Environmental behavior of arsenic(III) and (V) in soils

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)This paper presents an evaluation of the environmental behavior of arsenic species in soils (F. F. Dias, Master Thesis, University of Delaware, 1997). The results obtained were used to determine adsorption constants that were incorporated in mathematical models using forward and backward stepwise linear regression to correlate data. The amount of adsorption was significantly different depending on soil properties, such as organic matter, iron oxide content, and surface area. Arsenic speciation on the soil surface was deduced from desorption data, with As(V) being more strongly retained in the soil. As(III) was oxidized on the soil surface and desorbed as As(V); an important factor since As(V) is less toxic. In order to develop an adequate adsorption model, Langmuir and Freundlich isotherms were obtained for each soil without pH alteration. Results indicated that the maximum amount of As(V) adsorbed was greater than the amount of As(III) adsorbed. Adsorption edges for As(III) and As(V), with pH varying from 3 to 10, were obtained at concentrations that ranged from 0.1 to 200 mg L(-1). The soils studied exhibited an L-type Langmuir isotherm. Maximum As(III) adsorption occurred around pH 6 to 9, while maximum As(V) adsorption occurred in the 4 to 5 pH range. Experiments to determine arsenic kinetics were carried out and showed that adsorption and desorption equilibrium was reached within 48 hours for both species.o TEXTO COMPLETO DESTE ARTIGO, ESTARÁ DISPONÍVEL À PARTIR DE AGOSTO DE 2015.11714121420NJDEP-New Jersey Department for Environmental ProtectionConselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq

Chemistry and Mineralogy of Soils cultivated with Eucalyptus (Eucalyptus sp.)

Chemical and mineral analyses were performed with the objective of evaluating the content and availability of nutrients for Eucalyptus growth in forests of Rio Grande do Sul state, Brazil. The Quartzarenic Neosol presented a very simple mineralogy, with an extremely poor nutrient content. The Melanie Gleisol, Haplic Planosol and Red-Yellow Argisol revealed a low Ca and Mg content, while the Haplic Cambisol, Litholic Neosol and Red Argisol presented higher amounts of these nutrients. The data of the annual average increment (AAI) of seven-year old Eucalyptus permitted the distinction of three soil groups according to their differential attributes: the first group formed by well drained soils (AAI >= 46 m(3)/ha/year), the second group formed by waterlogged soils (AAI approximate to 40 m(3)/ha/year) and the third group formed by very sandy soils (AAI of 38 m(3)/ha/year).388864565

Eficiência no uso de fósforo de variedades de arroz cultivadas em solos de várzea irrigada

A cultura do arroz destaca-se como uma das mais importantes do mundo, por apresentar facilidade de adaptação a condições edafoclimáticas distintas. Cultivado e consumido em todos continentes, o arroz destaca-se pela produção e área de cultivo, desempenhando papel estratégico tanto em nível econômico quanto social. No Brasil, a maior parcela da produção de arroz é proveniente do ecossistema de várzea. Este trabalho objetivou estudar a eficiência e resposta ao uso de fósforo de variedades de arroz (Oryza sativa L.), em várzea irrigada, no Sudoeste do Estado de Tocantins. Os tratamentos envolveram oito variedades comerciais de arroz (BRS-Jaçanã, Best-2000, BRS-Guará, BRS-Alvorada, BRA-01381, AN-Cambará, BRS 7-Taim e EPAGRI-109), que foram cultivadas em dois ambientes distintos. Para simular ambientes com baixo e alto níveis de fósforo, foram utilizadas as doses de 20 e 120 kg ha-1 de P2O5, respectivamente. O delineamento experimental utilizado foi o de blocos casualizados, com quatro repetições. Por meio da produtividade de grãos, as variedades foram classificadas quanto à eficiência no uso e resposta à aplicação de fósforo. Demonstrou-se que apenas a variedade BRS-Alvorada é eficiente quanto ao uso de fósforo e responsiva a sua aplicação