Ascribing soil erosion types for sediment yield using composite fingerprinting technique

Abstract

Soil erosion and eroded sediment are serious threats to sound land management. However, less attention has been given to quantifying the importance of different soil erosion features based on appropriate control measures that could be designated. Accordingly, this research was planned to quantify the contribution of potential sediment sources, i.e. sheet, rill and gully erosion, in Idelo watershed in Zanjan Province, Iran, using composite fingerprinting. Toward this aim, 16 geochemical and organic tracers were detected in sediment sources and sediment deposited at the outlet. The results of applying the composite fingerprinting technique, with a relative error of 16%, showed that sheet, rill and gully sources contributed 56%, 44% and 0%, respectively, to sediment yield. It was also apparent from the results that the composite fingerprinting approach could be successfully utilized to assess the provenance of sediment deposited at the main outlet of the study watershed by soil erosion type.

Editor Z.W. Kundzewicz     

Removal of Hydrogen Sulfide by Physico‐Biological Filter Using Mixed Rice Husk Silica and Dried Activated Sludge

This study investigated the effectiveness of a new packing material, namely mixed rice husk silica with dried activated sludge for removing H₂S. Dried sewage sludge was collected from Putrajaya sewage treatment plant in Malaysia. Rice husk silica was prepared at temperature of 800°C, after acid leaching and mixed with dried sewage sludge to be utilized in a polyvinyl chloride filter. The system was operated under variable conditions of two parameters, different inlet gas concentration and different inlet flow rate. H₂S was passed through the filter with one liter of the packing material. More than 99.96% removal efficiency (RE) with empty bed residence time (EBRT) of 90–45 s and 300 ppm inlet concentration was observed. However, the RE decreased to 96.87% with the EBRT of 30 s. The maximum elimination capacity (EC) of 52.32 g/m³/h was obtained with the RE of 96.87% and H₂S mass loading rate of 54 g/m³/h, while at the RE of 99.96%, maximum EC was 26.99 g/m³/h with the H₂S mass‐loading rate of 27 g/m³/h. A strong significant correlation between increasing of H₂S mass loading rate and pressure drop was also detected (p < 0.01). Maximum pressure drop was 3.0 mm H₂O after 53 days of operating time, the EBRT of 30 s, and 54 g/m³/h of H₂S loading rate. These observations suggest that the mixture of rice husk silica with dried activated sludge is a suitable physico‐biological filter for H₂S removal.     

Magnetic Removal of Reactive Black 5 from Wastewater Using Ionic Liquid Grafted‐Magnetic Nanoparticles

Due to the unique chemical properties and therefore wide range of applications, significant amounts of reactive dyes often end up in waste waters and this issue raises the need for more efficient treatment technologies. This work investigates the ability of magnetite nanoparticles functionalized with imidazolium based ionic liquid (IL) as an efficient sorbent for the removal of the Reactive black 5 from wastewater. Fourier transform infrared spectroscopy, X‐ray diffraction, transmission electron microscopy, thermo‐gravimetric analysis, and zeta potential measurement were used to characterize the synthesized nanosorbent. The results showed that under optimal conditions, the dye removal efficiency of the grafted IL is 98.5% after a single run. Regeneration of the used sorbent could be possible and the modified magnetic nanoparticles exhibited good reusability. The isothermal data of RB5 sorption conformed well to the Langmuir model and the maximum sorption capacity of IL@Fe₃O₄ for RB5 was 161.29 mg g^?1. Thermodynamic study indicated that the adsorption is endothermic and spontaneous. The use of such a system can provide fast and efficient removal of the reactive dyes from wastewater by using an external magnetic field.     

Identifying geological hazards related to tunneling in carbonate karstic rocks - Zagros, Iran

The construction of tunnels in carbonate karstic rocks has always been the most hazardous and problematic task in civil and mining engineering, as it can threaten tunneling project from safety, time and economic aspects. Therefore, it is essential to identify hazards resulting from construction in early stages of a project. The present paper is aimed to identify main geological hazards related to tunneling in carbonate karstic rocks in the Zagros Mountains. The process of identification relies upon a review of construction experiences obtained from several projects with a focus on the Kuhrang Tunnels. Obviously, groundwater inrush and tunnel flooding, ground inflow and fill-back of the tunnel, instability of weak fill materials, and TBM jamming are the main potential hazards of tunneling in the Zagros Mountains, imposing huge problems during construction. Inadequate understanding of hazards and not being prepared enough to take appropriate countermeasures are the main sources of the problems. In addition, the investigation of the present study provides guidelines to reduce the risks of tunneling in the carbonate karstic rocks with similar geological condition.     

