background radioactivity

常见例句

At the surface, radioactivity of the conglomerates is locally as high as 30 X background.
在地表，砾岩的局部地段的放射性高达30倍本底值。
The results showed that the radioactivity levels of each nuclide in Yangtze River water system were still lower than that of background, and did not cause contamination.
结果表明，各核素均未对长江造成污染，长江水系放射性浓度仍在本底水平。
The results show that the radioactivity level of varied water bod-ies of the city was within normal natural background.
调查结果表明，上海市各类水体中天然放射性核素浓度属正常本底水平。