利用放射化学及地球化学方法追踪德基水库集水区之泥沙来源

用土壤中放射性原子落尘¹³⁷Cs因地表植生，坡度及土层厚度不同而有不同含量以及矿物抗风化及冲蚀程度不同，其所获石英或云母（抗风化）与长石（易风化）矿物含量比，可探测集水区内水库泥沙淤积之来源。就本研究结果，¹³⁷Cs在果园土壤最高，平均为302μμCi/kg，森林土壤次之为203μμCi/kg，而以崩塌地土壤147μμCi/kg最低，显示因地表坡度及植生不同造成表土厚度之差异，徒而影响¹³⁷Cs原子落坐在土壤中之分布。矿物抗风化及冲蚀作用因种类而异，石英/长石比（Q/F）或云母/长石比（Mi/F）之值愈高，表示抗风化之矿物含量高，矿物安定度大或不易受风化及冲蚀。由分析结果获知森林土壤Q/F值与果园土壤相近，而崩塌地土壤最低，就Q/F值或Mi/F值比较，果园土壤似较森林土壤更为安定，此与果园土壤之坡度较平坦，表土较厚有关。此项结果与放射化学方法所测得之¹³⁷Cs含量所表示之意义一致。无论以原子落尘或矿物比值测值，均显示不同植生这有其显着差异，用以追踪水库淤沙来源，具有辨异性辨就方法之设备及分析之难易与时间耗费，笔者建议采用地球化学之矿物测定法，更有应用价值。

Radiochemical and Geochemical Studies on Tracing of Soil Erosion Sources of Teh-Chi Reservior Watershed

Determination of specific activity of ¹³⁷Cs from radioactive fallout and measurement of mineral ratios of Quartz/Feldspar (Mi/F)in soils collected from different location on the Teh-Chi Reservioupper watershed could differentiate soil whether eroded from forest, orchard or landslide area.All.these criteria showed their higher values in orchard soils and forest soils and lower values in soils from landslide area.Based on the findings of this research, it may be suggested that methods of determination of radioactive fallout of ¹³⁷Cs and geochemical analysis of mineral ratio can be used in tracing soil erosion sources of reservior watershed.