Nelson Moura Brasil do Amaral Sobrinho

Proposição de valores de referência para a concentração natural de metais pesados em solos brasileiros

Para avaliar a extensao da poluicao de uma area, e comum se comparar os teores totais de metais pesados encontrados num dado solo com aqueles defrontados em condicoes naturais (nao poluidos) ou com valores de referencia (padroes). Propuseram-se atraves deste estudo: 1) valores de referencia (VR) e limites de tolerância (LT) para os mais representativos solos brasileiros, e 2) um modelo para obtencao das concentracoes naturais de Cd, Co, Cr, Cu, Ni, Pb e Zn em um solo, a partir dos teores de silte, argila, Mn, Fe e CTC. Reuniram-se 256 amostras de solo por similaridade, em sete grupos e se calcularam as concentracoes correspondentes ao quartil superior dos dados. Essas concentracoes sao propostas como valores de referencia (VR) em solos brasileiros; alem disso, obtiveram-se os limites de tolerância (LT) para cada grupo a partir da expressao antilog (m + 2s), cujos m (media) e s (desvio padrao) dos dados foram transformados em log10. As funcoes de classificacao da analise discriminante mostraram se apropriadas para alocar novas amostras nos grupos estabelecidos. Assim, e possivel avaliar solos sob atividade antropica e saber se ha motivo para suspeitar de que a area esteja poluida.

Chemical amendment and phytostabilization of an industrial residue contaminated with Zn and Cd

A fitoestabilizacao de solos contaminados com metais pesados e considerada uma boa alternativa para reduzir a erosao e dispersao de contaminantes no ambiente. Foi conduzido um experimento em casa-de-vegetacao com o objetivo de avaliar a contencao quimica (silicato de calcio e lodo do biodigestor de uma cervejaria) e a fitorremediacao pela Brachiaria decumbens, de um residuo industrial contaminado com Zn e Cd, utilizando vasos de 30 L. Os tratamentos foram: residuo industrial (testemunha); residuo industrial + 20% lodo; residuo industrial + silicato de calcio (2%; 3%); (residuo industrial + 20% lodo) + silicato de calcio (2,5%; 4%). Apos estabilizacao do pH, foram cultivados nos tratamentos plantas de B. decumbens, visando avaliar o potencial de tolerância a elevadas concentracoes de Zn e Cd presentes no residuo industrial. No plantio e colheita das plantas foram retiradas amostras dos diferentes tratamentos para determinacao do pH e extracoes simples com agua, nitrato de sodio, acido acetico e DTPA. A partir das concentracoes de Zn e Cd obtidas nas extracoes, foram estimadas, atraves das diferencas nas quantidades extraiveis, as concentracoes de Zn e Cd nas provaveis formas quimicas. A adicao de residuos industriais, alcalino e orgânico, provocou reducao nas percentagens de Zn e Cd nas fracoes soluvel e trocavel, e predominância dos mesmos em fracoes quimicas mais estaveis como complexados e precipitados. A B. decumbens apresentou tolerância ao Zn e Cd presentes no residuo industrial apos tratamento de contencao quimica.

Estimation of reference values for cadmium, cobalt, chromium, copper, nickel, lead, and zinc in Brazilian soils

Abstract The objectives of this study were 1) to recommend reference values (RVs) and tolerance limits (TLs) for representative Brazilian soils and 2) to propose a model to calculate natural contents of cadmium (Cd), cobalt (Co), chromium (Cr), copper (Cu), nickel (Ni), lead (Pb), and zinc (Zn) in a soil from the silt, clay, manganese (Mn), iron (Fe), and cation exchange capacity (CEC) values. A set of 256 soil samples was classified by similarity in seven groups, and the concentrations corresponding to the upper quarter of data collected were then calculated. These concentrations are proposed as RVs for Brazilian soils. Additionally, TLs were obtained for each group from the antilog expression (m+2s), where m=mean value and s=standard deviation of data transformed in log10. The classification functions of discriminant analysis proved to be suitable to allocate new samples in the established groups. Thus, it is possible to evaluate soils under anthropic activity and, by comparison with reference values, to be aware of pollution risks in a given area.

Effect of variations in the redox potential of Gleysol on barium mobility and absorption in rice plants.

