Environmental fate of polycyclic aromatic hydrocarbons (PAHs) in different layers of tar balls in the Bohai Sea, China

Several tar balls were transversely cut to investigate the fate of polycyclic aromatic hydrocarbons (PAHs) in different layers of tar balls under natural conditions. The highly recalcitrant C30 alpha beta-hopane was used as an in-ternal biomarker to quantify the weathering levels of different PAHs compounds. The data showed that the values of 16 parent PAHs and their alkylated PAHs in the surface layer were lower than that in the center layer of tar balls, which indicated that the surface layer of tar balls were suffered more serious degradation. In addition, the loss rates of different isomers of the same series were almost the same, indicated that the degradation rate of different isomers in the same series was the same. Despite some degradation, the relative diagnostic ratios of alkylated PAHs in the different layers of the tar balls remained stable. Compare the loss rate of parent and alkylated PAHs, it revealed that the loss rates increased with the increase of alkylation degree. This is the first report on the fate of PAHs in different layers of tar balls. This study provides a quantitative analysis of the PAHs in different layers of tar balls under natural conditions, which is very important for understanding the fate of oil spills.