Organic geochemical parameters for estimation of petrogenic inputs in the coastal area of Kavala City,Greece

Background, aims, and scope  Sediments and soils in coastal areas are frequently polluted by anthropogenic contaminants as the result of both riverine or terrestrial discharge and autochthonic marine emissions. In order to determine petrogenic contamination in the coastal industrial area of Kavala City in northern Greece, a combination of polycyclic aromatic hydrocarbon (PAH) and organic geochemical petroleum biomarker analyses has been performed on marine and freshwater sediments as well as soils. Materials and methods  Soils, freshwater, and marine sediments have been treated by standard extraction methods. The dried and desulphurized sample extracts have been fractionated by column chromatography, followed by addition of surrogate standards. Qualitative and quantitative data were obtained by gas chromatograph connected with a flame ionization and electron capture detector (GC-FID/ECD) and by GC linked to a mass spectrometer (GC/MS), whereas identification of compounds was based on EI⁺-mass spectra and gas chromatographic retention times. Quantitative data were obtained by integration of specific ion chromatograms. Results  The total PAH concentrations measured in the area varied highly, showing different levels from 18 up to 318,000 ng g⁻¹ dry weight (dw). Several PAH ratios, as well as the ratio of pristane (Pr) to phytane (Phyt), have been considered. Out of 39 samples, 22 revealed a specific distribution of hopane fingerprints indicating petrogenic input. Finally, in numerous samples, the ratio of 17α(H)-22,29,30-trisnorhopane (Tm) and 18α(H)-22,29,30-trisnorhopane (Ts) was calculated, as well as the ratio of 22S-17α(H),21β(H)-30 homohopane (αβC₃₁-hopane 22S) and 22R-17α(H),21β(H)-30 homohopane (αβC₃₁-hopane 22R). Discussion  Based on the specific PAH ratios, a group of samples was clearly characterized to be contaminated dominantly by combustion-derived emissions, whereas a second group of samples exhibited mixed influence from petrogenic and pyrogenic PAHs. On the other hand, the exhibition of specific hopane fingerprints in many samples indicates a direct petrogenic input. Finally, the values of the ratio of Tm/(Ts + Tm) and of αβC₃₁-hopanes 22S/(22S+22R)-isomer demonstrated an input of highly mature organic matter that has to be clearly attributed to petroleum-derived contamination, while the ratio of Pr/Phyt showed that most samples exhibited an input of organic matter. Conclusions  The coastal area of Kavala is strongly affected by anthropogenic contaminants. Petrogenic emissions were pointed out firstly by PAH analyses that separated dominantly pyrogenic contaminated sites from areas affected by both pyrogenic and petrogenic emissions. However, analyses of organic geochemical biomarkers revealed a much higher sensitivity in identifying petroleum-derived contaminations and were successfully used to differentiate several petrogenic contaminations in the marine and terrestrial samples. Recommendations and perspectives  Based on this study, it was recommended to use a complementary approach of source-specific substances to successfully characterize petrogenic emissions. Generally, a PAH-based source identification of petrogenic versus pyrogenic contaminations should be combined with petroleum biomarker analysis. PAH and biomarker ratios as well as individual biomarker fingerprints revealed a more comprehensive view on the quality and quantity of petrogenic emissions in sediments and soils.