| Analyzing uranium isotope concentrations can give valuable information for hydrologic and environmental studies such as insights to weathering processes, estimating water mixing ratios, and identifying water sources. Besides naturally occurring uranium, depleted or enriched uranium can also be present in environmental samples if human activities have taken place in the vicinity. We employed an inductively coupled plasma mass spectrometer (ICP-MS) and a kinetic phosphorescence analyzer (KPA) to perform environmental level uranium concentration measurements on three hundred and eighty groundwater samples from various locations within the State of Idaho. These techniques can be used for detection of ground and surface water contaminations with high sensitivity and great precision. The lower limits of detection (LLD) were determined to be 0.532μg/L and 0.099μg/L for ICP-MS and KPA respectively. As a reference, the Environmental Protection Agency (EPA) drinking water limit for uranium is 30μg/L. Also, for the first time uranium concentrations were mapped on the Idaho grid. Some parts of the state exhibit elevated uranium concentrations (over 30μg/L in some cases). The uranium activity ratios (UAR) for these samples range between 0.91 and 6.21, which suggests that the parent 238U is not in equilibrium with its daughter product 234U. Therefore, uranium is mobile in the groundwaters in Idaho. Determining the UARs for the samples that represent the whole state was accomplished for the first time as well in the frame of this project. In addition, a novel approach for determining the total uranium concentration was proposed. EPA uses a few different methodologies to determine the uranium concentrations in aqueous samples. But all these methodologies assume the presence of only natural uranium in the medium. Hence, in the presence of depleted/enriched uranium in the sample, all the EPA methods overestimate/underestimate the true uranium concentration. We propose a new method which determines the true uranium concentration even in the presence of depleted/enriched uranium. Finally, no enriched or depleted uranium was detected outside the Idaho National Laboratory (INL) as determined within the framework of this project. |