of vegetation to be cropped to natural island vegetation that can grow in one year during the rainy season. Considering one annual crop of vegetation, the observed C.R. of about 3 or 4, and the maximum density of vegetation growth of about 1.5 to 2 kg/m@-y, repeated annual cropping would only reduce the time required to reach current Federal guidelines for !37Cs in the soil column from 90 y to 75 y. This is not an efficient method for reducing the dose in view of the extraordinary effort and commitment required to debrush the island and dispose of the material on an annual basis for the next several decades. Matrix immobilization (clinoptilolite). matrices. has been*#evaluated using mica and a zeolite These materials sequester or bind !37Cs in their structural We have observed a reduced uptake of !37Cs in plants grown with these materials added to the soil. these materials in the soil breadfruit, Pandanus trees, However, the application and mixing of with the massive surface roots from coconut, and scrub vegetation is not practical. In addition, these materials bind the !37cs and keep it in the soil system and interfere with the natural flow mechanism for !37Cs out of the soil column into the ground water. The clays and zeolites would also be totally foreign soils to the natural carbonate matrix of the Atoll ecosystem. The two most competition. reasonable alternatives are excavation and chemical Excavation of the top 40 cm of the soil column is an effective way of removing !37cs, 90sr, 239+240py, and 241Am from the island. The major drawback to excavation is the tremendous environmental insult that results. The 30,000 mature coconut trees would have to be knocked down, along with the existing breadfruit, Pandanus, papaya trees, and all natural scrub vegetation, — and disposed of along with the soil. Also, the top 40 cm of soil contains almost all of the organic and humic material in the soil column. The organic material supplies the majority of the water-retention capacity of the soil and most of its nutrient capacity. As a result of excavation, the island surface would be void of, or very limited in, organic matter and water-retention capacity, and would resemble the carbonate sands of the beach. if this method were chosen, a long-term commitment would be required to rebuild the soil and revegetate the island (BARC, 1988). to rebuild the develop, soil organic is uncertain. Consequently, matter, which has taken The length of time decades or more to Plants can be grown on the sandy soil devoid of organic material, but a long-term commitment of supptying required nutrients and water would be required. 7\