RESUMO As concentrações de metais na solução do solo são reguladas, principalmente, pelos processos de sorção. Neste estudo foi avaliada a dinâmica de sorção de Cd e Pb em 19 amostras de solos da Região do Médio Rio Paraíba - RJ, Brasil, através da comparação dos parâmetros de diferentes modelos de isotermas obtidos pelo software ISOFT após ensaios de sorção pelo método da batelada. Os resultados mostraram que a isoterma Linear é mais adequada para representar a sorção de Cd e o modelo de Freundlich para Pb e que a adsorção de Cd é fortemente influenciada pelo pH e pelas concentrações de Fe e Ca, enquanto que a adsorção de Pb é mais influenciada pelo pH, e pelas concentrações de Mn e Ca.

ABSTRACT Metal concentrations in soil solution are mainly regulated by sorption processes. In this study, Cd and Pb sorption dynamics have been assessed for 19 soil samples from the Middle Region of Paraíba River - RJ, Brazil, through parameters of different models of isotherms obtained by the ISOFT software following a sorption testing using the batch method. Results showed that the linear isotherm is more appropriate to describe Cd sorption and the Freundlich model for Pb. Cd sorption is strongly affected by pH and concentrations of Fe and Ca; while Pb sorption is mostly influenced by pH and the concentrations of Mn and Ca.

The objectives of this study were to determine the pseudototal and available contents of Cu, Fe, Mn and Zn as well as their speciation in Argiudolls located in the flat Argentine Pampas, in Santa Fe province, and to compare the contents extracted by EDTA with those by a sequential method. Four soils with different soil use intensity were selected for the study. Pseudototal micronutrient contents were determined and their concentrations were estimated by simple (EDTA) and sequential (BCR) extraction methods. The pseudototal average contents of Cu, Fe, Mn and Zn were: 14.4; 14010; 757 and 58.9 mg kg-1, respectively. The EDTA extractable levels were: 4.4; 174.8; 410.6 and 8.4 mg kg-1, respectively. The concentrations of Cu estimated by both methods were similar while higher contents of Fe, Mn and Zn were estimated by the BCR method. Iron, Zn and Cu were mainly found in the residual fraction. About 30% of total Cu was available in the oxidizable fraction and bound to soil organic matter. Zinc was primarily associated with the residual fraction and to a lesser degree to exchangeable, oxidizable and reducible forms. Manganese was mostly linked to the reducible, water-acid soluble and exchangeable fractions. These results confirm that in these soils the availability of all micronutrients determined by the EDTA method are above the critical values for crop growth.

Los objetivos del trabajo fueron determinar los contenidos pseudototales, disponibles y ligados a las distintas fracciones químicas de Cu, Zn, Mn y Fe en Argiudoles de la pampa llana santafesina y comparar la concentración de estos micronutrientes extraídos con EDTA y con un método secuencial. Para esto se seleccionaron cuatro suelos con distinta intensidad de uso en los que se determinó el contenido pseudototal de estos elementos y su concentración con un método simple (EDTA) y de extracción secuencial (BCR). Los contenidos promedios pseudototales de Cu, Fe, Mn y Zn fueron: 14,4; 14010; 757 y 58,9 mg kg-1 respectivamente. Los niveles extractables con EDTA fueron: 4,4; 174,8; 410,6 y 8,4 mg kg-1, respectivamente. Los niveles de Cu estimados por ambos métodos fueron similares mientras que BCR extrajo mayores contenidos de Fe, Mn y Zn. La mayor parte del Fe, Zn y Cu se encontró en la fracción residual. Alrededor del 30% del Cu está disponible en la fracción oxidable y ligada a la materia orgánica. El Zn se asoció fundamentalmente a la fracción residual y en menor medida a formas intercambiables, oxidables y reducibles. El Mn está principalmente en la fracción reducible y en la fracción soluble en agua-ácido e intercambiable. Los resultados confirman que en estos suelos la disponibilidad de todos los micronutrientes -determinados con EDTA- se encuentran por encima de los valores críticos.

O objetivo deste trabalho foi avaliar o potencial das espécies arbóreas Cordia africana Lam.,Mimosa caesalpineafolia Benth., Acacia angustissima (Mill.) Ktze. e Anadenanthera colubrina (Vell.) Brenan na fitoestabilização de metais pesados presentes em um substrato contaminado. Foram selecionados, aleatoriamente, quatro exemplares de cada espécie para realização do estudo. Amostras de substrato na projeção da copa de cada exemplar arbóreo foram coletadas nas profundidades de 0-10; 10-30 e 30-50 cm, para determinação da concentração pseudototal e fracionamento químico de metais pesados. De cada indivíduo, foram coletados dados referentes à profundidade das raízes, DAP (diâmetro a altura do peito), diâmetro de copa e altura das plantas. Amostras de folha, caule, casca e raiz foram coletadas para determinação dos metais pesados zinco (Zn), manganês (Mn), cádmio (Cd), chumbo (Pb) e cobre (Cu) nas diferentes partes da planta. A concentração de Cd no substrato foi acima do valor de investigação definido pelo CONAMA (3,0 mg kg-1), evidenciando contaminação com esse elemento. Os maiores teores dos metais pesados foram encontrados na fração residual (F5), indicando baixa disponibilidade destes elementos no substrato. Com relação ao Cd, elevadas concentrações também foram encontradas na fração trocável F2, considerada uma fração em que os contaminantes se apresentam com certa mobilidade e biodisponibilidade. As espécies vegetais estudadas apresentaram desenvolvimento dentro dos padrões normais, mostrando tolerância a áreas contaminadas com Cd, que tendeu a se acumular nas raízes das plantas, com exceção da Córdia - africana.

This study aims to evaluate the potential of tree species Cordia africana Lam.,Mimosa caesalpineafolia Benth., Acacia angustissima (Mill.) Ktze. and Anadenanthera colubrina (Vell.) Brenan in the phytostabilization of heavy metal from a substrate contaminated. Four specimens of each tree specie were randomly determined for evaluations. Substrate samples were collected in the projection of the canopy trees of each specimen at depths 0-10, 10-30 and 30-50 cm for determining pseudototal concentration and chemical fractionation of heavy metals.Were collected data on roots depth, diameter at breast height, canopy diameter and plant height for each specimen. Samples of root, stem, bark and leaf were collected for analysis of heavy metals zinc (Zn), manganese (Mn), cadmium (Cd), lead (Pb) and copper (Cu). The Cd concentration in the substrate was above the investigation value defined by CONAMA (3,0 mg kg-1), showing contamination with this element. However, the highest concentrations of other studied heavy metals were found in the residual fraction (F5), indicating low availability of these elements in the substrate. High concentrations of Cd were also found in the exchangeable fraction F2, which is considered a fraction in which contaminants are present with some mobility and bioavailability. The plants showed development within the normal patterns, showing tolerance to Cd-contaminated areas, which tended to accumulate in the roots, except in the Córdia - africana.

Two parallel tests were carried out to evaluate barium solubility in soils treated with barite under reducing conditions: one in leaching columns and another with potted plants cultivated with rice. Soils were treated with three doses of barite and kept at two humidity levels. The reduction (-200 mV) condition promoted an increase in barium in the geochemical fraction of higher liability, higher concentrations of barium in the leached extracts, and higher absorption by rice plants. As a result of increased uptake and accumulation of barium, the plants showed stunted growth