Vertical distribution and source identification of polycyclic aromatic hydrocarbons (PAHs) in southwest of the Caspian Sea: Most petrogenic events during the late Little Ice Age

In this study, 75 samples of two 210Pb-dated cores from the southwest of the Caspian Sea were analysed for 30 compounds of polycyclic aromatic hydrocarbons (PAHs). The TPAH29 flux of the last six centuries ranged from 16.3 to 177.3 and 22.3 to 426.2 ng cm−2 y−1 in the Rezvanshahr and Anzali core sediments, respectively. Prior to 1840, four distinct maxima in PAH fluxes (61-426.2 ng cm−2 y−1) with a low weathered petrogenic pattern were found in each of the core sediments. Simultaneity of distinct peaks of PAH fluxes before 1840 and Caspian Sea level high-stands during the Little Ice Age (LIA), revealed the high importance of this phenomenon in washing and transport of land-based oil pollution into the Caspian Sea. An overall increase in some diagnostic ratios (Flu/202, IP/276 and BaA/228), especially after 1940, indicated increase of pyrogenic PAHs as a result of industrial development in the catchment area.