João José Marques

Major element geochemistry and geomorphic relationships in Brazilian Cerrado soils

Abstract A thorough understanding of major and trace element geochemistry is important in assessing the impacts of rapid agriculturalization and increased human occupation of the Cerrado region of central Brazil, a region with some of the oldest soils on Earth. The objectives of this paper are to summarize the major element composition of Cerrado soils in the context of their morphology and geomorphology, to describe impacts of biogeochemical cycling on the chemical properties of Cerrado soils, and to use elemental data to provide insights on the possible origin of soil parent materials on the South American erosion surface and on the Serra Geral Basalts. We sampled three major subregions selected to be representative of the main areas of the Cerrado, namely: (i) eastern Goias, (ii) northwestern Minas Gerais, and (iii) the Triângulo Mineiro area of western Minas Gerais. Five soils were sampled in each subregion, each represented by three pedons sampled at 0–0.2 and 0.8–1.0 m depths. Geomorphologically, the soils were on the South American, Velhas I, and Velhas II erosion surfaces. All sites were carefully selected to minimize potential anthropogenic contamination. General chemical characterization was by standard procedures and total major and trace elemental contents were quantified using wavelength-dispersive X-ray fluorescence spectroscopy. The soils ranged from loamy sands to clays, with Si (142–947 g kg −1 SiO 2 ), Al (14–439 g kg −1 Al 2 O 3 ), Fe (10–331 g kg −1 Fe 2 O 3 ), and Ti (3–101 g kg −1 TiO 2 ) contents closely following the clay contents. Organic C averaged 17 g kg −1 for the surface, and 7 g kg −1 for the subsurface horizons. The Na, Ca, Mg, and K contents were very low, tended to be higher in surface than in subsurface horizons because of recycling by vegetation and addition due to atmospheric deposition, and were higher in soils containing hard plinthite nodules. The Th/Zr ratios suggest that the parent materials of the clayey soils on the South American erosion surface have a common origin in sediments from rocks in the Central Plateau of Brazil that were transported eastwards to cover the underlying sandstone. Trace element signatures indicate that basalt-derived soils occurring at different elevations in the Triângulo Mineiro area formed from distinctly different magmas that may have been deposited in different basalt flow events.

Comunidade arbórea de um continuum entre floresta paludosa e de encosta em Coqueiral, Minas Gerais, Brasil

The purpose of the present contribution was to describe the community of trees of a continuum extending from swampy to upland forest in Coqueiral, SE Brazil, assessing the correlations between the variations of community structure and those of the environment. Sampling was carried out in 25 plots of 20 X 20 m laid on the forest fragment to survey trees with a minimum circumference of 15.5 cm (registering their circumference, height and species) as well as topographic and soil variables. Species-environment correlations were analyzed using canonical correspondence analysis (CCA) and Spearmans test. The swampy and upland habitats differed substantially in both community structure and floristic composition. The general floristic profile was similar to that of other riparian forests of the Mid and Upper Rio Grande region, whilst the swampy portion of the forest differed from what is commonly found in SE Brazil. The species distribution was correlated mainly to soil drainage and proximity to the lake. The high soil diversity and the strong soil moisture gradient found over a small area resulted in different habitats and a diverse community of trees and shrubs that combined phyto-physiognomies of semideciduous and swampy forests, along with cerrado patches.

Análise de componentes principais de atributos físicos, químicos e mineralógicos de solos do bioma cerrado

Behavior differences between soils of the South-American and Velhas geomorphic surfaces of the Cerrado region, all of them under native vegetation cover, were evaluated by physical, chemical, and mineralogical characterizations, and principal component analyses. According to their sub-region and geomorphic surfaces, the soils were separated in three groups: 1. clayey to very clayey texture, low- and mesoferric; 2. medium to sandy texture, lowferric; 3. clayey to very clayey texture, ferric. Water retention in the surface horizons of the studied soils was positively correlated with the clay and organic carbon contents. Soils of Group 3 showed the greatest amount of exchangeable bases in the surface horizons, which is mainly a consequence of the greater recycling efficiency imposed by the local forest formation when compared to the Cerrado formation (verified in 31 of the 33 soil profiles of Groups 1 and 2). Soils of Group 3, formed from mafic rocks, were the most homogeneous in mineralogical terms, since all profiles were hematitic. In averages, Groups 1 and 2 presented an overlapping mineralogical composition, though Group 1 is more gibbsitic than Group 2. In comparison to the US Soil Taxonomy, the efficacy of the Brazilian Soil Classification System at discriminating the studied soils is higher owing to the use of the ferric character in conjunction with the other attributes both systems have in common. The principal component analysis supported the understanding of the pedologic environment differences and similarities identified in the field.

