O alumínio (Al) é um dos elementos mais abundantes em massa nos solos brasileiros, estando presente em diferentes minerais e formas. Considerando a carência de informações sobre a sua participação no comportamento físico do solo, buscou-se, no presente estudo, avaliar a relação entre a mineralogia da fração argila, formas de Al e atributos físicos de diferentes solos. Para tanto, foram coletadas amostras deformadas e indeformadas dos horizontes A e B de solos representativos das Zonas Fisiográficas Sul e Campos das Vertentes do estado de Minas Gerais. As amostras foram submetidas às caracterizações física, química e mineralógica. Estudos de correlação mostraram que os atributos físicos dos solos estudados estavam associados às diferentes formas de Al presentes e à mineralogia da fração argila: as formas de Al amorfas e menos cristalinas associaram-se mais aos atributos físicos relacionados com a agregação das partículas do solo, podendo esta associação ser atribuída à afinidade deste elemento com a matéria orgânica, enquanto os componentes cristalinos associaram-se mais aos atributos físicos relacionados com a organização estrutural dos solos.

The uptake of pesticides from water by two aquatic plants, the submersed Lagarosiphon major (Ridley) Moss and the floating duckweed Lemna minor L., was measured over periods of up to 72 h. Twelve non-ionised pesticides and analogues, chosen to span a wide range of physicochemical properties, and one analogue (3,5-D) of the phenoxyacetic acid herbicide 2,4-D were studied. Concentrations of the parent compound were determined in the plants following extraction and separation by chromatography. Quantification was by liquid scintillation counting for the (14)C-labelled compounds and by high-performance liquid chromatography for the four non-radiolabelled commercial pesticides. Uptake for all compound and plant combinations had reached equilibrium by 24 h. Accumulation of compound in the plant could be described well for most non-ionised compounds by equilibration into the aqueous phase in the plant cells together with partitioning onto the plant solids, this latter process becoming dominant in Lagarosiphon for compounds with log K(ow) > 1 and in Lemna for compounds with log K(ow) > 1.8. Lipophilic compounds with log K(ow) > 4 were concentrated more than 100-fold on a fresh-weight basis. However, the uptake of isoproturon and chlorotoluron was up to threefold less than expected from their K(ow) values, and their behaviour was better explained using solvation descriptors. Uptake of the acid 3,5-D was dependent on solution pH, this compound being strongly taken up at lower pH by the process of ion trapping, as previously observed in barley roots. Aquatic vegetation can thus rapidly accumulate pesticides, and could be an important sink especially for lipophilic pesticides reaching well-vegetated waters.

The distribution of eight pesticides between sediment and water held in 1-m square outdoor stainless-steel mesocosms was studied, simulating both spring and autumn applications. Pesticide behavior was largely independent of rate of application, chosen in the first three experiments to be 4% or 40% of the normal field rate so as to simulate spray drift or partial overspray. Following application by spray to the water surface, all compounds were uniformly distributed in the 30 cm of overlying water within 24 h. The lipophilic pesticides (chlorpyrifos, pendimethalin, and permethrin) moved into the sediment within 30 d but with little penetration below 2.5 cm depth, and only chlorpyrifos persisted beyond 30 d. The mass balance of these lipophilic pesticides at 1 d was only 26.3% to 61%, with these initial losses attributed to processes such as volatilization. Isoproturon and chlorotoluron persisted for around 120 d, remaining largely in the overlying water with a maximum of 15% in the sediment. Permethrin and difenoconazole were much less persistent in these mesocosms, with very little ever found in the sediment in contrast to previous findings in laboratory-scale stirred systems as used in registration tests. The polar mecoprop remained almost entirely in the water phase and was rapidly degraded. Two further experiments examined also the influence of the submerged plant Lagarosiphon major in the mesocosms, the first experiment simulating a full-rate overspray with chlorpyrifos and linuron and the second a repeat in spring of the earlier main autumn experiment. Both chlorpyrifos and linuron applied in the autumn were quite persistent over the winter period, with about 20% still remaining after 152 d. Uptake into L. major was correlated with pesticide lipophilicity, but was only a small factor compared to uptake by sediment and degradation in these lightly vegetated systems.

O objetivo deste estudo foi realizar a avaliação econômica da utilização de multiprodutos em um povoamento de Eucalyptus grandis através dos métodos do VPL, TIR, BPE e B/C. Foram consideradas duas opções de utilização das toras de madeira: produção para um único uso e produção para multiprodutos. Na análise de sensibilidade foram consideradas variações na taxa de desconto e no custo da terra. A partir dos resultados obtidos foi possível concluir que a destinação do povoamento a multiprodutos foi a opção que apresentou maior viabilidade econômica em todas as situações estudadas.

RESUMO -Este trabalho objetivou verificar a concentração do mercado internacional de madeira serrada, por meio dos índices de concentração e desigualdade de mercado e das estruturas de classificações de mercado. Utilizou-se como indicador a exportação de 154 diferentes nações nos anos de 1997 e 1999, sendo constatadas a alta concentração e desigualdade do mercado internacional de madeira serrada e a evolução desses parâmetros no período analisado.Palavras-chave: Concentração de mercado, mercado internacional e madeira serrada. O crescente destaque do setor florestal para a economia brasileira mostra-se no PIB florestal próximo a US$ 21 bilhões (4% do total), com US$ 5,4 bilhões (10% do total) em exportações no ano de 2003. Vale ressaltar que o setor desempenha importante papel socioeconômico, gerando dois milhões de empregos (diretos e indiretos), recolhendo em torno de US$ 2 bilhões anuais de impostos, consumindo em torno de 300 milhões de m 3 ano de madeira (nativa + plantada) (SBS, 2004). CONCENTRATION OF THE EXPORTS IN THE INTERNATIONAL MARKET OF SAWN WOOD ABSTRACT -The objective of this study was to analyze the concentration of the international market of sawn wood. Concentration and market inequality indexes and structures of market classifications were used. The base of information was the exportation of 154 different nations in 1997 andSegundo Ângelo et al. (1998), nesse contexto a produção e o comércio de madeira ocupam posição de destaque, sendo importante analisar o mercado internacional de madeira, tendo em vista a competitividade.A desaceleração da economia em mercados

No abstract

No abstract

RESUMO