Two assays were designed to obtain information about the influence of redox potential variations on barium mobility and bioavailability in soil. One assay was undertaken in leaching columns, and the other was conducted in pots cultivated with rice (Oryza sativa) using soil samples collected from the surface of Gleysol in both assays. Three doses of barium (100,300 mg kg(-1) and 3000 mg kg(-1)-soil dry weight) and two redox potential values (oxidizing and reducing) were evaluated. During the incubation period, the redox potential (Eh) was monitored in columns and pots until values of -250 mV were reached. After the incubation period, geochemical partitioning was conducted on the barium using the European Communities Bureau of Reference (BCR) method. Rainfall of 200 mm d(-1) was simulated in the columns and in the planting of rice seedlings in the pots. The results of the geochemical partitioning demonstrated that the condition of reduction favors increased barium concentrations in the more labile chemical forms and decreased levels in the chemical forms related to oxides. The highest barium concentrations in leached extracts (3.36 mg L(-1)) were observed at the highest dose and condition of reduction at approximately five times above the drinking water standard. The high concentrations of barium in the soil did not affect plant dry matter production. The highest levels and accumulation of barium in roots, leaves, and grains of rice were found at the highest dose and condition of reduction. These results demonstrate that reduction leads to solubilization of barium sulfate, thereby favoring greater mobility and bioavailability of this element.

Conseqüências de diferentes sistemas de preparo do solo sobre distribuição química e perdas de fósforo de um Argissolo

The research was accomplished in the Caetes watershed, municipal district of Paty do Alferes (RJ), from January to March of 1997, in the crop cycle of cucumber (Cucumis sativus L.). The research took place in an area of Yellow-Red Podzolic soil (Udult), of clayey texture, at a slope of 60%, where Wischmeier plots for studying soil erosion were installed. The treatments applied were: (a) MAQ - down hill mechanical tillage, and burning of crop residues; (b) MANQ - contour mechanical tillage, with plant residues remaining on the field; (c) AA - contour tillage, with animal traction and strips of grasses placed every 7,0 m; and (d) CM - minimum tillage. Soil samples were collected in crop rows, and planting pits, in the plow layer, before planting and after harvesting. After each rain that resulted in production of sediments, the material was collected, dried, weighed, and kept for analyzes of total P; labile, organic and inorganic P; organic carbon; and pH in water. The CM treatment reduced P losses and influenced the distribution of labile and organic forms of P. MAQ treatment implied in loss of 12.4% of the total applied P, while the CM lost only 1%. The remaining of the plant residues among the crop rows, on the MANQ plot, decreased in 40% the total P loss, when compared to MAQ. The plots MAQ and MANQ showed clay increase in the sediments, which favored the highest losses of P sorbed in the clay fraction.

Potencial de duas espécies de eucalipto na fitoestabilização de solo contaminado com zinco

With the aim of assessing the phytoremediation process to improve the soil contamination with zinc, it was used Eucalyptus urophylla and Eucalyptus saligna with slag from steelmaking and scales from hot-strip mills. The experiment was conducted in a greenhouse at the Universidade Federal Rural do Rio de Janeiro, using a soil contaminated with zinc, collected in an area near the ore yard at Itaguai harbor as well at the local of disposition of hazardous waste of Mercantil and Industrial Inga Co. at Itaguai-RJ. The substrate was treated with two inertizing agents: industrial waste with alkaline caracteristics (steelmaking slag) in 4 and 6% doses and another one with high content of iron oxide used as adsorption material (hot-strip mill scale) at single dose of 1%. After seedling transplant, the substrate was collected in order to determine pH and zinc fractionation in its different chemicals forms. It was verified that the not treated substrate showed high zinc content in bioavaiable fractions. This caused a reduction in the Zinc concentration in the water-soluble and exchangable forms and increase in more stable phases. The smallest dose of steelmaging slag was sufficient to cause a reduction of zinc concentrations solutions and this effect was showed clearly in the plant development, while the highest dose of steelmaging slag promote higher development in the species. The specie that obtained better development was E./ urophylla, that one showing higher zinc content was E. saligna.

