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Featured researches published by S.A.C. Furquim.


Clays and Clay Minerals | 2008

MINERALOGY AND GENESIS OF SMECTITES IN AN ALKALINE-SALINE ENVIRONMENT OF PANTANAL WETLAND, BRAZIL

S.A.C. Furquim; Robert C. Graham; Laurent Barbiero; José Pereira de Queiroz Neto; Vincent Valles

Smectite formation in alkaline-saline environments has been attributed to direct precipitation from solution and/or transformation from precursor minerals, but these mechanisms are not universally agreed upon in the literature. The objective of this work was to investigate the mineralogy of smectites in the soils surrounding a representative alkaline-saline lake of Nhecolândia, a sub-region of the Pantanal wetland, Brazil, and then to identify the mechanisms of their formation.Soils were sampled along a toposequence and analyzed by X-ray diffraction, transmission electron microscopy-energy dispersive X-ray analysis, and inductively coupled plasma-mass spectrometry. Water was collected along a transect involving the studied toposequence and equilibrium diagrams were calculated using the databases PHREEQC and AQUA.The fine-clay fraction is dominated by smectite, mica, and kaolinite. Smectites are concentrated at two places in the toposequence: an upper zone, which includes the soil horizons rarely reached by the lake-level variation; and a lower zone, which includes the surface horizon within the area of seasonal lake-level variation. Within the upper zone, the smectite is dioctahedral, rich in Al and Fe, and is classified as ferribeidellite. This phase is interstratified with mica and vermiculite and has an Fe content similar to that of the mica identified. These characteristics suggest that the ferribeidellite originates from transformation of micas and that vermiculite is an intermediate phase in this transformation. Within the lower zone, smectites are dominantly trioctahedral, Mg-rich, and are saponitic and stevensitic minerals. In addition, samples enriched in these minerals have much smaller rare-earth element (REE) contents than other soil samples. The water chemistry shows a geochemical control of Mg and saturation with respect to Mg-smectites in the more saline waters. The REE contents, water chemistry, and the presence of Mg-smectite where maximum evaporation is expected, suggest that saponitic and stevensitic minerals originate by chemical precipitation from the water column of the alkaline-saline lake.


Trace Metals and other Contaminants in the Environment | 2007

Natural arsenic in groundwater and alkaline lakes at the upper Paraguay basin, Pantanal, Brazil

Laurent Barbiero; S.A.C. Furquim; Vincent Valles; S. Furian; A. Sakamoto; A.R. Filho; Monique Fort

A distinctive feature of Nhecolândia, a sub-region of the Pantanal wetland in Brazil, is the presence of both saline (alkaline) and freshwater lakes. Saline lakes were attributed to a past arid phase during the Pleistocene, but recent studies have shown that the geochemistry of the saline lakes arises from the current concentration process of fresh waters that is supplied to the Pantanal every year. The region is mainly used for cattle farming, and more recently eco-tourism is becoming widespread and water conservation agencies have begun to worry about As contents in surface and shallow groundwater. The study was carried out along a 600-m-long transect that linked a freshwater lake to a saline lake. The spatial distribution of As is studied, based on soil morphology, according to pH, redox conditions (Eh) and dissolved organic carbon, and also compared to distribution of major elements. Three main processes, responsible for the chemical variability, were identified: (1) the concentration of the solution under the influence of evaporation and the associated precipitations (Mg-calcite, illite, sodium carbonate); (2) oxidation of sulphides included in clay layers and subsequent development of acid conditions and (3) buffering of acid conditions by clay dissolution. Arsenic contents are not affected by the last two processes (2 and 3), but evolve in proportion to the concentration. Arsenic concentrations in water ranged from 0.11 μg/l to 3.68 mg/l, i.e., 368 times higher than the World Health Organization guidelines for drinking water. The As speciation, as calculated from field conditions, indicated that the As(V) redox state dominated in the groundwater and in the lakes, whereas some proportion of As(III) could occur on the shore and in the sediments of the saline lake. Arsenic(III) from the sediment can be remobilized and dispersed into the water following the disturbance of the sediments by cattle that come to drink water. Arsenic contents increased with most of the other dissolved species; hence, competitive adsorption prevents dissolved As regulation by solid phase reaction. Moreover, the pH values increased above 8 with increasing As, favouring As(V) desorption. As a consequence, the good correlation established between As contents and electrical conductivity (r2 = 0.97) should help to indirectly evaluate the As contents in shallow groundwater and lakes of the region.


Geoderma | 2010

Soil mineral genesis and distribution in a saline lake landscape of the Pantanal Wetland, Brazil

S.A.C. Furquim; Robert C. Graham; Laurent Barbiero; J.P. Queiroz Neto; Pablo Vidal-Torrado


Geoderma | 2008

Soil morphological control on saline and freshwater lake hydrogeochemistry in the Pantanal of Nhecolândia, Brazil

Laurent Barbiero; A. Rezende Filho; S.A.C. Furquim; S. Furian; A.Y. Sakamoto; Vincent Valles; Robert C. Graham; Monique Fort; Rosely Pacheco Dias Ferreira; J.P. Queiroz Neto


Geoderma | 2010

Neoformation of micas in soils surrounding an alkaline-saline lake of Pantanal wetland, Brazil

S.A.C. Furquim; Laurent Barbiero; Robert C. Graham; José Pereira de Queiroz Neto; Rosely Pacheco Dias Ferreira; S. Furian


Catena | 2013

Lamellae formation processes in tropical soils in southeastern Brazil

S.A.C. Furquim; Lylian Coltrinari; Rosely Pacheco Dias Ferreira; Selma Simões de Castro; Gabriel R. Pugliese


Archive | 2004

Mg-Mica formation in alkaline environment of the Nhecolândia, south Mato Grosso, Brazil

S.A.C. Furquim; J.P. Queiroz Neto; S. Furian; Laurent Barbiero; Robert C. Graham


Catena | 2019

Salt-affected soils on elevated landforms of an alluvial megafan, northern Pantanal, Brazil

Jairo Calderari de Oliveira Junior; S.A.C. Furquim; Alexandre Ferreira do Nascimento; Raphael Moreira Beirigo; Laurent Barbiero; Vincent Valles; Eduardo Guimarães Couto; Pablo Vidal-Torrado


Águas Subterrâneas | 2013

CONSUMO DE PERSULFATO PARA OXIDAÇÃO QUÍMICA EM SOLOS TROPICAIS

Fernanda Campos de Oliveira; Renata de Mello Rollo; S.A.C. Furquim; Claudio A. O. Nascimento; Juliana Gardenalli de Freitas


Geoderma | 2008

Hydrogeochemistry around two adjacent saline and freshwater lakes in the Pantanal of Nhecolândia, Brazil .

Laurent Barbiero; S.A.C. Furquim; Robert C. Graham; A. Rezende Filho; Vitor Bacani; S. Furian; Monique Fort; R.P. Dias Ferreira; J.P. Queiroz Neto; A.Y. Sakamoto

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S. Furian

University of São Paulo

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Alexandre Ferreira do Nascimento

Empresa Brasileira de Pesquisa Agropecuária

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