Settling and compaction of chromite cumulates employing a centrifuging piston cylinder and application to layered mafic intrusions

The time scales and mechanics of gravitationally driven crystal settling and compaction is investigated through high temperature (1,280–1,500 °C) centrifuge-assisted experiments on a chromite-basalt melt system at 100–1,500g (0.5 GPa). Subsequently, the feasibility of this process for the formation of dense chromite cumulate layers in large layered mafic intrusions (LMIs) is assessed. Centrifugation leads to a single cumulate layer formed at the gravitational bottom of the capsule. The experimentally observed mechanical settling velocity of a suspension of ~24 vol% chromite is calculated to be about half (~0.53) of the Stokes settling velocity, with a sedimentation exponent n of 2.35 (3). Gravitational settling leads to an orthocumulate layer with a porosity of 0.52 (all porosities as fraction). Formation times for such a layer from a magma with initial chromite contents of 0.1–1 vol% are 140–3.5 days, equal to a growth rate of 0.007–0.3 m/day for grain sizes of 1–2 mm. More compacted chromite layers form with increasing centrifugation time and acceleration through chemical compaction: An increase of grain contact areas and grain sizes together with a decrease in porosity is best explained by pressure dissolution at grain contacts, reprecipitation and grain growth into the intergranular space and a concomitant expulsion of intergranular melt. The relation between the porosity in the cumulate pile and effective pressure integrated over time (Δρ · h · a · t) is best fit with a logarithmic function, in fact confirming that a (pressure) dissolution–reprecipitation process is the dominant mechanism of compaction. The experimentally derived equation allows calculating compaction times: 70–80 % chromite at the bottom of a 1-m-thick chromite layer are reached after 9–250 years, whereas equivalent compaction times are 0.2–0.9 years for olivine (both for 2 mm grain size). The experiments allow to determine the bulk viscosities of chromite and olivine cumulates to be of magnitude 10⁹ Pa s, much lower than previously reported. As long as melt escape from the compacting cumulate remains homogeneous, fluidization does not play any role; however, channelized melt flow may lead to suspension and upward movement of cumulate crystals. In LMIs, chromitite layers are typically part of a sequence with layers of mafic minerals, compaction occurs under the additional weight of the overlying layers and can be achieved in a few years to decades.     

Sulfate Reduction and Sulfur Cycles at Two Seagrass Beds Inhabited by Cold Affinity <Emphasis Type="Italic">Zostera marina</Emphasis> and Warm Affinity <Emphasis Type="Italic">Halophila nipponica</Emphasis> in Temperate Coastal Waters

To evaluate the impact of invading seagrass on biogeochemical processes associated with sulfur cycles, we investigated the geochemical properties and sulfate reduction rates (SRRs) in sediments inhabited by invasive warm affinity Halophila nipponica and indigenous cold affinity Zostera marina. A more positive relationship between SRR and below-ground biomass (BGB) was observed at the H. nipponica bed (SRR = 0.6809 × BGB ? 4.3162, r ² = 0.9878, p = 0.0006) than at the Z. marina bed (SRR = 0.3470 × BGB ? 4.0341, r ² = 0.7082, p = 0.0357). These results suggested that SR was more stimulated by the dissolved organic carbon (DOC) exuded from the roots of H. nipponica than by the DOC released from the roots of Z. marina. Despite the enhanced SR in spring-summer, the relatively lower proportion (average, 20%) of acid-volatile sulfur (AVS) in total reduced sulfur and the strong correlation between total oxalate-extractable Fe (Fe_(oxal)) and chromium-reducible sulfur (CRS = 0.2321 × total Fe_(oxal) + 1.8180, r ² = 0.3344, p = 0.0076) in the sediments suggested the rapid re-oxidation of sulfide and precipitation of sulfide with Fe. The turnover rate of the AVS at the H. nipponica bed (0.13 day^?1) was 2.5 times lower than that at the Z. marina bed (0.33 day^?1). Together with lower AVS turnover, the stronger correlation of SRR to BGB in the H. nipponica bed suggests that the extension of H. nipponica resulting from the warming of seawater might provoke more sulfide accumulation in coastal sediments.     

