The Odd Nitrogen Cycle
						q N2O: from Earth’s surface, where it is produced by microbial activity in soil and in the ocean. è  In the stratosphere, some of N2O reacts to form NO, the rest is photolyzed back to N2 and O2. è The NO so produced participates in the ozone-destroying nitrogen catalytic cycle. è Once for a while, the resulting NO2 molecule interacts with a hydroxyl radical (OH), producing nitric acid (HNO3). è Nitric Acid (HNO3) then diffuses down into the troposphere and dissolves into rain.