Hydraulic conductivity and geophysics (ERT) to assess the aquifer recharge capacity of an inland wetland in the Brazilian Savanna

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 char- acteristics, 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 con- ductivity 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

Aquifer recharge capacity assessment of an anthropogenically impacted wetland by the DC resistivity geophysical method

Population growth and social and economic development demand increasing volumes of water for public supply, especially in scenarios where surface sources such as rivers may not meet the basic demands for the population. In southeastern Brazil, with emphasis on the Piracicaba region, there is a conflict over water use regarding agricultural and industrial activities, where the sugar-alcohol sector is widely highlighted. The region has thousands of hectares of sugarcane cultivated, which requires intensive use of fertilizers and pesticides, in addition to the need for large volumes of water in the production of sugar and ethanol, where the main effluent produced is represented by vinasse, used as fertilizer complement and soil hydration in sugarcane fields. This work presents the results of a geophysical diagnosis in a closed wetland, located in a sugarcane field region, to evaluate the hydrogeological function of this environment in aquifer recharge and the risks that land use can cause in the quality and availability of surface and underground water resources. The geophysical survey consisted of nine lines of electrical resistivity tomography in Schlumberger arrangement, submitted to 2D processing and inversion followed by interpolation and generation of 3D visualization models. The results indicate a direct connection between water accumulated in the wetland and the aquifer underneath, separated by an aquitard interface about 44 m thickness. The study points out to the high vulnerability to the input of pesticides and vinasse effluent from the surrounding sugarcane fields to the interior of the wetland, given the absence of riparian forest or buffer zone, in addition to the risk of contamination of surface and groundwater. Understanding the local hydrological dynamics should subsidize the sustainable use of the soil providing preservation of water resources, with emphasis on aquifers, a source of increasing importance in the face of the imminent scarcity of surface resources

INTEGRAÇÃO DE DADOS AEROGAMAESPECTROMÉTRICOS E ELETROMAGNÉTICOS TERRESTRES EM REGIÃO DE OCORRÊNCIAS DE COBRE NO EXTREMO NOROESTE DA BACIA DO CAMAQUÃ, SUL DO BRASIL: Integration of aerogammaspectrometric and ground electromagnetic data in a copper occurrences region in the extreme northwest of the Camaquã Basin, Southern Brazil

In the different phases of prospective campaigns for metallic minerals such as copper, Geophysics acts as a support tool both in the recognition of new exploratory targets and the expansion of known deposits, due to the achievement of contrasts in physical properties between mineralizations and host rocks. The present study presents the results of the aerogammaspectrometry recognition phase, followed by the detailing of potential copper targets through the inductive terrestrial electromagnetic method in an area covered by the occurrences named Victor Teixeira and Capão Grande, both located to the interior of the municipality of Caçapava do Sul, in the state of Rio Grande do Sul, Brazil. The Victor Teixeira occurrence is part of the metamorphic rocks of the Sul-Riograndense Shield, while the one in Capão Grande has as its host the Camaquã Basin’s volcano-sedimentary lithotypes. The outcrop mineralization of both occurrences comprises carbonate disseminations predominantly in fractures. The aerial radiometric data allowed the demarcation of potassium-enriched areas associated with hydrothermal alteration products as indirect guides for the location of copper targets. The correlation of this potassium guide with high concentrations of thorium was also a promising indication. The apparent conductivity data obtained along the aeroradiometric targets made it possible to suggest the presence of copper sulfides in conductive areas in the metamorphic basement’s schists and the arcosian conglomeratic sandstones of the Camaquã Basin.Nas diferentes fases de campanhas prospectivas de minerais metálicos como o cobre, a geofísica atua como ferramenta de apoio tanto no reconhecimento de novos alvos exploratórios, quanto na ampliação de jazidas conhecidas, devido à obtenção de contrastes de propriedades físicas entre as mineralizações e as rochas hospedeiras. O presente estudo apresenta os resultados da fase de reconhecimento pela aerogamaespectrometria seguidos de detalhamento de alvos potenciais de cobre pelo método eletromagnético indutivo terrestre em área contemplada pelas ocorrências denominadas Victor Teixeira e Capão Grande, localizadas no interior do município de Caçapava do Sul, Rio Grande do Sul, Brasil. A ocorrência Victor Teixeira está inserida em rochas metamórficas do Escudo Sul-Riograndense, enquanto a de Capão Grande tem como encaixante os litotipos vulcanossedimentares da Bacia do Camaquã. A mineralização aflorante de ambas as ocorrências compreende disseminações de carbonatos dominantemente em fraturas. Os dados radiométricos aéreos possibilitaram a definição de áreas enriquecidas em potássio associadas a produtos de alteração hidrotermal como guias indiretos para a localização de alvos de cobre. A correlação desse guia potássico com concentrações elevadas de tório também constituiu indicativo promissor. Os dados de condutividade aparente obtidos ao longo dos alvos aeroradiométricos possibilitaram sugerir a presença de sulfetos de cobre em áreas condutivas nos xistos do embasamento metamórfico e nos arenitos arcosianos conglomeráticos da Bacia do Camaquã

SÍSMICA DE REFRAÇÃO NO DOMO ESTRUTURAL DE PITANGA, RIO CLARO (SP)

Este trabalho apresenta a interpretação dos ensaios de sísmica de refração executado no Alto Estrutural Domo de Pitanga., localizado entre as cidades de Rio Claro e Piracicaba, nordeste do Estado de São Paulo. Foi executada uma seção de refração sísmica com aproximadamente 14.100m de comprimento onde foram dispostos 12 conjuntos de geofones e registradores digitais. Como fontes de ondas sísmicas foram utilizadas explosões de pedreiras localizadas nas extremidades da seção. Os resultados obtidos com a interpretação tomográfica e a do método plus-minus mostrou a existência de um alto do embasamento da Bacia do Paraná localizado em 1000m e 4000 m da Pedreira Bonança, foi também detectado um grande corpo de diabásio próximo à Pedreira Stavias. O alto estrutural encontrado pode ter sido causado por esforços compressivos resultantes das intrusões básicas. Este alto pode ter elevado a coluna de sedimentos, expondo sedimentos mais antigos