灰化

例句：

1. 1. The old tree had been graying for years.
   这棵老树已经灰暗多年了。
2. 2. The smoke from the fire was turning the room into a grayish-black hue.
   火烟让房间变成了灰色和黑色。
3. 3. The coal mine has been graying over the years due to pollution.
   煤矿由于污染而变得灰暗多年。