劍橋詞典a chemical element that is a radioactive gas formed when radium decays and found naturally in rock and soil 氡（鐳衰減時形成的一種放射性元素，發(fā)現(xiàn)自然存在于巖石和土壤中） Tests showed high radon levels . 試驗表明氡含量較高。 返回 radon