Arabian Journal of Geosciences最新文献

In this paper, k-means algorithm has been used to disaggregate seismic parameters to evaluate their inter-correlations. A goal is to quantify in a disaggregated way the weights and effects of each parameter with respect to other ones. From the database, about 4900.0 data, divided into 22.0 categories, have been collected. The main divisions regard the wave components in horizontal and vertical axis and the soil characteristics. The studied seismic zone is the “Norpirenaica oriental,” placed in the Pyrenees area between Spain and France, classified as a very high seismic hazard. Numerical and analytical analyses have been carried out to implement the algorithm. Preliminary analyses and results would quantify the role of the sand horizontal stratigraphy, the non-linear effects, the elasticity of the soil, and the energy damping phenomenon. Curves are plotted in stochastic distributions and elastic spectra accelerations. Results show good prediction for vertical spectral accelerations and for far and relative strong events. Rigorously, results are valid only for the studied seismogenic zone under predefined constrictions and ranges.

Alkaline hydrolysate of chicken manure (HCM) containing artificially formed humic-like substances (HLSs) was investigated in combination with specially loaded cells (bacteria and microalgae) for oil degradation in soil. After 7 days in the laboratory experiment, the oil biodegradation efficiency in the polluted soil (50 g oil/kg soil) was 5–78% in 11 soil samples depending on the soil characteristics and used combination of additives. Higher level of oil-degradation corresponded to soil with high initial concentration of humic substances (HSs) (85–107 g/kg of dry matter). The best result in bioremediation (degradation of 82% of oil for 7 days) was achieved in experiment under field conditions with the similar initial oil pollution in the soil, when the HCM was used as additive (up to 220 mg HLSs/kg dry soil) in combination with an artificial symbionts composed of Rhodococcus erythropolis and Chlorella vulgaris cells. The introduction of HCM into oil-polluted soil with the mentioned cells led to an increase in all controlled enzymatic activities (peroxidase, dehydrogenase, phosphatase, protease, amylase, and urease) in the soil. The observed effects testified to activation of cell metabolic processes in the soil. As a result, the introduction of HCM in combination with artificial symbionts into the soil increased the rate of oil biodegradation under environmental conditions up to 1.8 times.

Graphical Abstract

This work investigates the soil stabilization impact of adding silica fume and phosphogypsum on the hydro-mechanical behavior of clayey sand. Laboratory tests were performed on natural soil samples containing 5%, 10%, 15%, and 20% of silica fume and 3%, 6%, 9%, and 12% of phosphogypsum by weight of dry soil. The tests included particle size distribution, compaction characteristics, liquid limit, plastic limit, direct shear test, and hydraulic conductivity. The addition of phosphogypsum from 3 to 6% by weight of dry soil improved the engineering properties of the soil, resulting in an increase in the maximum dry density from 15.73 to 16.22 kN/m³. The highest shear strength of 17.91 kPa was obtained with an addition of 6% of phosphogypsum waste by the weight of dry soil. Similarly, a 10% substitution of silica fume in natural soil resulted in the highest shear strength of 20.37 kPa, providing improved resistance against liquefaction. The results show that the addition of phosphogypsum and silica fume stabilizers can be successfully used to treat clayey sand for various construction activities. The research outcomes will help engineers and construction professionals in implementing cost-effective and sustainable solutions for soil stabilization of clayey sand in practical applications.

In Algeria, one of the most alarming effects of climate change is drought. These periods of low rainfall have significant social and environmental implications, prompting investigations into management strategies, associated risks, and resulting crises. This study focuses on the Wadi Lakhdar watershed, a semi-arid region in northwestern Algeria, aiming to demonstrate the historical presence of drought and its impact on the environment and agriculture. To quantify long-term meteorological droughts and identify wet and dry periods from 1999 to 2021, we will utilize three drought indices: the Standardized Precipitation Index (SPI-12 months), the Standardized Precipitation and Evapotranspiration Index (SPEI-12 months), and the Palmer Drought Severity Index (PDSI-12 months). These indices are currently valuable tools for implementing various countermeasures, including drought early warning systems, monitoring, and contingency planning. Our analysis employing SPI, SPEI, and PDSI data will reveal distinct value ranges for wet years (1.01 to 2 for SPI, 0.64 to 1.28 for SPEI, and 1.35 to 2.68 for PDSI) and extremely dry years (− 1.07 to − 2.1 for SPI, − 0.68 to − 1.34 for SPEI, and − 1.43 to − 2.81 for PDSI). The wettest years were 2009, 2010, and 2013, while the driest years occurred in 2000, 2005, 2006, and 2007. Understanding drought characteristics is crucial for effective drought management. Drought indices provide a practical way to convert vast amounts of data into quantitative information for applications such as drought forecasting, communication of drought severity levels, and raising public awareness about the potential consequences of drought. This study’s social benefit lies in raising public awareness of these implications and anticipated consequences.

