答：从空气中或者通过雨水落下来的放射性物质可以沉积到诸如水果和蔬菜等食物的表面或动物饲料中。
Answer: Radioactive material falling from the air or carried in rain water or snow, can deposit on the surface of foods like fruits and vegetables or animal feed.
研究者通过对包裹化石的沉积层进行放射性元素年代测定，推断出中华龙鸟生活在1.25亿年前。
It lived around 125 million years ago, based on the dating of radioactive elements in the sediments that encased the fossil.
本文叙述了核设施气态流出物采样系统中气载放射性物质(放射性气体和放射性气溶胶)在采样系统管路中的沉积问题。
This paper presents an issue of the precipitation in sampling system pipeline of airborne radioactive substances, radioactive gases and aerosols, from nuclear facility effluents.
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