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The effect of the presence of gasoline and diesel on the speciation and mobility of inorganic arsenic species in tropical topsoils was investigated. Topsoil samples (n = 25) were contaminated with gasoline and diesel (500 mg kg

Made available in DSpace on 2022-04-28T19:52:00Z (GMT). No. of bitstreams: 0 Previous issue date: 2022-01-01 For the evaluation of the internal water fluxes of wetlands and comprehension of their function within the hydrological cycle, the electrical resistivity tomography technique is a high-performance tool for the modeling of hydrodynamic environments, comprising data acquisition procedures based on transmission and reception sensors of electric potential fields as a result of predetermined configuration and the selection of arrays. The utilization of appropriate arrays is fundamental to obtaining data that truly represent the local geology, while an incorrect geometric configuration of electrodes might lead to failure to detect anomalies, impacting the comprehension of the dynamic processes. This research was conducted to make a comparative analysis of electrical resistivity tomography data acquired through Schlumberger, Wenner, and dipole–dipole arrays, which were supported by direct soil hydraulic conductivity data and vegetation analysis, allowing the correlation of surface infiltration zones and their continuity in depth, making possible an evaluation of the array that best represents the study area in terms of soil, rock, and flux dynamics. The results revealed the Schlumberger array as the best electrode configuration for modeling, with the best correlation with direct surface data, which might be explained by the predominance of a horizontalized potential electric field flux, good signal-to-noise ratio, and discrimination capacity of vertical flux structures. Therefore, the results indicate the existence of a structure of water access and direct recharge for the regional aquifer (Tubarão aquifer system), characterized as a closed topographic depression located in a region of sugarcane farming. Department of Geology (DG) University of São Paulo State (UNESP), 24A Avenue, Bela Vista, SP Department of Soil Science University of São Paulo (ESALQ-USP), Alameda do Brejo-Agronomia, SP Department of Geology Earth Sciences Sector Federal University of Paraná (UFPR) Centro Politécnico-Cel, Francisco H. dos Santos Avenue, Jardim das Américas, PR Department of Geology (DG) University of São Paulo State (UNESP), 24A Avenue, Bela Vista, SP

Made available in DSpace on 2022-04-28T19:42:49Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-12-01 Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) In Brazil, since 2013 the Southeast region has been dealing with recurrent hydric stress resulted from the prolongation of the dry season, whose tendency is to be more dramatic in the function of climate change. The situation is more critical in some areas, including Cordeirópolis, projecting a reduction of 50%–100% in water availability in the next 15 years, demanding urgency in water availability-use balance. Considering the significant presence of small Geographic Isolated Wetlands (GIW) in the region, it is crucial the recognition of the link between wetlands and hydrology in the catchment since these ecosystems store rainwater and can act as aquifer recharger zones. The objective of this study is to evaluate the effectiveness of non-invasive methods, such as UAV-mapping and DC resistivity, and low-invasive (in situ hydraulic conductivity) to unveil the hydrological ecosystem services of a GIW in terms of surface and groundwater. From the high-resolution orthomosaic and digital elevation model, three compartments were qualified and quantified; (i) current wetland, (ii) Flooding area and, (iii) Potential wetland expansion. From the DC resistivity, the interaction between surface water and groundwater was identified, indicating the presence of a shallow saturated only beyond the perimeter of the current wetland as a possible result of land-use conversion or climate change. In addition, the local igneous intrusion comprises the connection between shallow/surface waters and deep aquifers made by fractures. Thus, the association of both methods showed high applicability concerning the identification of GIW superficial hydrological functions (UAV) and the system's subsurface dynamic (DC resistivity). São Paulo State University (Universidade Estadual Paulista) Department of Geology, Av. 24A, 1515, CEP: 13506-900 São Paulo State University (Universidade Estadual Paulista) Department of Geology, Av. 24A, 1515, CEP: 13506-900 FAPESP: 2020/03207-9

Made available in DSpace on 2021-06-25T10:25:07Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-04-01 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) The protection of wetlands is essential for sustainable development. The particular hydrology of wetlands creates conditions for the formation of hydric soils. Hydric soils are formed in oxide-reducing environments and perform important removal and re-oxidation of Fe and Mn oxides and hydroxides. They are also characterized by the formation of a superficial horizon enriched by the accumulation of organic matter. The objective of this study was to determine the concentration of essential (Co, Cu, Fe, Mn, Ni, Zn) and toxic (Al, Cd, Pb) elements in the soil solution in a wetland, surrounded by an intense agricultural activity area. The concentrations of the elements were evaluated according to the level of hydromorphy (border to the center) and the depth of the soil. The physical fractionation of these elements was also assessed (total and < 30 kDa), and the results were compared with the chemical speciation of these elements. Despite the high total concentrations of Al and Fe, the concentration of these elements was very low in the < 30 kDa fraction, which suggests that these elements are complexed with organic matter, in the form of hydroxides. Evidence of removal of Fe and Mn from the surface horizon was observed at the center of the wetland, where the highest level of hydromorphy is found. The results showed that the concentration of metals in the fraction < 30 kDa is insignificant, suggesting that the mechanisms of precipitation and/or adsorption to soil colloids play an important role in the regulation of this ecosystem. Geosciences and Exact Sciences Institute São Paulo State University (UNESP), 24-A Avenue, 1515, Bela Vista Geosciences and Exact Sciences Institute São Paulo State University (UNESP), 24-A Avenue, 1515, Bela Vista FAPESP: 2017/14168-1

