Pre-industrial accumulation of anthropogenic polycyclic aromatic hydrocarbons found in a blanket bog of the Iberian Peninsula

Studies on the temporal deposition of polycyclic aromatic hydrocarbons (PAHs) in peatlands are scarce, and none have been carried out in the Iberian Peninsula. To address this gap, ten PAHs were determined in a short peat core (spanning the last 1000 years) sampled in NW Iberian Peninsula, by HPLC-fluorescence. Fluoranthene, pyrene, benzo[b]fluoranthene and indeno[1,2,3-cd]pyrene predominated in the upper layers (10 cm), whereas fluoranthene and pyrene were the most abundant in the lower layers (40 cm), which showed an absence of high molecular weight PAHs (benzo[ghi]perylene and Indeno[1,2,3-cd]pyrene). Although increased PAH contents have been detected since 1700 A.D., coinciding with the beginning of the Metallurgical and Industrial Revolution, high levels of fluoranthene and pyrene were present in peat samples dating back to the 12th century A.D. The results suggest that changes in sources, type of emission (global or local) and transport could be responsible for the different PAH content and composition of the peat core. These changes are consistent with the history of the use of natural resources in the NW of the Iberian Peninsula.

► The deposition of anthropogenic PAHs began earlier than industrial revolution.
► PAHs composition and other environmental proxies marked changes in sources.
► Anthropogenic fires cause accumulation of PAHs in the Middle Ages from local sources.
► Regional anthropogenic sources of PAHs increased from industrialisation.