Sorptive Potential of Beach Sand to Remove Ni(II) Ions: An Equilibrium Isotherm Study

The potential to remove Ni(II) ions from aqueous solutions using sea beach sand, a carbonate‐quartz mineral, was thoroughly investigated. The effects of relevant parameters such as solution pH, adsorbent dose, metal ions concentration, and temperature on Ni(II) sorption onto beach sand were examined. The sorption data followed the Langmuir, Freundlich and Dubinin‐Radushkevich (D‐R) isotherms. The adsorption was endothermic in nature at ambient temperature and the computation of the parameters, ΔH, ΔS and ΔG indicated the interactions between sorbate and sorbent to be thermodynamically favorable. Equilibrium was achieved very quickly within 30 min of shaking. A pseudo‐first order Lagergren equation was used to test the adsorption kinetics. Other kinetic models, e. g., the Morris‐Weber and Reichenberg equations, were used to calculate the rate constant of intraparticle diffusion and the fate of the diffusion process, respectively. The influence of some of the common cations and anions were also a subject of this study.     

Fate and Behavior of Organochlorine Pesticides in the Indonesian Tropical Climate: A Study in the Segara Anakan Estuarine Ecosystem

The fate and behavior of organochlorine pesticides (OCPs) in the Segara Anakan Estuarine ecosystem was studied in the Indonesian tropical climate, which is characterized by heavy rainfall in the rainy season and low rainfall in the dry season. Since OCPs have high affinity for soil, a field study on the dissipation and degradation pattern of soil‐applied 1,1,1‐trichloro‐2,2‐bis (4‐chlorophenyl) ethane (p,p′‐DDT) and 1,1‐dichloro‐2,2‐bis (4‐chlorophenyl) ethylene (p,p′‐DDE) as model OCPs was carried out. They occurred at a faster rate in the biphasic mode in wet conditions and at a slower rate in dry conditions. In wet conditions, the conversion from p,p′‐DDT to p,p′‐DDE and p,p′‐DDD (1,1‐dichloro‐2,2‐bis (4‐chlorophenyl) ethane) was governed by a parallel reaction. In dry conditions, only p,p′‐DDE was formed. The fate and behavior of OCPs in sediment estuary are similar to those in soil under wet conditions, except that their sorption‐desorption constants are influenced by estuarine surface water salinity. In the dry season, due to high salinity, the sediment acts as an OCP sink and a secondary source for the ecosystem, causes higher OCP concentration of local bio‐monitors, i. e., Geloina spp. and Mugil spp. In the rainy season, high water inflow washed the desorbed OCP pesticides out of the estuarine ecosystem, and caused lower concentrations of bio‐monitors. A risk evaluation for the uptake of OCP pesticides during the dry season suggests that adult fish meal consumers are safe, but risk management is required for pregnant woman.     

U, Th, K and Cs activity concentrations along the southern coast of the Caspian Sea, Iran

The determination of activity concentrations of the radioactive elements ²³⁸U, ²³²Th, ⁴⁰K and ¹³⁷Cs was performed on grab samples taken from a polluted environment. The samples were sliced into strata from 5 cm depth, dried and ground to sieved through a 170 mesh size prior to the analysis. Activity concentration was quantified using gamma spectroscopy. The results showed that the concentrations of activity in the sediment samples are 177 ± 12.4, 117 ± 11.5, 1085 ± 101.6 and 131 ± 4.8 Bq kg⁻¹ for ²³⁸U, ²³²Th, ⁴⁰K and ¹³⁷Cs, respectively. In general, the distribution of activity concentrations along the southern coast of the Caspian Sea area exceeded international limits. The hazard index of the samples was 0.19-0.88, with an average of 0.49. The mean values of radium equivalent activity and dose rate are 176 Bq kg⁻¹ and 63 nGy h⁻¹, respectively.     