Made available in DSpace on 2021-06-25T10:22:29Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-02-01 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) In seasonal flooding isolated wetlands, the degree of wetness suggests a close synergy between soil processes, landscape evolution and hydrology along space and time. Until now, that subject has received insufficient attention despite natural wetlands supply essential environmental services to society and are surrounded by intensive agriculture that uses agrochemicals and fertilizers in their management. The objectives of this study were to propose an infiltration architecture model based on local surface and subsurface water-fluxes in isolated wetland embedded in lateritic plateau covered by savanna and qualify the environmental sensitivity as an area of aquifer recharge. Grain size, soil bulk density, and hydraulic conductivity were determined in five profiles in a soil catena. Unmanned Aerial Vehicle high-resolution images were obtained to generate a digital elevation model and discriminate areas with different vegetation, water accumulation, and environmental sensitivity. Electrical tomography was performed to unveil the soil architecture and infiltration. The soils (Plinthosols) developed on aquic conditions determine the linkage between the surface–subsurface hydrodynamics with the soil's physical properties. We have identified vertical and lateral water-flows in the soil architecture. Vertical flow occurs exclusively at the center, where the wetland is characterized as a recharge zone. Lateral flow towards the borders characterizes a discharge zone. The recharge zone is a depression surrounded by crops; therefore, it is a point of high environmental sensitivity. This hydrodynamic model is essential to support studies related to the dispersion of contaminants since soybean agriculture dominates the whole area of well-drained soils in the Brazilian Cerrado. Geosciences and Exact Sciences Institute (IGCE) São Paulo State University (UNESP), Av. 24A, 1515, Bela Vista, CP 178 Instituto de Estudos Sócio-Ambiental (IESA) Federal University of Goiás (UFG), Av. Esperança, s/n - Chácaras de Recreio Samambaia Geosciences and Exact Sciences Institute (IGCE) São Paulo State University (UNESP), Av. 24A, 1515, Bela Vista, CP 178 FAPESP: 2017/14168-1 CNPq: 43048622861

Made available in DSpace on 2022-04-28T19:49:30Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-12-01 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) The inland wetlands can perform the storage of water on the surface and the recharge of aquifers. Even a small wetland can work as a local point of water infiltration, influencing and sustaining the hydrodynamics in the hydrology landscape. These zones have complex mechanisms, as they integrate soil chemical and physical characteristics, and relate both surface and groundwater systems. The study area is an inland wetland located in the Ecological Station of Itirapina, São Paulo State (Brazil). The present work aims to unveil the relationship between hydrodynamics and pedological architecture through a detailed study that combines hydraulic conductivity tests in situ, geophysical method of electrical resistivity (Electrical Resistivity Tomography technique, ERT), and morphological soil descriptions aiming the validation of the ERT and hydraulic conductivity surveys. Two-dimensional (2D) and pseudo-three-dimensional (3D) ERT have been used to investigate the water flow in the subsurface, the pedological architecture that keeps the wetland hydroperiods, and the link between surface water and groundwater that can set a recharge capacity. The results showed areas with distinct surface patterns related to the density of vegetation cover and water infiltration. The lower infiltration areas are characterized by the presence of a perched water table in grassy areas while higher infiltration is associated with exposed topsoil. ERT 2D and pseudo-3D identified these areas as zones with a connection between soil-water and groundwater systems. Hydrodynamics in the flat plateau is associated with the geochemical evolution of soil cover due to the structural complexity acquired by the iron crust dissolution (laterite) which has sustained the relief. Future studies concerning inland wetlands need to be carried out to certify the role of soil-landscape in the water cycle in the Savanna biome. São Paulo State University (Universidade Estadual Paulista) Department of Geology, Av. 24A, 1515, CEP “Luiz de Queiroz” College of Agriculture University of São Paulo (USP/ESALQ) Soil Science Department, Pádua Dias, Avenue 11, CEP Facultad de Ciencias Universidad de la República Montevideo Departamento de Montevideo, Uruguay. Iguá 4225. 11400, Montevideo São Paulo State University (Universidade Estadual Paulista) Department of Geology, Av. 24A, 1515, CEP FAPESP: 2017/14168-1 FAPESP: 2020/03207-9

Made available in DSpace on 2020-12-12T02:02:45Z (GMT). No. of bitstreams: 0 Previous issue date: 2020-09-01 Landslides have environmental, social, and economic impact in the Brazilian Atlantic coast (Serra do Mar). In addition to meteorological, geological, and geomorphological settings, mineralogical and pore space heterogeneities in soil covers are considered important characteristics that can influence landslide occurrence. Since soil covers are very clayey, the evaluation of macro- and micromorphological soil features (soil structures, soil materials, and pores) resulted by mass movement during slope instability is difficult. This field of investigation practically does not exist in the Serra do Mar. The objective of this paper is to analyze the soil cover in a toposequence to identify macro- and microscopic soil features resulted from landslide processes, and assess the role of pedogenesis on landslide development. Macro- and micromorphological approaches were used to study the architecture of the soil cover and soil was sampled to determine chemical and mineralogical composition by XRF and XRD. Undisturbed clods were used to determine pore size and pore compartment by mercury porosimetry. It was recognized a brecciated and an undulating parallel-striated fabric. Both features were generated from mass movement and were unclear in the clayey horizons in the bottom of the toposequence. In this level, the occurrence of mottles suggesting short-term soil saturation and the presence of micropores < 1000 nm in soil could be the factors that drive soil movement downslope. Department of Applied Geology Institute of Geosciences and Exact Sciences São Paulo State University (Unesp), 24A Avenue, 1515, Bela Vista Department of Petrology and Metallogeny Institute of Geosciences and Exact Sciences São Paulo State University (Unesp), 24A Avenue, 1515, Bela Vista Department of Atmospheric Sciences Institute of Astronomy Geophysics and Atmospheric Sciences University of São Paulo, Matão Street, 1226 Department of Applied Geology Institute of Geosciences and Exact Sciences São Paulo State University (Unesp), 24A Avenue, 1515, Bela Vista Department of Petrology and Metallogeny Institute of Geosciences and Exact Sciences São Paulo State University (Unesp), 24A Avenue, 1515, Bela Vista

