25th International Meeting on Organic Geochemistry IMOG 2011

P-387
The use of phospholipid fatty acid analysis and isotopic
techniques to track the fate of organic contaminants in
environmental systems
Brian Murphy 1 , Chris Allen 2 , Leonid Kulakov 2 , Anna Kulakov 2 , Michael Larkin 2 , Brian
Kelleher 1
1 Dublin City University, Dublin, Ireland, 2 Queens University, Belfast, Ireland (corresponding
author:Brian.kelleher@dcu.ie)
This project focuses on analysis of soils and
sediments contaminated with petroleum compounds.
By using gas chromatograph mass spectroscopy
(GCMS) to identify and quantify 1)petroleum
pollutants 2)pospholipid fatty acids (PLFA‘s) then
combining the use of stable isotope studies, an
improved understanding of the fate of particular
organic compounds in complex microbial systems can
be gained. PLFA‘s are particularly useful as
biomarkers as they are contained solely in the cell
membrane as storage products. This is important as
the cell membrane rapidly degrades after cell death;
therefore PLFA‘s are good indicators of living
microbial biomass rather than non-living microbial
biomass [1] .
Total petroleum hydrocarbon (TPH) analysis
is an accepted benchmark used to evaluate the extent
of petroleum contamination in environmental
samples [2] . Sediment contaminated with petroleum
hydrocarbons was sourced from a petroleum
company (See Chromatogram 3). Volatile compounds
from another sample contaminated with heavy fuel oil
were extracted using solid phase micro extraction
(SPME). Lipid extraction: PLFA‘s are extracted and
isolated from soil using a modified Bligh Dyer
extraction and solid phase extraction (SPE)
respectively. The total lipid (TLE) extracts are then
transferred to SPE columns the PLFA‘s are isolated
and derivitised to fatty acid methyl esters
(FAME‘s).(See Chromatograms 1&2). Isotopic
analysis is performed using GCMS hyphenated to
isotope ratio mass spec (IRMS). Soils amended with
C 13 labelled tracers are extracted and enriched
PLFA‘s are identified using the C 12 /C 13 ratio.
Chromatogram 5 shows enriched PLFA‘s from soil
incubated with C 13 Vanillin.
GCMS Chromatogram 1: Total lipids extracted from park soil
GCMS Chromatogram 2: Isolated PLFA‘s after SPE
GCMS Chromatogram 3: TPH with Hrdrocarbons and known
oil spill biomarkers
GCMS Chromatogram 4: SPME results contaminated site
containing C11 to C16 Hydrocarbons and naphthalene.
IRMS Chromatogram 5: C13 enriched Fatty acids
Discussion: SPE allows the isolation of PLFA‘s so
they can be used as taxonomic discriminators for
microbial species [1] . Analysis of volatile and non
volatile petroleum contaminants gives an indication of
the level of soil pollution. Fluorene, anthracene,
phenanthrene and naphthalene are known markers
for oil spills this preliminary analysis helps in
identifying a suitable compound for C 13 labelled tracer
studies. Microbes which degrade the labelled marker
will incorporate C 13 into their PLFA‘s. By tracing all the
enriched PLFA‘s using IRMS and lipid fingerprinting,
the microbial species responsible for uptake of the
labelled compound can be identified.
References: [1] G.T.Hill et al. Applied Soil Ecology 15 (2000)
25-36. [2] Guibo Xie, Journal of Analytical Chemistry 71
(19199) 1899-1904
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