Chemical weathering rates and atmosphere/soil CO 2 consumption of igneous and metamorphic rocks under tropical climate in southeastern Brazil were evaluated using the chemical composition of surface waters and fresh rocks and soil (horizon C) in the Upper Sorocaba River basin. Surface water samples were collected between June/2009 and June/2010, and analyses were performed to assess pH, electrical conductivity (EC), temperature and total dissolved solids (TDS), including Na + , K + , Ca 2+ , Mg 2+ , Cl − , SO 4 2− , PO 4 3− , NO 3 − and SiO 2 . Fresh rocks and C horizon samples were also collected, taking into account their geological context, abundance and spatial density, to analyze major elements and mineralogy. The concentration of TDS and dissolved cations, anions and silica increased during the dry period in relation to the wet period, and the same behavior was observed for pH, EC and temperature. After corrections of anthropogenic contributions (ca. 21 t/km 2 /yr) and atmospheric inputs (ca. 19 t/km 2 /yr), the annual flux due to chemical weathering involving the igneous and metamorphic rocks was ca. 29 t/km 2 /yr. The CO 2 atmospheric/soil consumption in the Upper Sorocaba River basin was ca. 0.2 × 10 6 mol/km 2/ yr, and when extrapolated to the entire Mantiqueira Orogenic Belt, accounted an estimated consumption of 0.07 × 10 12 mol/yr, representing 0.6% of the total CO 2 consumption flux derived from global average silicate weathering. The chemical weathering rates of igneous and metamorphic rocks in the Upper Sorocaba River basin were estimated at 15 m/My, respectively. The main weathering process in this watershed was the monossialitization, with partial hydrolyses of bedrock minerals, except quartz, which was not weathered and remained in the soil profile. The annual specific flux derived from igneous and metamorphic rocks at Upper Sorocaba River basin could be compared with watersheds in tropical climates. However, this value is higher than in other North American, European, Asian and African granitoid watersheds, and lower than in montane watersheds. Anthropogenic and atmospheric influence Water-rock interactions the basic function of moderating the Earth's climate. The physical erosion is related to soil loss, acts on the weathered surface by removing the cover and carrying the particulate matter. In both processes, the dissolved and particulate materials are transported through rivers to the oceans, resulting in the deposition of Ca and Mg carbonates (and smaller amounts of Fe and Mn) and sediments, respectively.The chemical weathering can be evaluated from the silica mass balance or from models using the dissolved sodium, calcium, potassium, magnesium and silica and total dissolved load concentrations, where inputs from rainfall require corrections (Amiotte-Suchet and Probst, 1993; Bain et al.

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The society of the 21st century is permeated by advances and diffusion of technologies that generate a way of life highly de-pendent on natural resources. This dependence requires a deep awareness of the importance of geodiversity and the education of the new generations and this is the way by which it will be possible to guarantee sustainable development. Geoparks are a new form of territorial management, whose characteristics are economic and social development based on the preservation and enhancement of geological and cultural heritage. This paper presents a discussion that involves this aspect in the relationship between geoparks and Geosciences teaching, divided into three parts: a discussion about the meaning of geoparks, followed by an analysis of the relationship between field work and geoscience teaching, and finally , it should be highlighted that geoparks can be excellent areas for field activities, which are essential to strengthen the understanding of geodiversity components and processes, without which the sensitization and perception of geoscientific concepts are limited. Geoparks can meet the demands of these areas for the teaching of geosciences in basic education.

The fractionation of heavy metals in riverbed sediments along the Tietê River basin, a highly polluted river in southeast region of Brazil, was investigated using a four-step sequential extraction procedure, in order to determine the concentration and distribution of Cu, Co, Cr, Cd, Zn, Ni and Pb, in the river bottom sediments, related to the potential mobility of geochemical phases. Around the metropolitan area of the City of São Paulo, which has 25 million people, the pollution is associated with municipal wastes and industrial effluents. Potentials of high mobility were observed for Cu and Zn along the entire river basin, associated mainly to the organic fraction, while at the Pirapora and Anhembi stations (upper and middle parts of the basin, respectively) the reactive forms of Ni and Pb were more associated to the Fe and Mn oxides. Near the mouth of the Tietê River, no significant contaminations caused by Cr and Ni in riverbed sediments was verified confirming the presence of these metals in the residual or lithogenous phase.

Approximately 40% of the volume of domestic sewage generated in the São Paulo State is untreated and released into water bodies, causing serious pollution problems that affect the water quality and especially the suspended sediments transported by rivers. Thus, this paper investigates the seasonal influence on the origin and fluxes of Cu, Co, Cr, Zn, Cd, Ni, Sc and particulate organic matter (POM) in sediments transported by a disturbed watershed in the São Paulo State, i.e. the Sorocaba River basin. POM was characterized using particulate organic carbon, particulate organic nitrogen, C:N ratio and δC and δN stable isotopic composition. Eight sample collections of fine suspended sediments (FSS) were carried out at the mouth of the Sorocaba River from July 2009 to May 2010. During the study period, the discharge rate followed the seasonal variation trend of the past 25 years. Zn was the most abundant trace element in the FSS, followed by Cr, Cu, Ni, Co, Sc and Cd. There was a higher concentration of trace elements during the dry season, except for Sc and Co, which did not vary seasonally. The POM showed the same trend, with higher concentrations during the dry season. The calculated enrichment factors and geoaccumulation index indicated that most of the trace elements are of geogenic origin, except for Zn, which showed significant anthropogenic contributions (55%). The elemental and isotopic analysis of C and N and C:N ratio indicated that the anthropogenic origin of POM found in the FSS is related mainly to domestic sewage (97%), while the significant correlation found between the concentrations of Zn and POM indicates that the main anthropogenic source of Zn is related to this domestic sewage. The FSS load transported during the study period was of 373,194 t y, of which 87% occurred during the rainy season.

This study aims to evaluate the mechanical erosion processes that occur in a tropical river basin, located in the São Paulo state, southeastern Brazil, through the chemical characterization of fine suspended sediments and the transport mechanisms near the river mouth, from March 2009 to September 2010. The chemical characterization indicated the predominance of SiO2, Al2O3, and Fe2O3and showed no significant seasonal influences on the major element concentrations, expressed as oxides. The concentration variations observed were related to the mobility of chemical species. The evaluation of the rock-alteration degree indicated that the physical weathering was intense in the drainage basin. The fine suspended sediments charge was influenced by the variation discharges throughout the study period. The solid charge estimate of the surface runoff discharge was four times higher in the rainy season than the dry season. The transport of fine suspended sediments at the Sorocaba River mouth was 55.70 t km−2 a−1, corresponding to a specific physical degradation of 37.88 m Ma−1, a value associated with the mechanical erosion rate that corresponds to the soil thickness reduction in the drainage basin.