GPS observations at quasi-conjugate points under disturbed conditions

The conjugacy effects of the GPS scintillation activities during the geomagnetic storms of October 2003, November 2003 and July 2004 have been investigated at the approximately geomagnetically conjugate stations: Scott Base, Antarctica (SBA) and Resolute Cornwallis Island (RESO) in the high Arctic region. The measurements aim at investigation of the similarities and differences of the scintillation activities occurring at the conjugate points in the polar regions under storm conditions and examine the relationship between the Storm Enhanced Density (SED) and scintillation activity. The measurements of the scintillation activities obtained from total scintillation index during these storm periods at both hemispheres showed asymmetry in the ionospheric scintillation occurrence at the conjugate points. Pronounced scintillation activity was observed at the nightside hemisphere with the total scintillation index higher than at the dayside hemisphere. The results also show that the durations of severe scintillation activity were longer at the nightside hemisphere. The measurements showed that the intense scintillation periods were corresponding to the presence of the SED events where more pronounced SED events were observed over the nightside hemisphere.     

Sustainable soil stabilisation with ground granulated blast-furnace slag activated by olivine and sodium hydroxide

Acta Geotechnica - Ground granulated blast-furnace slag (GGBS), activated with olivine (Mg2SiO4) and sodium hydroxide (NaOH), was used to stabilise a clayey soil. Mechanical and microstructural...     

Combining process-based and surface-based models to simulate subsurface heterogeneity in volcanic aquifers

Realistic models of lithologic structure are critical for predicting flow and transport through heterogeneous volcanic aquifers. Existing models of lava flows based on physical processes are able to realistically simulate flow geometry and lithology, but the computational intensity limits applicability in generating entire aquifers. Fast surface-based models have been developed for hazard mapping, but these do not incorporate 3D geometry or lithology critical for hydrogeologic applications. Here we develop a hybrid modeling method (HMM) based on a combination of a process-based model (PBM) and a surface-based model. The methodologies are presented and compared to a known single flow and to each other in a full aquifer simulation. Results indicate that both the PBM and HMM simulations reasonably reproduce the flow geometry (length, branching, thickness) of the 1984 eruption of Mauna Loa in Hawai’i. Simulations of a volcanic aquifer built from 100 flows with the PBM and HMM are similar in spatial distribution and overall proportions of lithology (aa, transitional, pahoehoe, ash), flow geometry, and aquifer geometry. Thus, the hybrid method is an efficient method to generate geologically realistic models of volcanic aquifer structure. Model realism and parameterization can be improved as more field data become available.     

Implementation of a hybrid MLP-FFA model for water level prediction of Lake Egirdir,Turkey

The predictive ability of a hybrid model integrating the Firefly Algorithm (FFA), as a heuristic optimization tool with the Multilayer Perceptron (MLP-FFA) algorithm for the prediction of water level in Lake Egirdir, Turkey, is investigated. The accuracy of the hybrid MLP-FFA model is then evaluated against the standalone MLP-based model developed with the Levenberg–Marquadt optimization scheme applied for in the backpropagation-based learning process. To develop and investigate the veracity of the proposed hybrid MLP-FFA model, monthly time scale water level data for 56 years (1961–2016) are applied to train and test the hybrid model. The input combinations of the standalone and the hybrid predictive models are determined in accordance with the Average Mutual Information computed from the historical water level (training) data; generating four statistically significant lagged combinations of historical data to be adopted for the 1-month forecasting of lake water level. The proposed hybrid MLP-FFA model is evaluated with statistical score metrics: Nash–Sutcliffe efficiency, root mean square and mean absolute error, Wilmott’s Index and Taylor diagram developed in the testing phase. The analysis of the results showed that the hybrid MLP–FFA4 model (where 4 months of lagged combinations of lake water level data are utilized) performed more accurately than the standalone MLP4 model. For the fully optimized hybrid (MLP-FFA4) model evaluated in the testing phase, the Willmott’s Index was approximately 0.999 relative to 0.988 (MLP 4) and the root mean square error was approximately 0.029 m and compared to 0.102 m. Moreover, the inter-comparison of the forecasted and the observed data with various other performance metrics (including the Taylor diagram) verified the robustness of the proposed hybrid MLP-FFA4 model over the standalone MLP4 model applied in the problem of forecasting lake water level prediction in the current semi-arid region in Turkey.     

