FACTORS AFFECTING LYSINE SORPTION IN A COASTAL SEDIMENT

Abstract

Sediment sorption capacity was measured in a coastal environment over a 2-year period using lysine as a model compound. Sorption capacity was found to vary over time but did not seem to follow a clear seasonal pattern or relate to organic carbon, sediment grain size distribution, or sediment specific surface area. Instead, adsorption capacity appeared to be more related to annual precipitation patterns. Years of below normal precipitation apparently created conditions with high adsorption capacity, while years with higher than normal precipitation were associated with lower adsorption capacity. Laboratory experiments showed that adsorption capacity of anoxic sediments is lower than for oxidized sediment, and the magnitude of this difference changed with time. Adsorption of lysine, glutamic acid, leucine, melanoidin and naphthalene was enhanced to different degrees when anoxic sediment was oxidized. Laboratory experiments showed that natural dissolution/precipitation cycling of manganese or iron oxide could not explain either changes in sorption with time or differences between anoxic and oxic sorption. Sediment amended with manganese oxyhydroxide at forty times background values showed a slight increase in adsorption. Iron oxyhydroxide amendment showed no effect. This study also addressed potential problems inherent to slurry sorption experiments such as the use of biocide and the effect of slurry solid to water ratio. Using HgCl2 as a biocide did not markedly affect lysine sorption. Although slurry ratio of solid to water did affect distribution coefficients, normalization of distribution coefficients to slurry porosity provides a meaningful way to report sorption and results in relatively constant estimates of adsorption capacity when using slurries of variable ratios of total suspended solid to water.