Department of Earth Sciences, University of Bristol
Environmental Geochemistry
Prof. D.M. Sherman

Lecture 3: Organic Geochemistry


Natural organic compounds in the environment result from the breakdown of biomass. In aquatic systems, biomass (principally lignin) from plants breaks down into humic and fulvic acids. Lipids hydrolyse to fatty acids, carbohydrates to sugars and proteins to amino acids. In sediments, humic/fulvic acids transform to kerogen which, in turn, transforms to petroleumand natural gas. Synthetic organic compounds comprise a major fraction of chemical pollutants in soil and groundwater. However, these compounds (if the carbon is in a low oxidation state) can be broken down by microbial respiration if electron acceptors (e.g., O2, SO4-2) are present. Chlorinated hydrocarbons are a very serious type of organic pollutants; they usually have carbon in a high oxidation state; these compounds can be broken down by methanogens under very anaerobic conditions.


You should be able to outline:

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