The effects of pervasive dolomitization on geochemical records and the mechanism of formation of Cambrian series-3 evaporite-bearing dolomites in the Bachu Uplift are assessed from petrography, geochemistry, and fluid inclusion. Near-surface diagenetic dolomites (dolomicrite (DM), microbial (algal) dolomite (MD)) and shallow-deep diagenetic dolomites (fine- to medium-crystalline dolomite (FM) and medium- to coarse-crystalline dolomite (MC)) were identified. Secondary fracture and pore-filling cements (dolomite (CD), early-stage calcite (ESC), later-stage calcite (LSC), gypsum/anhydrite, and authigenic quartz were identified. Weak relationships exist between δ¹³C, δ¹⁸O, ⁸⁷Sr/⁸⁶Sr, and Mg/Ca versus Mn/Sr ratios, which are tools used to evaluate the impact of the diagenetic environment on C-O-Sr isotope composition of the carbonates. The replacement dolomites (MD, FM, MC) and DC with high Mg/Ca ratios (0.61–1.23) have low depleted δ¹⁸O, δ¹³C values, compared to the ESC and LSC with more depleted δ¹⁸O, δ¹³C values, indicating that the C-O-Sr isotope composition suffered diagenetic alteration by higher-temperature and equilibrium isotopic fractionation. The decreasing trend of halogens/(Ca + Mg) ratios in DM and MD compared to the increasing trend in these ratios in FM, MC, and CD confirms that dolomitization had substantial effects on halogens/(Ca + Mg) ratios of dolomites formed in sabkha and evaporative-lagoon environment due to the mixing of dolomitization fluids with halite derived from seawater and halogen-enriched saline fluids during fluid-rock interaction. The DM and MD mechanisms of formation were respectively seepage-reflux penecontemporaneous dolomitization and microbial dolomitization of the underlying carbonate sediments and organic substrates at near-surface diagenetic burial settings in ancient sabkha environment. The ⁸⁷Sr/⁸⁶Sr, δ¹⁸O, δ¹³C values, and δ¹⁸O VSMOW values revealed that the FM and MC were formed during shallow-deep burial dolomitization from radiogenic-strontium, and Mg-enhanced saline dolomitization fluids at relatively high-temperatures. The growth of dolomite cement in fractures was the result of higher-temperature ⁸⁷Sr/⁸⁶Sr, Mg-enhanced saline basinal fluids squeezed upward and laterally along fractures and other permeable horizons by geothermal squeegee-fluid flows dolomitization mechanism from deep to shallow burial settings.

The subsurface condition of Addis Ababa City is heterogeneous and distinctly varies from place to place, ranging from very soft soil formation to competent rock mass units. This study characterized subsurface variations and estimated site-specific average shear wave velocity changes within the upmost 30 m (Vs30) geological medium at representative sites. We implemented combined active-source Multichannel Analysis of Surface Waves (MASW) and passive-source Microtremor Array Measurements (MAM) surface wave methods to effectively characterize and estimate the shear wave velocity (Vs) of shallow and deep subsurface materials at nine selected sites in the city. The Vs30 of geological profile at the selected sites was attained by joint dispersion inversion analysis of active and passive surface wave data. The result shows that the Vs30 calculated at the selected sites in the city ranges from 256 to 1787 m/s. The study results were used for site classification of near-surface geological materials according to the Vs30 classification guideline proposed by the National Earthquake Hazards Reduction Program (NERHP) and Eurocode-8 (EC-8) classification. Based on Vs30 results, the near-surface materials at the representative sites of the study area are categorized as site types C and D as per NEHRP and as site types B and C as per EC-8. Exceptionally, the rocky Arat Killo site is classified as a site type A in accordance with both NEHRP and EC-8. In addition, we validated acquired shear wave velocity profiles with local geological and engineering geological mapping and geotechnical boreholes proximate to measured sites to control the final inversion quality of Vs values to the corresponding layers. Since this study is the first in Addis Ababa City, the findings will be used for preliminary local site characterization and site specific seismic response analysis.

