Filter bed should be exposurd as less as possible because alternation of exposure and immersion is disbennifit to the penetrability of filter bed.

依据水资料分析水源水安全保障。

This paper discussed water liquor acts on micrinite in the calcareous clay at the bottom of saline aquifer and put forward the concept of filter bed of salinity.

本文讨水组底部钙化粘土微观粘粒与水溶液的相互作用，提出“滤盐层”的概念。