Mercury concentrations in groundwater collected from wells on and near the Nevada Test Site, USA

摘要

Groundwater from southern Nevada has been studied extensively and characterized chemically on a number of occasions due to its proximity to the Nevada Test Site (NTS), Yucca Mountain, and Death Valley National Park (e, g., Winograd and Eakin 1964; Dudley and Larson 1976; White and Chuma 1987; Farnhamet al. 2000; Stetzenbach et al 2001). The NTS is of interest because a number of nuclear devices were detonated within its boundaries at or below the water table; Yucca Mountain is relevant because it is the proposed geologic repository for storage of the nation's high-level nuclear waste; and Death Valley National Park because there exist numerous natural springs throughout the Park. Many of these more recent studies have taken advantage of inductively coupled plasma mass spectrometry (ICPMS) to determine concentrations of trace (mu g/L) and ultra-trace (ng/L) elements. The technique, developed in the mid-1980's, is ideally suited for groundwater analyses because of its low detection limits and multi-element capabilities. The data generated by ICPMS for southern Nevada groundwater has proved useful in evaluating groundwater sources and flow histories, including mixing patterns (e. g, Tohannesson et al, 1997a,b). Noticeable absent from all these studies is the element mercury. This is understandable considering the difficulty in reliably determining mercury at ng/L levels, typically found for groundwater away from point sources of mercury. Problems with determining mercury at these levels include sample contamination, mercury is ubiquitous at low-levels, and relatively poor detection limits by ICPMS due to mercury's poor ionization in the plasma.