Seismic source characteristics in Kachchh and Saurashtra regions of Western India: <Emphasis Type="Italic">b</Emphasis>-value and fractal dimension mapping of aftershock sequences

Seismic source characteristics in the Kachchh rift basin and Saurashtra horst tectonic blocks in the stable continental region (SCR) of western peninsular India are studied using the earthquake catalog data for the period 2006–2011 recorded by a 52-station broadband seismic network known as Gujarat State Network (GSNet) running by Institute of Seismological Research (ISR), Gujarat. These data are mainly the aftershock sequences of three mainshocks, the 2001 Bhuj earthquake (M _w 7.7) in the Kachchh rift basin, and the 2007 and 2011 Talala earthquakes (M _w ≥ 5.0) in the Saurashtra horst. Two important seismological parameters, the frequency–magnitude relation (b-value) and the fractal correlation dimension (D _c) of the hypocenters, are estimated. The b-value and the D _c maps indicate a difference in seismic characteristics of these two tectonic regions. The average b-value in Kachchh region is 1.2 ± 0.05 and that in the Saurashtra region 0.7 ± 0.04. The average D _c in Kachchh is 2.64 ± 0.01 and in Saurashtra 2.46 ± 0.01. The hypocenters in Kachchh rift basin cluster at a depth range 20–35 km and that in Saurashtra at 5–10 km. The b-value and D _c cross sections image the seismogenic structures that shed new light on seismotectonics of these two tectonic regions. The mainshock sources at depth are identified as lower b-value or stressed zones at the fault end. Crustal heterogeneities are well reflected in the maps as well as in the cross sections. We also find a positive correlation between b- and D _c-values in both the tectonic regions.     

DEM simulations of sandstone under true triaxial compressive tests

Numerically simulated true triaxial compression tests (σ ₁ ≥ σ ₂ ≥ σ ₃) are conducted in this study to elucidate the failure mechanism of sandstone using 3D discrete element method (DEM), in particular the effect of the intermediate principal stress (σ ₂). Eight series of tests (σ ₃ = 0, 10, 20, 30, 40, 50, 70, and 100 MPa) are conducted. Within each series, σ ₂ is varied from σ ₂ = σ ₃ to σ ₂ = σ ₁ from test to test. For each test, σ ₁ is raised monotonically to failure while keeping σ ₂ and σ ₃ constant. The DEM simulations reveal the effect of σ ₂ on the variations of peak stress, Young’s modulus, failure plane angles, the brittle–ductile transition, and the evolution of failure modes, the effect beyond the well-understood effect of σ ₃. The simulation is in qualitative agreement with the results obtained experimentally. Detailed analyses performed on the particle-scale responses further the understanding of the microscopic mechanisms. The distribution of contact force becomes more homogeneous with the increase of σ ₃, which leads to the resulting damage being more localized rather than diffused. The interaction between contact force distribution and coalescence of cracks determines the processes and patterns of fracturing in the sample scale. σ ₂ is found to affect the microscopic stress distribution as well as structure evolution, and this effect weakens with the increase of σ ₃.     

Location-based environmental factors contributing to rainfall-triggered debris flows in the Ba river catchment,northwest Viti Levu island,Fiji

Mass movements in tropical Pacific small island developing states (SIDS) can be devastating although studies are relatively few and contributing environmental factors are not often investigated in detail. On 25 January 2012, following 3 days of heavy monsoonal rainfall (c. 550 mm) during a La Niña episode, more than 150 debris flows were triggered in the western part of the Ba river catchment of northwest Viti Levu island, Fiji. Reconnaissance field survey and geographical information system (GIS) analyses using high-resolution satellite imagery were carried out to investigate factors that may have led to the occurrence of the debris flows in the catchment. We evaluated the correlation between the density of mass movements (number of mass movements/km²) and several continuous variables using data measured within the GIS. There was a weak but significant positive correlation between mass movement density and elevation (r = 0.38, p value < 0.01), cyclonic precipitation (r = 0.37, p value < 0.01) and stream density (r = 0.31, p value < 0.01). Ninety-three percent of the mass movements occur within a plantation of Pinus caribaea (Caribbean pine) on slopes oriented mainly to the northeast and east on (trade) windward slopes and may be significant factors for their development. Although forests generally have a stabilizing effect on slopes, the plantation at Ba was a mature stand on its second plantation cycle and is a species that has a shallow rooting system making it more susceptible to failure.     

