Migration of Chlorophenolic Compounds at the Chemical Waste Disposal Site at Alkali Lake, Oregon – 2. Contaminant Distributions, Transport, and Retardation

The behaviors of five chlorophenols and three chloro‐phenoxyphenols (CPPs) have been investigated at the chemical waste disposal site at Alkali Lake, Oregon. All of the compounds demonstrated similar trends in areal distribution hydraulically downgradient from the site. The transport distances for the di‐ and trichlorophenols were influenced greatly by their ionization in the high pH (˜10) ground water. In batch equilibrium experiments, these compounds were found to have K_p values of ˜0.0 for the soil and ground water taken from the site. While also largely ionized at pH ∼ 10, a tetrachlorophenol, pentachlorophenol, and the CPPs demonstrated substantial sorption in the batch equilibrium experiments as well as retardation relative to the di‐ and trichlorophenols at the site. The retardations observed relative to 2,6‐dichlorophenol were less than predicted based on the batch equilibrium results. Possible reasons include cosolvent effects due to the plume itself, nonuniform contaminant distributions at the time of the original burial, the fractures which are present in the aquifer, and a decreasing ground‐water velocity with distance westward of the site. Evidence is presented to support the last reason. These results show, for the first time, well‐behaved concentration contours embodying compound‐dependent retardation in the transport of sorbing and nonsorbing organic compounds from an existing waste disposal site.