envirochem test prep - organic geochemistry

Contaminants

________ that are found in coal are primarily sulphur due to sulphur being present in salt water swamps due to bacteria in the swamp that converted sulphate in saltwater to pyrite (FeS2) which became a part of the coal.

HM

________ is a class of substances that are produced and reside in soil and water.

Biomarkers

________ are organic molecules that are derived from living matter but are resistant to degradation.

Sterane

They are fully saturated (carbons bonded to 4 other things and all bonds are taken) (terpenes contain double bonds, terpanes contain single bonds) ________ is a terpane that is derived from steroids or sterols via diagenesis and catagenesis breakdown Hopane (C30H48) is a triterpene that originates from bacteria There are over 150 naturally occurring hopanoids.

Degradation

________ pathway- The degradative pathway hypotheses that the formation of HM occurs from modification of plant biopolymers through ________.

Coal

________ was formed over 300 million years ago due to dead plant matter that fell into swampy water.

Monomethyl tin

________ (CH3 Sn3+) is more toxic to aquatic biota than inorganic tin because it can cross cell membranes.

Petroleum

________ comes from OM that is deposited on seabed which are buried by sediments which are then broken down and transformed over millions of years.

Components of petroleum

________ are separated through fractional distillation and it is the boiling point of each fraction that allows this separation to occur.

Humic material

________ (HM) is made up of decayed organic material of plant or microbial origin.

Gas Chromatography Mass Spectrometry

In order to analyse biomarkers, ________ is used to separate compounds through two phases: Stationary phase (column) a stationary phase which is coated with material that interacts whatever compound we are looking for and it slows it down, giving a chance to separate out into fractions Mobile gas phase (He gas- inert and does not react with the compounds) and that carries that through the system and is heated.

Biomarkers

________ are formed by organic material that dies and undergoes anaerobic diagenesis, which turns organic matter into kerogen (we do this by losing oxygen, nitrogen, and sulphur)

Biomarkers

________ are used for characterising oil by looking at the molecules present.

As we move along the pathway of humin → humic acid → fulvic acid we have decreasing

molecular weight (breaking down molecules), carbon and nitrogen content, degree of polymerisation (related to weight, breaking down), intensity of colour

Cap rock

Impermeable rock to prevent fluids and gas escaping upward

what is natural organic matter

Natural sources of organic matter are those derived mainly from plant or microbial residues. Examples include things such as the degradation of plant and animal matter as well as microorganisms and fungi found in soil.

what is anthropogenic organic matter

organic matter that has come from human activity and can include point and non-point sources. An example of a point source would be discharge pipes, while a non point source would be sediment runoff from farmland.

define total carbon

The sum of all carbon-containing compounds in a sample, including both organic and inorganic carbon.

What subcategories can total carbon (TC) be divided into

Subcategories of Total Carbon (TC): Organic Carbon (OC) and Inorganic Carbon (IC). OC comes from living organisms, while IC comes from non-living sources like rocks and minerals. this can further be broken down into particulates, dissolved, particulate organic carbon, and dissolved organic carbon

3 main environmental issues related to aqueous organic matter:

1. Toxicity of specific organic compounds - e.g pesticides and their breakdown products
2. 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.
3. 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

what is humic material

HM is a class of substances that are produced and reside in soil and water.

what is humic material made up of

decayed organic material of plant or microbial origin.

subcategories of humic material

Humin (Hu) •Humic acid (HA) •Fulvic acid (FA)

two main theories hypothesise the formation of Humic Material by two main pathways:

1. 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
2. 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

humic material structure contains many ____

functional groups

What are the general chemical changes that take place as you move from HM to Fulvic acid?

Decreasing : molecular weight (breaking down molecules), carbon and nitrogen content, degree of polymerisation (related to weight, breaking down), intensity of colour. However, we also have increasing: oxygen, and degree of solubility (because molecules smaller, easier to dissolve)

The interactions of Humic Material are dependent on the ____

environment

Explain how coal was formed

Coal was formed over 300 million years ago due to dead plant matter that fell into swampy water. Anaerobic conditions caused the plant matter to not decompose and over time it was buried and built up. Overall, pressure, heat, and time converted the organic matter into coal. This process is called coalification.

what contaminants are found in coal

primarily sulphur due to sulphur being present in salt water swamps due to bacteria in the swamp that converted sulphate in saltwater to pyrite (FeS2 ) which became a part of the coal. There is also some mercury in coal present due to its affinity for sulphur.

how is low sulphur coal made

Low sulphur coal was formed in freshwater swamps

where does petroleum come from

Petroleum comes from OM that is deposited on seabed which is buried by sediments which are then broken down and transformed over millions of years. There are special conditions that are required to form petroleum. All seven conditions need to exist in one place, hence why petroleum is only found in certain areas of the world

what are the 7 conditions required to form petroleum

1. Source rock with a High organic content (marine organisms) - would come from marine organisms because most petroleum reserves found from old oceans
2. Rapid burial to create a reducing environment - anoxic conditions (no O2) as we don’t want organisms to degrade
3. Overburden pressure – created by burial to depths of \~7-15 km -> helps in maturation process
4. Structure (e.g Anticline trap) - fold structure with an arch of non-porous rock overlying reservoir rock to trap oil and gas
5. Cap rock – Impermeable rock to prevent fluids and gas escaping upward
6. 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
7. Movement easiness from the source rock to the reservoir rock

How are components of petroleum separated and what property allows this separation to occur

Components of petroleum are separated through fractional distillation and it is the boiling point of each fraction that allows this separation to occur

If there is an oil spill at sea what will happen to the different fractions

Light fractions will evaporate and heavy fractions will float/sit on top of the water

what are biomarkers

rganic molecules that are derived from living matter but are resistant to degradation.

how are biomarkers formed

by organic material that dies and undergoes anaerobic diagenesis, which turns organic matter into kerogen (we do this by losing oxygen, nitrogen, and sulphur ). With increasing temp and pressure we push kerogen into oil (biomarker) through catagenesis.

what are some important features of biomarkers

need to be resistant to degradation, need to be easily identifiable in low concentrations, need to have various concentrations

what are biomarkers used for

differentiation and correlation of oils to oil spills, allowing for identification of contamination (e.g if there was an oil spill) and allows for the monitoring of its breakdown for its relation to the environment and environmental effects.

What technique is used to analyse biomarkers

Gas Chromatography Mass Spectrometry is used to separate compounds through two phases: Stationary phase (column) a stationary phase which is coated with material that interacts whatever compound we are looking for and it slows it down, giving a chance to separate out into fractions

how are biomarker compounds identified in gcms

The compounds can be identified based on their retention time.