Long-term mobility of fallout ⁹⁰Sr in ploughed soil, and ⁹⁰Sr uptake by wheat grain

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• 关键词：Radiostrontium ; Ploughed soil ; Mobility ; Decreasing trend ; Wheat ; Concentration ratio
• 刊名：Science of the Total Environment
• 出版年：2007
• 期刊代码：63_00489697
• 类别：env
• 出版时间：1 January 2007
• 卷：372
• 期：2-3
• 页码：595-604
• 文件大小：261 K

摘要

In this study, we evaluated the mobility of ⁹⁰Sr in ploughed upland soil, which affects the residual amount in the soil and plant uptake on the basis of long-term monitoring data. Paired samples of soil and wheat grain were taken annually from 1961 to 1995 from 8 agricultural fields in Japan, and the concentrations of exchangeable ⁹⁰Sr in soil and total ⁹⁰Sr in wheat grain were determined. The concentration of exchangeable ⁹⁰Sr in ploughed soil decreased exponentially with time. The environmental factor responsible for the decrease of exchangeable ⁹⁰Sr in the ploughed layer, λ_e, was determined from the monitoring data of exchangeable ⁹⁰Sr in the ploughed soil and the amount of fallout-derived deposition. The λ_e was larger from 1970 to 1980 than it was from 1980 to 1995, suggesting that an easily removable fraction of ⁹⁰Sr in soil was preferentially lost from ploughed soil. Among various soil properties that we investigated, the main factor controlling the long-term mobility of ⁹⁰Sr from ploughed upland soil and ⁹⁰Sr uptake by wheat grain was the cation-exchange capacity (CEC) of soil. Our experimental results indicate that the entrapment of ⁹⁰Sr on a cation-exchange site retards the downward migration and wheat uptake of ⁹⁰Sr from ploughed soil. The empirical parameters that we obtained based on the long-term observation of a wheat-cultivated upland field in Japan could be used as reference data in order to roughly estimate the mobility of ⁹⁰Sr in ploughed soil and soil-borne ⁹⁰Sr transfer to wheat grain in the humid Japanese climate.