Prediction of Strontium-85 Transferred from Soils to Water Convolvulus Based on Soil Properties

• Main Authors: Chang Jun An, 張君安
• Other Authors: 王敏昭
• Format: Others
• Language: zh-TW
• Published: 2000
• Online Access: http://ndltd.ncl.edu.tw/handle/68661974480506446805

碩士 === 國立中興大學 === 土壤環境科學系 === 88 === After nuclear bomb explosion test, the main radionuclides in fallouts are 90Sr and 137Cs. They finally enter into soils. 90Sr and Ca as well as 137Cs and K are the same groups at periodic table and are of similar chemical behaviors, respectively. Both 90Sr and 137Cs are easily absorbed by plant, then enter into human bodies via food chain, and are subsequently harmful to human body. However, predictive models regarding the transfer of radionuclides from soil to plant have not been established. This study was, thus, to investigate the effect of the applications of Ca fertilizers on the transfer factor of 85Sr from the soils to water convolvulus, and estimate whether prediction of 85Sr from the soils to water convolvulus based on soil properties is advisable or not. Six soil series in western part of Taiwan were collected. They were red soil of Pingchen series (Diluvial), alluvial soil of Chunliao series (Slate calcareous new alluvial), alluvial soil of Shuipientou series (Slate noncalcareous new alluvial), alluvial soil of Chengchung series (Sandstone-shale calcareous new alluvial), alluvial soil of Tsochia series (Sandstone-shale noncalcareous new alluvial), and alluvial soil of Nanhsing series (Sandstone-shale and slate mixed alluvial). Each of the six soils were added with 85Sr-containing solution to make radioactivity of 1.5×104 Bq kg-1 soil. The soils were added with three level of Ca (as CaCO3) fertilizer. All the treated soils including the controls were planted with water convoluvlus at outdoor. On the day of harvest, the pot soils as well as the vegetable as determined their gamma-ray radioactivity by a gamma spectrometer equipped with a high purity germanium detector. Then the transfer factors were calculated, and the predictive model of 85Sr from the soils to water convolvulus based on soil properties was estimated and identified. The results showed that the yield of water convolvulus grown in alkali soils decreased with increasing application of CaCO3. It maybe results from the over-high pH or the accruing of Ca poison after applying of CaCO3. As to acid soils, the yield of water convolvulus increased with increasing pH originally, and then decreased because of the reason described above. Besides, the transfer factor of 85Sr decreased with increasing application of CaCO3. Thereby, it is suggested that Ca competes with 85Sr at crop uptake. Namely, enhanced Ca supply reduces 85Sr uptake substantially at low Ca availability in soil. At high Ca availability in soil, however, enhanced Ca supply has only little effect. After estimating for the predictive model based on soil properties, predictive values for the soils are close to observed values, except for that of Chunliao soil series is slightly higher than the observed values. Therefore, predictions of the relative crop uptake of 85Sr in a set of soil/plant systems can be attempted on the basis of soil properties.