7 
spill. The analyst may also be able to indicate the general area where a crude oil originated, 
e.g. North Sea, Middle East, Nigeria, etc. 
But even if an oil spill sample is compared with a sample from a suspected source, the oil type 
must be known because the chemical methodology must be adapted to the peculiarities of 
different types of oil. This means that different analytical data must be chosen for sample 
comparison: 
In pure light fuels, for example, nearly the whole range of biomarkers are missing. Therefore, 
only a very limited set of parameters can be used in a comparison of two light fuel oil 
samples. By contrast, higher-boiling lubricating oils have been found to be rich in biomarkers 
while most aromatics are missing. 
The aromatic hydrocarbons present in the most common types of heavy fuel oil result 
primarily from production processes (cracking) at the refineries. As identical processes lead to 
the same, or at least very similar, clusters of aromatic compounds, their value in the 
discrimination of different HFO samples is rather limited. 
Compounds or compound relations in the range of biomarkers may be very characteristic or 
even “unique” in the case of an unknown crude oil pollution. Examples are: 
28-bisnorhopane 
oleanane 
gammacerane. 
But their significance strongly depends on the circumstances of the particular case. Generally, 
their rapid recognition may save resources, in case they are present in the spill sample but not 
in the comparison sample. On the other hand, their presence in both samples may indicate a 
much stronger connection between these samples than other compounds. 
A The most suitable strategy for treating analytical data in Oil Spill Identification is 
different from case to case. Nevertheless, some general guidelines can be given 
with regard to different oil types and their occurrence and behaviour in the aquatic 
environment. The more guidance is provided to analysts, the more effective their efforts will 
be. 
Oil identification means, in fact, oil discrimination: generally, differences have to be found or, 
if there are no differences between two oil samples, they must be considered identical. 
However, when comparing oil spill samples with samples from suspected sources, it must be 
taken into account that the composition of an oil changes as soon as it is released into the 
environment (“weathering” of oil). This means that only those data can be used in the