Estuarine geochemistry of /sup 224/Ra, /sup 226/Ra, and /sup 222/Rn
Desorption from river borne sediments is the most likely source of the excess /sup 226/Ra. Laboratory mixing experiments on Pee Dee River sediments show an increase in /sup 226/Ra desorption with increasing salinities with maximum desorption occurring at or above 20/sup 0//oo salinity. Desorption and diffusion are the sources for /sup 226/Ra in the estuarine systems. In Winyah Bay the /sup 228/Ra//sup 226/Ra activity ratio does not change significantly with salinity, averaging around 1.4, indicating desorption as the major source of /sup 228/Ra. In the Yangtze River the /sup 228/Ra//sup 226/Ra activity ratio is constant (approx.1.90) until increasing linearly above 16/sup 0//oo. A diffusive flux from regeneration by /sup 232/Th decay in shelf sediments is the source of the increase. In Delaware Bay /sup 228/Ra increases faster than /sup 226/Ra in the less than or equal to22/sup 0//oo water, indicating a source in addition to desorption. The increase can be balanced by a 0.33 dpm/cm/sup 2/-year flux over the upper part of the Bay where fine grained sediments predominate. /sup 224/Ra behavior is controlled by its 3.64 day half-life. In Winyah Bay a flux of around 0.4 dpm/cm/sup 2/-day is necessary to support the standing crop of non-desorbed /sup 224/Ra in the water column. In Delaware Bay the nearly constant /sup 224/Ra in concentration over the 2.5/sup 0//oo to 12/sup 0//oo salinity range are maintained by regeneration from /sup 228/Th in the turbidity maximum zones and diffusion from bottom sediments. Water leaving on ebb tide from a salt marsh on Delaware Bay had increases in all three radium isotopes (/sup 224/Ra > /sup 228/Ra > /sup 226/Ra) compared to water coming in on the flood tide. Excess /sup 222/Rn concentrations in a fresh water section of the Pee Dee River show a decreasing downstream gradient. Using these gradients to determine evasion rates, stagnant film thicknesses range from 21..mu.. to 62..mu...
- OSTI ID:
- 6887181
- Resource Relation:
- Other Information: Thesis (Ph.D.)
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ESTUARIES
RADIONUCLIDE MIGRATION
RADIUM 224
RADIOECOLOGICAL CONCENTRATION
RADIUM 226
RADIUM 228
RADON 222
BAYS
DELAWARE RIVER
DESORPTION
DIFFUSION
GEOCHEMISTRY
SALINITY
SALINITY GRADIENTS
SEDIMENTATION
SEDIMENTS
YANGTZE RIVER
ALKALINE EARTH ISOTOPES
ALPHA DECAY RADIOISOTOPES
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
CHEMISTRY
DAYS LIVING RADIOISOTOPES
ECOLOGICAL CONCENTRATION
ENVIRONMENTAL TRANSPORT
EVEN-EVEN NUCLEI
HEAVY NUCLEI
ISOTOPES
MASS TRANSFER
NUCLEI
RADIOISOTOPES
RADIUM ISOTOPES
RADON ISOTOPES
RIVERS
STREAMS
SURFACE WATERS
YEARS LIVING RADIOISOTOPES
520301* - Environment
Aquatic- Radioactive Materials Monitoring & Transport- Water- (1987)