Geology Reference
In-Depth Information
(e.g., carbon dioxide, nitrogen oxides, sulfur oxides, and water) (Swaine, 1990). As a result, little or no liquid coal tar
is produced from the combustion of coal. Natural coal fires will predominantly involve carbonization (and thereby
the formation of coal tar) although combustion can also occur depending upon the conditions (oxygen availability).
Candidate
coal
sources
Coal
tar
residues
Sample
collection
Ambient
soil
Bulk properties
e.g., TOC
Tier 1
Hydrocarbon
sample preparation
TEH patterns and
concentrations
GC/FID and GC/MS
What are the
dominant features?
Tier 2
Identify differences
between source and
reference samples
Characterize dominant
hydrocarbon features
GC/FID
Are differences from
heat, weathering or
method artifacts?
YES
Characterize petrogenic
and pyrogenic
PAH patterns
GC/MS SIM
NO
Characterize saturate
& biomarker patterns
GC/MS SIM
Tier 3
Identify differences
between source and
reference samples
Do PAH & biomarker
source ratios
match?
Are differences from
heat, weathering or
method artifacts?
NO
Unknown
YES
Describe
thermal effect
Conclusion
Inconclusive
No match
Figure 11.1.1. The multiple lines of evidence approach is a systematic protocol for reviewing hydrocarbon
signatures. Tier 1 involves the review of bulk chemical features. Tier 2 incorporates dominant hydrocarbon
features from the GC/FID and summation data. Tier 3 folds in the detailed PAH and biomarker results. The
conclusions summarize the salient similarities and differences among the laboratory samples compared to each
other or reference samples. See subsequent text for acronyms.