The hydraulic retention time on the particle removal efficiency by <Emphasis Type="Italic">Daphnia magna</Emphasis> filtration on treated wastewater

The study of low-cost techniques for the tertiary treatment of wastewater is of global interest; above all low-energy techniques that do not require the use of chemicals. In this study, a wastewater treatment technology based on the filtration by a zooplanktonic population (Daphnia magna) is studied in controlled laboratory and mesocosm experiments for different hydraulic retention times (HRT). The efficiency of the treatment is evaluated in terms of particle removal efficiency. From laboratory experiments, HRT over 12 h and Daphnia concentrations above 50 individuals l^?1 guarantee a particle removal efficiency greater than 30 %. However, low HRT of 6 h would require Daphnia concentrations above 70 individuals l^?1 in order to obtain a particle removal efficiency of 20 %. The minimum removal efficiency of 2 % was for HRT = 3 h, independent of the Daphnia concentration. In the mesocosm, the growth of Daphnia individuals enhanced Daphnia magna filtering rates and higher removal efficiencies than those in the laboratory for the same HRT range. In the mesocosm experiments E. coli concentrations were reduced to a maximum of 2 logarithmic units. A balance equation model is proposed to predict particle removal efficiencies for varying HRT.     

Stability at high-pressure,elastic behaviour and pressure-induced structural evolution of CsAlSi<Subscript>5</Subscript>O<Subscript>12</Subscript>, a potential host for nuclear waste

The elastic and structural behaviour of the synthetic zeolite CsAlSi₅O₁₂ (a = 16.753(4), b = 13.797(3) and c = 5.0235(17) Å, space group Ama2, Z = 2) were investigated up to 8.5 GPa by in situ single-crystal X-ray diffraction with a diamond anvil cell under hydrostatic conditions. No phase-transition occurs within the P-range investigated. Fitting the volume data with a third-order Birch–Murnaghan equation-of-state gives: V ₀ = 1,155(4) ų, K _T0 = 20(1) GPa and K′ = 6.5(7). The “axial moduli” were calculated with a third-order “linearized” BM-EoS, substituting the cube of the individual lattice parameter (a ³, b ³, c ³) for the volume. The refined axial-EoS parameters are: a ₀ = 16.701(44) Å, K _T0a = 14(2) GPa (β_a = 0.024(3) GPa^?1), K′ _a = 6.2(8) for the a-axis; b ₀ = 13.778(20) Å, K _T0b = 21(3) GPa (β_b = 0.016(2) GPa^?1), K′ _b = 10(2) for the b-axis; c ₀ = 5.018(7) Å, K _T0c = 33(3) GPa (β_c = 0.010(1) GPa^?1), K′ _c = 3.2(8) for the c-axis (K _T0a:K _T0b:K _T0c = 1:1.50:2.36). The HP-crystal structure evolution was studied on the basis of several structural refinements at different pressures: 0.0001 GPa (with crystal in DAC without any pressure medium), 1.58(3), 1.75(4), 1.94(6), 3.25(4), 4.69(5), 7.36(6), 8.45(5) and 0.0001 GPa (after decompression). The main deformation mechanisms at high-pressure are basically driven by tetrahedral tilting, the tetrahedra behaving as rigid-units. A change in the compressional mechanisms was observed at P ≤ 2 GPa. The P-induced structural rearrangement up to 8.5 GPa is completely reversible. The high thermo-elastic stability of CsAlSi₅O_12, the immobility of Cs at HT/HP-conditions, the preservation of crystallinity at least up to 8.5 GPa and 1,000°C in elastic regime and the extremely low leaching rate of Cs from CsAlSi₅O₁₂ allow to consider this open-framework silicate as functional material potentially usable for fixation and deposition of Cs radioisotopes.     