The present study evaluated the Paleogene Sokor-1 clastic reservoirs in the Fana Field on the Agadem Block, Termit Basin, Niger Republic. The evaluation of the hydrocarbon prospect of the Field, which involved petrophysical analysis of six wells namely Fana_2, Fana E_1, Fana N_2, Fana W_1, Fana S_1, Fana SW_1, and sidewall core sample description of Fana_2 well. The petrophysical interpretation of the well-log data was carried out using Interactive Petrophysics software. The petrophysical properties of the hydrocarbon-bearing reservoirs were rated to be suitable reservoirs with average effective porosities varying from 25.8 to 31.6%, permeability varying from 123.6 to 427.7 mD, average water saturation values ranging from 15.2 to 33.0%, and the average range of hydrocarbon saturation is 67.0 to 84.8%. The values of volume of shale (V_sh) of the identified reservoirs indicated that the reservoirs are generally shaly to a high shale/clayey content. The dia-porosity and M-N cross plots revealed that the reservoirs of the Sokor-1 Formation are predominantly sandstone with shale/clay intercalations. The shale structural behaviour of the reservoirs revealed that the dominant shale was mainly dispersed and laminated shale volumes that could impact on the reservoir qualities. The spatial variations of petrophysical parameters indicated that lower ^N/_G values favour the northeast and southern part of the map while the south area has a higher average effective porosity value. This study identified the southern part of the Fana Field as the most prospective and should be considered for the future exploration and development of the Fana field.

This present study investigates grain size, sediment dynamics and lateral erosion processes along the Ghaghara River from Faizabad to Deoria, Ganga Plain, India. The grain size analysis reflects that surface sediments have silt (24.50%) and very coarse silty-sand (75.50%) composition. The mean grain size varies from 2.20 to 4.21 ϕ indicating fine sand to very coarse silt. The Skewness, which varies from 0.01 to 0.48 ϕ, indicates the dominance of fine-grain sediments. The kurtosis varying from 0.66 to 1.38 ϕ explains the dominance of finer sediments. The standard deviation varies from 0.78 to 1.36 ϕ, thus indicating poorly sorted to moderately sorted and fluctuation in energy of the depositional environment. These river valley deposits (sand and very coarse-grained silt) reflect a depositional environment under fluctuating energy conditions. This river is characterized by the variable discharge frequency and high sediment load. The lateral erosion has been monitored during field work near Sita Rampur (Faizabad), Kamhariya (Ambedkar Nagar), Gola Bazar, and Barhalganj (Gorakhpur). The river migration observed on the left valley side (NNE) is 6144, 4838, 6475, and 4755 m and on the right valley side (SSW) 7021, 4555, 4718, and 4257 m between 1975–1990, 1975–2000, 1975–2010, and 1975–2020, respectively. In addition, the presence of sandy and silty facies and sediment load in the river valley deposits enhances the lateral erosion. This recent investigation of sediment dynamics and lateral erosion phenomena will advance river management and environmental preservation in the area.

Dam vulnerability analysis is a process that assesses the susceptibility of a dam to various risks, including structural failure, overtopping, and other potential hazards. In the present study, dam vulnerability analysis of Rihand Dam has been done using multi-proxy methods such as thematic layers (rainfall, lineaments, geomorphology, geology, soil, slope, drainage density, elevation, and land use/landcover) using Analytic Hierarchy Process (AHP) in the ArcGIS and ERDAS IMAGINE platforms. AHP and overlay weighting technique of Multi-Criteria Decision-Making (MCDM) to understand the terrain and geological features of the area help in evaluating the vulnerability of dam sites. The Rihand Dam is situated at a low elevation (159–278 m), which can fill during heavy rains causing uncontrolled water. Due to hydro pressure, water can penetrate micro lineament which can cause large cracks. The moderately ranked rainfall (722.232–729.98 mm/year) are surrounding the dam. The strike direction of the lineament/faults (0.665–1.327 km/km²) is parallel to the dam axis, which is favorable for the foundation of the dam. In the study area, there are 672 lineaments identified, predominantly oriented in an east–west strike direction, with some oriented northeast–southwest. Geologically, the dam is constructed on granite formations, which is considered more favorable for the dam site. Rihand Dam area is composed of loamy soil which is less erodible than sandy soil, which is important for dams. High drainage density can contribute to increased sediment transport in the watershed. This accumulation of sediment can reduce the storage capacity of the reservoir and increase the frequency of maintenance activities, resulting in a greater load of sediment being carried into the reservoir. Thus, dam vulnerability analysis is essential to ensuring the safety and functionality of dams, protecting downstream communities, and ecosystems to reducing the risks associated with dam failures, water resource management, flood control, and energy production.