210Pb 추적자를 활용한 동해에서 용존 납의 대기 기원 유입량 연구

Abstract

We estimated the atmospheric depositional fluxes of 210Pb (half-life = 22.3 yrs) in the East Sea by establishing the oceanic budget of 210Pb. The atmospheric input fluxes are assumed to be balanced by the in-situ production from 226Ra (half-life = 1600 yrs), the in-situ decay of 210Pb, and the settling down to the deep ocean. This method is advantageous since it measures the actual fluxes of 210Pb to the ocean, relative to indirect measurements through land-based wet/dry deposition measurements or numerical modelling. The atmospheric input of 210Pb is estimated to be about 1.62±0.04 dpm cm-2 yr-1. This value falls into the range measured at the land sites around this region (0.44-4.42 dpm cm-2 yr-1). The mass balance also yields the residence times of dissolved 210Pb in the East Sea (about 5.8-6.0 years). Combined with the inventory of dissolved Pb in the East Sea, the atmospheric depositional fluxes of seawater-dissolvable Pb are estimated to be 1.8-2.0 mg m-2 yr-1, which is considered to be potentially bioavailable. This is about half of the total Pb flux (dissolvable in ~0.3 mol/L HNO3) measured at 10 stations in Japan for the year 2004. Our results show that 210Pb is a powerful tracer in understanding the fluxes and behaviour of bioavailable Pb in the ocean