Surface runoff and accelerated erosion in a peri‑urban wellhead area in southeastern Brazil

Degradation of hydrological conditions can adversely impact water resource quality and quantity. This degradation can generate social and economic losses, including losses for users outside the basin area. Therefore, studies focusing on surface runof and accelerated erosion processes are needed to enable interventions that address degradation-induced challenges. In the present study, the surface runof and accelerated erosion potential of the Feijão River basin were presented in charts at a 1:50,000 scale. The Feijão River basin has an area of 243.16 km2 and is used as the main water source for the city of São Carlos, Brazil. Geoenvironmental attributes, such as substrate, climate, relief, soil, water bodies and land cover and use, were integrated and assessed in a GIS environment, using a multicriteria analysis and weighted sum tool. The results show that a large part of the area (86.12% of the basin) exhibits a low surface runof potential and a moderate accelerated erosion potential. Accelerated erosive processes are triggered by changes in soil cover and have a direct relationship with the removal of existing vegetation and implementation of anthropogenic activities. In this case, as well as for most of the areas in southeastern Brazil, extensive grazing followed by sugar cane cultivation was the main driving force of erosion, acting as trigger for accelerated erosive processes at the water source area

Prolonged treatment with boosted protease inhibitor monotherapy is not associated with a higher rate of neurocognitive impairment than triple drug ART

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Stability of solid-phase selenium species in fly ash after prolonged submersion in a natural river system

Selenium (Se) chemistry can be very complex in the natural environment, exhibiting different valence states (-2, 0, +4, +6) representing multiple inorganic, methylated, or complexed forms. Since redox associated shifts among most of known Se species can occur at environmentally relevant conditions, it is important to identify these species in order to assess their potential toxicity to organisms. In June of 2009, researchers from the US Army Engineer Research & Development Center (ERDC) conducted investigations of the fly ash spilled 6. months previously into the Emory River at the TVA Kingston Fossil Plant, TN. Ash samples were collected on site from both the original ash pile (that did not move during the levee failure), from the spill zone (including the Emory River), and from the ash recovery ditch (ARD) containing ash removed during dredging cleanup operations. The purpose of this work was to determine the state of Se in the spilled fly ash and to assess its potential for transformation and resultant chemical stability from its prolonged submersion in the river and subsequent dredging. Sequential chemical extractions suggested that the river environment shifted Se distribution toward organic/sulfide species. Speciation studies by bulk XANES analysis on fly ash samples showed that a substantial portion of the Se in the original ash pile had transformed from inorganic selenite to a mixture of Se sulfide and reduced (organo)selenium (Se(-II)) species over the 6-month period. μ-XRF mapping data showed that significant trends in the co-location of Se domains with sulfur and ash heavy metals. Ten-d extended elutriate tests (EETs) that were bubbled continuously with atmospheric air to simulate worst-case oxidizing conditions during dredging showed no discernible change in the speciation of fly ash selenium. The enhanced stability of the organo- and sulfide-selenium species coincided with the mixture of the ash material with humic materials in the river, corresponding with notable shifts in the ash carbon- and nitrogen-functionality. © 2013