Application of ^239,240 Pu, ¹³⁷Cs and heavy metals for dating of river sediments

Abstract

The periodical nature of overbank sediment accumulation makes their detailed dating much more difficult than dating sediments in water reservoirs. To improve the commonly used dating with 137Cs, we combined this method with Pu isotopes and heavy metals in order to date sediments of the Chechło River (southern Poland), which was polluted by a lead-zinc mine. We analyzed 137Cs, Pu isotopes and heavy metal concentrations in three profiles of overbank sediments and in two profiles of subsidence basins in the lower river reach. The results indicate a lower accuracy and higher uncertainty of the overbank than the dating of reservoir sediments. The application of plutonium isotopes provided very important information validating caesium peaks or providing the principal information regarding horizons dated with heavy metals. The obtained dates give the earliest possible age of particular horizons with the actual sediment deposition delayed by several to a dozen years. This investigation shows that using plutonium radioisotopes can be a useful tool for dating, particularly of the youngest overbank sediments where numerous sedimentation gaps cause uncertainties in the application of other methods, e.g. radiocaesium and heavy metals.

Historical sedimentary and evolutionary characteristics of POPs and EDCs in typical regions of the three Gorges reservoir, China

“…Sediments are crucial in the circulation, transfer and storage of these pollutants in aquatic ecosystems, acting as both a sink and source [ 6 ]. Caesium 137 ( 137 Cs)—an artificial radionuclide produced during nuclear weapon testing—is widely used for sediment dating [ 7 ]. Yang et al used 210 Pb, 226 Ra and 137 Cs to measure the concentration and deposition flux of PAHs and indicated an increase in the contribution of anthropogenic sources from the bottom to the top of sediment cores in the East Lake in Wuhan [ 8 ].…”