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Toxicity of specific organic compounds - e.g pesticides and their breakdown products
Reaction with other aquatic species - Alkylation of metals by microbes e.g. Uses of organotin include in pesticides, preservatives of wood and antifouling paints. • Monomethyl tin (CH3 Sn3+) is more toxic to aquatic biota than inorganic tin because it can cross cell membranes.
Consumption of Oxygen - Non-living OM can be oxidised by oxygen and other oxidising agents in water Oxygen deprived water; anaerobic state - not enough o2 for living organisms to breathe.
Non living OM can also change the chemistry of the water as organic matter + o2 in water creates carbon dioxide which then reacts with water to form carbonic acid, and then dissociate further into carbonate and H+, making the water more acidic, harming aquatic life
Degradation pathway - The degradative pathway hypotheses that the formation of HM occurs from the modification of plant biopolymers through degradation. This theory proposes that labile macromolecules (e.g. carbohydrates and proteins) are degraded and lost. While biopolymers (e.g. lignin, macromolecules) are modified to produce the high molecular mass humin, then oxidised to produce the smaller components. Plant biopolymers → humin → humic acid → fulvic acid → small molecule
Synthetic pathway - The synthetic pathway hypotheses that plant biopolymers are first broken into small molecules then re-polymerised to form humic material. Individual molecules cannot be identified in humic material, So it is subdivided into 3 categories for operational purposes: •Humin (Hu) •Humic acid (HA) •Fulvic acid (FA) Plant biopolymers → small molecule → fulvic acid → humic acid → humin
Source rock with a High organic content (marine organisms) - would come from marine organisms because most petroleum reserves found from old oceans
Rapid burial to create a reducing environment - anoxic conditions (no O2) as we don’t want organisms to degrade
Overburden pressure – created by burial to depths of ~7-15 km -> helps in maturation process
Structure (e.g Anticline trap) - fold structure with an arch of non-porous rock overlying reservoir rock to trap oil and gas
Cap rock – Impermeable rock to prevent fluids and gas escaping upward
Reservoir rock – a porous permeable rock where petroleum and natural gas are found - has to move upwards as it forms and needs rock porous to hold oil and fluids need to be able to move from one rock to another - so important where capping layer occurs
Movement easiness from the source rock to the reservoir rock
