Download Topic 5.4

Why is nitrogen important?
• All living things need nitrogen to make DNA and proteins
• Nitrogen is the most abundant gas in the atmosphere
• Atmospheric nitrogen cannot be used by most plants and animals,
but some specialized micro-organisms can fix the nitrogen from the
atmosphere
• Plants get nitrogen from the soil
• Animals get nitrogen from eating the plants
• When animals excrete, they return nitrogen to the ground
• When animals and plants die, they decompose and return the
nitrogen to the soil
How do humans use nitrogen?
• Farmers since prehistoric times have been adding animal manure to
fields in order to increase crop growth.
• Traditional human activities have become part of the nitrogen cycle in
the form of the Haber Process.
Source
Point Sources
Type of problem
Power plants
Combustion of fossil fuels emit nitrogen
products into the atmosphere, which are carried
down by rainfall and other processes, causing
eutrophication in water bodies
Sewage Treatment Plants
Treatment process releases oxides of N and
P in effluents, which drain into water bodies
Industrial Plants
Industrial processes release N and P
products in effluents, which drain into water
bodies
Agriculture
Farming practices, including use of fertilisers rich
in N and P, deposit increased amounts of these
nutrients in the soil. Run-off from these farms
cause eutrophication in water bodies.
Sewage
Direct discharge of sewage from domestic sources,
not connected to treatment plants, will eventually
make its way into water bodies
Non-Point Sources