Compositional characteristics and geodynamic significance of late Miocene volcanic rocks associated with the Chah Zard epithermal gold–silver deposit,southwest Yazd,Iran

Whole‐rock geochemical and Sr–Nd isotopic data are presented for late Miocene volcanic rocks associated with the Chah Zard epithermal Au–Ag deposit in the Urumieh‐Dokhtar Magmatic Arc (UDMA), Iran, to investigate the magma source, petrogenesis and the geodynamic evolution of the study area. The Chah Zard andesitic to rhyolitic volcanic rocks are characterized by significant Large Ion Lithophile Element (LILE) and Light Rare Earth Element (LREE) enrichment coupled with High Field Strength Element (HFSE) depletion. Our geochemical data indicate an adakitic‐like signature for the volcanic rocks (e.g. SiO₂ > 62 wt%, Al₂O₃ > 15 wt%, MgO < 1.5 wt%, Sr/Y > 70, La/Yb > 35, Yb < 1 ppm, and Y < 18 ppm, and no significant Eu anomalies), distinguishing them from the other volcanic rocks of the UDMA. The Chah Zard volcanic rocks have similar Sr and Nd isotopic compositions; the ⁸⁷Sr/⁸⁶Sr(i) ratios range from 0.704 902 to 0.705 093 and the ε_Nd(i) values are from +2.33 to +2.70. However, the rhyolite porphyry represents the final stage of magmatism in the area and has a relatively high ⁸⁷Sr/⁸⁶Sr ratio (0.705 811). Our data suggest that the andesitic magmas are from a heterogeneous source and likely to result from partial melting of a metasomatized mantle wedge associated with a mixture of subducted oceanic crust and sediment. These melts subsequently underwent fractional crystallization along with minor amounts of crustal assimilation. Our study is consistent with the model that the volcanic host rocks to epithermal gold mineralization in the UDMA are genetically related to late Miocene Neo‐Tethyan slab break‐off beneath Central Iran.     

Fault slip and identification of the second fault plane in the Varzeghan earthquake doublet

An intraplate earthquake doublet, with 11-min delay between the events, devastated the city of Varzeghan in northwestern Iran on August 11, 2012. The first Mw 6.5 strike-slip earthquake, which occurred after more than 200 years of low seismicity, was followed by an Mw 6.4 oblique thrust event at an epicentral separation of about 6 km. While the first event can be associated with a distinct surface rupture, the absence of a surface fault trace and no clear aftershock signature makes it challenging to identify the fault plane of the second event. We use teleseismic body wave inversion to deduce the slip distribution in the first event. Using both P and SH waves stabilize the inversion and we further constrain the result with the surface rupture extent and the aftershock distribution. The obtained slip pattern shows two distinct slip patches with dissimilar slip directions where aftershocks avoid high-slip areas. Using the estimated slip for the first event, we calculate the induced Coulomb stress change on the nodal planes of the second event and find a preference for higher Coulomb stress on the N-S nodal plane. Assuming a simple slip model for the second event, we estimate the combined Coulomb stress changes from the two events on the focal planes of the largest aftershocks. We find that 90% of the aftershocks show increased Coulomb stress on one of their nodal planes when the N-S plane of the second event is assumed to be the correct fault plane.     

Performance evaluation of WAVEWATCH III model in the Persian Gulf using different wind resources

The third-generation wave model, WAVEWATCH III, was employed to simulate bulk wave parameters in the Persian Gulf using three different wind sources: ERA-Interim, CCMP, and GFS-Analysis. Different formulations for whitecapping term and the energy transfer from wind to wave were used, namely the Tolman and Chalikov (J Phys Oceanogr 26:497–518, 1996), WAM cycle 4 (BJA and WAM4), and Ardhuin et al. (J Phys Oceanogr 40(9):1917–1941, 2010) (TEST405 and TEST451 parameterizations) source term packages. The obtained results from numerical simulations were compared to altimeter-derived significant wave heights and measured wave parameters at two stations in the northern part of the Persian Gulf through statistical indicators and the Taylor diagram. Comparison of the bulk wave parameters with measured values showed underestimation of wave height using all wind sources. However, the performance of the model was best when GFS-Analysis wind data were used. In general, when wind veering from southeast to northwest occurred, and wind speed was high during the rotation, the model underestimation of wave height was severe. Except for the Tolman and Chalikov (J Phys Oceanogr 26:497–518, 1996) source term package, which severely underestimated the bulk wave parameters during stormy condition, the performances of other formulations were practically similar. However, in terms of statistics, the Ardhuin et al. (J Phys Oceanogr 40(9):1917–1941, 2010) source terms with TEST405 parameterization were the most successful formulation in the Persian Gulf when compared to in situ and altimeter-derived observations.