Influence of climate, mineralogy and mineral processing on the weathering behaviour within two, low-sulfide, high-carbonate, gold mine tailings in the Eastern Desert of Egypt

Despite its importance within environmental management strategies, little concern is shown to sulfide oxidation and/or hardpan formation at neutral pH where dry condition prevails. Two gold mine tailings in Egypt, El Sid and Barramiya, were studied for their geochemical/mineralogical properties, and climate influence on hardpan formation. The tailings are characterised by homogeneous silt-sized sediments (>42%), have high carbonate, predominantly as calcite for El Sid and dolomite-ankerite for Barramiya, and low-sulfide contents, chiefly as pyrite, galena and sphalerite for El Sid, and arsenopyrite–pyrite for Barramiya. El Sid is characterised by high average concentrations of Pb (2,758 mg/Kg) and Zn (2,314 mg/Kg), its lower part dominated by mafics, overlaid by granitoids. Barramiya has higher As (average 2,836 mg/Kg) content and represents a mixture of mica-schists/mafics-ultramafics. During field investigations, no hardpans were identified, only bassanite and gypsum were found at the surface of El Sid tailings, forming thin layers and desiccation crack fillings. Column experiments showed a thin crust consisting of gypsum, halite and sodium sulfate formed at the top of the column of El Sid tailings after 2 weeks, this was not recognized in the column from Barramiya. The homogenous thickened tailings deposition in both areas did not favour hardpan formation, since the critical amounts of reacting sulfides were never achieved in individual lamina, due to missing mineral/grain size fractionation. The high-temperature/low-water availability, characteristic for desert climate regions did not allow significant sulfides oxidation. Therefore, both tailings will suffer from continuous erosion and spreading out of contaminants to the environment for a prolonged period of time by sporadic flash floods.     

Problematic Soft Soil Improvement with Both Polypropylene Fiber and Polyvinyl Acetate Resin

Several methods are used to improve mechanical properties of loose soils including rewetting, soil replacement, compaction control, chemical additives, moisture control, thermal methods, and more recently, discrete fibers. All the methods are applied to soft soil to increase load bearing capacity and to improve other properties such as prevention of erosion and dust generation. In the present study, a new method of soil improvement using both discrete polypropylene (PP) fibers and polyvinyl acetate (PVAc) is introduced. The method is applied to improve load bearing capacity of a problematic sandy soil in both dry and saturated states. Based on the results from CBR tests on various specimens, it has been revealed that the combination of PP fiber and PVAc resin with weight percentages of 0.1 and 0.6 %, respectively, had the optimum effect in increasing the CBR value in both saturated and dry soil specimens. It should be mentioned that this method has caused a great increase in the CBR value in the saturated soil.     

Turbulence-particle interactions under surface gravity waves

The dispersion and transport of single inertial particles through an oscillatory turbulent aquatic environment are examined numerically by a Lagrangian particle tracking model using a series of idealised test cases. The turbulent mixing is incorporated into the Lagrangian model by the means of a stochastic scheme in which the inhomogeneous turbulent quantities are governed by a one-dimensional k- ε turbulence closure scheme. This vertical mixing model is further modified to include the effects of surface gravity waves including Coriolis-Stokes forcing, wave breaking, and Langmuir circulations. To simplify the complex interactions between the deterministic and the stochastic phases of flow, we assume a time-invariant turbulent flow field and exclude the hydrodynamic biases due to the effects of ambient mean current. The numerical results show that the inertial particles acquire perturbed oscillations traced out as time-varying sinking/rising orbits in the vicinity of the sea surface under linear and cnoidal waves and acquire a non-looping single arc superimposed with the high-frequency fluctuations beneath the nonlinear solitary waves. Furthermore, we briefly summarise some recipes through the course of this paper on the implementation of the stochastic particle tracking models to realistically describe the drift and suspension of inertial particles throughout the water column.     

Contribution of tuned liquid column gas dampers to the performance of offshore wind turbines under wind,wave, and seismic excitations

The main intention of the present study is to reduce wind, wave, and seismic induced vibrations of jackettype offshore wind turbines (JOWTs) through a newly developed vibration absorber, called tuned liquid column gas damper (TLCGD). Using a Simulink-based model, an analytical model is developed to simulate global behavior of JOWTs under different dynamic excitations. The study is followed by a parametric study to explore efficiency of the TLCGD in terms of nacelle acceleration reduction under wind, wave, and earthquake loads. Study results indicate that optimum frequency of the TLCGD is rather insensitive to excitation type. In addition, while the gain in vibration control from TLCGDs with higher mass ratios is generally more pronounced, heavy TLCGDs are more sensitive to their tuned frequency such that ill-regulated TLCGD with high mass ratio can lead to destructive results. It is revealed that a well regulated TLCGD has noticeable contribution to the dynamic response of the JOWT under any excitation.