Cosolvent flushing for the remediation of PAHs from former manufactured gas plants

Cosolvent flushing is a technique that has been proposed for the removal of hydrophobic organic contaminants in the subsurface. Cosolvents have been shown to dramatically increase the solubility of such compounds compared to the aqueous solubility; however, limited data are available on the effectiveness of cosolvents for field-contaminated media. In this work, we examine cosolvent flushing for the removal of polycyclic aromatic hydrocarbons (PAHs) in soil from a former manufactured gas plant (FMGP). Batch studies confirmed that the relationship between the soil-cosolvent partitioning coefficient (Ki) and the volume fraction of cosolvent (fc) followed a standard log-linear equation. Using methanol at an fc of 0.95, column studies were conducted at varying length scales, ranging from 11.9 to 110 cm. Removal of PAH compounds was determined as a function of pore volumes (PVs) of cosolvent flushed. Despite using a high fc, rate and chromatographic effects were observed in all the columns. PAH effluent concentrations were modeled using a common two-site sorption model. Model fits were improved by using MeOH breakthrough curves to determine fitted dispersion coefficients. Fitted mass-transfer rates were two to three orders of magnitude lower than predicted values based on published data using artificially contaminated sands

Effect of cues associated with an alcoholic beverage on executive function

Objective: To investigate whether alcohol-associated drink cues can elicit conditioned compensatory responses that counter alcohol’s effects on cognition. Method: A between-subjects design was used in which participants were randomly assigned to one of three drink groups: an alcohol-associated drink (lager based) or one of two drinks not usually associated with alcohol (a fruit squash-fl avored drink or an apple schnapps-flavored drink; n = 15 per group). The amount of alcohol in each was the same: 0.65 g/kg body weight for men and 0.57 g/kg for women. Executive functions of inhibition, updating of working memory, and attentional set shifting were measured using the CANTABeclipse computerized test battery before and after alcohol consumption. Self-reported mood was measured, and participants provided ratings of the drinks’ sensory and hedonic properties. Results: Participants in the lager drink group showed less disinhibitory responding in an affective go/nogo task and less of a reduction in alertness than participants in the two other groups. The lager group was also faster to respond in the set-shifting task than the group given the “squash” (nonassociated) drink. There were no significant differences between the groups in how they evaluated the drinks’ sensory/hedonic properties. Conclusions: These data provide provisional evidence to suggest that cues previously associated with alcohol in lager drinkers (particularly the taste and smell of lager) can elicit compensatory responses that counter alcohol’s cognitive effects and its effects on alertness

The effectiveness of the Virtual Environment Radiotherapy Training (VERT) system as a teaching tool for anatomy

The VERT system is an interactive 3D learning technology. It can simulate complex radiotherapy equipment, treatment plans and 3D anatomy. This 3D anatomy, in which the students can see various structures and their relationship to other structures within the body, is one way in which the system may lend itself to applications allied to radiotherapy training. This project investigated whether VERT teaching facilitates enhanced learning of structural anatomy compared to traditional teaching techniques. A counterbalanced mixed group design was used whereby students were offered tutorial support following their first and second anatomy lectures in the autumn semester. In Group 1 students attended tutorials incorporating the VERT system for the first anatomy topic (GI). Following the second anatomy topic (Urinary) students’ tutorial teaching styles were swapped over to Power-Point (Non-VERT). For Group 2 the reverse was true. At the end of the semester, students had a MCQ of topics covered during the semester. To assess whether VERT use effected learning of structural anatomy, questions covering the anatomy lectures were analysed to see if there was any significant difference in scoring depending on whether they had VERT or Non-VERT tutorials. The overall average for Group 1 on the MCQ was 38.16 (SD=7.46) and 41.37 (SD=4.59) for Group 2. A 2x2 mixed ANOVA was run, with group (Group 1, Group 2) serving as the between subjects factor and anatomy topic (GI, Urinary) serving as the within subjects factor. No significant effects or interactions were found (ps >.05). No significant impact of VERT teaching over traditional non-VERT teaching was found but the initial conclusion of no VERT effect should however be treated conservatively. In this experiment the participants VERT experience was largely passive, i.e. they observed the VERT system being used rather than actively using the system. The benefit of VERT use may lie in active use rather than passive observation; a common division in virtual reality/training literature

Cosolvent flushing for the remediation of PAHs from former manufactured gas plants

Cosolvent flushing is a technique that has been proposed for the removal of hydrophobic organic contaminants in the subsurface. Cosolvents have been shown to dramatically increase the solubility of such compounds compared to the aqueous solubility; however, limited data are available on the effectiveness of cosolvents for field-contaminated media. In this work, we examine cosolvent flushing for the removal of polycyclic aromatic hydrocarbons (PAHs) in soil from a former manufactured gas plant (FMGP). Batch studies confirmed that the relationship between the soil-cosolvent partitioning coefficient (K(i)) and the volume fraction of cosolvent (f(c)) followed a standard log-linear equation. Using methanol at an f(c) of 0.95, column studies were conducted at varying length scales, ranging from 11.9 to 110 cm. Removal of PAH compounds was determined as a function of pore volumes (PVs) of cosolvent flushed. Despite using a high f(c), rate and chromatographic effects were observed in all the columns. PAH effluent concentrations were modeled using a common two-site sorption model. Model fits were improved by using MeOH breakthrough curves to determine fitted dispersion coefficients. Fitted mass-transfer rates were two to three orders of magnitude lower than predicted values based on published data using artificially contaminated sands

Multivariate statistical methods for the environmental forensic classification of coal tars from former manufactured gas plants

Compositional disparity within a set of 23 coal tar samples (obtained from 15 different former manufactured gas plants) was compared and related to differences between historical on-site manufacturing processes. Samples were prepared using accelerated solvent extraction prior to analysis by two-dimensional gas chromatography coupled to time-of-flight mass spectrometry. A suite of statistical techniques, including univariate analysis, hierarchical cluster analysis, two-dimensional cluster analysis, and principal component analysis (PCA), were investigated to determine the optimal method for source identification of coal tars. The results revealed that multivariate statistical analysis (namely, PCA of normalized, preprocessed data) has the greatest potential for environmental forensic source identification of coal tars, including the ability to predict the processes used to create unknown samples

Mobilization of Manufactured Gas Plant Tar with Alkaline Flushing Solutions

This experimental study investigates the use of alkaline and alkaline-polymer solutions for the mobilization of former manufactured gas plant (FMGP) tars. Tar-aqueous interfacial tensions (IFTs) and contact angles were measured, and column flushing experiments were conducted. NaOH solutions (0.01–1 wt.%) were found to significantly reduce tar-aqueous IFT. Contact angles indicated a shift to strongly water-wet, then to tar-wet conditions as NaOH concentration increased. Column experiments were conducted with flushing solutions containing 0.2, 0.35, and 0.5% NaOH, both with and without xanthan gum (XG). Between 10 and 44% of the residual tar was removed by solutions containing only NaOH, while solutions containing both NaOH and XG removed 81–93% of the tar with final tar saturations as low as 0.018. The mechanism responsible for the tar removal is likely a combination of reduced IFT, a favorable viscosity ratio, and tar bank formation. Such an approach may have practical applications and would be significantly less expensive than surfactant-based methods