Maximum capacities for adsorption of phenanthrene in the slowly and very slowly desorbing domains in nineteen soils and sediments

Abstract

The maximum amounts of phenanthrene that can be taken up in both the slowly desorbing domain and the very slowly desorbing domain of 19 soils and sediments were determined by measuring the desorption of phenanthrene added at high loadings associated with equilibrium concentrations in water close to the aqueous solubility of phenanthrene. For two soils and one sediment, literature values for Langmuir phenanthrene adsorption capacities were available. These values were almost equal to the sum of the maximum amounts taken up in the slowly and in the very slowly desorbing domain. For the other soils, the range of the sum of the maximum amounts in the slowly and very slowly desorbing domains was comparable to the range for literature values of Langmuir phenanthrene adsorption capacities for soils and sediments. Results suggested that the maximum amounts determined from the desorption studies were Langmuir adsorption capacities. The correlation of maximum capacities for adsorption in both the slow desorption domain as well as the very slow desorption domain with soot content was virtually absent. In contrast, the variation of maximum amounts of phenanthrene adsorbed in either the slowly or the very slowly desorbing domains was substantially reduced by normalization to the total organic carbon content of the soils and sediments. It is suggested that adsorption in the slowly and very slowly desorbing domain took place in organic matter derived material such as kerogen, charcoal, or char.