The budget of 210Pb in the East Sea: atmospheric inputs versus in-situ production

Abstract

In order to determine the entire budget of 210Pb (half-life = 22.3 yrs) in the East Sea, we established the mass balance model that divided the East Sea into two layers, 0 &#8211 1000 m and 1000 &#8211 2000 m. The budget of 210Pb inventories in the water column (0 &#8211 2000 m) would be balanced by the in-situ production from 226Ra (half-life = 1600 yrs), the in-situ decay to 210Po (half-life = 138 days), the settling to the deep ocean, and atmospheric inputs. The in-situ ingrowth and decay fluxes are determined from the vertical profiles of 226Ra and 210Pb in the East Sea obtained in this (April 2015) and previous studies. The settling flux is determined from the sediment trap data obtained in 1999. The in-situ production, decay, and settling fluxes were 0.40, 0.24, and 1.57 dpm cm-2 yr-1 in the 0 &#8211 1000 m water column and 0.47, 0.18, and 2 dpm cm-2 yr-1 in the 1000 &#8211 2000 m water column. We calculated the atmospheric input through those fluxes of 210Pb in seawater and obtained a value of 1.41±0.16 dpm cm-2 yr-1, which is 1.6 times higher than in-situ production from 226Ra. This value is also consistent with previous studies about atmospheric depositional flux of 210Pb (1 &#8211 2 dpm cm-2 yr-1) observed on land sites. This atmospheric depositional flux of 210Pb using the water column budget in the ocean seems to be powerful tool for precisely calculating the atmospheric depositional fluxes of otheies in the water column (0 &#8211 2000 m) would be balanced by the in-situ production from 226Ra (half-life = 1600 yrs), the in-situ decay to 210Po (half-life = 138 days), the settling to the deep ocean, and atmospheric inputs. The in-situ ingrowth and decay fluxes are determined from the vertical profiles of 226Ra and 210Pb in the East Sea obtained in this (April 2015) and previous studies. The settling flux is determined from the sediment trap data obtained in 1999. The in-situ production, decay, and settling fluxes were 0.40, 0.24, and 1.57 dpm cm-2 yr-1 in the 0 &#8211 1000 m water column and 0.47, 0.18, and 2 dpm cm-2 yr-1 in the 1000 &#8211 2000 m water column. We calculated the atmospheric input through those fluxes of 210Pb in seawater and obtained a value of 1.41±0.16 dpm cm-2 yr-1, which is 1.6 times higher than in-situ production from 226Ra. This value is also consistent with previous studies about atmospheric depositional flux of 210Pb (1 &#8211 2 dpm cm-2 yr-1) observed on land sites. This atmospheric depositional flux of 210Pb using the water column budget in the ocean seems to be powerful tool for precisely calculating the atmospheric depositional fluxes of othe