弱放射性天然物质(沉积岩、淤泥、海、河悬浮物、土壤)中铀、镭和钍同位素浓度间的此例,具有很大的地球化学意义。现时,测定这些元素及共同位素所应用的方法之灵敏度和准确度,要求必须采用较多的称样,而当分析物质的量有限时,就不可能测定。在类似场合下,应当采用能 This case of uranium, radium and thorium isotope concentrations in weak radioactive natural materials (sedimentary rocks, silt, sea, river suspended solids, soils) is of great geochemical significance. At present, the sensitivity and accuracy of the methods used to determine these elements and isotopes require that more samples be used and that it is impossible to measure when the amount of analyte is limited. In similar circumstances, should be able to use