Time-trend analysis of PAH and PCB sediment fluxes in the northern Baltic proper using different dating methods

Abstract

A recent laminated sediment was collected in the northern Baltic Proper with a Kajak-type gravity corer. The sediment core was analysed for content of polycyclic aromatic hydrocarbons, (PAHs) and mono-, di- and non-ortho polychlorinated biphenyls (PCBs). To evaluate different dating methods and to make dating as accurate as possible, four sediment-dating methods were used: activity measurements of the radio nuclides ²¹⁰Pb, ²³⁹/²⁴⁰Pu and ¹³⁷Cs, and counts of the number of laminae in the core. According to the ²¹⁰Pb dating there was a peak in the annual flux of PAHs and ortho PCBs around 1950 after which the flux declined, but the peaks occurred during the 1970s according to the laminae counts. For non-ortho PCBs the trend was less clear, but a flux increasing with time was evident. Multivariate analysis showed a significant change in PAH composition over time, whereas the PCB composition was relatively constant.