Influence of radon diffusion on the /sup 210/Pb distribution in sediments

Journal Article · Wed Jan 20 04:00:00 EST 1982 · J. Geophys. Res.; (United States)

DOI:https://doi.org/10.1029/JC087iC01p00557· OSTI ID:5508741

Imboden, D M; Stiller, M

A mathematical model is presented which describes the distribution of radon 222 in sediments having a constant or variable depth distribution of radium 226. The model is extended to the distribution of lead 210, taking into account the mobility of radon (the precursor of /sup 210/Pb) within the sediment column. The /sup 210/Pb model is compared, at constant radium activity, with the conventional approach which disregards the radon diffusion when estimating sedimentation rates by the /sup 210/Pb method. The ratio between apparent and real sedimentation rate, s'/s, expressed as a function of three dimensionless parameters, demonstrates the importance of the radon diffusion effect. This effect is particularly important for sediments with small initial excess /sup 210/Pb activity, small sedimentation rate, large radon diffusivity, or a combination of these factors. Applied to Lake Geneva, the sedimentation is estimated to be larger by 30--50% than the original value by Krishnaswami et al, (1971). In sediments which are mixed at the surface (physical mixing or bioturbation), the /sup 210/PB activity in the mixed layer is diminished compared to that in the settling sediment material (Robbins et al., 1977), and radon diffusion makes the activity difference even larger, especially for low initial excess /sup 210/Pb activity, small sedimentation rate, and large mixing intensity. This result may be of importance for the balance of /sup 210/Pb in an aquatic system if the calculations are based on activities measured in the sediment.

• Research Organization: Swiss Federal Institute of Technology (EAWAG), Duebendorf, Zuerich, Switzerland
• OSTI ID: 5508741
• Journal Information: J. Geophys. Res.; (United States), Journal Name: J. Geophys. Res.; (United States) Vol. 87:C1; ISSN JGREA
• Country of Publication: United States
• Language: English

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ALPHA DECAY RADIOISOTOPES
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
DAYS LIVING RADIOISOTOPES
DIFFUSION
EVEN-EVEN NUCLEI
HEAVY NUCLEI
ISOTOPES
LEAD 210
LEAD ISOTOPES
MATHEMATICAL MODELS
NATURAL RADIOACTIVITY
NUCLEI
RADIOACTIVITY
RADIOISOTOPES
RADON 222
RADON ISOTOPES
SEDIMENTATION
SEDIMENTS
YEARS LIVING RADIOISOTOPES