Large-scale slope destabilization could be aggravated due to swift urbanization and ever-rising demands of geoengineering projects such as dams, tunnels, bridges and widening roads. National ...Highway-58 connects Delhi to Badrinath in India, which passes through complex geomorphological and geological terrain and often encounters cut slopes susceptible to slope failures. In the present investigation, a detailed geotechnical appraisal is conducted along the road cut slopes from Rishikesh to Devprayag in the Himalayas. Twenty vulnerable road cut slopes were demarcated for detailed slope stability analysis using Phase2D finite element modeling simulator. Nonlinear generalized Hoek-Brown (GHB) criterion was adopted for stability analyses. Out of 20 slopes, five slopes (S6, S7, S18, S19 and S20) are unstable with factor of safety (FoS) less than or equal to 1, and thus needs immediate attention. The FoS values of four slopes (S2, S9, S13 and S17) lie between 1 and 1.3, i.e. marginally stable, and slopes S1, S3, S4, S5, S8, S10, S11, S12, S14, S15 and S16 are stable. Mohr-Coulomb (MC) criterion was also adopted to compare the slope stability analysis with GHB criterion. The FoS calculated from GHB criterion is close to that using MC criterion for lower values of FoS whereas for higher values, the difference is marked. For the jointed rock in the Himalayan region, the nonlinear GHB criterion gives better results as compared to MC criterion and matches with the prevailing field conditions. Accordingly, some suggestions are proposed to strengthen the stability of cut slopes.
Extraction of bitumen from mined oil sands ores produces enormous volumes of tailings that are stored in settling basins (current inventory ≥ 840 million m(3)). Our previous studies revealed that ...certain hydrocarbons (short-chain n-alkanes C(6)-C(10) and monoaromatics toluene, o-xylene, m-xylene) in residual naphtha entrained in the tailings are biodegraded to CH(4) by a consortium of microorganisms. Here we show that higher molecular weight n-alkanes (C(14), C(16), and C(18)) are also degraded under methanogenic conditions in oil sands tailings, albeit after a lengthy lag (~180 d) before the onset of methanogenesis. Gas chromatographic analyses showed that the longer-chain n-alkanes each added at ~400 mg L(-1) were completely degraded by the resident microorganisms within ~440 d at ~20 °C. 16S rRNA gene sequence analysis of clone libraries implied that the predominant pathway of longer-chain n-alkane metabolism in tailings is through syntrophic oxidation of n-alkanes coupled with CO(2) reduction to CH(4). These studies demonstrating methanogenic biodegradation of longer-chain n-alkanes by microbes native to oil sands tailings may be important for effective management of tailings and greenhouse gas emissions from tailings ponds.
Microbial metabolism of residual hydrocarbons, primarily short-chain n-alkanes and certain monoaromatic hydrocarbons, in oil sands tailings ponds produces large volumes of CH(4) in situ. We ...characterized the microbial communities involved in methanogenic biodegradation of whole naphtha (a bitumen extraction solvent) and its short-chain n-alkane (C(6)-C(10)) and BTEX (benzene, toluene, ethylbenzene, and xylenes) components using primary enrichment cultures derived from oil sands tailings. Clone libraries of bacterial 16S rRNA genes amplified from these enrichments showed increased proportions of two orders of Bacteria: Clostridiales and Syntrophobacterales, with Desulfotomaculum and Syntrophus/Smithella as the closest named relatives, respectively. In parallel archaeal clone libraries, sequences affiliated with cultivated acetoclastic methanogens (Methanosaetaceae) were enriched in cultures amended with n-alkanes, whereas hydrogenotrophic methanogens (Methanomicrobiales) were enriched with BTEX. Naphtha-amended cultures harbored a blend of these two archaeal communities. The results imply syntrophic oxidation of hydrocarbons in oil sands tailings, with the activities of different carbon flow pathways to CH(4) being influenced by the primary hydrocarbon substrate. These results have implications for predicting greenhouse gas emissions from oil sands tailings repositories.
