tailieunhanh - Radionuclide Concentrations in Foor and the Environment - Chapter 5

ạt nhân phóng xạ tồn tại lâu dài một cách dễ dàng có thể được nghiên cứu trong khu vực không bị ảnh hưởng bởi gần đây (ngày) tai nạn hạt nhân. Đây là một trong những lý do mà hạt nhân phóng xạ trong thời gian ngắn không được bao gồm trong chương này. Hai nguồn gốc của hạt nhân phóng xạ tồn tại lâu dài trong đất có thể được xem xét. Đầu tiên, hạt nhân phóng xạ nhân tạo là những yếu tố phóng xạ (plutonium đồng vị) và các sản phẩm phân hạch tồn tại lâu dài ( 137 cs, 90 SR). Trong cả. | 5 Radionuclide Concentrations in Soils Guillermo Manjon Collado CONTENTS Behavior of Long-Lived Radionuclides in Vertical Influence of Microorganisms on the Behavior of Soil to Plant Transfer and Bioavailability of Radioactive Contamination and Scientific and Social Dose Radon in Soil and Dating .144 Tracers in Soil INTRODUCTION Long-lived radionuclides can easily be studied in zones not affected by recent days nuclear accidents. This is one of the reasons that short-lived radionuclides are not included in this chapter. Two different origins of long-lived radionuclides in soils can be considered. First artificial radionuclides are transuranic elements plutonium isotopes and long-lived fission products 137Cs 90Sr . In both cases the presence in the environment of these kinds of radionuclides is due to nuclear weapons tests or the nuclear power industry. Next natural radionuclides are radionuclides belonging to the three natural decay chains 238U 235U 232Th 40K and cosmogenic radioisotopes 3H 7Be 14C . In the case of natural decay chains radioelements might be inside the silicon dioxide crystals in soils. A fraction of the radon gas can be transferred from soils into the atmosphere by emanation. Then 222Rn decays in 210Pb which falls back associated with aerosols onto the Earth s surface. 113 2007 by Taylor Francis Group LLC 114 Radionuclide Concentrations in Food and the Environment On the other hand artificial radionuclides are stored in the stratosphere and fall to the Earth s surface according to atmospheric dynamics. Artificial and cosmogenic radionuclides and 210Pb are typical fallout radionuclides that are being deposited. In this chapter the behavior of radionuclides in soils is studied. The main .