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This study presents data from electrokinetic column experiments revealing no serious effects of HPCD on electrokinetic properties of kaolinite.

The results of a study of solution chemistry effects on surfactant sorption on kaolinite, surfactant micelle formation, and phenanthrene partitioning to sorbed surfactants and surfactant micelles are presented. For sodium dodecyl sulfate, an anionic surfactant, increasing ionic strength caused a decrease in critical micelle concentration values, but pH changes had no impact on such values.

Solution chemistry creates varying effects on surfactant micelle formation, surfactant sorption on kaolinite and phenanthrene partitioning to surfactant micelles and sorbed surfactants. In the case of anionic surfactant sodium dodecyl sulfate, an increase in ionic strength creates a decreasing effect on critical micelle concentration (CMC). In the case of nonionic surfactant Tween 80, changes in ionic strength and pH do not affect CMC.

Experiments on hydrophobic organic compound (HOC) partitioning to surfactants have provided evidence that surfactant sorption to the solid phase can increase HOC retardation in certain equilibrium conditions. The study however, finds the method undesirable for surfactant-enhanced remediation applications and finds that consideration of sorption and HOC partitioning to different phases are important considerations in determining applications.

A model to determine the effectivity of surfactant-enhanced remediation (SER) applications for hydrophobic organic compounds (HOC) is shown to provide useful guidelines for designing and deploying SER applications. The model computes surfactant losses by sorption to the subsurface media and for HOC partitioning thereafter and is also found to be effective for interpreting SER-related studies.

Analysis of sorption isotherms of phenanthrene, a hydrophobic solute probe applied to 27 different soil and sediment samples, revealed that a linear phase partitioning model was not useful to describe sorption behavior but that the Dual Reactive Domain Model and the Freundlich isotherm model were effective. Additionally, some caution was attached to the practice of extrapolating sorption behavior using the linear model and based on measurements using aqueous-phase solute concentrations that are at high and narrow levels.

The sorption of phenanthrene on surfaces of INNrganic mineral solids was investigated by sorption rate and equilibrium experiments. Sorption rates of the organic solute varied for the non-porous sorbents, porous silica gels and bentonite. The differences in sorption behavior were attributed to the differences in the surface chemistry properties, intraparticle porosities and pore size distributions of the mineral solids.

Granular activated carbon's (GAC) adsorption of nine different natural and synthetic macromolecular dissolved organic materials (DOMs) was studied to understand the roles of DOM molecular size and chemical structure in the process. Adsorption of polystyrene sulfonate was noted to decrease as macromolecular size increases. The same was true for Laurentian, peat and Aldrich humic acids which were fractionated by ultrafiltration. Such similarity indicates a relative uniformity of the chemistry of humic macromolecules from one fraction to another. It also indicates that physical size effects are the main factor behind the differences in GAC uptake of different fractions.

No sensitivity to oxygen was observed in the sorption of the low molecular weight fractions of Aldrich humic acid. This was gleaned from an examination of the influence of dissolved oxygen (DO) on the uptake of natural and synthetic macromolecular dissolved organic materials (DOMs) from aqueous solutions by granular activated carbon. The presence of DO enhanced the sorption behaviors of six of the nine DOMs evaluated, while sorptions of Aldrich and soil humic acids and polystyrene sulfonate showed no sensitivity to the presence or absence of DO.

The effect of aqueous solutions on the adsorption rate of perylene, a nonionic hydrophobic organic compound, on an inorganic silica surface was studied at different pH levels and ionic strength in the presence of bivalent cations. Specifically, the experimental adsorption rates were analyzed with respect to the perylene's aqueous activity coefficient and silica's surface speciation. The observations demonstrated the influence of cation binding at the silica surface on adsorption rates for neutral to high pH levels.

The ability of adsorbed humic substances to bind a nonpolar hydrophobic organic compound relative to freely dissolved humic material was investigated. The study protocol involved a fluorescence-quenching method to examine the binding of perylene by Suwanee River humic substances in the absence or presence of colloidal-sized aluminum oxide particles. The binding of perylene under various pH, NaCl and Ca2++ regimens are reported.

The effect of solution chemistry on the binding of polycyclic aromatic hydrocarbons by well-caharcterized Suwanee River humic and fulvic acid was investigated using fluorescence quenching techniques. The results showed that binding was finished within three minutes and that fluorescence was fully quenched. Increased pH enhanced binding while increased ionic strength caused a degradation.

Changes in pyrene binding by dissolved and mineral-associated humic substances (HS) due to I-IS adsorptive fractionation processes were examined in model environmental systems using purified Aldrich humic acid (PAHA) and Suwannee River fulvic acid (SRFA). For PAHA, carbon- normalized pyrene binding coefficients for nonadsorbed, residual fractions (Koc(res)) were different from the original dissolved PAHA Koc value (Koc(orig)) prior to contact with the mineral suspensions. A strong positive correlation between pyrene log Koc(res) and log weight-average molecular weight (MWw) for residual PAHA fractions was observed, which was relatively independent of the specific mineral adsorbent used and hypothesized fractionation processes. A strong positive correlation between log Koc(ads) and log MWw was also found for PAHA fractions adsorbed to kaolinite at low mass fraction organic carbon levels, although the relationship was statistically different from the one found with residual PAHA fractions. The same trends and correlations found for PAHA were not observed with SRFA, suggesting that the impacts of HS adsorptive fractionation on changes in hydrophobic organic contaminants binding are also influenced by the source and other biogeochemical characteristics of HS. [ABSTRACT FROM AUTHOR]

Discusses the removal of hydrophobic organic contaminants from saturated subsurface environments using a solubility-enhanced electrokinetic remediation process. Removal of phenanthrene from the model soil; Removal of phenanthrene by flushing the anode reservoir of the column with high hydroxypropyl-beta-cyclodextrin concentration.

