Long-lasting floods buffer the thermal regime of the Pampas

The presence of large water masses influences the thermal regime of nearby land shaping the local climate of coastal areas by the ocean or large continental lakes. Large surface water bodies have an ephemeral nature in the vast sedimentary plains of the Pampas (Argentina) where non-flooded periods alternate with flooding cycles covering up to one third of the landscape for several months. Based on temperature records from 17 sites located 1 to 700 km away from the Atlantic coast and MODIS land surface temperature data, we explore the effects of floods on diurnal and seasonal thermal ranges as well as temperature extremes. In non-flooded periods, there is a linear increase of mean diurnal thermal range (DTR) from the coast towards the interior of the region (DTR increasing from 10 to 16 K, 0.79 K/100 km, r ² = 0.81). This relationship weakens during flood episodes when the DTR of flood-prone inland locations shows a decline of 2 to 4 K, depending on surface water coverage in the surrounding area. DTR even approaches typical coastal values 500 km away from the ocean in the most flooded location that we studied during the three flooding cycles recorded in the study period. Frosts-free periods, a key driver of the phenology of both natural and cultivated ecosystems, are extended by up to 55 days during floods, most likely as a result of enhanced ground heat storage across the landscape (~2.7 fold change in day-night heat transfer) combined with other effects on the surface energy balance such as greater night evaporation rates. The reduced thermal range and longer frost-free periods affect plant growth development and may offer an opportunity for longer crop growing periods, which may not only contribute to partially compensating for regional production losses caused by floods, but also open avenues for flood mitigation through higher plant evapotranspirative water losses.     

Recent effects of tidal and hydro‐meteorological changes on coastal plains near the mouth of the Amazon River

The goal of this work was to understand the main hydrodynamic processes acting on tidal flats of the coast of Amapá near the mouth of the Amazon River, and how they change over the short term (~ 20 years). The analysis of morphological and geobotanical units was carried out by applying processing and interpretation methods to optical and synthetic aperture radar (SAR) images, combined with data on water salinity, maximum flood height, sedimentary facies data, rainfall and river discharge. The temporal analysis of morphological and geobotanical units suggests the relative stabilization of savannah, ‘várzea’ and mangrove areas during the drier period and increasing tidal amplitude between 1987 to 1997. The wetter period and decreasing tidal amplitude between 1997 to 2008 led to an increase in the area of ‘várzea’ and lakes over savannah, and the expansion of mangroves mainly over the inundated field and tidal mud/mixed flats. Therefore, the decrease in rainfall index during the drier period is well‐correlated with the reduction of the Calçoene River discharge and jointly with increasing tidal amplitude favored the increase of migration rate of the mud bank and erosion profile along the littoral. It was followed by the increase of the Calçoene River discharge and jointly with decreasing tidal amplitude during the wetter period, favoring the development of mangroves on muddy substrates near the coastline. Copyright © 2013 John Wiley & Sons, Ltd.     

Morphological Variation of the Sea Silverside Odontesthes regia in Regions with Dissimilar Upwelling Intensity along the Humboldt Current System

Ocean Science Journal - We evaluated the influence of areas with dissimilar upwelling intensity along the Humboldt Current System on the morphological variation of the economically important sea...     

A parsimonious crop-water productivity index: an application to Brazil

Reducing poverty in rural areas of developing countries requires sustained and sustainable increases in agricultural water productivity. However, aside from traditional measures of precipitation, little is known about water available to farmers or how productively they use it. We present a crop-water productivity index (a ratio of the value of annual crop production to a dimensionless potential water availability index) for large water basins using readily available low-resolution data. The index is transferable, permits direct inter-basin comparisons, and is simple to calculate. We calculate the index for each municipality in the São Francisco river basin in Brazil. No clear patterns linking water availability and value of agricultural output are evident, even though clusters of municípios with high- and low-crop-water productivity emerge, and the former may be useful in guiding policies aimed at increasing water productivity. Finally, analyses of the effects of information uncertainty on the crop-water productivity index suggest that the returns to agricultural investments in certain places in the São Francisco river basin are more risky than others. Improvements in data quality and quantity can help refine estimates of the index and reduce their uncertainty.     

Race,Space, and Struggles for Mobility: Transportation Impacts on African Americans in Oakland and the East Bay

Abstract

A long history of overt discrimination left an enduring racialized imprint upon the geography of the East Bay. While the benefits of a metropolitan decentralization of jobs, housing, and public investment fell to Whites, discrimination in employment and housing trapped African Americans in urban neighborhoods burdened by infrastructure encroachment and divestment. By circa 1970, overt discrimination succumbed to new, racially neutral, legal, and administrative forms, including regional planning processes. Using an environmental racism framework, we show that these new forms reproduced the existing racialized geography by means of new inequalities in representation and transportation service provision. These new regional transportation policies, like those challenged by a 2005 civil rights lawsuit, favored the mobility needs of more affluent suburbanites over those of African American East Bay bus riders. These policies, layered onto an existing racialized geography, reinforced existing inequalities by failing to address racial barriers to opportunity in the built environment. [Key words: transportation, race, segregation, Oakland]     

Confronting Power and Environmental Injustice: Legacy Pollution and the Timber Industry in Southern Mississippi

Research has documented how grass-roots activists deploy the environmental justice frame to convey their grievances and demand their right to health and safety. While scholars have highlighted the widespread success of this frame, little attention has been paid to instances where the environmental justice frame fails to resonate. Drawing from social movements and environmental justice literatures, we examine how local discursive and cultural contexts can pose barriers to environmental justice claims. Our case is based on legacy pollution from a decommissioned creosote facility in Southern Mississippi. When black residents discovered the pollution in their neighborhood, they made repeated appeals to authorities for remediation and compensation. After being denied inclusion in a lawsuit filed by white residents, they formed an environmental justice organization to mobilize support for their campaign. Findings reveal the importance of both historical contextualization and the social situation of frame deployers in analyses of the environmental justice frame.     

