Thorium-234 derived information on particle residence times and sediment deposition in shallow waters of the south-western Baltic Sea

Abstract Activities of the naturally occurring, short-lived and highly particle-reactive radionuclide tracer 234 Th in the dissolved and particulate phase were measured at three shallow-water stations (maximum water depths: 15.6, 22.7 and 30.1 m) in Mecklenburg Bay (south-western Baltic Sea) to constrain the time scales of the dynamics and the depositional fate of particulate matter. Activities of particle-associated (> 0.4 μm) and total (particulate + dissolved) 234 Th were in the range of 0.08–0.11 dpm L − 1 and 0.11–0.20 dpm L − 1 , respectively. The activity ratio of total 234 Th and its long-lived and conservative parent nuclide 238 U was well below unity (range: 0.09–0.19) indicating …