Potency of constructed wetlands for deportation of pathogens index from rural,urban and industrial wastewater

Pathogen removal is essential for wastewater treatment and its potential reuse in agriculture. Three field-scale wastewater treatment systems consisting of free surface flow were operated around 1.5 years receiving water from urban domestic, rural domestic and industrial sources. The study was conducted to evaluate seasonal performance of constructed wetland systems in removing Escherichia coli, Enterococci and total coliforms under continuous hydraulic flow. Results displayed that all three wetlands gain recognition in removing pathogen load with high removal efficacy till water reaches output ports. Removal efficiencies were even higher, 66–93, 78–92 and 80–94% for E. coli, Enterococci and total coliforms, respectively, within constructed wetlands. Remarkably at shorter temporal scales in CW-A, greater homogeneity of pathogen concentrations was assessed at wetland outlet sites. In outlet ports, results displayed a highly effective removal of E. coli concentration 80–90% (June 2015), 86–92% (October 2015) and 79–92% (February 2016), Enterococci 80–94% (June 2015), 83–94% (October 2015) and 80–94% (February 2016) and total coliforms 85–93% (June 2015), 87–95% (October 2015) and 88–96% (February 2016). Positive correlation was observed between bacterial indicators (E. coli–Enterococci, r = 0.038; p < 0.01 and E. coli–total coliforms, r = 0.142; p < 0.01). Removal of bacterial indicators in constructed wetland was also displayed by PCA in which three-component analysis of variance was 98.39% and showed a clear decrease in measured parameter gradients toward samples from outlet ports. Constructed wetlands provide cost-effective treatment systems for reducing the pathogen load in wastewater in variable agro-climatic conditions and thus improve water quality.     

Properties of the aftershocks sequences of the 2000 and 2002 earthquakes in Aksehir-Afyon graben,west-central Anatolia,Turkey

The b-value of the Gutenberg–Richter’s frequency–magnitude relation and the p-value of the modified Omori law, which describes the decay rate of aftershock activity, were investigated for more than 500 aftershocks in the Aksehir-Afyon graben (AAG) following the 15 December 2000 Sultandagi–Aksehir and the 3 February 2002 Çay–Eber and Çobanlar earthquakes. We used the Kandilli Observatory’s catalog, which contains records of aftershocks with magnitudes ≥2.5. For the Çobanlar earthquake, the estimated b-values for three aftershock sequences are in the range 0.34 ≤  b ≤ 2.85, with the exception of the one that occurred during the first hour (4.77), while the obtained p-values are in the range 0.44 ≤ p ≤ 1.77. The aftershocks of the Sultandagi earthquake have a high p-value, indicating fast decay of the aftershock activity. A regular increase of b can be observed, with b < 1.0 after 0.208 days for the Çay–Eber earthquake. A systematic and similar increase and decrease pattern exists for the b- and p-values of the Çobanlar earthquakes during the first 5 days.     

Factors controlling the changes and spatial variability of <Emphasis Type="Italic">Junipers phoenicea</Emphasis> in Jabal Al Akhdar,Libya, using remote sensing and GIS

The Junipers phoenicea, which covers 70 % of the Jabal Al Akhdar (Green Mountain) in Cyrene on the northeast coast of Libya, has deteriorated over large scales. To deal with this problem, the images of the Landsat 7 Enhanced Thematic Mapper Plus (ETM+) and Landsat 8 Operational Land Imager (OLI) in conjunction with the Shuttle Radar Topography Mission (SRTM) digital elevation model (DEM) were used to map factors controlling the J. phoenicea mortality using a set of automated algorithms and tools. These factors include altitude, slope, aspect, curvature, drainage pattern, seawater intrusion, and land cover. As a first step, changes of J. phoenicea and land cover during the period from the year 2000 to 2015 were mapped. The results showed a sharp decline in J. phoenicea covering an area of 396 km² (22 %) of the total area. The result also showed that areas at a lower elevation with steep slope and faced to the south and southeast directions have a higher probability of J. phoenicea distribution. The spatial analysis showed a positive correlation between wetness and the intensity of J. phoenicea mortality. The results also show that altitude and slope have the most influencing power on the J. phoenicea morality. This study is of great help for decision makers and agriculture engineers and permits a better understanding of ecological and biomass changes in the Jabal Al Akhdar, Libya, over a regional scale.     

