NITROGEN CYCLING IN A DEVELOPED WATERSHED
N2
NOx
Atmospheric nitrogen
Nitrogen oxides
NH4+ Ammonium ion
NO3SO2
SO42-
H+
hydrogen
ion
Nitrate ion
sulfate
NO3nitrate
NOx
SO2
Sulfur dioxide
NOx
NOx
N2
NOx
N2
NOx
rain
NOx
snow
N2
NO3Food delivered
to watershed
Furnaces and engines turn atmospheric
Treated sewage
nitrogen into nitrogen oxides
flows into river
NO3NH4+
NH4+
Excess fertilizer
runs into river
Nitrate and ammonium in river
Developed watersheds import nitrogen in food and fertilizer.
They also receive nitrogen from acid rain, which in turn gets
its nitrogen from the nitrogen oxides produced by furnaces,
boilers, and engines. About half the nitrogen a watershed
receives is stored in the soil or in trees or exported as crops.
The excess nitrate and ammonium flows into rivers.
Fertilizer applied
to crops
Power plants
generate
nitrogen oxides