Antonio Carlos de Azevedo

Partículas coloidais, dispersão e agregação em latossolos

Well-drained Oxisols are named Latossolos in the Brazilian Soil Classification System. These soils cover extensive areas in Brazil and are essential to food production and environmental quality maintenance. Both roles rely on the existence of stable, small aggregates. Although several studies have been published about it, there is no agreement on the factors and mechanisms involved in the genesis and stability of such aggregates. The reasoning used to explain such mechanisms in other soils cannot be used in Latossolos without difficulty because they do not have aggregate hierarchy. The main goal of this review is to gather information about mineralogical characteristics of pedogenic minerals and their association with organic colloids and relate it to aggregation and dispersion of Latossolos.

Mineral adsorbents for prevention of mycotoxins in animal feeds

Abstract Mycotoxins are toxic metabolites produced by several fungi species, with the aflatoxins, fumonisins, zearalenone, trichothecenes and ochratoxin A being the most important found in feedstuffs. The economic impact caused by mycotoxins motivated the investigation of detoxification strategies to reduce its bioavailability by enterosorption. Although there are several types of adsorbents, the efficiency of the adsorption depends on the physical and chemical characteristics of both the adsorbent and the mycotoxin. This review describes the most important types of mineral adsorbents [aluminosilicates, HSCAS, bentonites (montmorillonites), zeolites, sepiolite, diatomite and activated carbons] used in feeds, especially for poultry and pigs, and their adsorption mechanisms.

Intemperismo subtropical de minerais em saprolitos ácidos do Sul do Brasil

Because weathering of minerals releases chemical elements into the biogeochemical cycle, characterization of their weathering products helps to better model groundwater quality, formation of secondary minerals and nutrient flux through the trophic chain. Based on microscopic and elemental analyses, weathering of riodacite from Serra Geral formation was characterized and weathering paths proposed. Three weathering paths of plagioclase phenocrystals were identified: plagioclase to gibbsite (Pg1); plagioclase to gels and gibbsite (Pg2); and plagioclase to gels, gibbsite and kaolinite (Pg3). Pyroxenes weathered to smectite and goethite (Py1), or to goethite and gibbsite (Py2), and magnetite weathered directly into iron oxides. Rock matrix comprises 90% of rock volume, and weathered to kaolinite and gibbsite, which explains why these minerals were the most abundant in the weathering products of these saprolites.

La provisión de servicios de salud en Chile: aspectos históricos, dilemas y perspectivas

Realiza-se breve analise historica do sistema de saude no Chile, a partir do Servico Nacional de Saude, com enfase nas reformas ocorridas desde 1980,durante o regime militar, e as mudancas introduzidas a partir de 1990 pelos governos democraticos. Compara a oferta atual de servicos pelo sistema publico com a do setor privado utilizando como indicadores por mil beneficiarios: a taxa de consultas, de exames de laboratorio, de hospitalizacao, de altas e de cirurgias e a satisfacao dos usuarios. Analisa os principais dilemas do sistema de saude e suas perspectivas a luz das medidas presentemente tomadas. Ha boas perspectivas de que o subsistema publico mantenha sua lideranca historica na conducao e oferta de servicos no Chile devido a rigorosa logica geografica e demografica na prestacao de servicos, a disponibilidade estavel de recursos financeiros, uma rede de servicos suficiente e ainda a consideravel motivacao de seus recursos humanos. Sao mencionados aspectos inovadores que podem ser aproveitados por outros sistemas, especialmente na America Latina, como: organizacao e gestao de servicos regionais de saude, metodologias inovadoras de remuneracao de servicos, sistema de vigilância sanitaria e a regulamentacao estatal do financiamento privado em saude.

Alteração mineralógica de Neossolos em uma climo-litossequência no Planalto do Rio Grande do Sul

In the Rio Grande do Sul state (RS) Neossolos Litolicos (Leptosols) and Neossolos Regoliticos (Regosols) are soils that have been suffering strong use pressure, demanding better knowledge on their genesis and mineralogy than the existing one. The objective of this research was to determine the weathering degree of Neossolos Litolicos and Neossolos Regoliticos through the evaluation of the minerals alteration in profiles disposed in a climo-litossequence in the RS Plateau, using techniques of chemical dissolution and X rays diffraction. The authors identified two groups of soils with different alteration degree. The first one is composed by the profiles of the West portion of the climo-litossequence (P1, P2 and P3) which has the weathering degree between the bissialitization and the monossialitization, with high content of smectite with hidroxi-Al interlayers (EHE), caulinite and hematite in the clay fraction. The second one is represented by the profiles of the East portion (P4 and P5), with weathering degree between the monossialitization and the ferralitization, with high content of caulinite and goethite and presence of gibbsite and EHE in the clay. The results suggested an higher contribution of the climate on the weathering of the profiles. The ki and kr indexes were not efficient in representing the condition of secondary alteration of the profiles of Neossolos.

