Environment
Azadeh Agah; Faramarz Doulati Ardejani
Abstract
This study aimed to develop a model to illustrate the migration of petroleum hydrocarbons that penetrate the underground environment due to leakage from storage tanks located below the surface.The transport model for non-aqueous phase liquids was integrated with contaminant transport models in two dimensions ...
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This study aimed to develop a model to illustrate the migration of petroleum hydrocarbons that penetrate the underground environment due to leakage from storage tanks located below the surface.The transport model for non-aqueous phase liquids was integrated with contaminant transport models in two dimensions to forecast the contamination of groundwater and soil-gas resulting from the migration of light non-aqueous phase liquids on the water surface. The finite volume method was employed to obtain numerical solutions. The findings indicated that evaporation significantly influences the migration of non-aqueous phase liquids. The soluble plume's production and movement were impacted by the geological features of the location and the existence of the free phase plume. Comparing the model predictions and the results from the field studies for the thickness of non-aqueous phase liquids plume over water indicates a good agreement between the results of the two methods with an average error of less than 5%. The maximum thickness of non-aqueous phase liquids plume between 7 and 7.5 meters was obtained at a distance of 2250 meters from the beginning of the investigated profile. Although 36 years have passed since the leakage occurred, a significant amount of the spilled mass still remained in the non-aqueous phase liquids. The prolonged migration of non-aqueous phase liquids over this time period has led to the contamination of groundwater and the accumulation of significant quantities of contaminated soil.
Azadeh Agah; Faramarz Doulati Ardejani; Mohamad Javad Azinfar
Abstract
This work investigates the reactive transport of volatile hydrocarbons in the unconfined aquifer system of Tehran oil refinery and the industrial area of Ray, Tehran. A 2D finite volume model is presented to predict the soil gas contamination caused by LNAPL traveling on the phreatic surface through ...
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This work investigates the reactive transport of volatile hydrocarbons in the unconfined aquifer system of Tehran oil refinery and the industrial area of Ray, Tehran. A 2D finite volume model is presented to predict the soil gas contamination caused by LNAPL traveling on the phreatic surface through the vadose zone of the aquifer incorporating physical, chemical, and biological processes. A multi-purpose commercial software called PHOENICS is modified by incorporating extra codes to solve the model equations numerically. The model predictions closely agree with the field measurements, showing that the LNAPL migration is typically affected by the volatilization process. LNAPLs represent a potential long-term source of soil and groundwater contamination in the studied site. A comparison of the simulation results in a time step of 36 years with the results of field studies shows that the presented numerical model can simulate the reaction transfer of evaporated hydrocarbons in the unsaturated region. The concentrations have decreased in the time step of 36 years compared to the values shown in the time step of 50 years. This decrease in the hydrocarbon gas-phase concentrations in the unsaturated zone is due to excavations at the site for field studies. Through these excavations, a significant volume of the gaseous phase trapped below the earth's surface is released into the atmosphere, which reduces the accumulation of volatile gases beneath the earth's surface.
A. Agah; N. Falahati
Abstract
In this research work, the potential capability of nano-clay and tonsil, as low-cost and domestic adsorbents, for the elimination of a cationic dye, (CR18) from contaminated water is investigated. The surface properties of the adsorbents are studied by means of the scanning electron microscopy (SEM) ...
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In this research work, the potential capability of nano-clay and tonsil, as low-cost and domestic adsorbents, for the elimination of a cationic dye, (CR18) from contaminated water is investigated. The surface properties of the adsorbents are studied by means of the scanning electron microscopy (SEM) and X-ray diffraction techniques. The effects of the initial dye concentration, pH, stirring speed, contact time, and adsorbent dosage are investigated at 25 . The results obtained show that the dye adsorption data from the nano-clay and tonsil experiments fit well to the Langmuir and Freundlich isotherms, respectively. The results of dye adsorption kinetics demonstrate that the adsorption system follows a pseudo-second-order model with a satisfactory correlation value (R=99%).The adsorption thermodynamics is also studied, concluding that the adsorption process is spontaneous and physically controlled. Under the optimum conditions (pH of 7, stirring speed of 200 rpm, CR18 concentration of 30 ppm and contact time of 30 min), the adsorption capacities of the mixed adsorbents show the maximum adsorption efficiency at the tonsil:nano-clay weight ratio of 1:2.
