Determination of [13C]Pyrene Sequestration in Sediment Microcosms Using Flash Pyrolysis−GC−MS and 13C NMR

In this study, the use of a 13 C-labeled pollutant probe, [ 13 C]pyrene, and the application of flash pyrolysis−GC−MS and CPMAS 13 C NMR provided analytical capabilities to study pyrene interactions with soluble and insoluble compartments of sedimentary organic matter (S D OM) during whole sediments incubations in aerated microcosms. Surface sediments were collected from a site of previous hydrocarbon contamination in New Orleans, LA. Over a period of 60 days, humic acid and humin fractions of S D OM accumulated increasing amounts of pyrene that were resistant to exhaustive extraction with organic solvents. The sequestered pyrene was evident in CPMAS 13 C NMR spectra of humin fractions. The amount of sequestered pyrene in humic materials was quantified by flash pyrolysis−GC−MS, a technique that destroys the three-dimensional structure of macromolecular S D OM. Noncovalent binding of pyrene to humic materials in S D OM was greater in sediments incubated with biological activity than biocide-treated sediments. The combined analytical approaches demonstrate that the sequestered pyrene, or bound residue, is noncovalently associated with S D OM and has not undergone structural alteration. Implications of these data are discussed in reference to S D OM diagenesis and long-term availability of bound pollutant residues in sediments.