Examines removal of sorbed hydrophobic organic compounds (HOC) by hydroxypropyl-beta-cyclodextrin (HPDC) in surfactant-enhanced subsurface remediation. Role of HOC concentration in HOC-HPCD complex formation coefficients; HPDC ability of neglecting sorption to the solid phase; Impact of HOC size and hydrophobicity on HPCD role in HOC partitioning.

Presents information on a study which developed a surfactant enhanced remediation (SER) model, examined the rates of SER processes and applied to model for maximizing the efficiency of SER processes. Information on the development of the model; Modeling of a sandy aquifer column system; Details on the model.

Cites an experimental study which investigated the partitioning of two hydrophobic organic compounds (HOC) and examined the sorption characteristics of an anionistic surfactant (SDS) and nonionic surfactant. Identification of the HOC; Quantification of the HOC by fluorescence; Information on the micellular solubilization of HOC; Results of the study.

Examines the phenanthrene sorption by eight particulate mineral solids. Types of particle structure comprising the polar surfaces of the

States that the sensitivity of sorption of natural dissolved organic materials (DOMs) by granular activated carbon to dissolved oxygen generally increased with decreasing molecular size and with increasing DOM acidity.

Presents correspondence exchanged as a result of a report by Mark A. Schlautman and James J. Morgan on hydrophobic pollutant transport in aquatic systems. Recognition of research done on the hydrocarbon solubilization process; Authors' acknowledgement of earlier researches done in the light of their research on humic substances.

Oxidation of manganous manganese (Mn II ) is an important process driving manganese cycles in natural aquatic systems and leading to the formation of solid-phase Mn III,IV (hydr)oxide products. Previous research has shown that some simple ligands (e.g., phosphate, sulfate, chloride, fluoride) can bind with Mn II to make it unreactive to oxidation by dissolved oxygen. However, there is little to no understanding of the role played by stronger, complex-forming ligands in Mn II oxidation reactions. The objective of this study was to evaluate the rates of abiotic Mn II oxidation by O 2 in the presence of low concentrations of several complex-forming model ligands (pyrophosphate, tripolyphosphate, ethylenediaminetetraacetic acid, oxalate) in bicarbonate-carbonate buffered laboratory solutions of pH 9.42, 9.65, and 10.19. The influence of increasing ligand concentrations on observed autocatalytic profiles of Mn II oxidation was investigated, and initial oxidation rates were linked quantitatively to the initial Mn II speciation in experimental solutions. Observed rates of Mn II oxidation decreased with increasing ligand concentration for all four ligands tested. However, the profiles observed with time and the magnitudes of decrease in initial oxidation rates were different for the different ligands. Likely explanations for these observations include the denticity of the tested ligands, the relative strength of the ligands to complex Mn II versus Mn III , and the ability of some ligands to enhance the reduction of Mn III back to Mn II on a time scale comparable to the forward homogeneous Mn II oxidation reaction.

Changes in selected spectroscopic and chromatographic characteristics of water-soluble organic matter (WSOM) extracted from leaf litter and its ability to bind pyrene were monitored throughout 14 day microbial incubation experiments. To provide additional insight into the microbial transformation of the WSOM, incubation experiments were similarly conducted with controlled-composition mixtures of glucose and dissolved humic substances (HS) that were base extracted from the same leaf litter source. Microbial transformation increased the specific ultraviolet absorbance and number-average molecular weight of residual WSOM while polydispersity values decreased. Fluorescence measurements revealed loss of protein-like fluorescence and enhancement of fulvic- and humic-like fluorescence in residual WSOM. Overall, the incubation results suggest that nonaromatic and smaller sized carbon structures were being degraded while the microbial activity produced humic-like aromatic components in solution. Together, these changes resulted in enhanced pyrene binding by the altered WSOM. Consistent findings resulted from mixtures of glucose and the leaf litter HS. Changes in measured operational descriptors were more pronounced for mixtures containing a higher percentage of glucose, suggesting that utilization of labile constituents may be necessary for formation of unknown structures associated with high pyrene binding capabilities. Simple mass balance, end member mixing models often failed to predict changes in pyrene binding brought about by microbial transformation, suggesting that microbial utilization of labile constituents is not the predominant process governing the enhanced pyrene binding.

The heterogeneity within a bulk humic substance (HS) was investigated for ultrafiltration (UF) fractions of purified Aldrich humic acid (PAHA) using specific ultraviolet absorbance (SUVA), weight- and number-average molecular weights (MWw and MWn), and organic carbon-normalized pyrene binding coefficients (Koc). As expected, variations in these selected operational descriptors were found for the PAHA UF fractions, but the variations were smaller than the ranges observed for a small subset of different aquatic and terrestrial HS. In general, correlations among the operational descriptors for the different HS failed to predict the correct trends for the PAHA UF fractions. More variation in Koc was observed for the different HS versus the PAHA UF fractions despite comparable molecular weight ranges, suggesting that the extent of pyrene binding is more strongly influenced by HS source and chemical structure than merely by physical structural features. Size-exclusion chromatography (SEC) confirmed the structural stability of PAHA UF fractions, as demonstrated by a near-identical mathematical reconstruction of the original bulk chromatogram from a weighted summation of the individual UF fraction chromatograms. An ideal mixture model accurately predicted some operational descriptors of PAHA properties (i.e., SUVA and MWw), but failed to predict the PAHA reactivity for pyrene binding. Our Koc results at pH 4 and 7 suggest that the relative contribution of two mechanisms, partitioning and specific interactions, may account for the interactions between HS and pyrene.