Analysis of 210Po, 210Bi, and 210Pb in atmospheric and oceanic samples by simultaneously auto-plating 210Po and 210Bi onto a nickel disc

Abstract

²¹⁰Po and ²¹⁰Pb are commonly measured to study particle cycling and particulate organic carbon export (POC) flux from the upper ocean. ²¹⁰Bi is a potential oceanographic tracer. However, no convenient and rapid analytical method for ²¹⁰Bi has been developed in the marine environment due to its short half-life (5 days). The aims are to study factors influencing the simultaneous auto-plating of ²¹⁰Po and ²¹⁰Bi onto nickel disc and to develop an effective ship-board procedure for the rapid measurement of ²¹⁰Po, ²¹⁰Bi, and ²¹⁰ Pb at sea. The results suggest that the optimal conditions for auto-deposition of ²¹⁰Po and ²¹⁰Bi were achieved by using a 25 mm diameter nickel disc in 60 mL acidic solution (pH = 0.5) for 16 h at 25 ± 1 °C. By adding ²⁰⁹Po and ²⁰⁷Bi as yield tracers to the sediments, recoveries of Po and Bi were >90%. If ²¹⁰Po or ²¹⁰Bi were in equilibrium with ²¹⁰Pb, ²¹⁰Po and ²¹⁰Bi could also be potential proxies for ²¹⁰Pb in sedimentary chronology. The overall recoveries of ²⁰⁹Po and ²⁰⁷Bi were >70% for rainwaters and >60% for seawater samples, respectively, which indicates this analytical procedure is also applicable to marine and atmospheric environments. This method allows the rapid measurement of ²¹⁰Bi on a ship and help to obtain its vertical profile or spatial distribution in the marine environment within 1-2 days.

Keywords: (210)Bi-(210)Po-(210)Pb; Auto-deposition; Marine environment; Method optimization; Nickel disc; Rainwater.