Heavy metal pollution and human health risk assessment for exposure to surface soil of mining area: a comprehensive study

Climate change projections indicate an increase in intense rainfall events with consequent river flooding, which could lead to devastating natural disaster     

Monthly stream flow forecasting via dynamic spatio-temporal models

In this research, a dynamic linear spatio-temporal model (DLSTM) was developed and evaluated for monthly streamflow forecasting. For parameter estimation, coupled expectation–maximization (EM) algorithm and Kalman filter was adopted. This combination enables the model to estimate the state vector and parameters concurrently. Different forecast scenarios including various combinations of upstream stations were considered for downstream station streamflow forecasting. Several statistical criteria, nonparametric and visual tests were used for model evaluation. Results indicated that the spatio-temporal model performed acceptably in almost all scenarios. The dynamic model was able to capitalize on coupled spatial and temporal information provided that there is spatial connectivity in the studied hydrometric stations network. Moreover, threshold level method was used for model evaluation in drought and wet periods. Results indicated that, in validation phase, the model was able to forecast the drought duration and volume deficit/over threshold, although volume deficit/over threshold could not be accurately simulated.     

Nannostratigraphy and palaeoecology of uppermost Mozduran Formation in the Kopeh-Dagh range (NE Iran)

The Mozduran Formation includes light-coloured, thick-bedded to massive limestone and porous dolomitic limestone and dolomite. In this study, 13 samples from the uppermost Mozduran Formation were taken from two localities and examined for calcareous nannofossils. A total of 19 species and 12 genera were identified in the Mozduran section and19 species and 13 genera for the Taherabad section. Based on these assemblages, the uppermost Mozduran Formation is assignable to Sissingh's (1977) biozone CC1 (Early Berriasian) at the Mozduran section and to biozone CC3 (Late Valanginian) at the Taherabad section. Thus, the formation is younger from east to west across the basin.     

Nannostratigraphy and investigation of sedimentation conditions of the lower boundary and the upper boundary of the Aitamir Formation in the east and west Kopet Dagh,northeast of Iran

By attention to the stratigraphic value of calcareous nannoplanktons for the age determination of sedimentary beds, for the first time Late Cretaceous calcareous nannofossil taxa, their distributions and relative abundances were recorded from the lower and the upper boundary of Aitamir Formation located in northeast Iran. In the present study, biostratigraphy and paleoecological conditions were reconstructed. The Aitamir Formation comprises glauconitic sandstones and olive-green shales. In this work, samples were prepared with smear slides, and nannofossils of these boundaries are listed and figured. They were photographed under a light microscope. Based on nannoplanktons and as a result of biostratigraphic studies, the age of the lower boundary of the Aitamir Formation in the east Kopet Dagh is Early/Middle Turonian, the age of the lower boundary in the west Kopet Dagh is Late Turonian/Early Coniacian, the age of the upper boundary of the Aitamir Formation in the east Kopet Dagh is Late Santonian, and the age of the upper boundary of this Formation in the west Kopet Dagh is Early Campanian. Based on paleoecological interpretation, the Aitamir Formation was deposited in a shallow marine environment, at relatively low latitude. A deepening trend of the sedimentary basin is recognized passing from Aitamir Formation to the overlying Abderaz Formation while in the lower boundary from Sanganeh to Aitamir Formation depth decreased.     

Photometric modelling of close binary star CN And

The results of two color photometry of active close binary CN And are presented and analyzed. The light curves of the system are obviously asymmetric, with the primary maximum brighter than the secondary maximum, which is known as the O’Conell effect. The most plausible explanation of the asymmetry is expected to be due to spot activity of the primary component. For the determination of physical and geometrical parameters, the most new version of W-D code was used, but the presence of asymmetry prevented the convergence of the method when the whole light curves were used. The solutions were obtained by applying mode 3 of W-D code to the first half of the light curves, assuming synchronous rotation and zero eccentricity. Absolute parameters of the system were obtained from combining the photometric solution with spectroscopic data obtained from radial velocity curve analysis. The results indicate the poor thermal contact of the components and transit primary minimum. Finally the O-C diagram was analyzed. It was found that the orbital period of the system is changing with a rate ofd P/dt = − 2.2(6) × 10⁻¹⁰ which corresponds to mass transfer from more massive component to less massive with the rate ofd M/dt ∼4.82 × 10⁻⁸ M _sun/year.     

