Suspended particulate and colloidal organic matter (POM and COM) from the Pearl River were isolated using continuous flow centrifugation and a technique of combined reverse osmosis (RO) and ultrafiltration (UF). Elemental and isotopic composition were determined. Novel multi CP 13C solid-state NMR techniques included 13C cross-polarization/total sideband suppression (CP/TOSS) and CP/TOSS with recoupled dipolar dephasing were employed to investigate the major structural characteristics of POM and COM. The C/N ratio and δ13C value of particular organic matter and colloidal organic matter was 7.25±0.70 and -25.87±3.34‰, while the C/N ratio and δ13C value of colloidal organic matter was 9.38±2.31 and -23.19±2.75‰, indicating that phytoplankton was the dominant source for the SPM samples, while plankton and soil organic matter were the main source for the COM samples in the Pearl River. The NMR results indicated that POM and COM were structurally distinct. POM contained significantly higher alkyl carbon than COM did whereas COM was markedly enriched in alkoxy carbon. Carbohydrates (river: 38.0%-47.8%; lake: 44.7%-64.9%) and lipids (river: 18.5%-21.5%; lake: 17.1%-19.2%) were the major biomolecules in COM and SPM, respectively. It is interesting that considerable amounts of poly(methylene) carbon were detected in SPM and COM by multi CP/NMR. Black carbon and humification index was quantified respectively by nonprotonated aromatic carbon and nonprotonated O-Alkyl carbon.

Composition and structure of natural organic matter isolated by reverse osmosis and ultrafiltration

249th National Meeting (2015)

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