Made available in DSpace on 2020-12-12T01:37:36Z (GMT). No. of bitstreams: 0 Previous issue date: 2020-01-01 Human pressure on the water resources provided by natural isolated wetlands has intensified in Brazil due to an increase in agricultural land equipped with irrigation. However, the amount of water stored in these areas and its contribution to aquifer recharge is unknown. This study aimed to quantify the amount of water that can be retained in a natural wetland and to propose a model of groundwater recharge. We used remote sensing techniques involving unmanned aerial vehicle to map the wetland and highlight its internal morphology, using a red-green-blue orthomosaic and a digital surface model. The 2-D inversion and a pseudo-3-D model from electrical resistivity tomography data were used to visualize the subsurface structures and hydrologic flow paths. The wetland is a reservoir storing up to 416.996 m3 of water during the rainy months. Distinct internal compartments characterize the wetland topography and different water-volume storage, lower in the border and higher in the center. A leakage point connects surface water to groundwater through direct vertical flow, which constitutes the aquifer recharge zone. Remotely sensed very high-resolution images allied with geophysical techniques allowed complete surface and subsurface imaging and offered visual tools that contributed to understanding the hydrodynamics of the wetland. Department of Geology Universidade Estadual Paulista (UNESP-São Paulo State University), Av. 24A, 1515, Bela Vista Instituto de Estudos Sócio-Ambiental (IESA) Universidade Federal Goiás (UFG), Campus Samambaia Laboratoire PROTEE Université de Toulon, Avenue de l’Université Department of Geology Universidade Estadual Paulista (UNESP-São Paulo State University), Av. 24A, 1515, Bela Vista

Os perfis lateríticos cobrem vasta área do território brasileiro e seus estudos são motivados por fins diversos. Internamente se estruturam na forma de horizontes com variação vertical de suas composições químicas e mineralógicas. O desenvolvimento e preservação dos perfis lateríticos são indissociáveis das características do modelado. Assim, as exposições dos horizontes de um evento de intemperismo se associam a determinadas feições e posições do relevo. Tomando por base variações químico-mineralógicas e posição no relevo, é possível aplicar técnicas de sensoriamento remoto para delimitar respostas desses horizontes quando aflorantes. Nesse trabalho, uma área na região de Bom Jesus da Penha (MG) foi previamente visitada para descrição de campo de um perfil laterítico desenvolvido a partir de gnaisses, clorita-anfibólio xisto e quartzitos, seguido de caracterizações mineralógicas dos horizontes de intemperismo do xisto ultramáfico (difração de raio X). Na sequência, foram aplicadas composições de bandas espectrais de imagens de satélite Landsat-7/ETM+ e modelos digitais de elevação e declividade do relevo, gerados de imagem de radar SRTM 1Arc-sec. Buscou-se, assim, identificar respostas espectrais para os horizontes de intemperismo descritos em campo. A aplicação do sensoriamento remoto permitiu a delimitação de áreas com características relacionáveis aos horizontes superiores do perfil laterítico identificado em campo.

O processo de formação dos horizontes lateríticos é responsável pela reorganização química e mineralógica dos litotipos preexistentes. Esse arranjo é controlado pela mineralogia primária da rocha e pelas características de desenvolvimento do processo intempérico. Este artigo apresenta um estudo em um clorita-anfibólio xisto, a partir do qual se desenvolveram dois horizontes de intemperismo. No topo se observou solo caulinítico vermelho argiloso, enquanto abaixo se desenvolve um horizonte saprolítico verde com plintitas de cor ocre, o qual contém montmorillonita neoformada. Os elementos químicos analisados tiveram variações nos teores ao longo desse perfil, sendo que todos os metais tiveram, em determinadas amostras, picos de acúmulos superiores a 100% em relação à rocha. Al2O3, U, Th, Zr e TiO2 mostram concentração residual no topo do horizonte de solos, junto a caulinita e óxidos e hidróxidos de ferro; Fe2O3, V e Co tiveram maior acúmulo na base do horizonte de solos, próximo à transição para o saprolito; Mn, Cr2O3, Ni, Zn, Cu e elementos terras raras (ETR) apresentaram máximos de enriquecimento no horizonte plintificado, junto a montmorillonita; CaO, MgO e SiO2 tiveram redução dos teores ao longo de todo o perfil estudado. Tomando o litotipo metaultramáfico, destacam-se os enriquecimentos dos elementos terras raras e ítrio (ETRY) e escândio (Sc) no perfil de intemperismo, os quais são compatíveis com modelos de mineralização laterítica.

Made available in DSpace on 2019-10-06T16:14:40Z (GMT). No. of bitstreams: 0 Previous issue date: 2019-05-01 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Mound fields (MF), which consist of numerous isolated mounds, are characteristic of the Cerrado wetlands of Brazil. While there are numerous studies on soil redistribution by termites and by differential particulate erosion, a new hypothesis, supported by metal accumulation in these areas, needs to be tested. This study aimed to investigate the extent to which soil saturation by water, and the associated chemical erosion, might be a key driver of the geomorphological development of the Cerrado wetlands. The study was performed in a typical wetland of Minas Gerais that shows a typical succession from well drained Ferralsols on the plateau to Gleysols on the lowland and the presence of MF at the transition. Soil morphological description was used together with optical microscopy, X-ray fluorescence and physical analyses (grain size and bulk density) to discriminate between the biological (bioturbation) and geochemical origins. Additionally, geochemical mass balance was calculated to estimate the total amount of chemical erosion that had occurred in the area. The morphological observations and the results on soil texture did not point to material redistribution in the MF. In contrast, the results showed that iron-depleted aggregates in depressed zones were sensitive to collapse. Soil saturation by water as the main cause of geochemical erosion and geomorphologic development was confirmed by mass balance calculation. The results fill an important information gap on the formation and evolution of cerrado soil landscapes, which have important consequences for biodiversity and water conservation. Universidade Estadual Paulista (UNESP) Departamento de Petrologia e Metalogenia (DPM), Av. 24A, 1515, Bela Vista Universidade Federal Goiás (UFG) Instituto de Estudos Sócio-Ambiental (IESA) Agricultural Research Council - Agricultural Engineering, PB X519 Universidade Estadual Paulista (UNESP) Departamento de Geologia Aplicada (DGA), Av. 24A, 1515, Bela Vista Pontifícia Universidade Católica/MG, Av. Itaú, 505, Bairro Dom Cabral Laboratoire d'Océanographie et du Climat: Expérimentations et approaches numériques (LOCEAN) UMR 7159 IRD/CNRS/UPMC/MNHN Universidade Estadual Paulista (UNESP) Departamento de Petrologia e Metalogenia (DPM), Av. 24A, 1515, Bela Vista Universidade Estadual Paulista (UNESP) Departamento de Geologia Aplicada (DGA), Av. 24A, 1515, Bela Vista FAPESP: 2014/01131-4 FAPESP: 2017/14168-1