Relação da granulometria do solo e morfologia do saprolito com a infiltração de água em Neossolos Regolíticos do rebordo do Planalto do Rio Grande do Sul

Neossolos Regoliticos (Regosols) are fragile from a natural resource perspective because of their small depth, stones and/or rocks presence, near surface lithic contact, fractures in saprolite and frequent occurrence in steep slopes. These soils requires more specific analysis for a better interpretation of their capacity to filtrate water, retain and transform solute and fluids, contributing to the maintenance of the water quality that reaches the groundwater. In that sense, this study generates information on water infiltration in five areas from the the Rio Grande do Sul plateau edge. Three profiles were described and analyzed for each Regosol and the water infiltration was performed whit the double rings method. Even showing the same taxonomic classification, the Regosols showed hydraulic variation behavior, even though when compared among the profiles from the same location. The data suggest that the water infiltration in the Regosols is affected by the saprolite fracture configurations, granulometry, relief conditions and soil use.

Causes of morphological discontinuities in soils of Depressão Central, Rio Grande do Sul State, Brazil

Morphological, particularly textural, discontinuities between horizons increase soil erodibility in Depressao Central, Rio Grande do Sul State (Brazil). Characterization of such discontinuities would help to understand landscape evolution and to model near-surface hydrology. The objective of this research was to explore the relationship between morphological discontinuity and deposition of transported materials during pedogenesis. Transported material was meant to be mineral particles found in the soil profile, transported probably by water or gravity, that were not present neither in the parent material nor derived from it. Five soils of this region (two Alfisols, two Ultisols and one Mollisol) were sampled and morphological, sand grain size statistics, chemical and mineralogical analyses were used to search for evidences of deposition of transported materials. Two soils had abrupt textural change but no evidence of deposition of transported materials, two soils had less contrasting morphology and some characteristics that are possibly related to deposition, and one soil had no morphological discontinuity, but had deposition of material enriched in magnetite-maghemite in the sand fraction of the A horizon. Therefore, there were no relationship between morphological discontinuity and deposition of transported materials for these profiles in the Depressao Central.

Experiência de um programa de profilaxia medicamentosa coletiva da malária no sudeste do Pará, Brasil

Apresenta-se uma experiencia de 35 semanas com profilaxia medicamentosa coletiva da malaria numa regiao relativamente isolada do sudeste do Estado do Para, Brasil, onde a doenca se encontra num estado de hiperendemia. A associacao medicamentosa utilizada foi a de uma 4 aminoguinoleina com a pirimetamina. Sao discutidas as caracteristicas regionais da endemia, bem como problemas encontrados na ministracao periodica coletiva. Conclui-se pela eficacia do metodo, ressalvada a necessidade de uma administracao bastante eficaz para que os niveis de cobertura possam ser mantidos em torno de 75%. Nessa situacao, a incidencia da doenca baixou de 40 casos clinicos para cerca de 1,5 casos, por cem habitantes (avaliacao semanal). Este ultimo nivel mostrou-se perfeitamente compativel com o desenvolvimento dos trabalhos agropastoris na regiao estudada.

Where are we with whole regolith pedology? A comparative study from Brazil

An integrated knowledge of the soil and its deeper substratum is required when dealing with environmental issues and Critical Zone research. Though the lower boundary for classifying soils is set at 200 cm in both Soil Taxonomy (ST) and the World Reference Base (WRB), these systems are ill equipped for categorising layers below diagnostic horizons. The authors reflect on the need for classifying the solum–subsolum continuum based on data of four soil profiles from Brazil. The solum was classified with ST, WRB and the Brazilian Classification, and the subsolum with the Saprolite-Regolith Taxonomy (SRT) and the Subsolum Reference Groups (SRG). Soil classification systems provide limited information on shallow soils but this can conveniently be complemented with subsolum classification. SRT differs from SRG as it focuses on deeper material and on geotechnical applications, whereas SRG focuses on layers directly under diagnostic horizons and on environmental applications. Both systems still need more field testing. SRT seems to require more specialist knowledge on lithology than SRG and being a hierarchical classification system is less flexible than the open, low hierarchical organised SRG classification. It is concluded that future soil classification systems need more integration of the concept of ‘whole regolith pedology.’

Sustainability of Wood Productivity of Pinus TaedaBased on Nutrient Export and Stocks in the Biomass and in the Soil

the impact of intensive management practices on the sustainability of forest production depends on maintenance of soil fertility. the contribution of forest residues and nutrient cycling in this process is critical. a 16-year-old stand of Pinus taeda in a Cambissolo Húmico Alumínico léptico (humic endo-lithic dystrudept) in the south of brazil was studied. a total of 10 trees were sampled distributed in five diameter classes according to diameter at breast height. the biomass of the needles, twigs, bark, wood, and roots was measured for each tree. in addition to plant biomass, accumulated plant litter was sampled, and soil samples were taken at three increments based on sampling depth: 0.00-0.20, 0.20-0.40, 0.40-0.60, 0.60-1.00, 1.00-1.40, 1.40-1.80, and 1.80-1.90 m. the quantity and concentration of nutrients, as well as mineralogical characteristics, were determined for each soil sample. three scenarios of harvesting intensities were simulated: wood removal (a), wood and bark removal (b), and wood + bark + canopy removal (c). the sum of all biomass components was 313 mg ha-1. the stocks of nutrients in the trees decreased in the order n>ca>k>S>mg>P. the mineralogy of the Cambissolo Húmico Alumínico léptico showed the predominance of quartz sand and small traces of vermiculite in the silt fraction. clay is the main fraction that contributes to soil weathering, due to the transformation of illite-vermiculite, releasing k. the depletion of Received for publication on May 21, 2014 and approved on June 9, 2015. DOI: 10.1590/01000683rbcs20140297