arly in their uptake and metaof hydrogen and possibly some assume that a radioactive isotope opes of the same element through nent generally behave identically, is taken up and retained by an umount of the stable counterpart mment. The inhibition of uptake same element is known asisotope salth hazards from radioelements its closely related to each other imilarly and thus simulate isotope alcium tends to reduce the uptake ad naturally-occurring potassium the uptake of radioactive caesium. imilar chemically to caesium, is level of about 380 ppm. In comesent in extremely small amounts Because animals exhibit a limited slements, the uptake of. caesium jance of potassium. vel of about 440 ppm, and is very ke by marine organisms. In the he uptake of Sr® is not directly er. Sr* is discriminated against f caletum by factors of about 3 in arthropods, 2—7 in molluscs, fish (12). In addition to chemical rontium would result in reduced e strontium is present in the sea urally-occurring forms of the other . AS a consequence, the isotopic 3t 6 to 1,300 times that to which 1 because of the presence of their organisms against the uptake of v purely physical factor, including f calcite resulting from pulverized ontium as they sink through the sIyAMA and Uyepa (13) reported tonation which fell on the No. 5 of calcite approximately 100-400 u form was made by electron micro< in the sea according to Stoke’s the particles are smooth andrigid, » not interact with each other as by Miyoshi indicate that particles the surface to 260 m in 26 minutes, alcium from the pulverized islands and reefs on which the nuclear detonations occurred would probably be in the form of calcite and calcium oxide. Thus the mechanism for rapid scavenging of Sr®-% in fallout introduced into the sea is provided by calcite settling through the thermocline. Coprecipitation with calcium compounds would also scavenge radiostrontium from sea-water. When CaCo, is precipitated in sea-water, strontium is coprecipitated and carried down in the precipitate, a technique commonly used in chemical separations for sea-water. Because an appreciable amount of the calcium in fallout resulting from surface detonation is in the form of CaO and (‘a(OH),, a considerable amount of radioactive strontium would: be carried to deeper waters by this action. When strontium is coprecipitated with calcium in the particulate form, it would be available to filter-feeding organisms. However, an appreciable amount of the precipitate would probably settle out of reach of the biosphere into the deeper water. Some of the radiostrontium would undoubtedly be ingested by the filter-feeders. However, a rapid turnover rate for this element has been observed in all marine invertebrates and fishes studied up to now (14, 15). Because of the rapid turnoverrate, ingested radioactive strontium would be continually recycled to the sea in solution, where it would become more and more,diluted with the naturally-occurring non-radioactive form. Biological factors Biological factors affecting the uptake of radioisotopes include biomass, surface area of the biomass, adsorption, absorption, feeding habits and ingestion, physiological selectivity, deposition, excretion rates, reproductive rates, average life-spans and growth rates, mobility, including horizontal and vertical migrations, and symbiotic relationships. The ultimate source of all energy for living material is derived from the sun by photosynthetic processes in plants. This energy is utilized to convert basic inorganic raw materials into organic compounds, which are then passed throughout the food web to the various organisms of the biomass. Since the efficiency of conversion at each stage in the food web is low, usually 10 to 15%, the mass at each trophic level decreases with each step of conversion. Thus, with equal reproductive rates, the amount of total organic material and the average total of biochemically-combined minerals decreases as one passes through the food web, and the degree at which the mass decreases is dependent primarily upon the reproductive rate and average life-span of the populations making up a given Jevel in the food web. The marine biosphere may be divided into the following levels: (1) the primary synthesizers, which are mainly comprised of photosynthetic plants; (2) the omnivores, which in the sea are usually filter-feeders, and (3) the carnivores, which include fishes such as tuna and sharks. Metabolism in all forms of life at the cellular level is similar, although the organisms may differ markedly in body form and complexity. This similarity is present in organisms of both the plant and the animal kingdoms. Marine organisms tend to concentrate transition elements such as manganese, iron, copper, nickel, cobalt, zinc, and some of the anions. The transition elements, at least, are strongly bound to the organisms and are not easily removed by placing the organisms in sea-water containing lower amounts of these elements. They may be concentrated by factors up to 100,000. 119 -aqear way: STRUTS BPA a