Competition for adsorption between added phenanthrene and in situ PAHs in two sediments

A study was performed on the influence of the addition of a relatively large amount of phenanthrene to two in situ contaminated sediments on the fractions of native PAHs in both the slowly desorbing domain and the very slowly desorbing domain in comparison to the undisturbed situation. Added phenanthrene was found to be present in both the slowly desorbing domain and the very slowly desorbing domain. The extent of removal of native PAHs from the very slowly desorbing domain induced by the presence of a large excess of phenanthrene was in line with expectations based on the incubation time and the rate constants for desorption of native PAHs from the very slowly desorbing domain. In contrast, the addition of phenanthrene did not result in a removal of native PAHs from the slowly desorbing domain. This was tentatively explained by assuming that native PAHs in the slowly desorbing domain are at adsorption sites with dimensions specific to each PAH and which are, therefore, less suited to other PAHs.