Isotopic Studies of Sources of Uranium in Sediments of the Ashtabula River, Ohio, U.S.A.
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- 作者：Michael E. Ketterer ; William C. Wetzel ; Ricky R. Layman ; Gerald Matisoff ; and Everett C. Bonniwell
- 刊名：Environmental Science & Technology
- 出版年：2000
- 出版时间：March 15, 2000
- 年：2000
- 卷：34
- 期：6
- 页码：966 - 972
- 全文大小：184K
- 年卷期：v.34,no.6(March 15, 2000)
- ISSN：1520-5851
文摘
Uranium contamination of anthropogenic origin has beenidentified in unconsolidated sediments of a 1.5 km portion ofthe Ashtabula River near its confluence with Lake Erie.Uranium concentrations as high as 188 
g/g dry sedimentare present. A small tributary of the Ashtabula River,Fields Brook, is the apparent point of origin of the uraniumin the Ashtabula River sediments. 137Cs dating of asediment core indicates that the U contamination occurredduring the post-1964 time frame. The horizons of elevatedU concentration also exhibit > 10× elevations in Zr,Nb, Hf, Ta, and W. 238U/235U isotopic ratios indicate thatthe uranium is largely but not exclusively of naturalcomposition. Distinct horizons of slightly 235U-depleted (238U/235U > 137.88) and slightly 235U-enriched (238U/235U <137.88) uranium are also present. 210Pb activities and 232Th/230Th isotopic measurements indicate that a significantportion of the uranium contains 238U daughters in approximatesecular equilibrium. It is inferred that at least two distinctsources of anthropogenic U contamination exist: (A)discharges from the processing of enriched and depletedU metal by a DOE contractor facility and (B) U-bearingwastes from the production of TiO2 from ilmenite andassociated minerals. These isotopic methodologies arepotentially useful in settings where releases of nonnatural 238U/235U composition materials and/or "naturally occurringradioactive material" (NORM) have taken place.
g/g dry sedimentare present. A small tributary of the Ashtabula River,Fields Brook, is the apparent point of origin of the uraniumin the Ashtabula River sediments. 137Cs dating of asediment core indicates that the U contamination occurredduring the post-1964 time frame. The horizons of elevatedU concentration also exhibit > 10× elevations in Zr,Nb, Hf, Ta, and W. 238U/235U isotopic ratios indicate thatthe uranium is largely but not exclusively of naturalcomposition. Distinct horizons of slightly 235U-depleted (238U/235U > 137.88) and slightly 235U-enriched (238U/235U <137.88) uranium are also present. 210Pb activities and 232Th/230Th isotopic measurements indicate that a significantportion of the uranium contains 238U daughters in approximatesecular equilibrium. It is inferred that at least two distinctsources of anthropogenic U contamination exist: (A)discharges from the processing of enriched and depletedU metal by a DOE contractor facility and (B) U-bearingwastes from the production of TiO2 from ilmenite andassociated minerals. These isotopic methodologies arepotentially useful in settings where releases of nonnatural 238U/235U composition materials and/or "naturally occurringradioactive material" (NORM) have taken place.