Quantifying land use influences on event-based flow frequency,timing, magnitude,and rate of change in an urbanizing watershed of the central USA

There is a need for research that advances understanding of flow alterations in contemporary watersheds where natural and anthropogenic interactions can confound mitigation efforts. Event-based flow frequency, timing, magnitude, and rate of change were quantified at five-site nested gauging sites in a representative mixed-land-use watershed of the central USA. Statistically independent storms were paired by site (n = 111 × 5 sites) to test for significant differences in event-based rainfall and flow response variables (n = 17) between gauging sites. Increased frequency of small peak flow events (i.e., 64 more events less than 4.0 m³ s^?1) was observed at the rural–urban interface of the watershed. Differences in flow response were apparent during drier periods when small rainfall events resulted in increased flow response at urban sites in the lower reaches. Relationships between rainfall and peak flow were stronger with decreased pasture/crop land use and increased urban land use by approximately 20%. Event-based total rainfall explained 40–68% of the variance in peak flow (p < 0.001). Coefficients of determination (r²) were negatively correlated with pasture/crop land use (r² = 0.92; p = 0.007; n = 5) and positively correlated with urban land use (r² = 0.90; p = 0.008; n = 5). Significant differences in flow metrics were observed between rural and urban sites (p < 0.05; n = 111) that were not explained by differences in rainfall variables and drainage area. An urban influence on flow timing was observed using median time lag to peak centroid and time of maximum precipitation to peak flow. Results highlight the need to establish manageable flow targets in rapidly urbanizing mixed-land-use watersheds.     

Thermal equation of state of natural tourmaline at high pressure and temperature

Synchrotron-based in situ angle-dispersive X-ray diffraction experiments were conducted on a natural uvite-dominated tourmaline sample by using an external-heating diamond anvil cell at simultaneously high pressures and temperatures up to 18 GPa and 723 K, respectively. The angle-dispersive X-ray diffraction data reveal no indication of a structural phase transition over the P–T range of the current experiment in this study. The pressure–volume–temperature data were fitted by the high-temperature Birch–Murnaghan equation of state. Isothermal bulk modulus of K ₀ = 96.6 (9) GPa, pressure derivative of the bulk modulus of \(K_{0}^{\prime } = 12.5 \;(4)\), thermal expansion coefficient of α ₀ = 4.39 (27) × 10^?5 K^?1 and temperature derivative of the bulk modulus (?K/?T) _P  = ?0.009 (6) GPa K^?1 were obtained. The axial thermoelastic properties were also obtained with K _a0 = 139 (2) GPa, \(K_{a0}^{\prime }\) = 11.5 (7) and α _a0 = 1.00 (11) × 10^?5 K^?1 for the a-axis, and K _c0 = 59 (1) GPa, \(K_{c0}^{\prime }\) = 11.4 (5) and α _c0 = 2.41 (24) × 10^?5 K^?1 for the c-axis. Both of axial compression and thermal expansion exhibit large anisotropic behavior. Thermoelastic parameters of tourmaline in this study were also compared with that of the other two ring silicates of beryl and cordierite.     

