Use this URL to cite or link to this record in EThOS: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.488417
Title: Development of a mesoscale contaminant hydrogeology column and its application to environmental organic systems
Author: Middleton, Carl Nigel
Awarding Body: University of Manchester
Current Institution: University of Manchester
Date of Award: 2003
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Abstract:
Complete mixed batch reactor (CMBR) and column type experiments successfully investigated the migration of single solute and complex solute mixtures of hydrophobic organic compounds (HOCs) in subsurface environmental conditions and the importance of sorption kinetics. CMBR experiments proved relatively rapid and inexpensive, but their application to environmentally relevant settings was limited. Therefore, a large proportion of this research is devoted to the design, construction and validation of a mesoscale contaminant hydrogeology column for improved emulation of subsurface conditions. On-line solid phase extraction (SPE) of the column effluent facilitated convenient collection of complex mixtures of HOCs present at extremely low concentrations (0.1 - 1 μg L-1). Column 'miscible displacement' experiments and CMBR experiments were conducted to investigate sorption characteristics of the polycyclic aromatic compounds (PAHs) phenanthrene and benzo[e]pyrene (b[e]p) to quartzitic sands. CMBR experiments for phenanthrene sorption to two quartzitic sands of low soil organic matter (SOM) content, SMA (foc=0.000362) and SMB (foc=0.00025), determined equilibrimn sorption isotherms to be linear over the entire range of phenanthrene's aqueous solubility. The results indicate that SOM was the predominant sorption domain. CMBR determined values of the organic carbon distribution coefficient, Koc, were 1844 mL g-l and 2997 mL g-l for SMA and 5MB respectively, and are significantly less than previously reported. An empirical two-site model that accounted for observed bi-phasic sorption kinetics fitted the rate of sorption data well. Key model parameters were the fraction of instantaneous sorption (SMAf=0.37, 5MB f=0.42) and the rate constant (SMA k2-=0.044 hr-1, 5MB k2=0.076hr-1). Two column miscible displacement experiments investigated phenanthrene migration through SMA at high pore water velocities (v=56 cm hr-1). Results were fitted using the one-dimensional advection-dispersion equation, modified to account for kinetically limited sorption. Fitted parameters for duplicate experiments were: Koc=1229 mL g-l and 1237 mL g-l; /= 0.491 and 0.537; k2= 0.678 h{l and 0.589 hr-l. Parameters/and Koc were comparable to CMBR results. A single miscible displacement experiment was conducted investigating b[e]p migration through SMA. Fitted parameters were Koc=44503 mL g-l,/= 0.068 and k2 = 0.03 hr-1, and were contrary to previously published literature. Two column leachate experiments were successfully conducted that highlight the suitability of the column to complex environmental systems. The first experiment investigated desorption characteristics of environmentally important P AHs from historically contaminated manufactured gas plant (MGP) soil over a 62 day period. P AH desorption rates were small and indicated that the significant quantities of PAHs sorbed to the MGP soil were essentially irreversibly bound. The second experiment was a novel application of the column in which an organic unresolved complex mixture (the aromatic fraction of Venezuelan Tia Juana Pesado (ATJP) crude oil) was partially fractionated. SPE extracts of the column effluent were significantly less complex than the original ATJP crude oil sample, with many compounds completely resolved. Subsequent GC-MS analysis of SPE extracts identified four classes of compound: phenols, acids, straight chained and branched alkanes and alkenes, and aromatics.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID: uk.bl.ethos.488417  DOI: Not available
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