Made available in DSpace on 2018-12-11T17:19:45Z (GMT). No. of bitstreams: 0 Previous issue date: 2018-05-01 Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Due to its meteorological, geological and geomorphological settings, Brazilian’s Atlantic coast have suffered severe landslide phenomena, particularly along the cost of São Paulo, Rio de Janeiro, and Santa Catarina states. Studies have shown that these processes are complex and triggered by several factors. However, within the study area, many landslide locations are placed on gneiss migmatitic terrain with pronounced geological discontinuities. The objective of this paper is to assess landslide occurrences in Serra do Mar (Caraguatatuba, SP) and investigate, by means of kinematic analysis, how they correlate with foliation and fractures present on the rocks. Kinematic analysis is used to investigate which discontinuities are more favorable to landslides occurrence and their relationship with slope directions. Structural information and kinematic data models are used to evaluate cause–effect relationship of landslide processes. Results show that dip slopes, with NE–SW direction, have greatest potential for the occurrence of planar landslides. On the other hand, anti-dip and cross-dip slopes have a greater potential to develop wedge landslides. Rock weathering and fluid flux along foliation planes can intensify mass movement. Such effect is also seen in residual soil, since they are able to preserve relict structures of the rock. This study contributes to a better understanding of how geological structures, preserved in tropical residual soils, influence shallow landslides. Department of Applied Geology Institute of Geosciences and Exact Sciences São Paulo State University (Unesp), 24A Avenue, 1515, Bela Vista Institute for Technology Research of São Paulo State (IPT), Prof. Almeida Prado Avenue, 532, Cidade Universitária Department of Petrology and Metalogeny Institute of Geosciences and Exact Sciences São Paulo State University (Unesp), 24A Avenue, 1515, Bela Vista Department of Applied Geology Institute of Geosciences and Exact Sciences São Paulo State University (Unesp), 24A Avenue, 1515, Bela Vista Department of Petrology and Metalogeny Institute of Geosciences and Exact Sciences São Paulo State University (Unesp), 24A Avenue, 1515, Bela Vista

Made available in DSpace on 2018-12-11T17:16:49Z (GMT). No. of bitstreams: 0 Previous issue date: 2018-02-01 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) This paper presents the use of U-series radionuclides 238U and 234U to evaluate the biogeochemical disequilibrium in soil cover under a contrasted soil-water regime. The approach was applied in three profiles located in distinct topographical positions, from upslope ferralitic to downslope hydromorphic domain. The U fractionation data was obtained in the samples representing the saprolite and the superficial and subsuperficial soil horizons. The results showed a significant and positive correlation between U and the Total Organic Carbon (TOC). Soil organic matter has accumulated in soil due to hydromorphy. There is no evidence of positive correlation between U and Fe, as expected in lateritic soils. The advance of the hydromorphy on Ferralsol changes the weathering rates, and the ages of weathering are discussed as a function of the advance of waterlogged soil conditions from downslope. Also, the bioturbation could represent the other factor responsible to construct a more recent soil horizon. Departamento de Petrologia e Metalogenia Universidade Estadual Paulista (UNESP), Câmpus de Rio Claro, Av. 24-A, No.1515, C.P. 178 Instituto de Estudos Sócio-Ambientais Universidade Federal de Goiás (UFG), Campus II Departamento de Petrologia e Metalogenia Universidade Estadual Paulista (UNESP), Câmpus de Rio Claro, Av. 24-A, No.1515, C.P. 178 FAPESP: 2017/14168-1 CNPq: 465571/2014-0

Made available in DSpace on 2018-12-11T17:18:34Z (GMT). No. of bitstreams: 0 Previous issue date: 2018-08-15 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Wetland soils are an important component of the Global Carbon Cycle because they store about 20–25% of the terrestrial soil organic carbon (SOC). Wetlands occupy about 6% of the global land surface and any change in their use or management has potentially dramatic consequences on greenhouse gases emissions. However, the capacity of wetland soils to store carbon (C) differs from place to place due to reasons still not well understood. The objective of this review was to evaluate the global variations in wetlands SOC content (SOCC) and to relate it to key soil and environmental factors such as soil texture, intensity of soil hydromorphy, metallic element content and climate. A comprehensive data analysis was performed using 122 soil profiles from 29 studies performed under temperate, humid, sub-humid, tropical and sub-arctic conditions. The results point to average SOCC of 53.5 ± 15.8 g C kg−1 with a maximum of 540 g C kg−1. SOCC increased with increase in intensity of soil hydromorphy (r = −0.52), Al (r = 0.19) and Fe content (r = 0.21), and decreased with soil pH (r = −0.24). There was also a surprising tendency for intensity of soil hydromorphy, and thus SOCC, to decrease with increasing mean annual precipitation and soil clay content. These results contribute to a better understanding of the impact of soil hydromorphy in wetlands on organic C stabilization in the soils. However, further studies with additional information on soil bulk density to assess carbon C stocks, still need to be performed. Universidade Estadual Paulista (UNESP) Departamento de Petrologia e Metalogenia (DPM), Av. 24A, 1515, Bela Vista Agricultural Research Council-Institute for Agricultural Engineering, PB X519 School of Agricultural Earth and Environmental Sciences University of KwaZulu-Natal, PB X01 Laboratoire d'Océanographie et du Climat: Expérimentations et approaches numériques (LOCEAN) UMR 7159 IRD/CNRS/UPMC/MNHN, 4, Place Jussieu Universidade Estadual Paulista (UNESP) Departamento de Petrologia e Metalogenia (DPM), Av. 24A, 1515, Bela Vista FAPESP: 2017/14168-1 FAPESP: N°2014/001131-4

