Determination of [13C]pyrene sequestration in sediment microcosms using flash pyrolysis GC-MS and 13C NMR

In this study, the use of a C-13-labeled pollutant probe, [C-13]pyrene, and the application of flash pyrolysis-GC-MS and CPMAS C-13 NMR provided analytical capabilities to study pyrene interactions with soluble and insoluble compartments of sedimentary organic matter (SDOM) 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 SDOM accumulated increasing amounts of pyrene that were resistant to exhaustive extraction with organic solvents. The sequestered pyrene was evident in CPMAS C-13 NMR spectra of humin fractions. The amount of sequestered pyrene in humic materials was quantified by flash pyrolysis-SC-MS, a technique that destroys the three-dimensional structure of macromolecular SDOM. Noncovalent binding of pyrene to humic materials in SDOM 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 SDOM and has not undergone structural alteration. Implications of these data are discussed in reference to SDOM diagenesis and long-term availability of bound pollutant residues in sediments.