Quantification of photosynthetic inorganic carbon utilisation via a bidirectional stable carbon isotope tracer

The amount of bicarbonate utilised by plants is usually ignored because of limited measurement methods. Accordingly, this study quantified the photosynthetic assimilation of inorganic carbon (CO₂ and HCO₃ ^?) by plants. The net photosynthetic CO₂ assimilation (P _N), the photosynthetic assimilation of CO₂ and bicarbonate (P _N’), the proportion of increased leaf area (f _LA) and the stable carbon isotope composition (δ¹³C) of Orychophragmus violaceus (Ov) and Brassica juncea (Bj) under three bicarbonate levels (5, 10 and 15 mm NaHCO₃) were examined to determine the relationship among P _N, P _N’ and f _LA. P _N’, not P _N, changed synchronously with f _LA. Moreover, the proportions of exogenous bicarbonate and total bicarbonate (including exogenous bicarbonate and dissolved CO₂-generated bicarbonate) utilised by Ov were 2.27 % and 5.28 % at 5 mm bicarbonate, 7.06 % and 13.28 % at 10 mm bicarbonate, and 8.55 % and 17.31 % at 15 mm bicarbonate, respectively. Meanwhile, the proportions of exogenous bicarbonate and total bicarbonate utilised by Bj were 1.77 % and 3.28 % at 5 mm bicarbonate, 2.11 % and 3.10 % at 10 mm bicarbonate, and 2.36 % and 3.09 % at 15 mm bicarbonate, respectively. Therefore, the dissolved CO₂-generated bicarbonate and exogenous bicarbonate are important sources of inorganic carbon for plants.     

Textural and micro-analytical insights into mafic–felsic interactions during the Oruanui eruption,Taupo

Quenched juvenile mafic inclusions (enclaves) are an occasional but informative component in the deposits of large felsic eruptions. Typically, the groundmasses of these inclusions rapidly crystallize as the mafic magma is chilled against a more voluminous, cooler felsic host, providing a physical and chemical record of the nature and timing of mafic–felsic interactions. We examine mafic inclusions of two compositional lineages (tholeiitic and calc-alkaline) from deposits of the 25.4 ka Oruanui eruption (Taupo, New Zealand). 2-D quantitative textural data from analysis of back-scattered electron images reveal a marked diversity in the groundmass textures of the inclusions, including median crystal sizes (amphibole: 14–45 µm; plagioclase: 21–75 µm) and aspect ratios (amphibole: 1.7–4.2; plagioclase: 2.1–4.0), area number densities (amphibole: 122–2660 mm^?2; plagioclase: 117–2990 mm^?2), area fractions (?) of minerals (?_plag?=?23–45%, ?_amph?=?0–28%, ?_cpx?=?0–6%, ?_oxides?=?0.6–5.5%), and the relative abundance of plagioclase and amphibole (?_plag/?_amph?=?1.0–4.6). Textural parameters vary more significantly within, rather than between, the two compositional lineages, and in some cases show marked variations across individual clasts, implying that each inclusion’s cooling history, rather than bulk composition, was the dominant control on textural development. Groundmass mineral compositions are also diverse both within and between inclusions (e.g. plagioclase from An_34–92, with typical intra-clast variability of ~?20 mol%), and do not correlate with bulk chemistry. Diverse groundmass textures and mineral and glass chemistries are inferred to reflect complex interplay of a range of factors including the degree and rate of undercooling, bulk composition, water content and, possibly, intensive variables. Our data are inconsistent with breakup of a crystallizing ponded mafic layer at the base of the Oruanui melt-dominant body, instead implying that each inclusion partially crystallized as a discrete body with a unique cooling history. Extensive ingestion of mush-derived macro-crystals suggests that mechanical breakup of mafic feeder dikes occurred within a transition zone between the mush and melt-dominant magma body. In this zone, the mush lacked yield strength, as has been inferred from field studies of narrow (meters to few tens of meters) mush-melt transition zones preserved in composite intrusions. Evidence for plastic deformation of inclusions during eruption and the abundance of fresh residual glass in inclusions from all eruptive phases suggest that the inclusions formed syn-eruptively, and must have been formed recurrently at multiple stages throughout the eruption.     

