SCAVENGING AND PARTICLE DEPOSITION IN THE SOUTHWESTERN BLACK-SEA - EVIDENCE FROM CHERNOBYL RADIOTRACERS

The pulse of fallout tracers from the Chernobyl accident in April 1986 is used to examine scavenging and particle deposition in the southwestern Black Sea. Data on the distribution of 137Cs, 134Cs, 106Ru and 144Ce between the dissolved, suspended and sinking phases are presented. As expected by their different chemistries, the more particle-reactive 106Ru and 144Ce tracers are preferentially removed from surface waters relative to Chernobyl Cs, a predominantly conservative tracer. By comparing the tracer isotopic ratios is suspended fine particulates and rapidly sinking large particulates caught in sediment traps, an indication of the sediment source can be obtained. During the spring and summer, biological blooms drive rapid vertical transport of particles and tracer to depth, while during the autumn and winter months the lateral transport of shelf-derived particulates dominates the sinking flux. By the end of this annual cycle, much of the Chernobyl 106Ru and 144Ce have been scavenged from surface waters and removed to depth on sinking particles; however, there is significant release of these tracers back into the mid-waters during this process. © 1990.