et al., 1974; Nevissi and Schell, 1975; 1976). Other procedures have been developed for the radiochemical separation of transuranic elements from natural waters (Lai and Goya, 1967; Miyake and Sugimura, 1968; Wong, 1971; Hodge and Gurney, 1975; Livingston et al., 1975; Scott and Reynolds, 1975). Most of these procedures are not adaptable to sample large volumes of water for Pu analysis from remote environments. For our analytical requirements, a large-volume water sample using Mn0O9 Impregnated Cartridge Extraction, MICE, was developed (Wong et al., 1978) to preconcentrate low-level plutonium and other radionuclides from fresh and saltwaters. Preconcentration of Pu by the MICE procedure is similar in principle to collection using the BLVWS. The MICE sampler is considerably less expensive to build; it is more efficient for preconcentration of plutonium from seawater; it is easily adaptable for field operation; and the subsequent plutonium analysis of the MnO» cartridges is much easier than the Al ,03 beds used in the BLVWS. The purpose of this report is to discuss the results obtained by the MICE sampler in field operations for the preconcentration of plutonium from marine and groundwaters. SAMPLE COLLECTION AND ANALYSIS A schematic of the MICE sampler is shown in Figure 1. Water is pumped through a 1 um prefilter cartridge at a flow rate of 4-8 liter/m to isolate Pu associated with particulate materials. The filtrate is passed through two (or more) MnO» impregnated cartridges connected in series to separate the exchangeable plutonium. The cartridges are then dry ashed and each cartridge is analyzed separately for plutonium by standard radiochemical techniques. The detailed procedure has been reported by Wong et al. (1978). The collection efficiency, E, can be calculated from the activity deter- mined in each of the two cartridges in series using the equation: E = 1-B/A Where, A B (1) Plutonium absorbed on the first MnO» cartridge (pCi) Plutonium absorbed on the second MnO» cartridge (pCi) If the sample volume, V, is measured in m3, the plutonium concentration in the filtrate in pCi/m? may be calculated by the relationship: pCi/m? = A2/(A-B)V (2) The derivation of the collection efficiency is based on the assumption that the adsorption efficiency for any plutonium chemical species in the 584