Agricultural rainfed areas of Pakistan have been facing several issues in recent years, e.g., soil erosion, nutrient runoff, and soil dependency on rainfall for crop growth. Wheat is considered a ...major staple crop in Pakistan. The main concern in these regions is to conserve soil moisture as the crop depends on the moisture obtained by rainfall. Gypsum is considered one of the best moisture conservers, especially for rainfed areas. Hence, this study was initiated (1) to explore the effects of gypsum on soil moisture conservation and (2) to reveal the effects of gypsum on soil macronutrients, sulfur (S), calcium (Ca), nitrogen (N), phosphorus (P), and potassium (K) uptake, and, eventually, wheat yield. The study was conducted from July 2014 to April 2015 in the rainfed Pothohar region of Pakistan. The recommended mineral fertilizers (N120P80K60) along with the following gypsum treatments: T1 = gypsum @ 0 Mg ha−1 (0 kg plot−1), T2 = gypsum @ 1 Mg ha−1 (0.6 kg plot−1), T3 = gypsum @ 3 Mg ha−1 (1.8 kg plot−1), and T4 = gypsum @ 4 Mg ha−1 (2.4 kg plot−1) were applied. The Chakwal-50 wheat variety was sown, followed by gypsum application. The maximum moisture was recorded under the soil of treatment T4 each month. The soil moisture was conserved up to 21% (surface) and 23% (sub-surface) in January and February 2015, respectively, with a 4 Mg ha−1 gypsum application. The highest nitrogen (N, 448.68 kg ha−1), phosphorus (P, 50.6 kg ha−1), potassium (K, 185.7 Kg ha−1), sulfur (S, 9.75 kg ha−1), and calcium (Ca, 35.5 kg ha−1) uptake values were observed in treatment with a 3 Mg ha−1 gypsum application (p < 0.05). The mean values of the grain yield ranged between 1903.4 (T1) and 2387.2 (T4) kg ha−1. Compared with the yield under T1, the grain yields under treatment T2, T3, and T4 were increased by 11%, 24%, and 25%, respectively. The straw yield ranged between 2446 and 2767 kg ha−1. There was no noticeable impact of gypsum application rates on the straw yield of the wheat crop (p > 0.05). Overall, treatment T3 was found to be optimal for conserving soil moisture, a better nutrient uptake, and, ultimately, the wheat crop yield with less input cost.
A wide variety of sampling techniques and strategies are needed to analyze polycyclic aromatic compounds (PACs) and interpret their distributions in various environmental media (i.e., air, water, ...snow, soils, sediments, peat and biological material). In this review, we provide a summary of commonly employed sampling methods and strategies, as well as a discussion of routine and innovative approaches used to quantify and characterize PACs in frequently targeted environmental samples, with specific examples and applications in Canadian investigations. The pros and cons of different analytical techniques, including gas chromatography – flame ionization detection (GC-FID), GC low-resolution mass spectrometry (GC-LRMS), high performance liquid chromatography (HPLC) with ultraviolet, fluorescence or MS detection, GC high-resolution MS (GC-HRMS) and compound-specific stable (δ13C, δ2H) and radiocarbon (Δ14C) isotope analysis are considered. Using as an example research carried out in Canada’s Athabasca oil sands region (AOSR), where alkylated polycyclic aromatic hydrocarbons and sulfur-containing dibenzothiophenes are frequently targeted, the need to move beyond the standard list of sixteen EPA priority PAHs and for adoption of an AOSR bitumen PAC reference standard are highlighted.
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•Review of methods to collect samples for PAC analysis in the Canadian environment.•Review of techniques used to quantify or characterize PACs in environmental samples.•High-resolution MS and compound-specific isotope analysis offer unparalleled insight.•The list of 16 EPA PAHs is insufficient for studies in Canada’s oil sands region.•The adoption of an Athabasca oil sands bitumen PAC reference standard is proposed.
A comprehensive review of sampling methods, strategies and analytical techniques used to quantify and characterize PACs in the Canadian environment.
In this study, the thermoluminescence characteristics of naturally occurring salt (NaCl) were assessed for the development of a radiation dosimeter. For this purpose, mined crystalline samples of ...salt were procured directly from Khewra salt mines in Pakistan. The samples were hand crushed, sieved, and compressed to pellets comparable in size to standard TLD chips, and irradiated to gamma radiation doses in the range of 5 mGy and 5000 mGy. Thermoluminescence (TL) response showed three main peaks in the glow curve around 115–130 °C, 150–170 °C, and 220–240 °C. A linear TL response was observed for the dose range of 5–100 mGy. The TL response became supra-linear for the dose ranges of 100–1000 mGy and 1000–5000 mGy. The T
m
-T
stop
method was applied to identify the overlapping peaks of the glow curve. Computerized glow curve deconvolution (CGCD) was then employed for the characterization of electron trap parameters such as frequency factor (s), activation energy (E), and the kinetic order (b), using General Order (GO) kinetics. The figure-of-merit (FOM) was found to be 1.08%, 0.94%, 0.77%, and 0.75%, at 500 mGy, 1 Gy, 2 Gy, and 5 Gy, respectively. The TL intensity faded by 20% within the first 24 h after irradiation and finally stabilized after two weeks. In addition, structural, morphological, and elemental analyses, were also performed using various analytical techniques. X-ray diffraction (XRD) showed that the salt crystallizes in a face-centered cubic structure. Scanning electron microscope (SEM) micrographs indicated that the crystallites are closely packed and cubic-shaped with non-uniform size, and mostly found in the agglomerated form. Similarly, the elemental analysis confirmed the presence of impurities such as Mg, Sr, S, K, O, and Ca, in the samples. The present study concludes that the pellets made from salt samples from Khewra mines have a potential for use as radiation dosimeters.
