An interdisciplinary analytical approach can unravel environmental liability at contaminated sites.

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Aspects of a nine‐month characterization of the physical‐chemical dynamics of a dissolved inorganic fertilizer plume in a shallow sand and gravel aquifer are reported. The work was undertaken to establish the extent of ground‐water contamination due to extremely high levels of total ammonia (>2,000 mg L−1) and to provide a basis for remedial action. The results from a numerical solute transport model showed the plume of contaminated ground water persisted at steady‐state conditions within the study site. This conclusion is supported by a comparison of the time of source emplacement (three years) to the calculated requirement of approximately one year for the plume at the field location to achieve a steady‐state configuration. Simulations suggested once the source was removed, about 420 days would be required to naturally flush the contaminant plume from the site. Chemical equilibrium calculations demonstrate that phosphate and carbonate mineral equilibria control calcium solubility in contaminated ground water. The most probable natural sink for ammonia removal from the plume is by the activity of nitrifying microorganisms, presumably well‐acclimated to the extreme conditions.

This is. an mlorma -eporl inKJnded primarily (Of inter; ui \,tni\nay nci tie iriLiie o' i h e 'tiDOia'ury This work was supported bv itit? U.S. Nuclear fleguJaio/y Commission under Interagency Agreement DOE 40-550-75 wnh the US. Depart ment O* Energy.

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