Table 3

Major triterpanes in fragmentogram m/z 191

Peak Compound Carbon no.

1 18a(H)-22, 29, 30 trisnorhpane(T_s) 27

2 17a(H)-22, 29, 30, trisnorhopane(T_m) 27

3 17a(H), 21b(H)-30-norhopane 29

4 17b(H), 21a(H)-30-norhopane(normoretane) 29

5 17a(H), 21b(H)-hopane 30

6 17b(H), 21a(H)-hopane(moretane) 30

7, 8 17a(H), 21b(H)-29-homohopane (22S and 22R) 31

9, 10 17a(H), 21b(H)-29 bishomohopane (22S and 22R) 32

11, 12 17a(H), 21b(H)-29 trishomohopane (22S and 22R) 33

13, 14 17a(H), 21b(H)-29 tetrakishomohopane (22S and 22R) 34

15,`16 17a(H), 21b(H)-29 pentakishomohopane (22S and 22R) 35

Petroleum Markers for Geochemical Investigations 9

Figure 3. Sterane (m/z 217) mass fragmentogram of a weathered oil spill.

Unaltered after weathering. This is evident from their very comparable values. As a consequence, these biomarkers seem appropriate for environmental monitoring applications. In contrast with these, neither the trisnorhopanes, T_m and T_s, nor the moretane constituents resulted in a reliable marker. However, the V/Ni parameter has a greater dynamic range does the parameter based on epimer rations. The V/Ni marker of the crude oils has values ranging from less than unity up to 3.5. by contrast, epimerization at chiral centers in biological markers has a restricted range of application in that it reaches equilibrium either before or at about the stage of maximum oil generation in sediments.

Evaluation of the biomarkers in fact provided additional parameters to the investigation, thus allowing the spills to be certainly and unambiguously monitored. The results also indicate that GC/MS, since its pioneering application in organic geochemistry (Seifert, 1974), is an effective technique in detecting the suspicious origin of oil spills. However, the IR and GC profiles can lead to the necessary information only if the oil spill is spotted early, before any considerable weathering commences.

References

Abu-Elgheit,