Disequilibrium between [sup 226]Ra and supported [sup 210]Pb in a sediment core from a shallow Florida lake

Journal Article · Fri Jul 01 00:00:00 EDT 1994 · Limnology and Oceanography; (United States)

DOI:https://doi.org/10.4319/lo.1994.39.5.1222· OSTI ID:6854194

Brenner, M; Peplov, A J; Schelske, C L ^[1]

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1. Univ. of Florida, Gainsville, FL (United States)

[sup 210]Pb dating can be used to assign ages in lake sediment cores, calculate rates of sediment accumulation, and determine the timing of recent changes in lake-watershed ecosystems. We used low-background gamma counting to measure [sup 226]Ra and total [sup 210]Pb activity in a core from Lake Rowell, Florida. [sup 226]Ra activity was high and strongly variable throughout the core, even exceeding total [sup 210]Pb activity in recently deposited sediments. We traced one source of Ra-rich sediments to the only inflow, Alligator Creek, where stream-bottom deposits display disequilibrium between [sup 226]Ra and supported [sup 210]Pb. High and variable [sup 226]Ra activity in the Lake Rowell profile argues for direct estimates of in situ Ra in lake sediment cores from disturbed watersheds that have Ra-bearing bedrock. Isotopic disequilibrium between [sup 226]Ra and supported [sup 210]Pb makes it difficult to distinguish between supported and unsupported [sup 210]Pb activity throughout the Lake Rowell core and would require special assumptions and nonconventional dating models to establish age-depth relationships. 78 refs., 3 figs., 1 tab.

• OSTI ID: 6854194
• Journal Information: Limnology and Oceanography; (United States), Vol. 39:5; ISSN 0024-3590
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
SEDIMENTS
ISOTOPE DATING
EQUILIBRIUM
LAKES
LEAD 210
RADIUM 226
AGE ESTIMATION
ALKALINE EARTH ISOTOPES
ALPHA DECAY RADIOISOTOPES
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
CARBON 14 DECAY RADIOISOTOPES
EVEN-EVEN NUCLEI
HEAVY ION DECAY RADIOISOTOPES
HEAVY NUCLEI
ISOTOPES
LEAD ISOTOPES
NUCLEI
RADIOISOTOPES
RADIUM ISOTOPES
SURFACE WATERS
YEARS LIVING RADIOISOTOPES
540330* - Environment
Aquatic- Radioactive Materials Monitoring & Transport- (1990-)