Emerging grassroots resilience and flood responses in informal settlements in Accra,Ghana

In the last five decades, many informal communities in Accra, Ghana have suffered from annual flood hazards. Residents of these communities appear to have successfully resisted evictions by city authorities; survived flood hazards and poor environmental health conditions. These flood affected households continue to survive with increasing housing and population densities in the face of these annual floods. Are they becoming resilient? Have residents built adaptive capacities through learning experiences from previous flood occurrences and evictions attempts? What has produced and continued to shape their responses to flooding? What can be learned from this supposed grassroots resilience to inform flood management in urban Africa? Using case studies of three informal communities of Glefe, Agbogbloshie and Old Fadama, this paper explores the gradual and evolving adaptive capacities and social resilience to flood hazards among poor urban dwellers. The paper reveals the depth of understanding and embodied nature of flood experiences among affected slum dwellers and how these are gradually being transformed into adaptive capacities and shaping their responses. In the absence of efficient state flood interventions, there are emerging and enduring flood responses and adaptation practices shaped by residents’ social networks, political alliances and sense of place. These responses translates into continuous re-structuring of housing units, construction of communal drains, creation of local evacuation teams and safe havens. Urban policy contributions that can be learned from these emerging grassroots capacities for flood vulnerability management have been proposed.     

Dewatering Behaviour of a Uranium Ore Slurry Containing Clays

The main objective of this paper was to investigate the dewatering behaviour of a clayey uranium ore slurry. The slurry (containing 28% clay size) exhibited moderate water adsorption (w _l  = 83% and w _p  = 30%). Primarily composed of muscovite (46%) and quartz (30%), the clay minerals included illite (8%), chlorite (5%) and kaolinite (2%) alongside a CEC of 41 (cmol(+)/kg) with Ca²⁺ and Mg²⁺ as the dominant cations. Likewise, the high EC (17,600 μS/cm) and ionic strength (1.15 mol/L) indicated a flocculated microstructure due to the presence of SO₄ ^2? (22,600 mg/L) and Mg²⁺ (1340 mg/L) in the slurry water. Settling included sedimentation and consolidation at low initial solids condition (25–35%) whereas only consolidation was observed at high initial solids contents (40–50%). The average k reduced from 1.2 × 10^?6 m/s (initial s = 25%) to 5.3 × 10^?8 m/s (initial s = 50%) along with a void ratio reduction from 7.4 to 2.6. Due to thixotropic strength, volume compressibility during consolidation showed apparent pre-consolidation at low effective stress (0.3–2 kPa) with a reduction in void ratio from 2.6 to 2.5. The e _s was found to be 2.46 at σ′ = 2 kPa and was followed by a steeper slope with the void ratio reducing to 2.1 at σ′ = 31 kPa. Likewise, the hydraulic conductivity during consolidation decreased from 2.6 × 10^?9 m/s (at e = 2.6) to 2.0 × 10^?10 m/s (at e = 2.1).     

Biosorption optimization and equilibrium isotherm of industrial dye compounds in novel strains of microscopic fungi

The aim of this study was to evaluate the biosorption capacity of selected strains of microscopic fungi. We optimized the biosorption process and used the Freundlich isotherm for three strains: H. haematococca BwIII43, K37 and T. harzianum BsIII33 to describe the biosorption equilibrium of anthraquinone dye, Alizarin Blue Black B (ABBB) and alkali lignin (AL). In optimal conditions (1 g of mycelium biomass, pH = 7.0, 28 °C) for ABBB and AL sorption, the live biomass of H. haematococca BwIII43 was characterized by a higher sorption capacity, amounting to 247.47 and 161.00 mg g^?1, respectively. The highest sorption properties toward anthraquinone dye (K _F = 19.96 mg g^?1) were shown for the biomass of H. haematococca K37. In the presence of alkali lignin, the highest sorption capacity and bond strength exhibited the biomass of H. haematococca BwIII43 (K _F = 28.20 mg g^?1, n = 3.46). Effective decolorization of ABBB and AL by the selected strains of microscopic fungi indicated that the biosorption process additionally enhanced the removal of color compounds from the solution.     

