http://hdl.handle.net/10027/7258 Fri, 24 May 2013 14:32:22 GMT 2013-05-24T14:32:22Z http://hdl.handle.net/10027/8586 Reactivity of Aluminum Lactate-Modified Nanoscale Iron Particles with Pentachlorophenol in Soils Darko-Kagya, Kenneth; Khodadoust, Amid P.; Reddy, Krishna R. Due to the hindered transport of nanoscale iron particles (NIP) in the subsurface caused by the agglomeration and adsorption of NIP during transport, the NIP surface has to be modified to improve the transport of NIP in the subsurface. This study assessed the effectiveness of surface-modified NIP for in situ degradation of contaminants using aluminum lactate as the modifying agent, where aluminum lactate had been earlier shown to be an effective dispersant for enhanced transport of modified NIP in the subsurface. The reactivity of bare-NIP and lactate-modified NIP (LM-NIP) was investigated using pentachlorophenol (PCP) as a representative chlorinated hydrophobic organic contaminant in kaolin and field sand as low permeability clayey soil and high permeability soil, respectively. Kaolin and field sand were spiked at 100mg/kg PCP and at 89mg/kg PCP, respectively. NIP dosages of 4, 10, 20, 50, 75, and 100 g/L were applied for a reaction period of 24 h. For the bare-NIP dosage of 100 g/L, PCP degradation of 98% and 99% was obtained in 24 h for field sand and kaolin, respectively. The effect of reaction time on reactivity of bare-NIP and LM-NIP was evaluated using a lower NIP dosage of 4 g/L for 1, 2, 4, 7, and 14 days. After 14 days, greater PCP degradation occurred in bare-NIP systems than in LM-NIP systems, where 95% and 99% degradation was obtained for field sand and kaolin with bare-NIP, respectively, whereas 90% and 91% degradation was obtained for field sand and kaolin with LM-NIP, respectively. Differences in PCP degradation between bare-NIP and LM-NIP diminished with time more rapidly for field sand than for kaolin. For both field sand and kaolin, nearly complete dechlorination of PCP to phenol occurred with bare-NIP with a more rapid dechlorination in field sand than in kaolin. This is a copy of an article published in the journal Environmental Engineering Science © 2010 Mary Ann Liebert, Inc.; Environmental Engineering Science is available online at: http://www.liebertonline.com DOI: 10.1089/ees.2010.0081 Wed, 10 Nov 2010 06:00:00 GMT http://hdl.handle.net/10027/8586 2010-11-10T06:00:00Z http://hdl.handle.net/10027/8571 A dynamic hazard-based system of equations of vehicle ownership with endogenous long-term decision factors incorporating group decision making Rashidi, Taha Hossein; Mohammadian, Abolfazl The transportation system affects all aspects of our daily lives including relatively long-term decisions on work and home location choice and automobile ownership decisions. The interdependency existing among these three decisions jointly influences household mobility and overall travel patterns. Therefore, a dynamic modeling framework that can account for the effects of interdependencies between vehicle transaction behavior and residential and job location choices is highly desirable. These decisions are made in the household level while individuals’ decisions influence the overall outcome; therefore, it is also important to incorporate a group decision making process within such modeling frameworks. This study introduces a dynamic model for vehicle ownership, residential mobility, and employment relocation timing decisions. These decisions are modeled at the individual level and then sequentially aggregated to the household level if it is required. A hazard-based system of equations is formulated and applied in which work location and residential location changes are included as endogenous variables in the vehicle transaction model while other important factors such as land-use and built environment variables, household dynamics, and individuals’ socio-demographics are also considered. NOTICE: this is the author’s version of a work that was accepted for publication in Journal of Transport Geography. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Journal of Transport Geography, [June 29, 2011] DOI: 10.1016/j.jtrangeo.2011.05.001. The original publication is available at www.elsevier.com. Wed, 29 Jun 2011 05:00:00 GMT http://hdl.handle.net/10027/8571 2011-06-29T05:00:00Z http://hdl.handle.net/10027/8546 Modeling interdependencies between vehicle transaction, residential relocation and job change Rashidi, Taha H.; Mohammadian, Abolfazl; Koppelman, Frank S. This paper introduces a vehicle transaction timing model which is conditional on household residential and job relocation timings. Further, the household residential location and members’ job relocation timing decisions are jointly estimated. Some researchers have modeled the household vehicle ownership decision jointly with other household decisions like vehicle type choice or VMT; however, these models were basically static and changes in household taste over time has been ignored in nearly all of these models. The proposed model is a dynamic joint model in which the effects of land-use, economy and disaggregate travel activity attributes on the major household decisions; residential location and members’ job relocation timing decisions for wife and husband of the household, are estimated. Each of these models is estimated using both the Weibull and log-logistic baseline hazard functions to assess the usefulness of a non-monotonic rather than monotonic baseline hazard function. The last three waves of the Puget Sound Panel Survey data and land-use, transportation, and built environment variables from the Seattle Metropolitan Area are used in this study as these waves include useful explanatory variables like household tenure that were not included in the previous waves. Post print version of article may differ from published version. The original publication is available at springerlink.com; DOI: 10.1007/s11116-011-9359-4. Thu, 14 Jul 2011 05:00:00 GMT http://hdl.handle.net/10027/8546 2011-07-14T05:00:00Z http://hdl.handle.net/10027/8539 Remediation of Chlorinated Solvent Plumes Using In-Situ Air Sparging-A 2-D Laboratory Study Adams, Jeffrey A.; Reddy, Krishna R.; Tekola, Lue In-situ air sparging has evolved as an innovative technique for soil and groundwater remediation impacted with volatile organic compounds (VOCs), including chlorinated solvents. These may exist as non-aqueous phase liquid (NAPL) or dissolved in groundwater. This study assessed: (1) how air injection rate affects the mass removal of dissolved phase contamination, (2) the effect of induced groundwater flow on mass removal and air distribution during air injection, and (3) the effect of initial contaminant concentration on mass removal. Dissolved-phase chlorinated solvents can be effectively removed through the use of air sparging; however, rapid initial rates of contaminant removal are followed by a protracted period of lower removal rates, or a tailing effect. As the air flow rate increases, the rate of contaminant removal also increases, especially during the initial stages of air injection. Increased air injection rates will increase the density of air channel formation, resulting in a larger interfacial mass transfer area through which the dissolved contaminant can partition into the vapor phase. In cases of groundwater flow, increased rates of air injection lessened observed downward contaminant migration effect. The air channel network and increased air saturation reduced relative hydraulic conductivity, resulting in reduced groundwater flow and subsequent downgradient contaminant migration. Finally, when a higher initial TCE concentration was present, a slightly higher mass removal rate was observed due to higher volatilization-induced concentration gradients and subsequent diffusive flux. Once concentrations are reduced, a similar tailing effect occurs. © 2011 by the authors; licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution license (http://creativecommons.org/licenses/by/3.0/. DOI: 10.3390/ijerph8062226 Thu, 16 Jun 2011 05:00:00 GMT http://hdl.handle.net/10027/8539 2011-06-16T05:00:00Z