Made available in DSpace on 2018-12-11T17:15:50Z (GMT). No. of bitstreams: 0 Previous issue date: 2017-11-01 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Extensive flat plateaus are typical landforms in the cratonic compartment of tropical regions. Paleoclimate, pediplanation, laterization, and dissection have created complex and distinct geological, geomorphological, and pedological features in these landscapes. In the Brazilian territory, the flat plateau sculpted in sandstone of Marília Formation (Neocretaceous) belonging to the Sul-Americana surface presents a very clayey and pisolitic Ferralsol (Red and Yellow Latossolo in the Brazilian soil classification). The clayey texture of soil and the pisolites have been considered as weathering products of a Cenozoic detritical formation which is believed to overlay the Marília Formation sandstones. Using data of petrography (optical microscopy and SEM), mineralogy (RXD), and macroscopic structures (description in the field of the arrangement of horizons and layers), a complete profile of Ferralsol with ferricrete and pisolites was studied. The complex succession of facies is in conformity with a sedimentary structure of Serra da Galga member (uppermost member of Marília Formation). The hardening hematite concentration appears as layered accretions in the subparallel clayey lenses of sandstone saprolite, preserving its structure. Iron contents varied according to different soil fabrics. Higher concentrations of iron are found in the massive ferricrete or in pisolites in the mottled horizon. Kaolinite is a dominant clay mineral and shows two micro-organizations: (1) massive fabric intrinsic to the sedimentary rock, and (2) reworked in pisolites and illuviated features. The pisolites are relicts of ferricrete in the soft bioturbated topsoil. The continuous sequence of ferricrete from saprolite to the Ferralsol indicates that the regolith is autochthonous, developed directly from sandstones of Marília Formation, through a long and intense process of laterization. Universidade do Estado de São Paulo (UNESP) Departamento de Petrologia e Metalogenia (DPM), Av. 24A, 1515, Bela Vista Universidade Federal de Goiás (UFG) Instituto de Estudos Sócio-Ambiental (IESA) University of São Paulo (USP) Núcleo de Pesquisa em Geoquímica e Geofísica da Litosfera e Instituto de Energia & Ambiente (NUPEGEL/IEA) Universidade de São Paulo (USP) Centro de Energia Nuclear na Agricultura e Núcleo de Pesquisa em Geoquímica e Geofísica da Litosfera (CENA/NUPEGEL) Universidade do Estado de São Paulo (UNESP) Centro de Estudos Ambientais (CEA) Universidade do Estado de São Paulo (UNESP) Departamento de Petrologia e Metalogenia (DPM), Av. 24A, 1515, Bela Vista Universidade do Estado de São Paulo (UNESP) Centro de Estudos Ambientais (CEA) FAPESP: N° 2014/01131-4

The expansion and intensification of agriculture are responsible for the increase in nonpoint pollution and the release of chemical considered toxic to flora, fauna and human health. Since 1970s, the Cerrado Biome in the State of Minas Gerais (Brazil) has been converted to agriculture. This land use change has not been accompanied by research to evaluate pollution levels associated with inorganic elements in natural wetlands and river sediments. In this study samples were collected in natural wetlands and river sediments recently deposited in floodplain areas to determine the total concentration of inorganic compounds that can be considered potentially toxic and to perform risk assessment. The total concentration of 18 elements (As, Ba, Ca, Cr, Cu, Fe, K, Mg, Mn, Na, Ni, P, Pb, Sr, Ti, V, Zn and Zr) and oxides present at the organic soil layer (0–30 cm) and at the mineral subsurface horizon (30–60 cm) of the wetlands in the upper oxidized layer (0–10 cm) of sediments was determined by ICP-OES and XRF. Contamination levels were determined and a risk assessment performed by comparing the obtained values with those proposed by the Guidelines for Agricultural Soils of Brazil (CONAMA no. 420) as well as the pedogeochemical background for soils formed from sandstone. The results showed high average concentrations of As, Cr and Cu in soils and floodplain sediments (as well as of Ba, Pb and Ni in some samples) with values exceeding (p significant at 5%) the pedogeochemical background and the threshold value for clean soil established by CONAMA. The concentrations of As and Cr in the soil were above the threshold level in 100% and 60% of samples, respectively, which may impact the environment and living organisms. The calculated contamination index (Pi) indicates that the wetlands exhibit moderate contamination (2 Cr > Cu in the topsoil and in the sub-superficial horizons whereas the floodplain sediments exhibit either no contamination (Pi ≤ 1) or low level of contamination (1

Made available in DSpace on 2018-12-11T17:16:15Z (GMT). No. of bitstreams: 0 Previous issue date: 2017-01-01 The vegetation of the Cerrado has been replaced by pastures and agriculture, affecting the stock and dynamic of soil organic matter (SOM). The present study was conducted in a cultivated chronosequence with a mixed system (agriculture+pasture for 15 years; Agric+P15) and cultivated pasture (30 years; P30), taking the native Cerrado as a reference to assess changes in the stock of SOM, the dynamics (δ13C) and the carbon replacement derived from the C3 in native vegetation to C4 in cultivated vegetation. Compared to Cerrado, there was a reduction in C stock in cultivated soils at 0-15-cm depth (reduction of 26.5% in Agri+P15 and 6% in P30). The close similarity between Cerrado and P30 indicates that the pasture management enhanced the stock relative to Agri+P15, but was not effective in sequestering C. Only in the 0-15cm depth was there a marked replacement of C derived from the C3 of Cerrado plants associated with cultivation time. In the chronosequence, the isotopic signature of C4 plants dominated in the soil below 30cm depth, suggesting a paleoclimatic effect on SOM. Universidade Federal de Uberlândia (UFU), Avenida João Naves de Ávila Universidade Estadual Paulista (UNESP) Instituto de Geociências e Ciências Exatas (IGCE), Avenida 24A Food and Agriculture Organization of the United Nations (FAO), Viale delle Terme di Caracalla Universidade de São Paulo (USP) Centro de Energia Nuclear Na Agricultura (CENA), Avenida Centenário Centro de Estudos Ambientais (CEA)/UNESP, CEA24A, 1515 Universidade Estadual Paulista (UNESP) Instituto de Geociências e Ciências Exatas (IGCE), Avenida 24A Centro de Estudos Ambientais (CEA)/UNESP, CEA24A, 1515

