The sanitary landfills in Brazil are, generally, characterized by their high organic material content (around 60%), presence of different types of mixed wastes, and low compaction energy, which differentiates them from the landfills of developed and high-income countries. To prevent environmental and slope stability risks, it is crucial to understand the behavior of such landfills and the changes in their physical properties over time. The compression wave velocity (V p ) and shear wave velocity (V s ) are important parameters to subsidize the mechanical characterization of sanitary landfills, using which can be derived the dynamic elastic properties of municipal solid waste (MSW) for stability analysis. Using the geophysical methods of seismic refraction, active and passive multichannel analysis of surface waves, and crosshole test, it was obtained the values of Vp and Vs by employing an experimental cell and a lysimeter filled with MSW in the City of Campinas, São Paulo State, Brazil. The results obtained from the crosshole test showed that Vp ranged from 217 to 252 m/s and Vs ranged from 86 to 89 m/s. These low values can be attributed to the high content of organic material, low compaction energy, and climatic conditions such as high pluviometry index and high temperatures that together lead to changes in the pore fluid saturation, effective stress, and pore pressure. These values are indicative of the lower limit of the corresponding velocities reported in most literature; however, they are in accordance with the values reported for landfills located in countries with similar socioeconomic and climatic conditions.
Urban centers radically alter hydrological cycles, causing unintended consequences for the environment, such as the creation of extensive contamination plumes in unconfined aquifers. The Environmental Agency of the State of São Paulo has observed this issue since 1994. Therefore, this study aimed to create a method using nitrate as an indicator of contamination that permits an assertive interpretation of changes in the groundwater quality in monitoring wells of regional networks. The method was applied in ten cities with monitoring wells in the Bauru Aquifer System. The results correlated the presence of nitrate with the time and dynamics of land use in the capture zones of the wells over 54 years . In areas with sewer networks installed before 2001 and urban occupation greater than 60% of urban occupation in the capture zones, there was an increase in nitrate concentration of at least 35%. Likewise, extending this new method to other wells will make it possible to identify the causes of nitrate and other contaminants in the groundwater-monitoring network in the State of São Paulo.
Un análisis geomorfológico y sedimentológico fue realizado en el sector medio del Valle de Pueblo Llano con la finalidad de comprender la génesis de los sedimentos y geoformas cuaternarias presentes en el área. Cuatro sectores con características morfológicas y sedimentológicas distintivas fueron identificados: (i) depósitos en masa de flujos de detritos con una expresión superficial cónica interpretados como abanicos aluviales, (ii) depósitos de flujos unidimensionales que constituyen terrenos relativamente planos con bajas pendientes característicos de terrazas fluviales, (iii) depósitos de diamicton que constituyen un conjunto de lomos y depresiones en forma de arco asociados a un complejo de morrenas frontales, y (iv) depósitos de flujos unidimensionales que conforman terrenos con forma de lomos asimétricos, asociados a condiciones fluvio-glaciares. Estos resultados ponen en evidencia que los glaciares asociados a la Glaciación Mérida en el Valle de Pueblo Llano, alcanzaron elevaciones al menos 300 m más bajas que las reportadas previamente en la literatura para los Andes de Mérida. Además, sugieren que otros valles glaciares presentes en los Andes de Mérida pudieron haber experimentado fenómenos similares.
Palabras clave: Andes de Mérida, Geomorfología y Sedimentología, Morrenas, Glaciación Mérida, Pueblo Llano.
Abstract:
A geomorphological and sedimentological analysis was carried out in the Middle reach of the Pueblo Llano Valley to understand sediment genesis and quaternary geoforms present in the area. Four zones with distinctive morphological and sedimentological characteristics were identified: (i) mass deposits of debris flow with a cone-shaped surface interpreted as alluvial fans, (ii) unidirectional flow deposits with relatively flat topography, with little slope, characteristic of fluvial terraces, (iii) arc-shaped diamicton deposits that constitute a set of crests and valleys, associated to a complex of frontal moraines, and (iv) unidirectional flow deposits that form terrains with the shape of asymmetric ridges, associated to a fluvio-glacial conditions. These results show that the glaciers of the Mérida Glaciation in the Pueblo Llano Valley reached elevations of at least 500 m lower than those previously reported in the literature for the Mérida Andes. In addition, they suggest that other glacial valleys present in the Andes of Mérida might have experienced similar phenomena.
Keywords: Mérida Andes, Geomorphology and Sedimentolology, Moraine complex, Mérida Glaciation, Pueblo Llano.
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