生物圈地球化学及其环境效益

7.2 Organic Geochemistry 中国科学技术大学 环境地球化学概论

Composition of Living Matter Proteins Carbonhydrates Lipids Lignin Vascular plants 7 50 10 33 Phytoplankton 23 66 11 Diatoms 29 63 8 Zooplankton 60 22 18 木质素 维管

Composition of Living Matter Molecular Components of Biomass Carbonhydrates and Polysaccharides （水解多糖）

Composition of Living Matter Molecular Components of Biomass

Composition of Living Matter Hydrolysis Products of Biomass

Composition of Living Matter Biological Breakdown of Biomolecules (发酵) (醋酸纤维)

Composition of Living Matter Abiotic Breakdown Products of Biomass 富里酸

Composition of Living Matter Complexation of Metals by Humic/Fulvic Acids OH Some metals (Cu, Hg) are complexed by HA and FA. This may play a role in ore-forming processes.

Composition of Living Matter Organic Carbon in Terrestrial Aquatic Systems

Composition of Living Matter Organic Carbon in Sediments Sediments contain < 1% organic C. Nearly all DOC and POC in the water column is oxidized by respiration. For organic C to accumulate in sediments, the flux of POC must be high and the redox conditions must be anaerobic.

Composition of Living Matter Diagenesis and Kerogen Formation Hydrolysis of complex organics Functional groups are removed. Double bonds are hydrogenated to give saturated hydrocarbons Aromatic compounds increase relative to aliphatic Condensation of molecular fragments to complex macromolecules End product is kerogen a mixture of complex organic compounds that dominate organic matter in sediments.

Composition of Living Matter Catagenesis of Kerogen to Oil and Gas Diagenesis(成岩作用): methanogens produce methane. Organic matter converted to kerogen. Catagenesis(后生作用): breakdown of kerogen Metagenesis(变生作用): breakdown of oil into gas + graphite

Composition of Living Matter Methane Hydrates At the pressures and temperatures of the ocean bottom, biogenic methane is trapped as clathrates(天然水合物).

Composition of Living Matter Methane Hydrates The stability field of methane hydrates is limited to shallow sediment depths. Methane is an extremely potent greenhouse gas and release from sediments could greatly accelerate global warming.

Organic Compounds Pollution by Organic Compounds

Organic Compounds Organic Pollutants: BTEX Compounds

Organic Compounds Biodegradation of Organics (Cont.)

Organic Compounds Biodegradation of Organics (Cont.) Spatial Distribution of electron acceptors after biodegradation progresses in soil

Organic Compounds PAH (Polycyclic Aromatic Hydrocarbons) in Creosote(杂芬油) Creosote is a common wood preservative but is now banned because it contains PAHs(carcinogenic). These are slow to degrade in soil.

Organic Compounds Synthetic Chlorohydrocarbons

Organic Compounds Organohalide Breakdown by Methanogens(产烷生物) Breakdown of vinyl chloride (CH2=CHCl) requires aerobic conditions:

Summary Abiotic Breakdown of Biomolecules