Pyrene sorption by natural organic matter

Sorption of pyrene on various types of natural organic matter (NOM) varying in chemical composition (e.g. high aliphaticity or aromaticity) was examined in batch sorption studies. The NOM samples (cuticle, humin, humic acid, degraded lignin, peat and lignite) were characterized by elemental analyses and solid-state C-13 NMR spectra. Previous studies on polycyclic aromatic hydrocarbons (PAHs) sorption on soils and sediments led to the conclusion that aromatic component of the NOM determines the binding of nonionic compounds and that the polarity of the NOM reduces the binding coefficient of the aromatic NOM moieties. In this study we tested the hypothesis that aliphatic moieties of NOM derived from soils or sediments can contribute significantly to the binding of PAHs in aqueous media. Cuticle and a humin sample from an algal deposit exhibited the highest distribution coefficients (K-oc). Both samples were rich in aliphatic structures and had very low aromaticity (4.6 and 8.8% for cuticle and humin samples, respectively). A positive trend was observed between the K-oc level and the aliphaticity of the NOM, calculated from the C-13 NMR spectra. This study demonstrates that aliphatic NOM compounds significantly sorb pyrene in aqueous solution, thus leading to the conclusion that the contribution of these groups to the sorption of aromatic nonionic pollutants in complex NOM matrices can be significant.