1979 0 
Rosenfeld, J. K. (1979) Ammonium adsorption in nearshore anoxic sediments. Limnol. 
Oceanoar.. 24(2):356-64. 
[DATE OF SAMPLING UNKNOWN OR NOT APPLICABLE.] The distributions of dissolved, 
exchangeable, and fixed ammonium were measured in sediment cores from Long Island 
Sound, Florida Bay, and Pettaquamscutt River, Rl, and in laboratory experiments to 
determine the importance of ammonium adsorption in anoxic sediments. Two sites were 
sampled in Florida Bay, at Ramshorn and Mangrove, north of Tavernier. 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. 
1979 0 
Rosenfeld, J. K. (1979) Interstitial water and sediment chemistry of two cores from 
Florida Bay. J. Sediment. Petrol. . 49(3):989-94. 
[DATE OF SAMPLING UNKNOWN OR NOT APPLICABLE.] The interstitial water and 
sediment chemistry of cores from two different environments in Florida Bay, 
mangrove swamp and submerged mudbank, were analyzed. The interstitial water 
profiles showed that sulfate reduction, along with the resulting ammonium, phosphate, 
and alkalinity production, was occurring in Florida Bay sediments. However, the sulfate 
concentration profile was not typical of other anoxic environments, in that the sulfate 
concentration increases below a depth of approximately 20 cm. The ammonium, 
phosphate, and alkalinity concentrations all decrease below this depth. It is suggested 
that these interstitial water profiles might be explained in terms of a balance between 
the mixing of the interstitial water with the overlying seawater and decreasing rates 
of organic matter decomposition with depth. The rates of organic matter decomposition 
were measured in laboratory experiments, which indicated that sulfate reduction and 
ammonium generation were much faster (a factor of 3 to 9 times) between 0 and 10 cm 
than between 10 and 20 cm. Organic carbon, organic nitrogen, and amino acid profiles 
showed decreases as large as a factor of 2 in the organic content of Florida Bay 
sediments in the top 60 cm of the sediment column. 
1979 0 
Rosenfeld, J. K. (1979) Amino acid diagenesis and adsorption in nearshore anoxic 
sediments. Limnol. Oceanoar.. 24(6): 1014-21. 
[DATE OF SAMPLING UNKNOWN OR NOT APPLICABLE.] Amino acid diagenesis and free 
amino acid adsorption by sediments were studied in cores of nearshore anoxic 
sediments from Long Island Sound, Florida Bay, and Pettaquamscutt River, Rl. Two 
sites were sampled in Florida Bay, at Ramshorn and Mangrove Keys, north of 
Tavernier. Both organic nitrogen and amino acid content decreased by a factor of about 
two in the top meter of the sediment. Individual amino acid profiles showed that the 
acidic and neutral amino acids, despite their different chemical composition, appeared 
249 
