secondary emission coefficient

例句：

1. 1.The secondary emission coefficient of the vehicle is very low, which means it has a good air quality.
   车辆的次级排放系数很低，这意味着它的空气质量很好。
2. 2. The study found that the secondary emission coefficient of the pollutant was reduced by 30% through the new technology.
   研究发现，通过新技术，污染物的次级排放系数降低了30%。
3. 3. The researcher used the secondary emission coefficient to calculate the emission levels of different vehicles.
   研究者使用次级排放系数来计算不同车辆的排放水平。