本帖最後由 lo_pak 於 2010-9-28 21:18 編輯
回復 9# tiffiant
Precipitation is rain, snow, hail... etc.
That's why everytime after rain you feel the air is fresher...
For any pollutants that're heavier than air by density, they will go nowhere but falling down eventually. It's just a matter in time...
For heavily polluted air, eg. industrial area, you may always heard of the term "acid rain", it is harmful.
However, the condition is well depends on the weather. Since precipitation is a pretty well buffer system, water falls on the ground is usually "neutral", so to speak. |