Samples of fresh and weathered Florida phosphate rock were analyzed for several uranium decay-series radionuclides. In bulk samples, almost all radionuclides display higher activities in weathered samples compared to fresh material. ('230)Th is normally in isotopic equilibrium with ('234)U in fresh material but is often depleted and occasionally enriched in highly weathered samples. ('226)Ra is close to equilibrium with its parent ('230)Th in most samples. ('210)Pb/('226)Ra activity ratios were less than 1.00, as expected, due to radon leakage. Less than unity activity ratios of ('210)Po/('210)Pb in a few weathered samples indicates a preferential release of ('210)Po under some conditions. / Highly weathered samples contain the most significant portion of their activity within the finest size fraction, while radionuclide activity in fresh samples tends to follow the predominant size of the phosphate particles. The finest size material of nearly all weathered samples shows a significant depletion of ('226)Ra relative to ('238)U, while fresher samples show a small excess ('226)Ra activity. Radionuclide concentrations are governed by 2 processes which occur during intense weathering of phosphate rock: (1) increased surface area with enhanced adsorption and (2) transformation of phosphate pellets into more CARFAP-pure "pebble" phases. / Based on over 2 years of measurements, the mean concentration of dissolved ('226)Ra in the Suwannee River is 26 dpm 100L('-1), 2-4 times higher than most other world's rivers. Radium in the Suwannee River appears to be controlled by two processes: (1) relative mixing of water from surface drainage (low radium); and (2) interaction between soluble radium and particulate matter in the suspended load of the river. / The annual long-term discharge of dissolved ('226)Ra to the Gulf of Mexico is approximately 3.3 x 10('12) dpm yr('-1), about two orders of magnitude less than that discharged by the Mississippi River. Upon entrance into the Gulf, a portion of the particulate radium is released accounting for part of the high ('226)Ra concentrations observed in the estuary. Other possible radium sources to the estuary include submarine springs, seepage of coastal ground water and salt marshes. / Source: Dissertation Abstracts International, Volume: 47-12, Section: B, page: 4811. / Thesis (Ph.D.)--The Florida State University, 1986.
| Identifer | oai:union.ndltd.org:fsu.edu/oai:fsu.digital.flvc.org:fsu_76007 |
| Contributors | DEETAE, SUCHINT., Florida State University |
| Source Sets | Florida State University |
| Detected Language | English |
| Type | Text |
| Format | 149 p. |
| Rights | On campus use only. |
| Relation | Dissertation Abstracts International |
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