Long term sorption kinetics of phenanthrene in aquifer materials

Most aquifer materials are heterogeneous in terms of grain size distributio n and petrography. To understand sorption kinetics, homogeneous subfraction s, either separated from heterogeneous sands and gravels (lithocomponents) or fragments of fresh rocks, have to be studied. In this paper we present d ata on long-term sorption kinetics of phenanthrene for homogeneous samples consisting of one type of lithocomponents or fresh rock fragments in differ ent grain sizes. Diffusion rate constants were determined in batch experime nts using a numerical model for retarded intraparticle pore diffusion and c orrelated to grain size and intraparticle porosity of the lithocomponents. Sorption isotherms were nonlinear for all samples investigated (Kleineidam et al. (1)). The numerical model described the sorption kinetics very well for coarse sand and gravels. Tortuosity factors, which were obtained as fin al fitting factors, agreed with Archie's law predictions based on the intra particle porosity. The dependency of sorptive uptake on grain size revealed that for smaller grains intrasorbent diffusion may become significant. Thi s is attributed to relatively large particulate organic matter (POM) within the sedimentary rock fragments. Specifically, charcoal and coal particles, which were found in some of the sandstones, controlled the sorptive uptake rates.