Perdas de solo e água por erosão hídrica em sistemas florestais na região de Aracruz (ES)

SUMMARY : SOIL AND WATER LOSSES BY EROSION IN FORESTECOSYSTEMS IN THE REGION OF ARACRUZ, STATE OFESPIRITO SANTO, BRAZIL Soil and water losses by erosion were measured in forest ecosystems and were relatedto the calculated maximum tolerable soil losses. Main soil classes in the Coastal Plains ofthe region of Aracruz (ES) were studied, with the aim of obtaining indicators of managementadequacy for this production system. The experimental plots were set on loamy/clayeyYellow Argisol (PA1), Haplic Plinthosol (FX), and moderately rocky Yellow Argisol (PA8).The slopes ranged from 2-8 %, 1-12 %, and 29-36 %, for each soil class. Three soil coverswere studied of each soil class: eucalyptus trees, native forest, and bare soil. Soil and waterlosses under eucalyptus followed the order: PA8 > PA1 > FX. Water losses ranged from 9-70 mm, equivalent to 1-6 % of the total annual rainfall. Soil losses in the eucalyptus plotslay well below the calculated maximum tolerable soil losses in all soil classes, which indicatesadequacy of management in this production system regarding water erosion. The fact thatsoil losses in eucalyptus were relatively close to those in native forest indicates thesustainability of the former environment regarding erosion.Index terms: Ultisol, Plinthosol, erosion, eucalyptus, native forest, bare soil.

Baseline Concentration of Heavy Metals in Brazilian Latosols

Knowledge of baseline concentrations for heavy metals of environmental and agricultural concern in tropical soils is meager. Latosols are highly weathered soils that cover ∼40% of the Brazilian territory and are by far the most important agricultural soil order in Brazil. This paper aimed to compare two methods for heavy metal extraction from soils, and to provide baseline values of heavy metals for Brazilian Latosols. The soil samples came from the 0–0.2-m layer of 19 different Latosols from the various geographic regions of Brazil. The first experiment compared the USEPA method 3051A (microwave digestion with concentrated HNO3 in closed vessels) with the aqua regia extraction (hot plate digestion with concentrated HCl and HNO3, 3:1, in open vessels) regarding Pb determination. The second analyzed contents of Cd, Cu, Ni, Pb, and Zn, and for this the USEPA method 3051A was used. Heavy metal contents were assessed by flame atomic absorption spectroscopy. Although both methods were highly correlated, the USEPA-3051A rendered Pb contents 29% higher in average than the aqua regia. Average (n=57) and standard deviation values for heavy metals in Brazilian Latosols are 0.66±0.19 mg Cd kg−1, 65±74 mg Cu kg−1, 18±12 mg Ni kg−1, 22±9 mg Pb kg−1, and 39±24 mg Zn kg−1. Considerably variation is due to the inclusion of Latosols derived from a variety of parent materials. The values provided could be useful as reference baseline concentrations for heavy metals in Brazilian Latosols.

Mineralogy of soils with unusually high exchangeable Al from the western Amazon Region

Abstract Some soils from the western Amazon region contain KCl-extractable Al contents 5 to 10 times greater than is typical for highly weathered soils containing predominantly kaolinite and gibbsite. We studied a soil sequence from the Brazilian western Amazon consisting of two Typic Udifluvents on the levee of the Javari River, one Aeric Endoaquent in the backswamp, and two Typic Hapludults on an adjacent terrace. We used wet chemical and X-ray diffraction (XRD) analysis to characterize several size fractions of the 0 to 0.2 m layer of the soils. The exchangeable Al content was very high in the Aquent and Udults (up to 180 mmolc kg-1), but the ‘total’ Fe content was low in all samples (<60 g kg-1). Smectite, vermiculite, hydroxy-interlayered smectite and kaolinite dominate the fine silt and clay fractions of all soils. The Fluvents contain illite in all size fractions and chlorite in the coarse clay and fine silt fractions. The Aquent and Udults have no chlorite, and small amounts of illite occur only in the coarse clay and fine silt fractions. Lepidocrocite was identified in the Aquent. Chlorite, which occurs in the sand, fine silt, and coarse clay fractions of the Fluvents, and pyrophyllite, which occurs in the fine silt fractions of all soils and in the coarse clay of the two Ultisols, appears to be inherited from the parent sediments. The hydroxy-interlayered 2:1 phyllosilicates that form as a result of weathering are the cause of the very high exchangeable Al contents.

