isotopic tracer

例句：

1. 1. The isotope tracer was used to studythe movement of water in the river.
   同位素示踪剂被用来研究河水在河流中的流动。
2. 2. The isotopes were analyzed todetermine the origin of the sample.
   对同位素进行分析以确定样本的来源。
3. 3. The isotopes were used asa tracer to track the movement ofpollutants in the environment.
   同位素被用作示踪剂，追踪污染物在环境中的移动。