Sobre as chapadas do Planalto Central sao comuns as areas umidas na forma de cabeceiras de drenagem, depressoes fechadas e vales hidromorficos. Essas areas umidas sao ainda relativamente pouco estudadas em nivel de detalhe, assim como as paisagens de campos de murundus, a elas associadas. O objetivo da pesquisa e compreender a organizacao da paisagem de uma area de campo de murundus em escala local, sobre a chapada Uberaba-Uberlândia-MG, identificando os processos pedogeneticos envolvidos. Os compartimentos de paisagem da area umida com murundus foram mapeados em funcao das caracteristicas dos murundus; da vegetacao; dos solos e da profundidade do nivel freativo. Constatou-se a existencia de um gradiente nas caracteristicas dos murundus e dos solos da borda ao centro de uma area umida da chapada, interpretado como indicador de uma sequencia evolutiva: compartimentos mais antigos na borda; mais recentes no centro. Os processos pedogeneticos maiores relacionam-se a Laterizacao e a Gleizacao, que determinam o comportamento dos elementos quimicos e da materia orgânica nos solos.

Os solos do Cerrado sofrem impactos resultantes da substituição da vegetação original em sistemas agrícolas traduzidos na forma de desequilíbrios nos estoques e natureza do carbono. A região do Triângulo Mineiro vem sendo intensamente desmatada por ser uma área pioneira de expansão do agronegócio e apresenta sérios problemas relacionados à erosão do solo. Esta pesquisa teve como objetivo avaliar as mudanças na quantidade (Ctotal) na natureza (δ13C) do carbono do solo após conversão do cerrado denso em áreas com diferentes usos agrícolas (pastagem, soja e rotação soja/milho), manejos (sistemas convencionais e plantio direto). Os resultados mostraram que as mudanças nos valores relacionados ao uso e manejo são determinados também pelas características texturais dos solos formados pela alteração de litotipos distintos. Dentre os diferentes usos e manejo, o maior enriquecimento da taxa de carbono foi determinado na área com soja/milho no sistema de plantio direto em solo argiloso e o maior empobrecimento em pastagens não manejadas em solos desenvolvidos da alteração do arenito das Formações Adamantina e Marília. Estes estudos são úteis para serem usados como indicadores de qualidade para a conservação ambiental. The Cerrado soils suffer impacts related to the conversion of the original vegetation in agricultural systems, e.g., in the imbalances of stocks and nature of carbon. The Triângulo Mineiro region has been deforested by supporting the expansion of agribusiness and presents serious problems related to soil erosion. This study aimed to assess changes in content (Ctotal) and in nature (δ13C) of soil organic carbon after conversion of cerrado in different agricultural uses (pasture, soybean and soybean / corn), management (tillage and no-tillage). The results showed that changes in the values related to the use and management are also determined by the textural characteristics of soils formed by the alteration of different rock types. Among the different uses and management, the greater enrichment of the carbon content was determined in the no-tillage soybean / corn in a clayey soil and the further impoverishment was determined in not managed pastures developed in sandy soils from sandstones of Adamantina and Marília Formations. These studies are useful for use as quality indicators for environmental conservation.

Made available in DSpace on 2018-11-12T17:27:46Z (GMT). No. of bitstreams: 0 Previous issue date: 2015-12-01. Added 1 bitstream(s) on 2021-07-14T17:51:46Z : No. of bitstreams: 1 S1982-45132015000300501.pdf: 2472095 bytes, checksum: 07068bdd1547e5f0e4c1ded99bb09e3a (MD5) RESUMO A pastagem é uma importante atividade econômica no Cerrado. A partir das décadas de 1970 e 1980, programas para melhoria das pastagens introduziu gramíneas principalmente do gênero Brachiaria. Quando manejada adequadamente, a pastagem é reconhecida como eficiente em sequestrar carbono e contribuir com a mitigação das concentrações de gases do efeito estufa na atmosfera, condição que será atingida em função do tempo de uso e das propriedades de cada tipo de solo. A microrregião de Uberlândia no Triângulo Mineiro (MG) é tradicionalmente ligada à pastagem. No entanto, as condições geológicas, naturais do solo e do clima são fatores que podem acelerar a degradação dos solos quando a pastagem não é manejada adequadamente. O objetivo deste artigo foi comparar as mudanças das propriedades do solo e a incorporação de C em áreas recobertas com [1] Cerrado arbóreo natural, [2] sistema misto convertido inicialmente ao uso agrícola e os últimos 15 anos de pastagem, e [3] pastagem cultivada há 30 anos. Os resultados mostram a influência de uso sobre a dinâmica da matéria orgânica, e avalia o potencial de degradação dos solos mediante a atividade, o manejo e o tempo de uso do solo. ABSTRACT The pasture is an important economic activity in the brazilian Savannah. From the 1970s and 1980s, the implementation of the programs to improve the productivity of pastures, was introduced grasses, especially Brachiaria. When handled properly, the pasture is an efficient method to contribute to carbon sequestration and to the mitigation of concentrations of greenhouse gases in the atmosphere, which are dependent to the time of the land-use and the properties of each soil type. The microregion of Uberlandia in Triangulo Mineiro (MG) is traditionally linked to the pasture. However, the geological and natural soil conditions and climate are factors that can accelerate soil degradation when pasture is not handled properly. The objective of this article was to compare the changes of soil properties and the incorporation of C in covered areas [1] natural brazilian Savannah, [2] mixed system initially converted to agricultural use and the last 15 years of pasture, and [3] pasture cultivated with 30 years of implantation. The results show the influence of the land use on organic matter dynamics, and evaluate the potential degradation of soil by the activity, management and time of land use. Universidade Federal de Uberlândia Universidade Estadual Paulista Institut de Recherche pour le Développement Universidade Estadual Paulista

