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Field tests were carried out to estimate effective unsaturated soil hydraulic properties of layered residual soils in Rio de Janeiro, southeastern Brazil. Data of this type are important for understanding the initiation of rainstorm-induced soil landslides, which often occur in the state of Rio de Janeiro as well as other areas having similar geologic settings and climate conditions. Tests were carried out using a simplified field approach, referred to as the Monitored Infiltration Test, which requires only a tensiometer to measure pressure heads below the wetting front, triggered by flow from a Mariotte bottle which maintains a constant pressure at the top edge of the soil profile. The data can then be analyzed by numerical inversion using the HYDRUS-2D software package. The test is relatively fast since no steady-state flow conditions are needed, and versatile since the test can be carried out quickly on steep slopes with the help of a manual auger. Soil water retention and the unsaturated hydraulic conductivity functions were obtained for a range of young, mature and saprolitic residual soils. The effective hydraulic properties of the distinct residual soil layers can be quite large, reflecting a need to provide a careful analysis of field-scale hydraulic heterogeneity in geotechnical analyses.

The design of open-pit mines should balance safety and economy. However, safe geotechnical conditions generally involve redesigning the geometry of slopes and groundwater drawdown, signi cantly increasing the costs of mining operations. The use of numerical models to simulate groundwater drawdown and slope stability can be an alternative to assess cost-bene t trade-offs for decision-making. This study documents a mining plan using groundwater drawdown scenarios that illustrate how geotechnical, economic, and environmental indicators can be combined to obtain optimum slope geometry for open-pit mining. The optimization approach analyzed different scenarios of groundwater drawdown for the nal pit of a phosphate mine to improve the pit slopes stability. The groundwater simulation scenarios included the combination of deep horizontal drains and pumping wells. Stability analyzes using the limit equilibrium method were used to obtain the bench, inter-ramp, and overall factors of safety of different representative sections. The factors of safety obtained, the drawdown costs and the water table elevation of each section were selected as indicators for obtaining the optimal drawdown scenario using a multi-objective tool. The groundwater control system obtained with 11 horizontal drains and 1 pumping well was considered the most adequate from the geotechnical and economic perspectives. Slope geometry optimization obtained with this drawdown scenario led to adequate inter-ramp and overall safety factors for the nal pit design, reducing the barren-to-ore ratio to 0.38, much less than the present ratio (≈ 3). The results are important for optimizing the slope geometry of open-pit mines and can be replicated in other regions.

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This study aims to assess the COVID-19 partial lockdown influence on air quality in the Metropolitan Region Rio de Janeiro (MRRJ). Criteria pollutants (CO, SO2, O3, and NO2) sampled at four sites under vehicular and industrial influences were investigated, between March 1st to April 12th, 2019 and 2020. Results showed that the partial lockdown affected pollutant levels through emission sources reduction. High decreased concentrations were observed for SO2, NO2, and CO; while an increase in the ozone concentration was recorded. Pollutant time variation evaluations helped to understand the trend and sources in the different periods.   Este estudo tem como objetivo avaliar a influência do lockdown parcial da COVID-19 na qualidade do ar na Região Metropolitana do Rio de Janeiro (RMRJ). Poluentes de critérios (CO, SO2, O3 e NO2) amostrados em quatro locais sob influências veiculares e industriais foram investigados, entre 1º de março e 12 de abril de 2019 e 2020. Os resultados mostraram que o bloqueio parcial afetou os níveis de poluentes por meio da redução das fontes de emissão. Reduções nas concentrações de SO2, NO2 e CO foram registradas; enquanto um aumento na concentração de ozônio foi observado. As avaliações da variação temporal dos poluentes ajudaram a entender a tendência e as fontes nos diferentes períodos.