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The subsurface transport of ionic and nonionic pollutants may be strongly impacted by the movement of naturally occurring dissolved organic carbon (DOC) in aquifers. Thus, the adsorption, desorption, and transport of DOC in laboratory columns containing well‐packed aquifer material was investigated. Data showed that the breakthrough of DOC from aquifer columns was the result of complex adsorption reactions between DOC and the aquifer material. Breakthrough curves (BTCs) of the DOC were characterized by an initial rapid concentration increase followed by extended tailing to long times. The extensive tailing of the BTCs was attributed primarily to the slow adsorption kinetics of DOC to the aquifer material and the nonlinear nature of the adsorption isotherm. Independent experiments suggested that the size exclusion of DOC from aquifer pores was negligible. The time required to saturate the aquifer material with organic C was dependent on the influent DOC concentration, with lower organic influent levels requiring longer pulse durations to fully saturate the aquifer sediment with organic C. Hydrophobic constituents of the DOC were preferentially adsorbed while hydrophilic components were rapidly transported through the aquifer columns. Spectral analysis (light absorbance at 260 nm) of the column effluents confirmed that the composition of the mobile organic C changed during the breakthrough of DOC. Data from this investigation demonstrate that DOC can be mobile in soil systems, and emphasizes the need to evaluate the cotransport of pollutants by DOC.

rn Quantitative structure-property relationship (QSPR) models have been developed which accurately calculate the congener-specific aqueous solubilities (S) and Henry's Law constants (HLCs) of polychlorinated biphenyls (PCBs). QSPRs were generated based on molecular models which were sensitive to slight changes in chemical structure. PCB aqueous solubilities were found to be a function of total surface area, melting point, and third shadow area. Observed HLCs were a function of the second moment of inertia, path-four connectivity index, path-three K index, and the second and third principal polarizabilities. These newly developed models agree well with other model predictions and expand, as well as complement, previous approaches because the new models are capable of accurately calculating S and HLC for structurally similar PCB congeners. Results from this work provide a better understanding of the chemical and structural characteristics governing the solubility of hydrophobic compounds.