O procedimento de extracao em tres etapas sequenciais recomendado pelo Programa de Normas Europeias de Medicoes e Ensaios (SM&T), anteriormente nomeado por Gabinete Comunitario de Referencia (BCR), foi aplicado para a especiacao quimica de metais pesados (Cu, Pb, Cr e Zn) em sedimentos provenientes de diferentes regioes urbanizadas da Cidade de Uberlândia (MG, Brasil). Para obter o balanco de massa, uma quarta etapa, ou seja, a digestao do residuo foi realizada atraves do processo de digestao assistida por micro-ondas em meio acido. Maiores concentracoes dos elementos metalicos foram encontradas em pontos de amostragem que recebem descarga de uma area urbana e uma zona industrial. Todos os metais, exceto Zn, estavam presentes em maiores concentracoes nas fracoes residuais (fortemente associados com as estruturas cristalinas dos minerais), indicando que Cu, Pb e Cr foram menos moveis e potencialmente menos biodisponiveis nesses sedimentos. Em sedimentos de zonas de descargas industriais e urbanas, a sequencia de mobilidade dos metais estudados foi Pb > Zn > Cu > Cr. Maiores concentracoes de Pb foram encontradas nas fracoes residuais no ponto de amostragem localizado no afluente que drena a zona industrial (102 mg kg -1 ), indicando que este elemento metalico foi fortemente ligado aos sedimentos. Portanto, sob os pontos de vista toxicologico e ambiental, o Pb nao causa impacto ao meio ambiente e consequentemente a saude humana. A soma das quatro fracoes (soluvel em acido, redutivel, oxidavel e residual) apresentou boa concordância com o teor total, o que comprova a exatidao do procedimento de extracao por micro-ondas em conjunto com o metodo analitico FAAS. A three-step sequential extraction procedure recommended by the European Standards, Measurements and Testing (SM&T) Program, formerly the Community Bureau of Reference (BCR), was applied to the chemical speciation of heavy metals (Cu, Pb, Cr and Zn) in sediments from different populated zones of Uberlândia City (MG State, Brazil). To obtain a mass balance, a fourth step, i.e., digestion and analysis of the residue, was performed using a microwave-assisted acid digestion procedure. The highest metallic elements concentrations were observed at one of the sampling points which receive discharge from an urban area and an industrial zone. All metals, except Zn, were present at higher concentrations in the residual fractions (strongly associated with the crystalline structures of the minerals) indicating that Cu, Pb and Cr were less mobile and potentially less bioavailable in these sediments. In sediments from industrial and urban discharge zones the mobility sequence of the heavy metals studied was Pb > Zn > Cu > Cr. The highest Pb concentrations were found in the residual fractions at the sampling point located in the tributary stream that drains the industrial district (102 mg kg -1 ), indicating that this metallic element was strongly bound to the sediments. Therefore, under the contamination and toxicological point of view, Pb has no impact to the environment and consequently to the human health. The sum of the four fractions (acid-soluble + reducible + oxidizable + residual) was in good agreement with the total content, which verifies the accuracy of the microwave extraction procedure in conjunction with the FAAS analytical method.

Made available in DSpace on 2015-10-21T20:18:07Z (GMT). No. of bitstreams: 0 Previous issue date: 2015-04-01 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Fundação de Amparo à Pesquisa do Estado de Minas Gerais (FAPEMIG) Vereda and Murundu wetlands are widespread in the Cerrado (Brazilian savannah). The wetlands occupy topographic depressions on the flat plateau, which are permanently or seasonally waterlogged, with topsoil that has high contents of organic matter and endemic fauna and flora. These systems are important for regulating the water flux in the riverine network. Despite their environmental importance, the wetlands are largely neglected in planning policy, environmental legislation and scientific research, resulting in their degradation by the expansion and intensification of agriculture. In the studied catchment, a typical tropical savannah landscape and a region of typical agribusiness land use in the state of Minas Gerais was considered, where the Vereda and Murundu ecosystems are completely surrounded by agriculture. The transition zone between dry and wet soils is the most fragile and susceptible to degradation because it is subjected to the continuous expansion of land tillage. If the agribusiness model deployed in the region is responsible for the increase in wetland destruction, then changes in regulatory laws to define and preserve permanent preservation areas in the Brazilian Forest Code, for the years 1934, 1965, 1989 and in the two versions from 2012, are an impediment to the effectiveness of forest and wetlands protection and the policy of sustainable development. Universidade Estadual Paulista (UNESP) - Department of Petrology and Metallogeny, Bela Vista, Rio Claro, Brasil Universidade Federal de Uberlândia (UFU) - Instituto de Geografia, Uberlândia, Minas Gerais, Brasil Pontifícia Universidade Católica de Minas Gerais (PUC-Minas), Belo Horizonte, Minas Gerais, Brasil. Universidade Estadual Paulista (UNESP) - Department of Petrology and Metallogeny, Bela Vista, Rio Claro, Brasil FAPESP: 2014/001131-4 FAPEMIG: CRA-APQ-01103-11

O Cerrado é um bioma brasileiro com imensa relevância socioambiental. Destaca-se pela biodiversidade e por ser reconhecidamente área de expansão agrícola. A mesorregião do Triângulo Mineiro/Alto Paranaíba (MG) pode ser usada como um exemplo que reflete os resultados das políticas agrícolas e ambientais no Cerrado. A análise da dinâmica agrícola na mesorregião avaliada pelos Censos Agropecuários de 1995/96 e de 2006 mostra que os cultivos permanentes tradicionais como o café e a pecuária perdem área para o cultivo temporário, especialmente nas duas microrregiões de maior dinamismo econômico (Uberlândia e Uberaba). A evidente tendência de transformação no uso das terras reflete forte heterogeneidade regional. A expansão da atividade sucroalcooleira e o plantio da soja que substituíram antigas pastagens também são mais evidentes nas microrregiões Uberlândia e Uberaba. Apesar das transformações, com exceção da microrregião de Uberaba, a pastagem ainda é a atividade que domina o uso da terra. As pastagens plantadas com boas condições (manejadas) ocupam área entre 28% e 53% da mesorregião. As áreas com lavouras permanentes são pouco extensas e o sistema soja-milho parece dominar as novas áreas de conversão, e o número de estabelecimentos com cultivo convencional supera sensivelmente à queles manejados com cultivo mínimo ou cultivo na palha, mesmo nas microrregiões de Uberlândia e Uberaba. Situação similar de não adoção de práticas de manejo mais conservacionistas foi determinada nas pastagens, nas quais os teores de carbono dos solos refletem susceptibidade à degradação, com futura redução da produtividade e da biodiversidade.

