Organic matter facies and equilibrium sorption of phenanthrene

Remediation of groundwater contamination in unconsolidated aquifers by diss olved hydrophobic compounds (HOC) requires detailed information on the sorp tion parameters present in the sediments. Equilibrium sorption isotherms we re measured for phenanthrene for a wide variety of lithe components (consti tuents of sand and gravel sediments) and unweathered rock fragments (limest ones and sandstones). The lithocomponents were separated based on macroscop ic appearance of different lithologies (e.g. limestones, sandstones, shales , mudstones, and igneous rocks) and characterized in terms of organic carbo n content and specific surface area. In addition the organic matter (OM) wa s characterized using coal petrography methods (white and UV light microsco py). As confirmed by heat-treated samples sorption was solely due to OM. Or ganic carbon normalized sorption coefficients (K-OC) varied by almost 3 ord ers of magnitude among the samples investigated. The different origin and m aturity of isolated organic matter (organic facies) is believed to be respo nsible. For example, extremely high K-OC values were found for particulate organic matter such as charcoal and coal particles which were preserved wit hin the sandstone and limestone grains. In a second paper we report data on sorption kinetics of the samples used in this study (1).