normal residual

例句：

1. 1. The normal residual of the soil is an important factor in determining its fertility.
   土壤的正常残余量是决定其肥力的一个重要因素。
2. 2. The study found that the normal residual of heavy metals in the soil was significantly reduced after the treatment.
   研究发现，经过处理后，土壤中重金属的正常残余量显著降低。
3. 3. The residual analysis showed that the pollutants had a normal residual in the environment.
   残留分析显示，污染物在环境中有正常的残余。