Phytoplankton Spatial Variability in the River-Dominated Estuary,Apalachicola Bay,Florida

In shallow estuaries with strong river influence, the short residence time and pronounced gradients generate an environment for plankton that differs substantially in its dynamics from that of the open ocean, and the question arises “How is phytoplankton biomass affected?” This study assesses the small-scale spatial and temporal distribution of phytoplankton in Apalachicola Bay, a shallow bar-built estuary in the Florida Panhandle. Phytoplankton peaks were characterized to gain insights into the processes affecting spatial heterogeneity in biomass. Chlorophyll a (Chl a) distribution at 50-m spatial resolution was mapped using a flow-through sensor array, Dataflow©, operated from a boat that sampled four transects across the bay every 2 weeks for 16 months. Chl a peaks exceeding background concentrations had an average width of 1.3?±?0.7 km delineated by an average gradient of 3.0?±?6.0 μg Chl a L^?1 km^?1. Magnitude of E-W wind, velocity of N-S wind, tidal stage, and temperature affected peak characteristics. Phytoplankton contained in the peaks contributed 7.7?±?2.7% of the total integrated biomass observed along the transects during the study period. The river plume front was frequently a location of elevated Chl a, which shifted in response to river discharge. The results demonstrate that despite the shallow water column, river flushing, and strong wind and tidal mixing, distinct patchiness develops that should be taken into consideration in ecological studies and when assessing productivity of such ecosystems.     

Sequence signal processing of 2012 Ahar–Varzaghan earthquake (<Emphasis Type="Italic">M</Emphasis><Subscript>W</Subscript> 6.4) of NW Iran

Before starting seismic cycle of Ahar–Varzaghan 2012 event, a partial gap in the form of a pre-seismic calm sequence (seismicity rate, r = 0.46 event/year, b = 1.4) with duration of 303 days spatially has dominated over the entire seismogenic area. From April 17, 2012, to May 31, 2012, r significantly increased to 2.16, indicating strong foreshock sequence, and b value changed to 1.9, remarkably. In the last two months before the mainshock, foreshocks have partially migrated toward the earthquake fault (with a decrease in size, b = 2.0). Significantly, high rate of seismicity and low V _P /V _S (1.64) in the foreshocks sequence and also very high seismicity rate (17.3) and high V _P /V _S (1.76) in the aftershocks sequence make substantial differences between the seismic cycle and the background seismicity. Moreover, a significant E–W migration of the microseismicity was confirmed in the study area.     

Spatio-temporal variations of respirable particles at residential areas located in the vicinity of opencast coal projects,India: a case study

The objective of the study is to investigate spatio-temporal variations of PM₁₀, PM_2.5, and PM₁ concentrations at seven residential sites, located in the vicinity of opencast coal projects, Basundhara Garjanbahal Area (BGA), India. Meteorological parameters such as wind speed, wind direction, relative humidity, and temperature were collected simultaneously with PM concentrations. Mean concentrations of PM₁₀ in the range 215 ± 169–526 ± 412 μg m^?3, PM_2.5 in the range of 91 ± 79–297 ± 107 μg m^?3, PM₁ in the range of 68 ± 60–247 ± 84 μg m^?3 were obtained. Coarse fractions (PM_2.5–10) varied from 27 to 58% whereas fine fractions (PM_1–2.5 and PM₁) varied in the range of 51–73%. PM_2.5 concentration was 41–74% of PM₁₀ concentration, PM₁ concentration was 31–62% of PM₁₀ concentration, and PM₁ concentration was 73–83% of PM_2.5 concentration. Role of meteorology on PM concentrations was assessed using correlation analysis. Linear relationships were established among PM concentrations using least square regression analysis. With the aid of principal component analysis, two components were drawn out of eight variables, which represent more than 75% of variance. The results indicated that major sources of air pollutants (PM₁₀, PM_2.5, PM₁, CO, CO₂) at the residential sites are road dust raised by vehicular movement, spillage of coal generated during transportation, spontaneous combustion of coal, and biomass burning in village area.