geochemical analysis of soils, marine sediments, and peat by shannon lee
TRANSCRIPT
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Title: Geochemical Analysis of Soils, Marine Sediments, and Peat Author: Shannon Lee
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Introduction This project was divided into 2 sections: 1. Elemental Analysis o Performed on Alpine soil, Galway Bay marine
sediment and Spiddal peat samples 2. Lipid Biomarker Analysis o Performed on Spiddal peat samples
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Elemental Analysis – Introduction o Can provide quantitative analysis of an unknown
sample o Determines amount and variation of organic matter
(OM)
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Elemental Analysis – Method o Samples are wrapped in tin capsules and placed in
a furnace with a stream of unreactive gas o Samples are burned in excess oxygen o Products (CO2, NO, H2O) are collected o % of Carbon, Hydrogen and Nitrogen can be found
using mass of sample o Marine samples are acidified with 2M HCl prior to
elemental analysis to remove carbonates
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Elemental Analysis – Results
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Lipid Biomarkers – Introduction o Organic biomarkers include n-alkyl compounds; n-
alkanes, n-alkanols, and n-alkanoic acids o Sources include terrestrial plants, marine algae and
micro-organisms o Highly resistant to degradation o Biomarkers from soil, marine sediments and peat can
give an indication of past climates and environmental conditions
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Lipid Biomarkers – Background o Storms revealed remains of a 7500 year old
drowned forest in Spiddal, Co. Galway o Plant debris of forest floor lead to the formation of a
blanket bog
(Photos of sampling of peat from drowned forest in Spiddel, Co. Galway)
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Lipid Biomarkers – Methods Free Lipid Extraction: o Sample lipids were extracted with ultrasonic solvent
extraction with organic solvents o Solvent extracts were combined and concentrated
under rotary evaporation Solid Phase Extraction (SPE): o SPE cartridges were conditioned with organic
solvents o Samples were fractionated into: Neutral Lipids, Fatty
Acids, and Polar Lipids o Lipids were collected in GC vials o
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Lipid Biomarkers – Methods Derivatisation: o Neutral lipids were converted to trimethylsilyl (TMS)
derivatives with BSTFA o Fatty acids were alkylated with BF3 o Lipids were analysed with GC-MS o Polar lipids were stored as they were not needed for
the project
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Lipid Biomarkers – Preliminary Results
o Abundance of C23 suggesting Sphagnum moss o Abundance of C31 suggesting Terrestrial plants
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Lipid Biomarkers – Preliminary Results
o Higher ratio at 105-110 cm suggests wetter
conditions
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Future Work
o Analysis of n-alkanoic acids, n-alkanols, and sterols o Extraction of the 9 remaining sample depths from
the peat profile o Carbon dating of peat profile