Rock-avalanche dynamics: insights from granular physics experiments

Rock avalanches are known to behave in extraordinary ways unlike other landslides, and their deposits in part reflect their unusual physical behavior. Recent experiments in granular physics suggest that many phenomena and features simply reflect the non-linear nature of granular flows, although some behavior cannot simply be reproduced in lab scale experiments. In a static configuration, grain–grain contact networks dominate the distribution of forces and stresses within a granular mass. During flow, granular collisions damp the system through energy dissipation, while gravitational potential drives the system. The energy distribution between static and collisional stresses within the system can change very rapidly. Threshold events dominate system response, and the challenge is to find which characterization of the static phase helps to predict failure (and thus flow) resistance. Once flowing, many “unusual” rock-avalanche phenomena are entirely consistent with the physics of flow of large granular masses, but the low energy dissipation rate required for long run-out events requires the presence of physical processes that are not involved in experimental flows in the current parameter range or in the assumptions of current models.     

Two-phase evolution of the Shadow Valley Basin, south-eastern California: a possible record of footwall uplift during extensional detachment faulting

Miocene strata of the Shadow Valley Basin rest unconformably on the upper plate of the Kingston Range - Halloran Hills detachment fault system in the eastern Mojave desert, California. Basin development occurred in two broad phases that we interpret as a response to changes in footwall geometry. In southern portions of the basin, south of the Kingston Range, phase one began with near synchronous initiation of detachment faulting, volcanism and basin sedimentation shortly after 13.4 Ma. Between c. 13.4 and c. 10 Ma, concordantly bedded phase one strata were deposited onto the subsiding hangingwall of the detachment fault as it was translated 5–9 km south-westward with only limited internal deformation. Phase two (c. 10 to 8–5 Ma) is marked by extensional dismemberment of the detachment fault's upper plate along predominantly west-dipping normal faults. Phase two sediments were deposited synchronously with upper-plate normal faulting and unconformably overlie phase one deposits, displaying progressive shallowing in dip and intraformational onlap. Northern portions of the basin, in the Kingston Range, experienced a similar two-phase development compressed into a shorter interval of time. Here, phase one occurred between c. 13.4 and 12.8–12.5 (?) Ma, whereas phase two probably lasted for no more than a few 100000 years immediately prior to c. 12.4 Ma. Differences in the duration of basin development in and south of the Kingston Range apparently relate to position with respect to the detachment fault's breakaway; northern basin exposures overlie the upper plate adjacent to the breakaway (0–15 km) whereas southern basin exposures occur far from the breakaway (20–40 km). We interpret the phase one to phase two transition as recording breakup of the detachment fault's hangingwall during footwall uplift. We propose a model for supradetachment basin evolution in which early, concordantly bedded basin strata are deposited on the hangingwall as it translates intact above a weakly deforming footwall. With continuing extension, tectonic denudation along the detachment fault leads to an increasing flexural isostatic footwall response. We suggest that isostatic footwall uplift may drive internal breakup of the upper plate as the detachment fault is rotated to a shallow dip, mechanically unfavourable for simple upper-plate translation. Additionally, we argue that continuing hangingwall thinning during phase two places geometrical constraints on the timing, amount and, thus, rate of footwall uplift. Kinematically determined footwall uplift rates (0.5–4.5 mm/yr) are comparable with rates determined independently by thermochronological and geobarometric methods.     

Thermal Drying and Alkaline Treatment of Biosolids: Effects on Nitrogen Mineralization

Biosolids from the Cañeveralejo WWTP were dehydrated by filter press and then applied two processes to reduce pathogens (PRP): thermally dried biosolid (TDB) and alkalinized biosolid (AB). Untreated, dehydrated biosolid (DB) was used as a control. We evaluated the impact of thermal drying and alkaline treatments on nitrogen mineralization in these substrates. Moreover, agronomic rates for biosolid applications to sugarcane were estimated for each of the treatments leading to application rates of 35.8, 36.4, and 54.5 t/ha for DB, TDB, and AB, respectively, to meet the nitrogen requirement (200 kg N/ha) for sugarcane cultivation (Saccharum officinarum). The results showed that the biosolid rates used increased the mineral nitrogen content of soils by an average of 93.8 and 439.8 mg/kg for all biosolids and the PRP (thermal drying and alkaline treatment) in biosolids had significant effects on mineralization rate, showing better results for the TDBs.     

Removal of Chromium from Synthetic Effluent using Nymphaea rubra

In the present work, biosorption of Cr(VI) by Nymphaea rubra was investigated in batch studies. Batch experiments were conducted to study the effect of initial sorbent dosage, solution pH and initial Cr(VI) concentration. The results showed that the equilibrium uptake capacity was increased with decrease in biomass dosage. The Cr(VI) removal was influenced by the initial chromium compound concentration. Langmuir and Freundlich adsorption isotherm models were used to represent the equilibrium data. The Freundlich isotherm model was fitted very well with the equilibrium data when compared to Langmuir isotherm model. The sorption results were analyzed for pseudo‐first order and pseudo‐second order kinetic model. It was observed that the kinetic data fitted very well with the pseudo‐second order rate equation when compared to the pseudo‐first order rate equation. Fourier transform infrared spectrum showed the presence of different functional groups in the biomass. The surface morphology of the sorbent was exemplified by SEM analysis. Aquatic weeds seem to be a promising biosorbent for the removal of chromium ions from water environment. This paper reports the research findings of a laboratory‐based study on the removal of Cr(VI) from the synthetic solution using the dried stem of N. rubra as a biosorbent.     

