The distributions of dissolved, exchangeable, and fixed ammonium were measured in sediment cores from Long Island Sound, Florida Bay, and Pettaquamscutt River, Rhode Island, and in laboratory experiments to determine the importance of ammonium adsorption in anoxic sediments. Apparently, a "dynamic equilibrium" exists between dissolved, exchangeable, and fixed ammonium in sediments. The concentration of exchangeable ammonium increased linearly with increasing concentrations of dissolved ammonium; exchangeable ammonium adsorption was rapid, reversible, and predominantly associated with the organic matter rather than the clay minerals. The concentration of fixed ammonium also increased with increasing concentrations of dissolved ammonium, but this change, due to diagenesis, is small compared to the total fixed ammonium in sediments and is also smaller than the corresponding increase in exchangeable ammonium. The ammonium adsorption coefficient for Long Island Sound sediment was between one and two: of the ammonium produced by organic matter decomposition, as much or twice as much is associated with the sediment as is dissolved in the interstitial water. Therefore, ammonium adsorption by sediments is an important process in the diagenesis of nitrogen in nearshore anoxic sediments. Ammoniumproduced by the decomposition of organic nitrogen compounds in anoxic sediments can accumulate in the pore water, diffuse out of the sediments into the overlying water column, or be adsorbed onto the sediments. The main purpose of my study was to determine how important ammonium adsorption was, relative to its production by organic matter decomposition, by determining the relationship between the amount dissolved in the pore water and the amount adsorbed on the sediments in both sediment cores and laboratory experiments.I also examined the mecha-

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The stoichiometry of nutrient regeneration in anoxic Long Island Sound sediments is examined through changes in the concentration of dissolved sulfate, ammonia, reactive phosphate, and other chemical species with depth in interstitial waters. In offshore sediments the mean AS04:ANH4:ACP ratio is -53:4.6:0.37; in shallow harbor sediment it is -53: 19:3.3 and ANI14:AZP ratios are half the offshore ratio. These indicated shoreward changes probably rcflcct more rapid deposition, and thus less preferential stripping of P and N from organic material before burial in shallow water harbor sediments, or selective stripping in the heavily bioturbated upper sediment layers offshore, or both. The effects of differential diffusion and adsorption of ammonia and phosphorus are considered.Phosphate concentration maxima in ammonia-and phosphate-rich shallow harbor sediments yield evidence for possible equilibrium with respect to vivianite, Fc3(P04)z*8Hz0, and struvitc, MgNI14P04+611z0.Martens and Berner (1977) reported on dissolved gases in the interstitial waters of nearshore Long Island Sound sediments. We here consider nutrient regeneration and phosphate removal in these same sediments, examine the stoichiometry of nutrient regeneration by using concentration vs. depth profiles of dissolved sulfate, ammonia, and reactive phosphate, and discuss possible authigenic phosphate mineral precipitation associated with high phosphate regcneration rates.We thank M. B. Goldhaber and J. Westrich for comments and discussion concerning this work. Remarks by J. Murray and S. Emerson led to significant improvements.A. Ruggiero provided analytical chemical assistance. M. Reed's assistance with coring operations was indispensable.

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Ground water contamination profiles from five wood treatment facilities across the country have been compared. The distributions of organic priority pollutants at the five sites are similar, with the most common contaminants being polynuclear aromatic hydrocarbons and phenolic compounds. These contaminants are the predominant constituents of creosote, which is a common wood preservative. Inorganic contaminants have also been detected at these sites, but their distributions are not uniform across all sites. The distributions of the organic priority pollutants at the five sites appear to differ from those at other hazardous waste sites. Suggested recommendations for choosing monitoring parameters for wood treatment facilities are presented.