¥, is the amount (pCi) of Pu in compartment } any time t (days), and h A - ij and ji are transfer coefficients (day ly for flows into and out of compartment j. The positive expression on the right side of Equation (1) represents the flow rate into compartment j while the negative expression represents the rate of Flow out of 4. The amount present in a given compartment at a given time, ¥,(t), is therefore dependent on the rates of input and output. Arbitrary Boundary a Aa AA a A SO EE at AR AF A 2-—e (Resuspension} FE8 EL AIR ee VEGETATION In a general way, Figure 1 and Equation (1) identify the principal kinds of information needed to estimate the transport of plutonium to man. The compartments of Figure 1 indicate the principal ecosystem components, and the arrows indicate the pathways of transport from environment to man via inhalation and ingestion, Equation (1) suggests that intercompartmental flow rates might be expressed as the product of a transfer coefficient and the quantity of plutonium in the transmitting compartment. It was recognized, however, that some parts of the transport system (Figure 1) might not behave in accordance with the first-order kinetics model suggested by Equation (1). Consequently, the objectives of the NAEG plutonium studies were stated in broader terms. The general objectives related to estimation of potential human ingestion and inhalation rates were simply (1) to determine plutonium concentrations in ecosystem components and (2) to quantify the rates of plutonium transfer among ecosystem components. HERBIVORES sot] Plutontum Concentration in Soil a eee ee in a a Various soil surveys have been areas at NTS, to determine the in contaminated soils, and for Dunaway and White, 1974; White conducted to delineate highly contaminated horizontal and vertical distribution of plutonium various other purposes (see several papers in and Dunaway, 1975, 1976, 1977). An inventory of 233°240py fn the surface soils (0-5 cm depth) of NAEG study areas is given FIGURE 1. PRENCIPAL PATHWAYS OF PLUTONIUM TRANSPORT TO MAN by Gilbert et al. (1975, p. 379) in terms of uCi/m?. As mentioned earlier, soil is the principal reservoir for plutonium at NTS and soil concentration (pCi/g) is the factor which drives or forces the transport system. In developing equations to estimate potential plutonium inhalation and ingestion rates for the hypothetical Standard Man, we shall relate the concentrations in air and foods to the average concentration in soil. Average soil concentrations were computed for each study area based on the inventory data provided by Gilbert et al. (1975, p. 379), and these are given in Table 1. In order to check the consistency of the algorithm in data used for conversion, strata averages were also computed and compared with data reported by Gilbert et al, (1975). These strata averages are also shown in Table 1. The algorithm for converting the inventory data to average soil concentrations was: 625 624