Thermal venting is a remediation technique suitable to the liquid unsaturated zone to enhance recovery of less-volatile residual hydrocarbon contaminants. Thermal venting is different to traditional ...soil venting because heated air instead of air at ambient conditions is applied to the contaminated zone. The vapor pressure of a less-volatile contaminants is typically increased by temperature causing the gas-phase concentrations to increase by three- to five-fold over a temperature increase of 20–30°C. The work described in this first paper provides the theoretical framework of analysis related to thermal venting. The analysis included nonisothermal gas flow, thermal energy transport and multicomponent mass transport in a multiphase porous medium. The transient gas flow analysis included the effect of temperature on fluid properties and gas compressibility. The heat energy transport analysis was performed under the thermodynamic equilibrium condition with phase-summed effective thermal properties. Multi-component mass transport was performed under local equilibrium for partitioning between phases. Model verification was performed to the extend possible using analytical and available experimental data for different physical processes. The second paper of this two-part series will demonstrate the applicability of thermal venting technique through numerical simulations of hypothetical laboratory and field-scale scenarios.
The first part (Kaluarachchi and Islam, this issue) of this two-part series of papers developed the theoretical framework of analysis describing thermal venting using nonisothermal gas flow, heat ...energy transport and multicomponent mass transport. The work presented in this paper demonstrated the applicability of thermal venting through a series of numerical simulations in one- and two-dimensional flow domains. In both cases, a four-component hydrocarbon mixture consisting of volatile benzene, moderately-volatile
n-dodecane, and less-volatile naphthalene and
n-hexylbenzene in equal mass fraction was used. The results from the one-dimensional laboratory-scale column simulations showed a total recovery of naphthalene,
n-dodecane and
n-hexylbenzene by thermal venting, where as corresponding removal by normal venting was < 33% for the same time period. Effect of thermal energy was negligible with volatile benzene due to high ambient vapor pressure. Similar results were obtained from the two-dimensional field-scale simulations too. The temperature distribution in the subsurface was affected by simultaneous evaporation of contaminants and moisture condensation from humid air. The simulations also considered the parameter sensitivity to overall recovery. The overall results of this theoretical analysis suggested that thermal venting may be a powerful remediation technique that is applicable to the unsaturated zone when normal soil venting fails to recover the less-volatile fraction of the residual plume. However, the results of this analysis need to be experimentally validated for complete evaluation of the overall technology.
Thermal venting is considered to be a promising technology for remediating semi-volatile hydrocarbon compounds from the unsaturated zone. In this study, the fundamental behavior and applicability of ...thermal venting were investigated using one- and two-dimensional hypothetical simulations. The source of heat energy to the system was through heated air. Theoretical analysis of thermal venting included analysis of unsteady gas flow, heat energy transport and multicomponent mass transport. Hydrocarbon contamination was assumed to be at residual saturation and partitioned to gas, aqueous, and solid phases under equilibrium conditions. The aqueous and hydrocarbon phases were assumed to be immobile with the aqueous phase at residual saturation during venting. Gas compressibility and temperature-dependent gas viscosity were considered in the gas flow analysis. The analysis of heat energy transport includes temperature-dependent thermal properties of the fluid and soil matrix. Multicomponent mass transport analysis was performed considering the temperature-dependent vapor pressure and gas phase concentration of hydrocarbon compounds. The gas flow, heat energy, and multicomponent mass transport equations were solved using an upstream weighted finite difference method. Cumulative remediation and change of residual saturation of the contaminant were investigated with time during thermal venting. The results obtained from thermal venting were also compared with that of normal venting to evaluate the overall applicability of this technique. Heat distribution in the system to be affected by the latent heat absorbed during contaminant volatilization and the latent heat released during condensation of water vapor of the incoming air. The results show that thermal venting can be a powerful remediation technique for semi-volatile organics due to enhanced contaminant recovery typically not attained by normal vapor extraction schemes. The applicability of thermal venting was found to be attractive for both one-dimensional soil column and two-dimensional axisymmetric domains.
In water-scarce regions, high yield and improved water use efficiency (WUE) of crops can be obtained if water and nitrogen (N) are properly applied. While water and N have been the subject of ...research worldwide, studies are needed to advance our understanding on the complexity of their interaction. A field experiment was conducted at the University of Wyoming Powell Research and Extension Center in 2014 and 2015 growing seasons to determine the effect of irrigation water and N on growth, dry matter (DM) yield, and WUE of silage corn (Zea mays L.) grown under on-surface drip irrigation (ODI). The experiment was laid out as a randomized complete block design in split-plot arrangement with three replications. Irrigation was the main treatment and included 100ETc (100% crop evapotranspiration), 80ETc, and 60ETc. Nitrogen was the sub-treatment and included 0, 90, 180, 270, and 360 kg N ha−1 as urea-ammonium-nitrate solution Results showed that irrigation water, N, and application timing significantly affected growth and DM yield, especially at late vegetative and mid reproductive growth stages. At harvest (R4), no significant difference was observed between 180 kg N ha−1 and 270 kg N ha−1 on DM yield and WUE. However, significant differences of DM yield were observed between irrigation treatments, and 100ETc and 80ETc did not differ in WUE. Our findings suggest that 100ETc and 180 kg N ha−1 is the best combination for high yielding corn for silage grown in a semi-arid climate under ODI.
Colorectal cancer (CRC) is a common tumor worldwide. CRC is influenced by several types of miRNAs and long non-coding RNAs. This study aims to evaluate the correlation of lncRNA ZFAS1/ miR200b/ ZEB1 ...protein with presence of CRC.
Quantitative real-time polymerase chain reaction was used to measure serum expression of lncRNA ZFAS1 and microRNA-200b in 60 CRC patients and 28 control subjects. ZEB1 protein in serum was measured by ELISA.
Lnc ZFAS1 and ZEB1 were up-regulated in CRC patients in compare to control subjects while miR-200b was down-regulated. There was a linear correlation between ZAFS1 expression and miR-200b and ZEB1 in CRC.
ZFAS1 is a key player of CRC progression and could be a potential therapeutic target by sponging miR-200b. In-addition the association between ZFAS1, miR-200b and ZEB1 highlights their potential value as a novel diagnostic biomarker in human CRC.
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