Deep conductivity structure beneath the northern Brasília belt,central Brazil: Evidence for a Neoproterozoic arc-continent collision

The Brasília belt, in central Brazil, experienced a broad range of tectonic events, including several periods of compressional and extensional deformations during the Proterozoic. Magnetotelluric data were collected at 27 sites along a profile crossing the northern part of the belt. Strike analysis and distortion decomposition indicated that most of the data are two-dimensional (2D) and fit a regional geoelectric strike angle of N20E, parallel to the tectonic grain. 2D conductivity model is constrained by available gravity and seismic refraction data and reveals the cumulative effects of the multiple tectonomagmatic episodes that affected the area in the past on current crustal and upper mantle structure. The results show that the resistive lithospheric root of the São Francisco cratonic plate is restricted to the easternmost part of the profile and does not extend westward beneath the Brasília belt. The external zone of the fold belt, composed of slightly metamorphosed rocks at the surface, presents crustal conductors that can be tentatively interpreted as regions with fossil fluid flows at mid-crust depth beneath a gold mineralization zone and as a very shallow mineralized zone within the metamorphic rocks. The external zone is separated to the west from the Goiás massif by a strong conductivity contrast, indicative of a suture zone along the Rio Maranhão fault system. Crustal conductivity structure under the Niquelândia complex is distinct from what is observed in other parts of the Goiás massif, in agreement with the proposal of the complex being an allochthonous block. In spite of the large tectonothermal events that affected the Goiás magmatic arc there are no significant conductive anomalies at crustal depths in its eastern side. The most prominent feature detected in the geoelectric model is a huge high conductivity anomaly below the entire Goiás massif in the central part of the belt, mainly concentrated at the uppermost mantle but also affecting mid to lower crustal depths. It can be interpreted as associated with thermal events either related to Mesoproterozoic and/or Neoproterozoic continental rifting processes or to delamination and detachment processes at the end of the evolution of the belt, in the Neoproterozoic. Effects related to oceanic lithosphere subduction during the collision and accretion of the Goiás massif and Goiás magmatic arc to the western passive margin of the São Francisco cratonic plate in the Neoproterozoic may alternatively explain the anomaly.     

Changes in the structural and magnetic properties of Ni–substituted hematite prepared from metal oxinates

Samples prepared by the novel method based on the thermal decomposition at 700 °C in air of mixed Fe and Ni oxinates were characterized by thermogravimetric analysis, X-ray diffraction, magnetization measurements, and variable-temperature Mössbauer spectroscopy. It is found that the combustion treatment produces Ni-hematite and trevorite, the fraction of the latter increasing with the increment of Ni in the metal oxinates. Results indicate that the substitution of Ni²⁺ for Fe³⁺ in the hematite structure, which was found to be less than 5.3 mol%, is accompanied by the presence of oxygen and structural vacancy sites. Both the metal replacement and the presence of defects cause the a and c cell hematite parameters to decrease. The Néel temperature and the difference between the saturation fields for the antiferromagnetic AF and the weakly ferromagnetic WF phases are also found to decrease with nickel content. These effects are due to the fact that the magnetic behavior of hematite depends on the presence of Ni, vacancy sites, and lattice distortion. The large decrease in the Néel temperature with Ni doping suggests that structural vacancies are also present On the contrary, Ni incorporation does not appreciably affect the Morin temperature and the temperature range in which both AF and WF phases coexist. It is suggested that these effects are probably due to the differing effects that Ni and defects can produce on the magnetic dipolar and the single ion anisotropies.     

Probabilistic modelling of auto-correlation characteristics of heterogeneous slopes

Spatial variability of soil materials has long been recognised as an important factor influencing the reliability of geo-structures. This study stochastically investigates the influence of spatial variability of shear strength on the stability of heterogeneous slopes, focusing on the auto-correlation function, auto-correlation distance and cross-correlation between soil parameters. The finite element method is merged with the random field theory to probabilistically evaluate factor of safety and probability of failure via Monte-Carlo simulations. The simulation procedure is explained in detail with suggestions on improving efficiency of the Monte-Carlo process. A simple procedure to create cross-correlation between random variables, which allows direct comparison of the influence of each strength variable, is discussed. The results show that the auto-correlation distance and cross-correlation can significantly influence slope stability, while the choice of auto-correlation function only has a minor effect. An equation relating the probability of failure with the auto-correlation distance is suggested in light of the analyses performed in this work and other results from the literature.