Download Photochemical smog, ozone and eutrophication notes

1. In car engines, nitrogen gas (N2) combines with oxygen (O2) to form a clear, odorless gas called nitrogen monoxide
(NO) which enters the atmosphere
N2 + O2  NO
2. In the atmosphere, NO can combine with O2 in the presence of sunlight to form a brownish-yellow, noxious gas called
nitrogen dioxide (NO2). This is photochemical smog.
NO + O2  NO2
3. Nitrogen dioxide can mix with water vapor in the atmosphere to form nitric acid (HNO3), a component of acid rain. In
the soil, HNO3 can dissociate into hydrogen ions (H+) and nitrate (NO3-). The latter can be used by plants as a source of
nitrogen to make amino acids and proteins/DNA.
NO2 + H2O (gas)  HNO3 (acid rain)
HNO3  NO3- + H+
4. NO2 can also be broken apart by ultraviolet (UV) light to form nitrogen monoxide (NO) and a highly reactive oxygen
radical.
NO2 ---UV light NO + O
5. The oxygen radical can react with an oxygen (O2) to form ozone (O3). Ozone is naturally found in our stratosphere but
when in the troposphere, it is a respiratory irritant. Ozone is relatively unstable and will eventually break down into
oxygen.
Eutrophication in Ponds
1. NO3- (nitrates) from inorganic fertilizers causes algae blooms
2. The algae grow and die rapidly falling to the bottom of the pond
3. Decomposers (fungi, bacteria etc) use up some of the available dissolved oxygen (DO)
4. Hypoxia begins when the DO< 4ppm.
This process is eutrophication (fish kills)