Determinação de cádmio, cobre, cromo, níquel, chumbo e zinco em fosfatos de rocha

The possibility of food chain transfer is a matter of concern on studies related to heavy metals in mineral fertilizers. The objective of this paper was to determine the content of heavy methods and to compare three extraction procedures (Embrapa, 1999; USEPA 3051A and USEPA 3050B) for Cd, Cr, Cu, Ni, Pb, and Zn in national and imported rock phosphates. The quantification of the trace elements content was performed by air-acetylene flame atomic absorption spectroscopy. Among the studied phosphates, the thermophosphate presented significantly greater concentrations of Cd, Cr, Cu, Ni, and Zn whereas Cu, Ni, Pb, and Zn were found in greater contents in the natural phosphate 2. The reactive phosphate 3 presented the greatest quantity of Cd (145±13 mg kg-1) and the natural phosphate 2, the highest quantity of Pb (234±9 mg kg-1). The tested methods can be applied in studies concerning heavy metals in phosphate fertilizers.

Frações de fósforo em Latossolos

The objective of this work was to verify if the historical use, phosphorus fertilization, mycorrhizal inoculation and cultivation with brachiaria and soybeans in greenhouse alter P fractions in three Oxisols. P linked to Al (P-Al), Fe (P-Fe), and Ca (P-Ca) were determined. The P fractions were separated with resin, NaHCO3, NaOH, HCl, and digestion with H2SO4 and H2O2. The organic and inorganic fractions were separated by autoclaving. In the cohesive Yellow Latosol (LAx) and acric Red Latosol (LVw), the P-Al, P-Fe, and P-Ca were higher in the cultivated soils, and in the dystroferric Red Latosol (LVdf), the P-Al and P-Fe were higher in the noncultivated soils, trends nonaltered by the cultivation with brachiaria and soybeans. P addition elevated mainly the labile inorganic (Pi-resin and Pi-NaHCO3) and the moderately labile (Pi-NaOH) fractions. Soils formerly cultivated presents less P in the organic fractions than the non-cultivated ones. In soils with brachiaria, less P in the less labile fractions and more P in the more labile ones were verified. The effect of mycorrhizae was smaller and less consistent than the cultivation and P application.

Levantamento pedológico e sistema de informações geográficas naavaliação do uso das terras em sub-bacia hidrográfica de Minas Gerais

A aptidao agricola das terras consiste em uma classificacao tecnica que identifica o potencial agricola de utilizacao das mesmas, considerando as limitacoes do solo em niveis de manejo diferenciados a partir das informacoes geradas em um levantamento pedologico. O cruzamento dos dados de aptidao agricola e uso atual das terras em ambiente SIG (Sistema de Informacoes Geograficas) consiste numa ferramenta adequada de planejamento, pois permite determinar a inadequacao entre uso e aptidao agricola, dando bases sustentaveis a exploracao. Neste estudo, foram realizadas a avaliacao da aptidao agricola das terras e seu uso atual com auxilio de imagens de satelite e observacoes de campo, e a identificacao de Areas de Preservacao Permanente (APPs) em uma sub-bacia hidrografica da Bacia do Alto Rio Grande, MG. Com base no levantamento de solos, a utilizacao do sensoriamento remoto, por meio de imagens de satelites, aliado ao ambiente SIG, constituem-se em ferramentas adequadas para avaliacao da aptidao agricola e uso atual das terras, e permitem o monitoramento das areas da sub-bacia hidrografica. O levantamento pedologico forneceu uma base segura e real para que, com o auxilio de ferramentas de geoprocessamento, os mapas resultantes tivessem melhor qualidade e representassem com acuracia os diferentes ambientes naturais na paisagem da sub-bacia hidrografica. Ocorreu o predominio de usos da terra menos intensivos que os das classes de aptidao agricola encontradas. As Areas de Preservacao Permanente (APPs) estao recebendo os mais diferentes usos agricolas, caracterizando uma inadequacao entre a legislacao ambiental e o uso atual da terra.

Índices de erosividade da chuva, perdas de solo e fator erodibilidade para dois solos da região dos cerrados - primeira aproximação

Os objetivos deste trabalho foram: testar a adequacao de diferentes indices de erosividade das chuvas, comparar duas equacoes propostas para calculo da energia cinetica das chuvas e estimar o fator K (erodibilidade) da equacao universal de perdas de solo (EUPS) para um latossolo vermelho-escuro (LE) alico muito argiloso e um podzolico vermelho-amarelo (PV) alico muito argiloso da regiao de Sete Lagoas (MG). Nao houve diferenca significativa entre as duas equacoes testadas para calculo da energia cinetica das chuvas. O indice EI30 mostrou ser um bom estimador da erosividade da chuva e pode continuar sendo utilizado como fator R (erosividade) da EUPS para a regiao estudada. Os valores do fator K, para o LE e o PV da regiao de Sete Lagoas, foram, respectivamente, 0,002 e 0,033 t h (MJ mm)-1.