EXPERIMENTAL CONDITIONS Probably one of the more significant factors affecting reported plant root uptake of plutonium has been the highly artificial conditions under which many of the experiments have been carried out. The uptake-translocation experiments have frequently involved highly unusual conditions such as one plant per 1 to 10 grams of soil along with growth and uptake periods of several days to several weeks using seedlings. Such experiments subject the soil to intensive extraction of nutrients and all other elements, including the transuranics. In addition, such intensive short term cropping precludes growing the crops to maturity, thus excluding significant plant parts such as grain, etc. Generally, at the time such work was carried out, there were very good reasons for performing the experiments in the manner chosen. Caution must be taken in application of data obtained from these experiments to more usual soil-plant systems. It should not be implied that such data are applicable to agricultural systems. For example, a review of the literature by Lipton and Goldin (1976) led them to conclude that "plant concentration factors for plutonium are in the order of 10-4," However, most of the articles referred to were reports of work where very high and unusual soil to plane ratios were employed. It will be shown later in this discussion that the concentration ratios are not in the order of 10-4, but range over many orders of magnitude. [t is most important that extrapolations not be made from specialized plant root uptake experiments to field conditions which govern introduction of plutonium and other transuranics into food chains via this pathway. Table 1. Plutonium concentration ratios for plants grown in potted soil (from Piant Panel, 1976). Plant Ladino clover Range of CR's Conditions \ 10°° to 10°" In 120 kg of NTS soil; 70 nCi g~' soil; CR's increased by seven times in 5 years. Alfalfa 10° to 10° Straw . 10_° to 10° Barley Grain 10° to 103 Soybean Forage Bean In 3 kg of NTS soil; 0.6 -, . 10_" to 10° In 3 kg of NTS soil; 5 nCi g-' soil; highest CR's involve chelate treatment. 107 NTS soil; high-fired Pu 10 ® to lo * Barley Grain Leaf Grain Leaf > R nci g™' soil; highest CR's involve chelate treatment. omney . ~ 10 -s oxide; 10 to 50 nCi g@! soil Wheat MAGNITUDE OF ROOT UPTAKE AND TRANSLOCATION Rapporteur ’ Schulz 10° to 10 ° Pu-chloride and Pu-nitrate 10 > to 10 3 Pu-nitrate (77"Pu and 10 ® to 10 3 (77%pu at 0.5 wCt g?) Barley A Workshop on Environmental Research for Transuranic Elements was held at Seattle, Washington, ih 1975. A group charged to discuss plant uptake of transuranium elements was designated the Plant Panel and will be referenced in this paper as "Plant Panel (1976)." The Panel listed data (Table 1) on plant uptake where plants were grown in containers and efforts were made to exclude foliar contamination. The concentration ratios (plutonium in plant/ plutonium in soil) ranged from 10-8 to 10-3. In addition to the plutonium concentration ratios, the Panel also summarized data on americium concentration ratios (Table 2). Here the range of concentration ratios was even larger than that of the plutonium CR's. The range of concentration ratios reported wag 10-7? to 10+. These experiments were also carried out in containers and attempts were made to exclude foliar contamination. The most striking feature of both the plutonium and americium concentration ratios was the enormous range reported; that is, for root uptake and translocation, and excluding foliar contamination, the range was 5 orders of magnitude for plutonium and 8 orders of magnitude for the americium uptake. 322 Leaf and sten Grain 10°” 239Pu) 10 ci gs}, Wildung