Ground water contamination with super(238)U, super(234)U, super(235)U, super(226)Ra and super(210)Pb from past uranium mining: cove wash, Arizona

• Published in: Environmental geochemistry and health 2014-06, Vol.36 (3), p.477-487
• Main Authors: Dias da Cunha, Kenya Moore, Henderson, Helenes, Thomson, Bruce M, Hecht, Adam A
• Format: Article
• Language: English
• ISSN: 0269-4042; 1573-2983
• DOI: 10.1007/s10653-013-9575-2

The objectives of the study are to present a critical review of the super(238)U, super(234)U, super(235)U, super(226)Ra and super(210)Pb levels in water samples from the EPA studies (U.S. EPA in Abandoned uranium mines and the Navajo Nation: Red Valley chapter screening assessment report. Region 9 Superfund Program, San Francisco, 2004, Abandoned uranium mines and the Navajo Nation: Northern aum region screening assessment report. Region 9 Superfund Program, San Francisco, 2006, Health and environmental impacts of uranium contamination, 5-year plan. Region 9 Superfund Program, San Franciso, 2008) and the dose assessment for the population due to ingestion of water containing super(238)U and super(234)U. The water quality data were taken from Sect. "Data analysis" of the published report, titled Abandoned Uranium Mines Project Arizona, New Mexico, Utah-Navajo Lands 1994-2000, Project Atlas. Total uranium concentration was above the maximum concentration level for drinking water (7.4 x 10 super(-1) Bq/L) in 19 % of the water samples, while super(238)U and super(234)U concentrations were above in 14 and 17 % of the water samples, respectively. super(226)Ra and super(210)Pb concentrations in water samples were in the range of 3.7 x 10 super(-1) to 5.55 x 10 super(2) Bq/L and 1.11 to 4.33 x 10 super(2) Bq/L, respectively. For only two samples, the super(226)Ra concentrations exceeded the MCL for total Ra for drinking water (0.185 Bq/L). However, the super(210)Pb/ super(226)Ra ratios varied from 0.11 to 47.00, and ratios above 1.00 were observed in 71 % of the samples. Secular equilibrium of the natural uranium series was not observed in the data record for most of the water samples. Moreover, the super(235)U/ super(total)U mass ratios ranged from 0.06 to 5.9 %, and the natural mass ratio of super(235)U to super(total)U (0.72 %) was observed in only 16 % of the water samples, ratios above or below the natural ratio could not be explained based on data reported by U.S. EPA. In addition, statistical evaluations showed no correlations among the distribution of the radionuclide concentrations in the majority of the water samples, indicating more than one source of contamination could contribute to the sampled sources. The effective doses due to ingestion of the minimum uranium concentrations in water samples exceed the average dose considering inhalation and ingestion of regular diet for other populations around the world (1 mu Sv/year). The maximum doses due to ing