本底值 meaning in English

background values
◇本底值监测 background value monitoring

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 sources , background value , environmental geochemistry features of fluorine , and its biological effects on animals , plants and human beings were reviewed
阐述了环境中氟污染的来源、本底值和氟的主要环境地球化学特征及氟对植物、动物和人机体的生物效应。
3 for example , if ambient gamma radiation is the only factor contributing to the radiation dose to a person , this dose of 5000 microsieverts may be reached when the ambient gamma dose rate is 1000 microsieverts per hour more than 3000 times above background and lasts for 5 hours ; or when the dose rate is 200 microsieverts per hour more than 600 times above background and lasts for 25 hours
3 .例如，假若环境伽玛剂量率持续高达每小时1000微希沃特超过本底值3000倍，则在5小时内，因为环境伽玛辐射所引致的总剂量便可能达到上述的5000微希沃特。若环境伽玛剂量率每小时200微希沃特超过本底值600倍，则个人须持续受此辐射影响25小时，所受的总剂量方可达到上述5000微希沃特。