Measuring bismuth-210, its parent, and daughter in aquatic systems

Abstract

210Bi (t1/2: 5.01 d)—the daughter of 210Pb and parent of 210Po—has rarely been measured in aquatic systems, and its behavior in the water column is poorly understood. In this article, I present a method for quickly measuring 210Pb, 210Bi, and 210Po in aquatic samples, where (1) 210Bi and 210Po are scavenged onto an anion solid-phase extraction disk within 15 min of pretreating the sample; (2) beta decay of 210Bi is counted on the disk immediately thereafter; (3) 210Po is subsequently removed from the disk and redeposited on a copper plate for α-spectroscopy; and (4) 210Pb is determined via the ingrowth of 210Bi. I present decay-corrected calculations for total, dissolved, and particle-bound fractions of each nuclide and conclude with an analysis of 210Pb, 210Bi, and 210Po activities in rain, dreissenid (quagga) mussels, and water samples from the Milwaukee Inner Harbor in Lake Michigan. Results show that the loss of lead on the anion solid-phase extraction disks was negligible (0.2% ± 2.1%; ± 1 SD, n = 4), and the sorption of bismuth was complete (99% ± 2%; ± 1 SD, n = 16). Relative mean absolute deviations of duplicate sample analyses of lake water were 2.4% ± 1.9% for 210Pb (geometric mean of total sample activity: 3.0 disintegrations per minute [dpm], n = 6), 7.7% ± 5.8% for 210Bi (geometric mean of total sample activity: 2.6 dpm, n = 8), and 2.7% ± 1.7% for 210Po (geometric mean of total sample activity: 1.4 dpm, n = 8).