Excess 210Pb and 137Cs concentrations, mass accumulation rates, and sedimentary processes on the Bering Sea continental shelf

Abstract

We used 210Pb and 137Cs concentrations in twelve cores from the continental shelf and slope of the Bering Sea to investigate recent mass accumulation rates in sediments and sedimentation processes. No decreases in exogenic 210Pb concentrations with depth were observed in sediments from the shallow shelf area, suggesting that there has been considerable mixing of the sediments there. However, we calculated mass accumulation rates from 210Pbex profiles for several cores collected from the outer shelf and the slope. Mass accumulation rates in the sediments from these cores ranged from 0.11 to 0.44gcm−2y−1. For the cores with a mixed surface layer, we showed that sediments that accumulated over the last 50–78 years were mixed. The 210Pbex inventories in the sediment cores suggested deposition of 210Pb particles was focused in the slope area. 137Cs was observed in the sediments collected from the northern to western shelf areas. The 137Cs inventories showed higher values in the shelf area, which suggests that fine-grained particles from the Yukon River have contributed to sedimentation there.