Sorption Behavior and Aerosol–Particulate Transitions of 7Be, 10Be, and 210Pb: A Basis for Fallout Radionuclide Chronometry

We investigated the partitioning of 7Be, 10Be, and 210Pb aerosols between operationally dissolved and >0.5 μm particulate fractions in wet and dry atmospheric deposition. Bulk deposition in situ-log­(K D ) averaged 4.27 ± 0.46 for 7Be and 4.79 ± 0.59 for 210Pb (±SD, n = 163), with corresponding a...

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Bibliographic Details
Published in:Environmental science & technology 2021-11, Vol.55 (21), p.14957-14967
Main Authors: Landis, Joshua D, Renshaw, Carl E, Kaste, James M
Format: Article
Language:English
Subjects:
Aerosols
Aluminum
Beryllium
Beryllium 10
Beryllium 7
Biogeochemical cycles
Biogeochemical Cycling
Colloids
Deposition
Fallout
Lead isotopes
Manganese
Measuring instruments
Nickel
Particulates
Partitioning
Radioisotopes
Solid surfaces
Sorption
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Summary:We investigated the partitioning of 7Be, 10Be, and 210Pb aerosols between operationally dissolved and >0.5 μm particulate fractions in wet and dry atmospheric deposition. Bulk deposition in situ-log­(K D ) averaged 4.27 ± 0.46 for 7Be and 4.79 ± 0.59 for 210Pb (±SD, n = 163), with corresponding activity-fractions particulate (f P) = 24 and 48%. K D was inversely correlated with particulate mass concentration (p C ), a particle concentration effect (p.c.e.) that indicates that dissolved 7Be and 210Pb are bound to submicron colloids. Experimental desorption-K D was higher than in situ by a factor of 20 for 7Be and 4 for 210Pb (n = 27), indicating that FRN sorption to particulates was irreversible. 7Be:10Be ratios confirmed that colloidal and particulate fractions were geochemically distinct, with corresponding ages of 120 ± 30 and 260 ± 45 days, respectively [mean ± SE, n = 9, p = 0.011]. Fractions particulate f Be7, f Be10, and f Pb210 each increased with 7Be:10Be bulk age, a particle-age effect (p.a.e). In multiple regression, f Be7 was best predicted by N, Mn, Al, and Ni [R 2 = 0.75, p < 0.0001], whereas f Pb relied on N, S, Fe, and Mn [R 2 = 0.69, p < 0.0001]. Despite differences in magnitude and controls on partitioning, the ratio f Be :f Pb converged to 1 with p C in the range of 10–100 mg L–1. Given sufficient solid surfaces, irreversible sorption and p.a.e. form a basis for 7Be:210Pb chronometry of aerosol biogeochemical cycling.
ISSN:0013-936X
1520-5851
DOI:10.1021/acs.est.1c03194