributed to the presence of clay minerals and Fe and Mn oxides in ferruginous and clay aggregates of silt size. The equations obtained in this paper, are useful to predict, in general terms, the amounts of those heavy metals in an unknown soil sample, if the soil material were not contaminated or affected by land usage. Thus, they may be applied to evaluate soil contamination by the studied heavy metals.

Two studies, both set up as completely randomized design, in a 5x5 and 7x5 factorial schemes, evaluated the interference of 5 and 7 ascorbic acid concentrations and 5 glucose or 5 sucrose concentrations, respectively, on the determination of total and reducing sugars by Lane and Eynon method. The ascorbic acid reducing power (AARP) over the Fehling liquor interfered in the results of total and reducing sugars. On average the AARP was equivalent to 74.83 and 69.71% of the reducing power of glucose and of hydrolyzed sucrose, respectively. The ascorbic acid was stable in all study conditions.

No Brasil ainda não foram definidos os níveis de referência de metais pesados, para avaliação da contaminação do solo. Objetivou-se com este trabalho caracterizar diversos solos brasileiros, em condições naturais, quanto aos teores totais dos metais pesados Cd, Cr, Cu, Fe, Mn, Ni, Zn e correlacionar algumas propriedades do solo com a ocorrência desses elementos. Utilizaram-se 162 amostras de solo, da soloteca da Embrapa Solos (RJ), correspondendo aos horizontes A e B de 81 perfis, das principais classes de solos brasileiros, especialmente os Argissolos (27%) e Latossolos (42%). Os teores totais de metais pesados extraídos com água-régia foram analisados em ICP-AES. À exceção do cádmio, as concentrações médias dos metais estudados foram, em geral, inferiores aos valores médios encontrados na literatura internacional, e inferiores aos valores desses metais considerados tóxicos para as plantas. As amostras de solo foram agrupadas por semelhança, utilizandose como variáveis os conteúdos de argila, silte, Mn e Fe e CTC (T). Estabeleceram-se as faixas de concentrações das variáveis de solos nos diversos grupos e uma aproximação dos teores naturais dos metais pesados para outras amostras de solos com características similares às de cada grupo.

The heavy metals background levels for evaluation of a possible contamination are still not defined in Brazilian soils. The objective of this study was to measure the content of the heavy metals Cd, Cr, Cu, Fe, Mn, Ni, Zn, in several brazilian soils, under natural conditions, and to correlate some soil properties with the occurrence of these elements. Soil samples from EMBRAPA Soils' (RJ) collection were used (162 in total), corresponding to A and B (or C) horizons from 81 profiles, of the main classes of Brazilian soils, especially Ultisols (Argissolos) 27% and Oxisols (Latossolos) 42%. Heavy metal levels were determined using an ICPAES, after extraction with acqua regia. The average metal concentrations were below average values reported in the literature for soils found abroad, with exception to Cd. They were also lower than values considered toxic to plants, including Cd values. Soil samples were clustered by similarity, based on the variables content of clay, silt, Mn, and Fe, and value of soil CEC (T value). This enabled separation of the soil samples in seven groups which have distinct ranges for the soil variables contents, which allowed an estimation of the heavy metals background levels for soil samples with characteristics within the range of each group.