Polycyclic Aromatic Hydrocarbons (PAHs) in Bulgarian Coals: Occurrence, Distribution and Carcinogenicity

The study fills the informative gap on occurrence, distribution, and carcinogenicity of polycyclic aromatic hydrocarbons (PAHs) in Bulgarian coals. It presents quantitative data for content and carcinogenicity of PAHs in different rank raw coals from eight basins with geological age from Late Carboniferous to Late Miocene, Ro=0.17–5.20%. The high amounts of alkylated naphthalene and alkylated phenanthrene determined in the bituminous coals reflect the diagenetic conversion of the plant-derived terpenoids into alkylated PAHs. In this first systematic study of PAHs in Bulgarian raw coals three concentration ranges are established: for Miocene/Eocene age coal – from 1.08 mg/kg to 5.79 mg/kg; for Late Cretaceous/Late Carboniferous age coal – from 77.9 mg/ kg to 137.2 mg/kg; and, for the Late Carboniferous coal – 1.85 mg/kg. The relationship of the total PAHs content vs. raw coal Ro shapes as a “bell” and matches with the published data for the native PAHs from all over the world provenance. The maximal PAHs amount of 137.2 mg/kg at Ro =0.96% for the Late Cretaceous coal lies within the “oil-generation window”, Ro =0.5–1.3% for the kerogen. For all raw coal studied relatively low carcinogenicity is determined based on the well correlated values for B[a]Peq and TEQ parameters.