Discussion of (anisotropic hydraulic conductivity and critical hydraulic gradient of a crushed sandstone–mudstone particle mixture)

A discussion is presented here to the work of Wang and Qiu including some notes about the analysis and the correlations of the results. First, we show that there is no clear relationship between the critical hydraulic gradient and the uniformity coefficient. Also we show that the internal erosion mechanism of soils with bimodal structure is different from that for soils with no bimodal structure. Finally, we emphasis that the anisotropy in the hydraulic conductivity is not related to the uneven compaction only but also to the particle arrangements and connectivity between pores.     

Removal of selenium from contaminated agricultural drainage water by nanofiltration membranes

Seleniferous agricultural drainage wastewater has become a new major source of pollution in the world. In the USA, large areas of farmland in 17 western states, generate contaminated salinized drainage with Se concentrations much higher than 5 μg/I, the US Environmental Protection Agency water-quality criterion for the protection of aquatic life; Se values locally reach 4200 wg/1 in western San Joaquin Valley, California. Wetland habitats receiving this drainage have generally shown Se toxicosis in aquatic birds causing high rates of embryonic deformity and mortality, or have indicated potential ecological damage.Results of our laboratory flow experiments indicate that nanofiltration, the latest membrane separation technology, can selectively remove > 95% of Se and other multivalent anions from > 90% of highly contaminated water from the San Joaquin Valley, California. Such membranes yield greater water output and require lower pressures and less pretreatment, and therefore, are more cost effective than traditional reverse osmosis membranes. Nanofiltration membranes offer a potential breakthrough for the management of Se contaminated wastes not only from agricultural drainage, but from other sources also.     

Hydrocarbon Generation Potential of the Organic-Rich Naifa Formation,Say’un–Masila Rift Basin,Yemen: Insights from Geochemical and Palynofacies Analyses

Natural Resources Research - The Say’un–Masila rift, one of the most important basins of Yemen, contains unconventional resources of organic-rich rocks. In the present work, geochemical...     

A Comparative Quantitative Study of an Omani Soil Using X-Ray Diffraction Technique

Two methods for the quantification of clay minerals using X-ray diffraction techniques: the Constant Mineral Standards Method and the Constant Clay Method were applied to soil samples from Al-Khod (Northern Oman). The first method was based on the addition of different concentrations of clay to constant mineral standards while the latter was based on the additions of known internal standards to the clay sample. The clay investigated in this study contained montmorillonite, palygorskite, illite and kaolinite. The areas of the reflection peaks were found to relate linearly with additions of different proportions of clay or mineral standards. Using the two methods, the concentrations of the different components and their experimental errors were determined. From the errors and self consistency of the results obtained, and the practicality of sample preparation, it is proposed to use the Constant Mineral Standards Method.     

The potential of spectral mixture analysis to improve the estimation accuracy of tropical forest biomass

A main limitation of pixel-based vegetation indices or reflectance values for estimating above-ground biomass is that they do not consider the mixed spectral components on the earth's surface covered by a pixel. In this research, we decomposed mixed reflectance in each pixel before developing models to achieve higher accuracy in above-ground biomass estimation. Spectral mixture analysis was applied to decompose the mixed spectral components of Landsat-7 ETM+ imagery into fractional images. Afterwards, regression models were developed by integrating training data and fraction images. The results showed that the spectral mixture analysis improved the accuracy of biomass estimation of Dipterocarp forests. When applied to the independent validation data set, the model based on the vegetation fraction reduced 5–16% the root mean square error compared to the models using a single band 4 or 5, multiple bands 4, 5, 7 and all non-thermal bands of Landsat ETM+.     

Verifying Indigenous based-claims to forest rights using image interpretation and spatial analysis: a case study in Gunung Lumut Protection Forest,East Kalimantan,Indonesia

GeoJournal - The decision of Indonesian’s constitutional court in May 2013, to review Law Number 41/1999 on Forestry, marked a significant step forward in Indonesian policy related to...     

A plasticity model for the mechanical behaviour of anisotropically consolidated clay

An incremental plasticity theory has been developed to describe the mechanical behaviour of anisotropically consolidated clays. The theory removes some of the shortcomings of the existing critical state models by incorporating the effects of the initial anisotropy due to a known depositional stress history and its subsequent alteration during further plastic deformation under a general stress system. From the extensive comparisons with the reported results in the literature, it is established that the model is satisfactory in predicting the various aspects of drained as well as undrained behaviour of K₀-consolidated clays.     

Simultaneous flow of water and solutes through geological membranes—I. Experimental investigation

The relative retardation by geological membranes of cations and anions generally present in subsurface waters was investigated using a high pressure and high temperature ‘filtration cell’. The solutions were forced through different clays and a disaggregated shale subjected to compaction pressures up to 9500 psi and to temperatures from 20 to 70°C.The overall efficiences measured increased with increase of exchange capacity of the material used and with decrease in concentration of the input solution. The efficiency of a given membrane increased with increasing compaction pressure but decreased slightly at higher temperatures for solutions of the same ionic concentration.The results further show that geological membranes are specific for different dissolved species. The retardation sequences varied depending on the material used and on experimental conditions. The sequences for monovalent and divalent cations at laboratory temperatures were generally as follows: Li < Na < NH₃ < K < Rb < Cs Mg < Ca < Sr < Ba.The sequences for anions at room temperature were variable, but at 70°C, the sequence was: HCO₃ < I < B < SO₄ < Cl < Br.Monovalent cations contrary to some field data were generally retarded with respect to divalent cations. The differences in the filtration ratios among the divalent cations were smaller than those between the monovalent cations. The passage rate of B, HCO₃, I and NH₃ was greatly increased at 70°C.     

An overview of phosphate rocks and their mining impact on groundwater,Eastern Desert,Egypt

The Eastern Desert of Egypt represents a remote arid area which is scarce in water resources. The area is characterized by many mining sites to exploit the phosphate deposits; thus, these activities can generate groundwater contaminants. The main objective of the present study is discussing the effect of the mining activities and phosphate bearing rocks on groundwater. The obtained results pointed out that the water bearing formations can be distinguished as Quaternary alluvial, Oligocene sandstone, Campanian phosphate limestone (Duwi Formation), and Precambrian basement rocks. Some of the investigated groundwater shows relatively high concentrations of trace elements compared to other samples, such as Pb, Zn, Cu, Cr, Ni, and Sr. This is consistent with the analyses of phosphate rocks which are also enriched in the same trace elements. The high groundwater salinity is due to evaporation, limited re-charge, and leaching of salts in rocks. The results of speciation modeling reveal that majority of groundwater samples are supersaturated with calcite, aragonite, and dolomite, and some samples are also at equilibrium or supersaturated with hydroxyapatite. The groundwater quality in the study area evaluated for human drinking, livestock and poultry domestic, and industrial purposes is not suitable in most wells. It is obvious that the groundwater contamination occurs when drilling wells penetrate the phosphate bearing beds and not only at mining activity sites. Therefore, it is recommended to avoid any groundwater exploration from the Duwi Formation and also select the drilling sites outside the mining areas.