我们现在的氦源，是地下天然气田中放射元素衰变的副产品，经过数十亿年的累积，逐渐形成的。
Our modern supply of helium has gradually built up over billions of years in subterranean pockets of natural gas as a byproduct of decaying radioactive elements.
放射性沉降物中含有非天然的重元素和同位素。
The fallout contained heavy elements and isotopes not found in nature.
氡主要来自建筑材料，如花岗岩、砖砂、水泥及石膏之类，特别是含有放射性元素的天然石材，易释放出氡。
Radon from building materials such as granite, brick sand, cement and gypsum and the like, in particular, contain elements of natural stone and easy to release radon.
对西安市生活饮用水源黑河与灞河水体中天然放射性元素铀含量进行了调查。
The investigation results on natural uranium concentrations in drinking water sources, Hei River and Ba River, in Xi 'an City are presented in this paper.
对西安市生活饮用水源黑河与灞河水体中天然放射性元素铀含量进行了调查。
The investigation results on natural uranium concentrations in drinking water sources, Hei River and Ba River, in Xi 'an City are presented in this paper.
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