30 
Oil Spill identification - Round Robin 20045 
Fig 5 
Percentage weathering (PW)-plots 
Corresponding big differences in the n-alkane distribution between 
source I and source II are obvious also in the weathering checks 
produced by NERI: 
Fig 6 
Weathering check (NERI) 
But these differences cannot be attributed to the fact that source II had 
a relatively lower fuel oil content then source I, as suggested here: n- 
alkanes are not present in the lub oil. So, these differences have 
nothing to do with the relation of fuel oil to lub oil. 
Differences between the spill samples and source II were not so obvious 
here: C19 is only slightly higher, whereas C22 and C23 are slightly 
lower in the spill samples. This might be due to the fact that the peaks 
are normalized to the mean of C19 to C22 here, where C19 could 
already have been affected by weathering.