| Abstract
| - Groundwater contamination by fuel constituents fromnonaqueous phase liquids (NAPLs) on top of the groundwatertable is a widespread problem. While leaching of classicalfuel constituents such as benzene, toluene, ethylbenzene,and xylenes (BTEX) from NAPLs into groundwater has beenstudied extensively, little is known about the identity andpartitioning of polar fuel components. Our work shows thatgasoline commonly contains appreciable amounts ofaniline, phenol, and their alkyl-substituted homologues aswell as a suite of other polar compounds. To assessthe potential for leaching of such compounds from NAPLsinto groundwater we measured the equilibrium fuel/water partitioning coefficients, Kfw, of some representativeconstituents in batch systems. Kfw values for theinvestigated phenols, anilines, benzotriazoles, and S-heterocycles ranged from 0.2 to 1700. These values areup to 3 orders of magnitude lower than the Kfw of benzene.The NAPL−water partitioning of anilines and phenolsstrongly depends on the compounds' structure as well ason pH and the gasoline composition (e.g., MTBE content).Linear free energy relationships (LFERs) using Kow orfailed to predict measured Kfw values of polar solutes. Incontrast, a polyparameter approach taking into accountmolecular interactions (van der Waals forces, hydrogenbonds) between solutes and major gasoline componentsallows precise a-priori predictions of Kfw values of both polarand BTEX fuel constituents without any fit parameters.Since most of the polar fuel constituents studied here areextracted from NAPLs by groundwater much moreefficiently than BTEX, such compounds could formcontaminant plumes threatening receiving wells beforedetectable concentrations of BTEX are present.
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