Impacts of heterogeneous organic matter on phenanthrene sorption: Equilibrium and kinetic studies with aquifer material

Sediment organic matter heterogeneity in sediments is shown to impact the s orption behavior of contaminants. We investigated the sorptive properties a s well as the composition of organic matter in different subsamples (mainly grain size fractions) of the Canadian River Alluvium (CRA). Organic petrog raphy was used as a new tool to describe and characterize the organic matte r in the subsamples. The samples studied contained many different types of organic matter including bituminous coal particles, Differences in sorption behavior were explained based on these various types of organic matter. Su bsamples containing predominately coaly, particulate organic matter showed the highest K-oc, the highest nonlinearity of sorption isotherms and the sl owest sorption kinetics. Soil subsamples with organic matter present as org anic coatings around the quartz grains evidenced the lowest K-oc, the most linear sorption isotherms and the fastest sorption kinetics, which was not limited by slow intraparticle diffusion. Due to the high sorption capacity of the coaly particles even when it is present as only a small fraction of the composite organic content (<3%) causes K-oc values which are much highe r than expected for soil organic matter (e.g. K-oc - K-ow relationships). T he results show that the identification and quantification of the coaly par ticles within a sediment or soil sample is a prerequisite in order to under stand or predict sorption behavior of organic pollutants.