Expansão dos solos hidromórficos e mudanças na paisagem: um estudo de caso na região Sudeste da Amazônia Brasileira / Expansion of hydromorphic soils and landscape changes: a case study in the Southwestern Brazilian Amazon

Na região sudoeste da Amazônia brasileira, foi realizado um estudo detalhado da cobertura pedológica em uma toposseqüência representativa da paisagem regional, caracterizada por baixos platôs com depressões topográficas. Os resultados indicaram que os processos pedogenéticos podem ser considerados como responsáveis pelo rebaixamento topográfico e mudanças da paisagem natural. O principal fator envolvido neste processo de transformação é a expansão remontante da hidromorfia, a partir das depressões topográficas desenvolvidas nas superfícies dos platôs. Este processo envolve transformações e degradações internas na matriz do solo acarretando em modificações na estrutura, composição química e diminuição do volume do solo.

In the Southwestern Brazilian Amazon, a detailed study on the pedological cover of a representative toposequence for the region, characterized by lowered plateaus with topographic depressions, was carried out. The results indicated that pedogenic processes can be considered to be responsible for topographic smoothing and changes of the natural landscape. The main factor involved in this transformation process represents the upwards expansion of hydromorphic soil conditions from the topographic depressions developed in lower parts of the plateaus. This process includes internal transformations and degradations of the soil matrix leading to changes in soil structure, chemical composition and, diminishment of the original soil volume.

Nitrogen forms, pH and total carbon in a soil incubated with treated sewage effluent

In this study, an experiment under controlled conditions was carried out to determine the effects of secondary-treated sewage effluent (STSE) application on soil nitrogen concentrations (mineral and total), total carbon and soil pH. The soil and STSE used were collected at Lins, São Paulo State, Brazil. A completely randomized design was used, in completed factorial 4x11 (weekly application rates of 0, 100, 150 and 200 mL STSE per kg soil; and, eleven soil incubation periods from 0 to 10 weeks) with four replicates. The STSE was applied simulating common surface irrigation. Seven days after each incubation period, ammonium and nitrate contents were determined. Additionally, pH and total carbon and nitrogen contents were measured in the soil after 10 weeks. STSE application increased the nitrogen content (total and mineral - mainly as nitrate) and soil pH. For the total carbon content no differences were observed.

A colocação dos efluentes de esgotos no solo, apesar de ser uma prática comum em diversos países, como meio de proteger os cursos d’água e fornecer nutrientes aos agrossistemas, tem sido pouco estudada no Brasil. Objetivou-se neste trabalho avaliar, em condições controladas, os efeitos da aplicação de efluente do tratamento secundário de esgoto nas concentrações de nitrogênio (mineral e total), carbono total e no pH do solo. O efluente e o solo foram oriundos de Lins (SP). Foi empregado delineamento experimental inteiramente casualizado, em fatorial completo 4x11 (aplicação semanal de 0, 100, 150 e 200 mL de efluente por kg de solo; e onze períodos de incubação do solo - 0 a 10 semanas), com quatro repetições. O efluente foi aplicado no solo simulando-se a irrigação por superfície. Sete dias após a última irrigação foram determinadas as concentrações de nitrogênio mineral e, para o solo incubado por 10 semanas, também foi determinado o pH e os teores totais de carbono e nitrogênio. O incremento da dose de efluente aumentou as concentrações de nitrogênio (total e mineral - principalmente nitrato) e o pH do solo, mas o teor de carbono total não foi influenciado pelos tratamentos.

Second German heavy-metal survey by means of mosses, and comparison of the first and second approach in Germany and other European countries.

This paper shows the geographic distribution in Germany of iron (Fe), nickel (Ni) and lead (Pb) analyzed in mosses in 1995/96 and compares it with the results of the 1990/91 pilot study within a European moss-monitoring programme. Other elements (As, Cd, Cr, Cu, Ti, V, Zn) are compared on basis of the overall element medians for Germany of the 1990/91 and 1995/96 survey. Samples of Pleurozium schreberi, Scleropodium purum, Hypnum cupressiforme and Hylocomium splendens were taken at a total of 1026 sites. In the 1995/96 monitoring campaign, 95% of the original sites of the 1990/91 study were resampled. The results from 1995/96 display local elevated values and many cases of areas affected by known sources of heavy-metal emissions. The industrialized and urban regions of Germany are shown up clearly by the 1995/96 moss-monitoring results: the Ruhr area, parts of Saarland and Baden-Württemberg, as well as areas in eastern Germany. Relatively low values for many elements were found in large areas of Lower Saxony and Bavaria. A comparison of the results of the 1990/91 and 1995/96 moss-monitoring programmes shows a fall in the concentration of the presented elements (except cadmium, copper and zinc) over the relevant period. Especially in the former GDR, chromium (Cr), iron (Fe), titanium (Ti) and vanadium (V) decreased significantly. This is, firstly, a reflection of the closure of and/or technological improvements to large power plants; secondly it is due to the fact that lignite has given way to other fuels. Vanadium (V) and nickel (Ni), typical constituents of crude oil, also show a decrease in the western part and thus document changes in the type of fuel consumed. The significant fall in lead concentration in 1995/96 as compared to 1990/91 in what used to be East and West Germany probably results from the increasing use of lead-free petrol. A comparison of the median values for 1990/91 and 1995/96 in mosses to the rate of emission of heavy metals in Germany for 1990 and 1995 shows similar trends in the case of elements such as arsenic (As), chromium (Cr), nickel (Ni), and lead (Pb). The comparison of the medians of the elements analyzed for 19 European countries indicates for most of the elements a general tendency to lower values in 1995, except for Lithuania, Netherlands, Portugal, Italy and United Kingdom.

Biogeochemical dynamics following land use change from forest to pasture in a humid tropical area (Rondjnia, Brazil): a multi-element approach by means of XRF-spectroscopy.

Forest burning for pastures in tropical areas represents an important component of biogeochemical cycles. In order to provide information concerning chemical modifications after forest burning, in this local study the total contents of 29 elements in topsoils were analyzed when forest is changed to pasture land. The work was carried out in 1999 in Rondjnia state (Brazilian Amazon Basin) focussing on a native forest site and four neighboring pastures established in 1987, 1983, 1972 and 1911 after forest conversion. Chemical fingerprint graphs of the pasture soils related to the forest soil illustrated mainly higher contents for the vast majority of macro- and micro nutrients, but for other elements as well (e.g. Ba, Sr, Cr, Ni, V or Pb). Also increases of pH levels were measured in all pastures, which remained higher than the forest values for decades. After initial increases of most of the elements in pasture of 1987 the decreases of some macro elements (e.g. C, N, K, Mg, S) in pasture 1983 as well as again the enhanced levels in pasture 1972 and 1911 suggest both a persistent leaching of these elements and a function of pasture age where external element inputs exceed outputs. Ash deposition, accumulation of organic matter, animal excreta as well as natural soil conditions are discussed as influencing factors on the element contents of the original forest and the pasture soils. Nevertheless, in this particular area continuous pasturing after forest clearing primarily enriched the soils in elements.