Paper No. 12
Presentation Time: 11:00 AM
CRITICAL REVIEW OF THE VALUES OF 238U, 234U, 235U, 226RA, AND 210PB CONTAMINATIONS IN WATER SAMPLES FROM NAVAJO AREAS
The aim of this study was to perform a critical review of the values of 238U, 234U, 235U, 226Ra, and 210Pb concentrations in water samples from four chapters (Cove, Red Valley, Sweetwater and Teec Nos Pos) collected in 2000 that were available in the literature. This review is important because this area encompasses 33.8% of the rural area in the Four Corners mining district and about 4,389 people live in these chapters and, they can be exposed to uranium. The EPA project titled Abandoned Uranium Mines Project Arizona, New Mexico, Utah - Navajo Lands 1994 – 2000 Project Atlas was implemented to assess the contamination of metals and radionuclides near by the inactive mines. This study concluded that in some areas the water could not be used for drinking. The risk for the human health was based on the radionuclide concentrations in water and assuming an ingestion of 2 L/day of water during 30 y. In the present study the values of 238U, 234U, 235U, 226Ra, and 210Pb concentrations in the water samples values were reviewed using a non-parametrical statistical test. The results of the statistical analysis showed that there were inconsistencies among the published data such as: the higher 234U concentrations compared to 238U concentrations that could not be explained by the natural decay series; the ratio of 235U mass to total U mass higher than the natural isotopic ratio (0.72 %). Lower than expected concentrations of 226Ra compared to U and 210Pb concentrations, might be explained by chemical fractionation through adsorption and/or precipitation onto calcareous soils in the area. The 210Pb concentrations higher than 226Ra concentrations could not be explained by decay of 226Ra indicating that 210Pb compounds were probably soluble in water. The results suggested that could exist other sources of water contamination besides the natural leaching processes on the tailing from the mines and the natural transport of solid particles from the mines to underground water, stream or spring. This study also highlights the importance of assessing the quality of data through rigorous and more in-depth statistical analysis.