Water is essential for all forms of life. It
must be available to us in the quantity and degree of purity or quality
needed for living things to metabolize. The quality of the water
needed varies, according to the use to which it may be put. Water
used for household use needs to be of a higher quality than that used for
irrigation. Industries demand different degrees of water purity.
Absolutely pure water is almost unknown as each raindrop picks up particles
of atmospheric dust and smoke as it falls.
Nitrogen is an essential nutrient for plant growth.
Over a period of time, the accumulation of
these nutrients increases the rate of plant growth that can eventually
clog a lake or waterway,
remove the oxygen and cause aquatic organisms to die. Human activities
accelerate a process that would normal take thousands of years. Fertilizers
washed off farmlands contain nitrogen; runoff from pastures with animal
wastes deposit nitrogen on the soils and into the water and untreated domestic
sewage contains human wastes with nitrogen. Since the 1950's, concentrations
of nitrates in freshwater rivers and lakes throughout Europe and North
America have increased significantly. The nutrients from fertilizers
and animal wastes were found to be the main contaminants in nearly 60%
of the polluted lakes surveyed in the United States.( Environmental Atlas
p.61) Nitrates from fertilizers are seeping into the groundwater aquifers.
In 1984, a survey by EPA showed that out of 124,000 wells, 24,000 had elevated
levels of nitrates and 8,000 were above natural health limits. Nitrate
pollution of groundwater is less of a problem in developing countries.
It often takes decades for nitrates to work their
way down through the earth to contaminate
groundwater: so the problem will worsen as pollution from recent
heavy applications of fertilizer worldwide reaches water supplies. They
are the main cause of pollutants in US lakes and implicated in toxic
algal blooms in Britain in 1989, as well as algal fish kills in Scandinavian
coasts of 1988. World Resources 1988-1989 states that nitrates
may cause blood poisoning in infants, hypertension in children, gastric
cancers in adults and fetal malformations. The combination of high nitrates
with pesticides may form nitrosamines, which are both carcinogenic and
mutagenic.
Therefore, increased population density in urban
and suburban sprawl and increased demand on agriculture have combined to
stress our natural waterways. The result in the nutrient enrichment
of bodies of fresh water with nitrogen compounds. This results in
the depletion of oxygen and rapid aging and death of a body of fresh water.
Entrance into waterways can be in several ways and in several forms:
*normally present in sewage effluent as nitrate
with ammonia
*farmland treated with nitrate fertilizers
run off; seepage from cattle feedlots (it is estimated
that 10,000 cattle can cause water
quality problems equivalent to those caused by a
city of 45,000!)
*natural decay of plants and animals
*dissolved atmospheric nitrogen, nitrites,
nitrates and ammonium compounds
*present as ammonia from decomposition of
fecal matter
*industrial waste effluent