Fingerprinting of ground water by ICP-MS. Final report

Geochemical investigations of groundwater sources and mixing have relied heavily on the major solutes (Na{sup +}, K{sup +}, Ca{sup 2+}, Mg{sup 2+}, Cl{sup -}, SO{sub 4}{sup 2-}, HCO{sub 3}{sup -}, CO{sub 3}{sup 2-}, {plus_minus}F{sup -}, Br{sup -} , PO{sub 4}{sup 3-}), stable isotopes of hydrogen and oxygen ({delta}D and {delta}{sup 18}O), and, occasionally, radionuclides such as tritium ({sup 3}H) and carbon-14 ({sup 14}C). Problems with geochemical interpretations of such analyses arise from the low number of major solutes (typically between 7 and 8 are reported) which results in insufficient information for definitive interpretations. Moreover, isotopic analyses can be very costly. We present an alternative approach using numerous trace elements that occur naturally in all ground waters and that can now be measured rapidly and routinely using the inductively coupled plasma-mass spectrometer (ICP-MS) at the Harry Reid Center for Environmental Studies (HRC) at a fraction of the cost of isotopic analysis. The tremendous number of solutes that can be measured by ICP-MS necessitates the examination of each data set by multivariate statistical techniques that help to reduce the data and illuminate correlations between trace elements and, therefore, ground waters of similar and/or different origins