Geochemical modeling of cyanide in tailing dam gold processing plant

This research is aimed at investigating possible neutralization of cyanide in tailing dam of Muteh gold processing plant in Isfahan, Iran at various conditions such as pH and temperature using USEPA Visual MINTEQ geochemical model simulation. The model is based on geochemical equilibrium which uses the simultaneous solution of the non-linear mass action expressions and linear mass balance relationships to formulate and solve the multiple-component chemical equilibrium problems. In this study the concentration of aqueous species in tailing dam as an aqueous, solid and gaseous were used as input in the model. Temperature and pH variation were simulated. The results of the model indicated that cyanide may be complexes in 10 < pH < 5. In other pH values complexation is not important. The results also indicated that cyanide reduction mechanism in acidic pH and temperature above 30°C is due to cyanide acid formation which is vaporized.     

Advantage of almond green hull over its resultant ash for chromium(VI) removal from aqueous solutions

The discharge of industrial effluents containing hexavalent chromium can be very harmful for the environment. Therefore, Cr(VI) should be removed from contaminated water, and especially from wastewater, to prevent its discharge into the environment. This study is aimed at analyzing the factors that affect the removal of Cr(VI) with the use of almond green hull and ash adsorbent. The effects of pH (2–10), adsorbent dose (2–24 g/L), Cr(VI) concentration (10–100 mg/L), exposure time (1–60 min), and temperature (5–50 °C) were examined. The surface morphology, pore size of adsorbent surfaces were characterized with SEM, EDX, FTIR. Maximum removal occurred at pH = 2. Results showed that the removal yield increased with the rise of exposure time and temperature. The data indicate that due to limited site on adsorbent surface, the removal efficiency decreased as initial Cr(VI) concentration increased. When the adsorbent dose was increased, the removal yield increased in the case of the bioadsorbent as well; however, in the ash adsorbent, there was an increase followed by a decreasing trend. The study highlights that almond green hull can be more efficient than its ash in the removal of Cr(VI) from aqueous solution. As a general result of study, it can be argued that almond green hull bioadsorbent and the obtained carbon are able to remove Cr(VI) from aqueous solutions; thus, they can be used as efficient and economical substitutes for existing adsorbents like activated carbon, for the removal of chromium from polluted aqueous solutions.     

Estimation on ureolysis-based microbially induced calcium carbonate precipitation progress for geotechnical applications

There are some key challenges in the geotechnical applications of microbially induced CaCO₃ precipitation technique. These challenges mainly arise from lack of enough control on precipitation patterns within the soil. Monitoring precipitation progress in treatment solution (biogrout) before injection provides useful information on controlling the precipitation pattern. In this study, a hybrid of electrical conductivity change measurements and precipitation mass measurements was proposed for the monitoring. The results were described as characteristic curves which would provide useful information on interpreting, estimating, and steering the precipitation pattern within the soil. The effects of some influencing factors on the precipitation patterns were also statistically investigated. XRD, FTIR, and SEM were used for the microscale identification analysis of the precipitated solids.     

Isolation and characterization of a novel native Bacillus strain capable of degrading diesel fuel

The ability of native bacteria to utilize diesel fuel as the sole carbon and energy source was investigated in this research. Ten bacterial strains were isolated from the oil refinery field in Tehran, Iran. Two biodegradation experiments were performed in low and high (500 and 10000 ppm, respectively) concentration of diesel fuel for 15 days. Only two isolates were able to efficiently degrade the petroleum hydrocarbons in the first test and degraded 86.67% and, 80.60 % of diesel fuel, respectively. The secondary experiment was performed to investigate the toxicity effect of diesel fuel at high concentration (10000 ppm). Only one strain was capable to degrade 85.20 % of diesel fuel at the same time (15 days). Phenotype and phylogeny analysis of this strain was characterized and identified as diesel-degrading bacteria, based on gram staining, biochemical tests, 16S rRNA gene sequence analysis. These results indicate that this new strain was Bacillus sp. and could be considered as Bacillus Cereus with 98 % 16 S rRNA gene sequence similarity. The results indicate that native strains have great potential for in situ remediation of diesel-contaminated soils in oil refinery sites.