How does anisotropy in bedrock river granitic outcrops influence pothole genesis and development?          下载免费PDF全文

Jose Ortega‐Becerril  Miguel Gomez‐Heras  Rafael Fort  Ellen Wohl 《地球表面变化过程与地形》2017,42(6):956-968

Pothole formation and development may be influenced by joint sets and other heterogeneities within bedrock, as well as by hydraulics. Previous research indicates that most potholes found in rivers of the mountainous Spanish Central System exhibit preferred orientations associated with dominant joints and correlate more strongly with variations in substrate resistance than with hydraulics. Weathering and erosion weaken rock surfaces, which leads to decreased mechanical resistance. We start from the hypothesis that different mechanisms of pothole formation may create around the pothole a distinctive signature in terms of ultrasound pulse velocity and surface hardness. We develop a conceptual model and test it using potholes for which we know the mechanism of formation, demonstrating that the spatial and statistical distributions of dynamical mechanical properties and surface hardness of a pothole may provide insight into its genesis. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

A coupled ozonation–electrooxidation treatment for removal of bisphenol A,nonylphenol and triclosan from wastewater sludge     

C. de Leon-Condes  C. Barrera-Díaz  J. Barrios  E. Becerril  H. Reyes-Pérez 《International Journal of Environmental Science and Technology》2017,14(4):707-716

Organic emerging micropollutants are persistent during the biological process used in treatment plants and have the tendency to accumulate in the sludge. Since a common method of final sludge disposal is the land application, there are potential risks associated with the presence of contaminants within the sludge. In this work, the removal efficiency of endocrine-disrupting chemicals, namely bisphenol A, nonylphenol and triclosan from sludge was investigated using ozonation and electrooxidation using boron-doped diamond electrodes. Both procedures were studied to determine the optimal conditions (pH, current density and ozone flow) for removing these chemicals in an hour. With the obtained conditions, a coupled system ozonation–electrooxidation was used with the goal to have better pollutant elimination. Results indicate that these compounds could be effectively removed by the coupled system; the diminutions were Bisphenol A 86%, nonylphenol 68% and triclosan 67%. Also improvements in the quality of aqueous phase were obtained, and for instance, the chemical oxygen demand, color and turbidity, were abated in 62, 61 and 66%, respectively. Moreover, an additional advantage of the coupled system is the absence of any secondary pollution.  相似文献   

Explosive felsic volcanism on El Hierro (Canary Islands)     

Dario Pedrazzi  Laura Becerril  Joan Martí  Stavros Meletlidis  Inés Galindo 《Bulletin of Volcanology》2014,76(10):1-19

The Canary Islands consist of seven basaltic shield volcanoes whose submerged portion is much more voluminous than the subaerial part of each island. Like so many other volcanic oceanic islands, the indicative deposits of explosive felsic volcanism are not a common feature on the Canary archipelago. Hitherto, they have only been documented from the central islands of Gran Canaria and Tenerife, which are the largest volcanic complexes of the islands. On the other Canary Islands, the presence of felsic rocks is mostly restricted to intrusions and a few lava flows, generally within the succession in the oldest parts of individual islands. In this paper, we present a detailed stratigraphic, lithological and sedimentological study of a significant felsic pumice deposit on the island of El Hierro, referred here as the Malpaso Member, which represents the only explosive episode of felsic volcanism found on the Canary Islands (outside of Gran Canaria and Tenerife). The products of the eruption indicate a single eruptive event and cover an area of about 15 km². This work provides a detailed stratigraphic and chronological framework for El Hierro, and four subunits are identified within the member on the basis of lithological and granulometric characteristics. The results of this study demonstrate the importance of an explosive eruption in a setting where the activity is typified by effusive basaltic events. Given the style and the spatial distribution of the Malpaso eruption and its products, a future event with similar characteristics could have a serious impact on the population, infrastructure and economy of the island of El Hierro.  相似文献