underlying retention的意思|示意

A document retention policy that includes automatically deleting emails and electronic files, without also wiping the underlying data in those emails and files, is, however, simply not rational.

但是，单单自动删除电子邮件和电子文件，而没有清除邮件和文件下潜藏的信息，这样的文件保留政策并不完全合理。

The local geology favours the retention of contaminants by ion-exchange processes within the clay-rich soils and the shale layer underlying the burial site.

当地的地质条件有利于污染物的滞留，通过埋藏点之下的富粘土土壤和页岩层中的离子交换过程而进行。