Avaliação dos métodos de extração sequencial de Tessier, Keller e Miller na determinação de ferro nativo em três tipos de solos: orgânico, brunizem e latossolo

Sequential extraction is not totally effective to dissolve distinct forms of trace elements. The extractive solution, for example, can dissolve less of the target fraction and more than another not wished fraction. The goal of this work is to compare the extraction of native iron with three sequential extraction methods of the heavy metals, using three soils with different physical chemistry characteristics: a histosol, an oxisol, and a mollisol. The results obtained in this work demonstrate that a smaller relation soil/extractor results in a larger extraction in almost all phases. The use of many stages of the sequential extraction, with the purpose of more association of the metal with different components of the soil, can result, among other things, in modification of the substratum by the action of the reagents used, besides reducing the selectivity of the more specific extractors. Readsorption and redistribution of the heavy metals could have happened with larger intensity in the fraction where hidroxilamine was used with higher temperature. Sequential extraction of iron, without enrichment of soil samples, in the respective fractions in each method, it was important to better understand the behavior of the reagents considered specific to each form of the metal in soil.

Mobilidade de bário em solo tratado com sulfato de bário sob condição de oxidação e redução

In order to evaluate possible solubility of BaSO4 in soils under reducing conditions, column leaching assay was settled down, where the soil received three doses of BaSO4 (100, 300 and 3000 mg kg-1) at two humidities. After reaching an Eh of -200 mV rainfall of 200 mm per day-1 was simulated. The condition of reduction led to the increased levels of barium in the fractions of higher lability and the highest levels of barium in the leachate extract, which were above the potability standards. Only 0.05% of barium in the column that received the highest dose was removed by leaching.

Concentração de metais pesados em espécies arbóreas utilizadas para revegetação de área contaminada

RESUMO - O objetivo deste trabalho foi avaliar o potencial das especies arboreas Cordia africana Lam., Mimosa caesalpineafolia Benth., Acacia angustissima (Mill.) Ktze. e Anadenanthera colubrina (Vell.) Brenan na fitoestabiliz acao de metais pesados presentes em um substrato contaminado. Foram selecionados, aleatoriamente, quatro exemplares de cada especie para realizacao do estudo. Amostras de substrato na projecao da copa de cada exemplar arboreo foram coletadas nas profundidades de 0-10; 10-30 e 30-50 cm, para determinacao da concentracao pseudototal e fracionamento quimico de metais pesados. De cada individuo, foram coletados dados referentes a profundidade das raizes, DAP (diâmetro a altura do peito), diâmetro de copa e altura das plantas. Amostras de folha, caule, casca e raiz foram coletadas para determinacao dos metais pesados zinco (Zn), manganes (Mn), cadmio (Cd), chumbo (Pb) e cobre (Cu) nas diferentes partes da planta. A concentracao de Cd no substrato foi acima do valor de investigacao definido pelo CONAMA (3,0 mg kg -1 ), evidenciando contaminacao com esse elemento. Os maiores teores dos metais pesados foram encontrados na fracao residual (F5), indicando baixa disponibilidade destes elementos no substrato. Com relacao ao Cd, elevadas concentracoes tambem foram encontradas na fracao trocavel F2, considerada uma fracao em que os contaminantes se apresentam com certa mobilidade e biodisponibilidade. As especies vegetais estudadas apresentaram desenvolvimento dentro dos padroes normais, mostrando tolerância a areas contaminadas com Cd, que tendeu a se acumular nas raizes das plantas, com excecao da Cordia - africana. Palavras-chave: Arborizacao. Revegetacao. Solos-descontaminacao.

Soil Factors Related to the Severity of Clubroot in Rio de Janeiro, Brazil

Soil pH and calcium levels are determining factors in the success or failure of managing clubroot during the cultivation of Brassica spp. The aim of the present study was to evaluate the influence of soil attributes in tropical regions on the development of roots and clubroot and the accumulation of biomass and nutrients in cauliflower. One hundred and fifty-one samples of soil and plants were collected from 16 family farms that have a history of more than 50 years of regular cauliflower cultivation in Nova Friburgo, Rio de Janeiro, Brazil. Chemical and physical analyses were performed on the soil samples, and the severity of clubroot and the accumulation of biomass and macronutrients in individual plants and plant tissues. Clustering and main principal component analyses were performed on the data. The disease occurred on all farms, but with different intensities. A direct relationship was observed for the soil attributes (acidity and exchangeable aluminum content in particular) with the percentage of roots with clubroot and with the accumulation of biomass and macronutrients in the different plant organs. To reduce losses from clubroot in weathered soils, practices should aim to reduce the pathogens inoculum potential and improve the physical and chemical conditions of the soil, which would favor root development of the plants.