Os sedimentos dos rios podem estocar grande quantidade de substâncias tóxicas que agem como fontes secundárias de poluição quando liberadas para as águas. Várias atividades antrópicas como industrialização, urbanização e agricultura são responsáveis pelo lançamento de elementos tóxicos na água que podem afetar negativamente tanto a qualidade ambiental quanto à saúde da população. O presente artigo tem como principal objetivo avaliar a concentração de metais pesados (As, Cd, Pb, Cu, Cr, Ni e Zn) presente nos sedimentos coletados em vários córregos urbanos da cidade de Uberlândia (MG) e sua influência na qualidade ambiental dos corpos hídricos, além de apontar os riscos à saúde humana em função dos parâmetros de qualidade estabelecidos pelo CONAMA. Observou-se que nos pontos P3 e P4, ambos influenciados pelo distrito industrial, que os valores de Cu, Cr e Ni foram significativos, podendo ser considerados fatores patogênicos.

The Brazilian savannah (cerrado) is an area of expansion of agribusiness. Among the various environmental changes related to deforestation of the savannah stand out impacts related to soil organic matter such as the imbalances in stocks and the changing nature of soil organic carbon. The objective of these study was to evaluate changes in nature (δ 13 C) and quantity (C%) of soil carbon after conversion of the dense savannah vegetation in areas under different lan duses (pasture, soybeans, corn / soybean rotation), management (conventional and zero tillage) developed in soils with different textural characteristics. The results showed that the average data set of non–managed grazing was the most distanced from the value obtained in cerrado soil. Another factor that determined the lowest concentrations of organic carbon was the presence of sandy soil. The results showed that the carbon C 4 grasses in areas occupied by pastures, with or without management, replaced the original C 3 carbon originated by cerrado. In the areas of conventional tillage, and no–tillage soybean, and consortium soybean/corn, no clear trend of impoverishment or enrichment of carbon and the carbon substitution as well as the incorporation of different nature of the carbon could be found.

A rapida degradacao do solo sob exploracao agropecuaria no mundo, especialmente nos paises tropicais em desenvolvimento, despertou, nas ultimas decadas, a preocupacao com a qualidade do solo e a sustentabilidade da exploracao agricola. No Brasil, as areas originalmente recobertas com vegetacao de Cerrado (savanas) vem sendo desmatadas e substituidas por sistemas agropecuarios. As mudancas no uso da terra deste bioma podem induzir alteracoes no teor de carbono nos solos, de acordo com os tipos de uso e praticas de manejo. Este trabalho objetiva avaliar o teor e a origem do carbono orgânico do solo em uma area de Cerrado nativo apos a conversao da vegetacao em area de pastagem, visando apresentar o nivel de degradacao do solo em relacao a atividade, ao manejo e ao tempo de uso do mesmo. A pesquisa foi desenvolvida na Bacia do Ribeirao Bom Jardim, situada entre as porcoes sul do municipio de Uberlândia e norte do municipio de Uberaba, estado de Minas Gerais. Os resultados das analises de carbono total (%C) e carbono isotopico (?13C), representativas dessas duas categorias de uso – remanescente de cerrado arboreo e pastagem degradada –, revelaram maior empobrecimento no teor de carbono nas areas sob pastagem degradada.

O rápido aumento de esgoto gerado pelos municípios e a necessidade de medidas para a disposição e tratamento têm levado à expansão de tratamentos alternativos como o sistema de escoamento à superfície. A disposição de esgoto doméstico na superfície do solo provoca importantes mudanças nas características físicas, químicas e morfológicas. O principal produto responsável por estas mudanças é a presença de grande quantidade de carbono orgânico presente no esgoto doméstico.

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.

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.

A mottled horizon in a laterite cover (without any duricrust) was studied by microscopy and quantitative chemical microanalysis. Apart from the voids, light red spots consisting of Fe-rich particles (≈2 μm) are set in clayey plasma. Dark red spots consisted of concentrations of Fe-rich particles. These patterns are inherited. On the border of structural or biological voids, where Fe-depletion features are systematic, gray or yellow spots result from dissolution of the Fe-rich particles and impregnation of the plasma by iron, respectively. The present Fe-depletion is the dominant process that explains the mottled differentiation and the absence of lateritic duricrust. To cite this article: V. Rosolen et al., C. R. Geoscience 334 (2002) 187–195.

Carbon isotope data on soil organic matter (SOM) were collected along an ecosystem transect 90 m in length that includes a tropical forest on the plateau, a transitional forest-savanna and savanna in a depression. Total organic carbon data show a significant increase in carbon content from sites representing forest ecosystem to sites representing savanna ecosystem. It was hypothesized that carbon accumulation in the depression is controlled by flooding conditions that slow down carbon decomposition and in part by carbon transport from the upper part of the transect (the savanna and the transition forest-savanna areas) into the depressions by water during the rainy season. The origin of the carbon was confirmed by using soil 13 C analysis. The savanna sites located in the depression showed δ 13C values between –19.5‰ and –22.5‰ indicating a mixture of C3 and C4 plants. The vegetation cover in the depression is predominantly C3 grasses with d 13C values of about –27‰ and –26‰. In the site under savanna located at an elevation slightly higher, the d 13C value was more enriched (–16‰) showing the predominance of C4 plants (d 13C of –13.6‰). At the forest-savanna transition and in the forest ecosystem the d 13C values were characteristic of C3 plants (–25‰ and –28.1‰). 14C and 13C data indicate that the organic matter of mixed origin has been deposited for at least the last 7000 years in the savanna depressions. The 13C pattern observed in the soil organic matter profiles indicate a predominance of C3 plants in the early part of the Holocene. About 7000 to 4000 years ago, the data show the influence of C4 plants, indicating forest regression associated with a drier climate than at present. The more recent 13 C records suggest forest expansion, and the return to a climate similar to the present.