Environmental Engineering Reference
In-Depth Information
for filtering out much of the harmful ultraviolet (UV) radiation from the sun and keeping it from hitting the
Earth. The chemical reaction for the formation of ozone is:
O
2
+ UV → O + O
O + O
2
→ O
3
As you can see from the carbon and oxygen cycles, both carbon and oxygen are common in the two cycles.
Photosynthesis produces O
2
and cellular respiration burns O
2
.
Nitrogen Cycle
Our atmosphere is composed of 78 percent nitrogen and 21 percent oxygen. However, this atmospheric nitro-
gen cannot be used by organisms without some assistance. The nitrogen cycle is unique because it has stages
