Geochemical Analysis of Soils, Marine Sediments, and Peat

1. Title: Geochemical Analysis of
Soils, Marine Sediments, and
Peat
Author: Shannon Lee

2. 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

3. Elemental Analysis – Introduction
o Can provide quantitative analysis of an unknown
sample
o Determines amount and variation of organic matter
(OM)

4. 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

5. Elemental Analysis – Results

6. 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

7. 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)

8. 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

9. 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

10. Lipid Biomarkers – Preliminary Results
o Abundance of C23 suggesting Sphagnum moss
o Abundance of C31 suggesting Terrestrial plants

11. Lipid Biomarkers – Preliminary Results
o Higher ratio at 105-110 cm suggests wetter
conditions

12. 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