Dust ion-acoustic shock waves in nonextensive dusty plasma

A parametric survey on the propagation characteristics of the dust ion-acoustic (DIA) shock waves showing the effect of nonextesivity with nonextensive electrons in a dissipative dusty plasma system has been carried out using the reductive perturbation technique. We have considered continuity and momentum equations for inertial ions, q-distributed nonextensive electrons, and stationary charged dust grains, to derive the Burgers equation. It has been found that the basic features of DIA shock waves are significantly modified by the effects of electron nonextensivity and ion kinematic viscosity. Depending on the degree of nonextensivity of electrons, the dust ion-acoustic shock structures exhibit compression and rarefaction. The implications of our results would be useful to understand some astrophysical and cosmological scenarios like stellar polytropes, hadronic matter and quark-gluon plasma, protoneutron stars, dark-matter halos, etc., where effects of nonextensivity can play the significant roles.     

Nonlinear propagation of dust-acoustic waves in a magnetized nonextensive dusty plasma

A theoretical investigation has been made of obliquely propagating dust-acoustic solitary waves in a magnetized three-component dusty plasma, which consists of a negatively charged dust fluid, ions, and nonextensive electrons. The reductive perturbation method has been employed to derive the Korteweg-de Vries equation which admits a solitary wave solution. It has been shown that the combined effects of external magnetic field (obliqueness), ions, and electron nonextensivity change the behavior of these electrostatic solitary structures that have been found to exist with positive and negative potential in this dusty plasma model. The implications of our results in astrophysical and cosmological scenarios like vicinity of the Moon, magnetospheres of Jupiter and Saturn, dark-matter halos, hadronic matter, quark-gluon plasma, protoneutron stars, stellar polytropes etc. have been mentioned.     

Disturbance,geomorphic processes and recovery of wildfire slopes in North Tyrol

Wildfires in the sub‐alpine belt of the Austrian Limestone Alps sometimes cause severe vegetation and soil destruction with increased danger of secondary natural hazards such as avalanches and debris flows. Some of the affected areas remain degraded to rocky slopes even decades after the fire, raising the question as to whether the ecosystems will ever be able to recover. The mean fire interval, the duration of recovery and the role of geomorphic processes for vegetation regeneration are so far unknown. These questions were tackled in a broad research approach including investigation of historical archives to determine the frequency of historical wildfires, mapping vegetation regeneration on 20 slopes of different post‐fire ages, and soil erosion measurements on two slopes. To date, > 450 historical wildfires have been located in the study area. The mean fire interval per square kilometre is c. 750 years, but can be as low as 200–500 years on south‐facing slopes. Vegetation regeneration takes an extremely long time under unfavourable conditions; the typical window of disturbance is between 50 and 500 years, which is far longer than in any other wildfire study known to us. Soil erosion constantly increases in the years after the fires and the elevated intensity can be maintained for decades. A two‐part vegetation regeneration model is proposed depending upon the degree of soil loss. In the case of moderate soil erosion, spreading grassland communities can slow down shrub re‐colonization. In contrast, after severe soil destruction the slopes may remain degraded for a century or longer, before rather rapid regeneration occurs. The reasons are not fully understood but are probably governed by geomorphic process intensity. The interdependence of vegetation regeneration and geomorphic processes is a paradigm of ecology–geomorphology interaction, and is a unique example of a very long‐lasting disturbance response caused by wildfire in a non‐resilient ecosystem. Copyright © 2012 John Wiley & Sons, Ltd.     

An overview of geological originated materials as a trend for adsorption in wastewater treatment

Adsorption is a unit operation widely used for the tertiary treatment of the most diverse effluents,whose mechanism is based on removing recalcitrant compounds from the organic and inorganic origin.In this process,choosing a suitable adsorbent is a fundamental point.This review article focuses on the adsorbents with natural geological origin:minerals,clays,geopolymers,and even wastes resulted from mining activity.Therefore,over 450 articles and research papers were explored.These materials’main sources are described,and their characteristics,composition,and intrinsic properties are related to adsorption.Herein,we discuss the effects of several process parameters,such as p H,temperature,pollutant,and adsorbent concentration.Furthermore,equilibrium,kinetics,and thermodynamic aspects are also addressed,and relevant regeneration prospects and final disposal.Finally,some suggestions and perspectives on applying these adsorbents in wastewater treatment are presented as future trends.     

Polycyclic aromatic hydrocarbons (PAHs) associated with atmospheric particles in Higashi Hiroshima, Japan: Influence of meteorological conditions and seasonal variations

This work studied the influence of meteorological conditions on particulate polycyclic aromatic hydrocarbons (PAHs) in the atmosphere of Higashi Hiroshima, Japan. The seasonal variation of particulate PAHs was also covered. It was found that ambient temperature, solar intensity and weekly rainfall had significant influence on the particulate PAH concentration based on correlation studies. Correlation of particulate PAHs with ambient temperature, solar intensity, weekly rainfall, wind speed and humidity was studied by using Pearson correlation analysis. Particulate PAHs had a strong negative correlation with ambient temperature and solar intensity. A moderate negative correlation with weekly rainfall was also observed. There was no significant correlation between particulate PAHs with wind speed as well as humidity. Besides, particulate PAHs were found to have significant positive correlation with sulfur dioxide and nitrogen dioxide while having a moderate negative correlation with ozone. The particulate PAHs in Higashi Hiroshima exerted distinct seasonal variation with a higher concentration in winter and lower concentration in summer. When compared among PAHs with different numbers of aromatic rings; 5-ring PAHs was found to exert the most distinct seasonal variation. The contribution of carcinogenic PAHs to total particulate PAH concentration was fairly constant at about 50% throughout the year.