Time Dependence of the 137Cs Concentration in Particles Discharged from Rice Paddies to Freshwater Bodies after the Fukushima Daiichi NPP Accident

详细信息    查看全文

• 作者：Kazuya Yoshimura ; Yuichi Onda ; Taeko Wakahara
• 刊名：Environmental Science & Technology
• 出版年：2016
• 出版时间：April 19, 2016
• 年：2016
• 卷：50
• 期：8
• 页码：4186-4193
• 全文大小：538K
• 年卷期：0
• ISSN：1520-5851

文摘

The concentration of particulate ¹³⁷Cs in paddy fields, which can be a major source of ¹³⁷Cs entering the water system, was studied following the Fukushima Daiichi Nuclear Power Plant accident. To parametrize the concentration and to estimate the time dependence, paddy fields covering various levels of ¹³⁷Cs deposition were investigated over the period 2011–2013 (n = 121). The particulate ¹³⁷Cs concentration (kBq kg_–SS^–1) showed a significant correlation with the initial surface deposition density (kBq m^–2). This suggests that the entrainment coefficient (m² kg_–SS^–1), defined as the ratio between the particulate ¹³⁷Cs concentration and the initial surface deposition density, is an important parameter when modeling ¹³⁷Cs wash-off from paddy fields. The entrainment coefficient decreased with time following a double exponential function. The decrease rate constant of the entrainment coefficient was clearly higher than that reported for other land uses and for river water. The difference in the decrease rates of the entrainment coefficient suggests that paddy fields play a major role in radiocesium migration through the water system. An understanding of the decrease rate of the entrainment coefficient of paddy fields is therefore crucial to understand the migration of radiocesium in the water system.