| The soils and sediments organic matter (SOM) are highly heterogeneous and comprise various complex organic macromolecules such as humus, kerogen, black carbon (BC), etc. The relative abundance, characteristics and structure of these SOM play a important role on the global carbon cycles, global change, transformation and fate of the organic and inorganic pollutants, the soil fertility. Therefore, it is important issue to quantified and characterized different SOM in soils and sediments.In this work, four representative samples paddy soil, river sediment, pond sediment and marine sediment from Pearl River Delta Southern China and Southern China Sea are studied. A comprehensive wet chemical procedure was used for fractionation and quantitative isolation of soil/sediment organic matter (SOM) into four fractions: humic acids + kerogen + BC (HKB); kerogen + BC (KB); humic acid (HA) and BC. Sources, character and structure of different SOM were analyzed with SEM, NMR, XRD, Py-GC-MS and optical, carbon isotope, and elemental analysis. The results show the SOM is highly heterogeneous.1. Besides humic acid and kerogen, four SOMs consist of a special organic fraction Black Carbon (BC), it accounts for the least 18.36% of TOC in marine sediment. And different fractions of SOM have different origin. Humic acid usually formed from phytoplanktons, zooplanktons, and epicontinental vascular plants through biodegraded and condensated reaction. Krogen derived either from humic acid or from the reworking materials. Differing from humic acid and kerogen, BC was produced from the incomplete combustion of fossil fuels and biomass. Different factions of SOM also have its own chemical characteristics and structure. From the elemental analysis of different samples, the oxygen/carbon (O/C) atomic ratio is decreasing from HA, HKB, KB to BC, which suggest the greater thermal alteration has been suffered from humic acid, kerogen to black carbon. The analysis of 13C NMR and Py-GC-MS also show each fraction of SOM has it's structural characterization. The aromatic carbon content increasing and carbohydrate, oxygen-function groups decreasing from humic acid, kerogen to black carbon, molecular structure became more condensed, rigid, and stable.2. An improved method for extraction of soil humic acid was used to isolated dissociative humic acid (HA-I) and enwrapped humic acid (HA-II) from paddy soil and Pohakee peat. Quantified and characterized HA-I and HA-II with 13C NMR, Py-GC-MS, optical and elemental analysis. The results indicate that two humic acidsare highly different in structure, and HA-II is more condensed.3. A certain mounts of asphaltenes always occur with BC particles were produced from the incomplete combustion of biomass or fossil fuels. Characterization of fresh BC and asphaltenes show that fresh BC structurally rigid and physically condensed. And different to graphite, BC contains a little aliphatic groups and oxygen-containing groups. BC asphaltenes similar to petroleum asphaltenes and consist of aromatic nuclei, aliphatic chains, and naphthenic ring structures combined in three-dimensional network. But black carbon asphaltenes contains more aromatic carbon, oxygen-function groups, and less aliphatic chains.4. Py-GC-MS and TMAH/Py-GC-MS analysis of various SOM fractions - HKB, KB, HA, and BC show SOM is heterogeneous. The aromatic carbon increasing from humic acid, kerogen to black carbon, and structure become more condensed, rigid, and stable.In addition, we also characterized the residue after Py-GC-MS, which show it structurally rigid and physically condensed. Although pyrolysis of humic acids only produced a few amount of compounds, which is very useful to study the sources and structure.The results of these work indicated that SOM in top soils and sediments are highly heterogeneous and conprise a wide range complex organic matter such as humic acid, kerogen, and black carbon, and SOM have a nice bit of black carbon. Differing from humic acid and kerogen,...
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