池塘底部的微生物通过反硝化作用将有害的硝酸盐转化为氮气。

Microorganisms in the pond sediment perform ___denitrification to convert harmful nitrates into nitrogen gas.

湿地生态系统在反硝化过程中将硝酸盐转化为氮气，从而减少水体污染。

Wetland ecosystems convert nitrates into nitrogen gas during ___denitrification, reducing water pollution.