Rock mass classification (RMC) systems in the realm of rock slope engineering have gathered a lot of attention. The present review article delves into the major RMC systems, elucidating their ...fundamental principles, key parameters and practical applications. Among the various RMC systems for rock slope designing, Romana's Slope mass rating (SMR) was found to be the most comprehensive; therefore, the focus of the discussion centres around the SMR method. The article provides a crisp overview of the major advancements, evolution and potential challenges of SMR. The radical concept of wedge failure in SMR and the use of continuous functions are discussed in detail. A thorough discussion is provided on the efforts made by different researchers, encompassing the inclusion of novel factors such as slope height, heterogeneity in rock mass or lithology, weighted consideration of existing discontinuities, fuzzy sets and overburden thickness. Various automated calculation techniques and empirical correlations of SMR with other classification systems and rock engineering parameters are also outlined. Moreover, a critical examination of the variations among major extensions of SMR and their geotechnical relevance have also been discussed. Based on a meticulous assessment of the susceptibility to toppling failure in SMR, two sub‐factors to include block shape and interlayer slip between discontinuities have been suggested. These sub‐factors were validated by Goodman's tests for toppling failure. The scope of future projections or possible aspects for revisiting and refinement of the SMR method are suggested to enhance the applicability of the method under a diverse initial set of geotechnical conditions.
Roxarsone (rox), an arsenic (As) containing organic compound, is a common feed additive used in poultry production. To determine if As present in rox is excreted into the poultry litter without any ...retention in chicken meat for safe human consumption, the transference of As from the feed to poultry excreta was assessed using two commercial chicken strains fed with and without dietary rox. The results revealed that both the strains had similar behaviour in growth (chicken weight; 2.17–2.25kg), feed consumption (282–300kgpen−1 initially containing 102 chicken) and poultry litter production (73–81kgpen−1) during the growth phase of 35days. Our mass balance calculations showed that chickens ingested 2669–2730mg As with the feed and excreted out 2362–2896mg As in poultry litter during the growth period of 28days when As containing feed was used, yielding As recovery between 86 and 108%. Though our complementary studies show that residual arsenic species in rox-fed chicken meat may have relevance to human exposure, insignificant retention of total As in the chicken meat substantiates our mass balance results. The results are important in evaluating the fate of feed additive used in poultry production and its potential environmental implications if As containing poultry litter is applied to soil for crop production.
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•First study that describes mass balance of arsenic intake and excretion by chickens•Two strains Ross and Cobb exhibited similar response to roxarsone-amended feed.•Arsenic did not retain in chickens during their growth on arsenic containing feed.•Poultry litter enriched in arsenic warrants investigations if used in crop production.
The engineered slopes along transportation routes in the Himalayan region are manifested by multiple sets of discontinuities and are vulnerable to structurally controlled failures. The hazard ...potential along one such route was assessed by an empirical Q-slope method. The investigated engineered slopes along the route are unstable, and the Q-slope value ranges from 0.0023 to 0.7701. By considering the ongoing road development and excavation works, optimal angles without any requirements of reinforcement measures (
β
) were determined for the probability of failure (PoF) as 1%, 15%, 30%, and 50%. The outcomes obtained by Q-slope were also correlated with the continuous slope mass rating (CSMR) values. A linear relationship was obtained between Q-slope and CSMR values, having the coefficient of determination as 0.67. The study also aims to assess the applicability of the existing Q-slope method for toppling mode of failure. A modified Q-slope method for toppling failure is proposed by considering the basic principles of toppling failure. The role of joint roughness parameter in topple mechanism is highlighted. Consequently, chart based modifications along with proper guidelines for the newly introduced parameter has also been proposed. It is also pointed out that the Q-slope chart is slightly conservative in nature particularly for
β
corresponding to low Q-slope values. The optimal slope angle for the PoF 1% was correlated with the slope angle at factor of safety as 2, and an extended stable zone is proposed with further scope of development. The modifications and suggestions for the refinement of the system will enhance the applicability of the method for a much broader range of initial ground conditions. The outcomes may be advantageous for the progressing road widening and development work along a section of the transportation route in Uttarakhand Himalaya.
The roadway networks serve as arteries for the ongoing socio-economic activities within the Himalayan region. The perilous conditions of geologically active and fragile terrain are sustained threats ...to various disasters, including landslides. Large numbers of casualties and fatal incidence associated with landslides are being reported every year. The stability of road cut slopes is a crucial component for safer mobility and transportation activities. To attain a hassle-free and hazard-resilient design along the critical transportation route, a schematic and rigorous geotechnical investigation has been undermined. The present case study was undertaken to envisage cut slope stability and optimal designing of engineered slopes along the national highway-94 (NH-94) from Rishikesh to New Tehri, Garhwal Himalaya, India. The major issues associated with road cut slope failures are getting highlighted. Various rock mass classification systems including rock mass rating (RMR), slope mass rating (SMR) and its extensions, geological strength index, and Q Slope method were used to determine the prevailing stability. Stable slope angle without any reinforcement are suggested for the different probability of failure. Failure pattern was also assessed by applying kinematic analysis. Modified RMR for slopes is suggested by adjusting the orientation factor by using kinematic feasibility. Numerical simulation technique was also applied to determine safety factor. Exponential relationships are derived among Q Slope, SMR, and strength reduction factor. The guidelines to improve safety in terms of landslides are also suggested by considering the outcomes obtained by different methods.
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