해양에서 Pb-210 - Po-210 쌍의 겉보기 불균형에서 Bi-210의 역할

Abstract

The 210Po (t1/2 = 138 days) - 210Pb (t1/2 = 22.3 years) pair as well as that in 238U-234Th pair has been used for estimating export fluxes of particulate organic carbon in the ocean. However, the role of 210Bi has not drawn sufficient attention in the 210Pb-210Po disequilibrium studies although 210Bi as an intermediate decay product of 210Po and substantially long half-life (5.01 days) to participate in the particle processes occurring in the sea, partly due to its short half-life to determine in situ concentration aboard the ship. Most current studies assume that 210Bi is not particle reactive but conservative. However, it is known that 210Bi is more enriched in particulate matter than 210Po and 210Pb as much as an order of magnitude. This indicates that the deficiency of 210Po to 210Pb activities (APbt - APot) in the surface ocean may include the deficiency of 210Bi to 210Pb (APbt - ABit) resulting from sinking of 210Bi attached to the particle in the ocean. We developed a model to elucidate a role of 210Bi in the behavior of 210Po-210Pb pair in the ocean. We assumed that the activities in the dissolved and particulate phases of 210Pb, 210Bi and 210Po in a given water column are determined by the concentration of particle in water column, input and output, distribution coefficients between dissolved and particulate phases, decay constants of these radionuclides. We estimated the 210Bi contribution to the 210Pb-210Ption in the 210Pb-210Po disequilibrium studies although 210Bi as an intermediate decay product of 210Po and substantially long half-life (5.01 days) to participate in the particle processes occurring in the sea, partly due to its short half-life to determine in situ concentration aboard the ship. Most current studies assume that 210Bi is not particle reactive but conservative. However, it is known that 210Bi is more enriched in particulate matter than 210Po and 210Pb as much as an order of magnitude. This indicates that the deficiency of 210Po to 210Pb activities (APbt - APot) in the surface ocean may include the deficiency of 210Bi to 210Pb (APbt - ABit) resulting from sinking of 210Bi attached to the particle in the ocean. We developed a model to elucidate a role of 210Bi in the behavior of 210Po-210Pb pair in the ocean. We assumed that the activities in the dissolved and particulate phases of 210Pb, 210Bi and 210Po in a given water column are determined by the concentration of particle in water column, input and output, distribution coefficients between dissolved and particulate phases, decay constants of these radionuclides. We estimated the 210Bi contribution to the 210Pb-210P