| Following the approval of the Manhattan Project in 1942, the United States experienced an increased need for uranium. As a result, extensive uranium mining occurred from the mid to late 1900's on Navajo tribal lands in Northern Arizona, an area rich in natural uranium. Although mining activities have ceased and remediation has been attempted, previous open pit mining still affects those living in the area today; environmental uranium contamination persists in the region. Radiological and chemical properties of uranium in combination with a lack of access to regulated drinking water sources present a serious health concern for residents on the Navajo Reservation.;The potential health effects associated with the ingestion of uranium in drinking water are dependent on a number of variables, including solubility and speciation. The speciation and solubility of uranium in an aqueous environment can be altered by various factors, including pH, water hardness, and concentrations of potential ligands. Environmental mobility of uranium can also be heavily influenced by solubility and speciation. Thus, to understand the potential toxicity of uranium in drinking water, it is important to characterize the water chemistry of the drinking water source as well as the uranium content. One approach to understanding the mobility of uranium in the environment is through the use of isotopic ratios.;Water samples from unregulated sources on the Navajo Reservation were analyzed to determine elemental uranium concentration, 234U/ 238U activity ratios, and existing inorganic anions. These data will provide a more complete understanding of uranium mobility and the formation of potentially toxic and bioavailable complexes. Various analytical techniques were utilized in this work, including inductively coupled plasma mass spectrometry, acid/base titration, flow injection analysis, flame atomic absorption spectroscopy, and ion chromatography.;Results of the current studies suggest that some wells on the Navajo Nation have uranium concentrations above the U.S. EPA guideline of 30 mug/L. Due to the presence of complexing agents, such as bicarbonate and calcium ions, the speciation of uranium in aqueous solution may be effectively altered. Further work should be conducted to determine the uranium species actually present in these unregulated water sources. |
