A distributed reactivity model for sorption by soils and sediments. 13. Simulated diagenesis of natural sediment organic matter and its impact on sorption/desorption equilibria

Subcritical water treatment was used to effect rapid compositional and func tional changes to peat organic matter that mimic those of the natural diage nesis process. Elemental, solid state C-13 NMR, FTIR, and calorimetry analy ses all indicated that the organic matter of the artificially aged peat was chemically similar to that of geologically mature coal kerogens. This pape r extends the work of the previous paper in this series, which investigated the effects of subcritical water treatment of humic topsoil on subsequent phenanthrene sorption and desorption equilibria. As opposed to the previous study, however, changes in sorptive reactivity herein were unequivocally r elated to changes in organic matter rather than other soil constituents, an d organic matter functional changes due to the simulated diagenesis were mo re accurately characterized. Phenanthrene sorption capacity and isotherm no nlinearity both increased with increasing degrees of artificial aging, supp orting the Viewpoint that hydrophobic organic contaminant sorption equilibr ium properties can be directly related to the degree of diagenesis of geoso rbent organic matter. In addition, this work investigated effects of subcri tical water treatment of a geologically mature, kerogen-containing shale sa mple. In contrast to the peat, the functional characteristics of the shale were unchanged by this treatment, and subsequent phenanthrene sorption equi libria were altered far less.