Accelerator Mass Spectrometry of Actinides in Ground- and Seawater: An Innovative Method Allowing for the Simultaneous Analysis of U, Np, Pu, Am, and Cm Isotopes below ppq Levels

U-236, Np-237, and Pu isotopes and Am-243 were determined in ground and seawater samples at :levels below ppq (fg/g) with a maximum, sample size of 250 g. Such high glensitivity was possible by using accelerator, Mass spectrometry (AMS) at the Vienna Environmental Research Accelerator (VERA) with extreme selectivity and recently improved efficiency and a; significantly simplified separation chemistry. The Use of nonisotopic tracers was investigated in order to allow for the determination of Np-237 and Am-243, for which isotopic tracers either are rarely available or suffer from various isobaric mass interferences. In the present study, actinides were concentrated from the sample matrix via iron hydroxide coprecipitation and measured sequentially without previous chemical separation from each other. The analytical method was validated by the analysis of the Reference Material IAEA 443 and was applied to groundwater samples from the Colloid Formation. and Migration (CFM), project at the deep underground rock laboratory Of the Grimsel Test Site (GTS) and to natural water samples affected solely by global fallout. While the precision of the presented analytical method is somewhat limited by the use of nonisotopic spikes, the sensitivity allows for the determination of similar to 10(5) atoms in a sample. This provides, eg., the capability to study the long-term release and retention of actinide tracers in field experiments as well as the transport of actinides in a variety of environmental systems by tracing contamination from global fallout.