394 EUTROPHICATION
The following are the most common sources of nitrogen
and phosphorus in bodies of water:1) Rainfall—Based on experimental data, it has been
found that rainwater contains between 0.16 and
1.06 ppm of nitrate nitrogen and between 0.04 and
1.70 ppm of ammonia nitrogen. Computations
based on the nitrogen content of rainwater show
that for Lake Mendota, Wisconsin, approximately
90,000 pounds of nitrogen are available each year
as a result of rainfall. Thus it can be seen that
rainfall plays a significant role in building up the
nitrogen content of a lake or reservoir especially
if the surface area is large.
An examination of the phosphorus content of rainwater
of different countries shows that a number of concentrations
may exist ranging from 0.10 ppm to as little as an unmeasur-
able trace, the latter reported in the Lake Superior region
of the United States. In view of the wide variation in the
determinations, little can be stated at present regarding the
degree of phosphorus build-up in impoundments resulting
from rainwater.
2) Groundwater—Studies conducted on sub-surface
inflows to Green Lake, Washington, show that this
water contains approximately 0.3 ppm of phospho-
rus. Other reports, however, claim that the amount
of phosphorus in groundwater is negligible.
Investigations into the nitrate content of groundwater pro-
duced variable results; however, it can be stated that 1.0 ppm
is a reasonable fi gure. The results of the above studies on both
nitrogen and phosphorus can be summarized by stating that
groundwater should not be discounted as a possible source of
nutrients and that quantitative values should be obtained for
the specifi c locality in question.
3) Urban Runoff—Urban runoff contains storm
water drainage, overflow from private disposal
systems, organic and inorganic debris from paved
and grassed areas, fertilizers from lawns, leaves,
etc. In view of the variable concentration of the
above material, precise figures cannot be obtained
on the phosphorus or nitrate content that would be
meaningful for all areas.
Studies conducted in 1959 and 1960 by Sylvester on
storm water from Seattle street gutters shows the following
nutrients:
Organic nitrogen—up to 9.0 ppm
Nitrate nitrogen—up to 2.8 ppm
Phosphorus—up to 0.78 ppm soluble and up to 1.4 ppm
total.
4) Rural Runoff—Rural runoff for the purposes
of definition may be considered as runoff from
sparsely-populated, wooded areas with little or
no land devoted to agriculture. Investigations by
Sylvester showed that the phosphorus content
of drainage from three such areas in the state of
Washington contained 0.74, 0.77 and 0.32 lb./acre/
year, or a total concentration of 0.069 ppm. The
corresponding nitrate nitrogen concentration andorganic nitrogen concentration amounted to 0.130
and 0.074 ppm, respectively.
5) Agricultural Runoff—Agricultural runoff is one
of the largest sources of enrichment material and
may be derived from two sources—wastes from
farm animals and the use of nitrogen and phos-
phorus-containing fertilizers.
Farm-animal wastes add both large quantities and high
concentrations of nutrients to adjacent streams and rivers.
The large concentrations are due primarily to the practice of
herding animals in relatively confi ned areas. A comparison
on the nutrient value of animal wastes and human wastes has
been made in a study by the President’s Science Advisory
Committee. According to the fi ndings, a cow generates the
waste equivalent of 16.4 humans, a hog produces as much as
1.9 humans and a chicken produces as much as 0.14 humans.
The use of chemical fertilizers in the United States has
grown almost 250% in the decade from 1953 to 1963. In
1964 the use of phosphorus-containing fertilizers and the use
of nitrogen-containing fertilizers reached approximately 1.5
and 4.4 million tons, respectively, per year. Most all of this
fertilizer is distributed to soil already high in natural-occurring
nitrogen. When nitrogen fertilizer and natural soil nitrogen
combine, there is a great increase in crop production, but
also a greater opportunity for loss of this nitrogen in runoff.
This loss will increase if the fertilizer is not properly applied,
if it is not completely utilized by the crops, if the crops have
a short growing season (the land being non-productive for a
time), if the land is irrigated, and if the land is sloped.
The addition of nitrogen-bearing fertilizers also increase
the quantity of mineral elements in the soil runoff which are
necessary for the growth of aquatic plants and algae. When
applied, the nitrogen in the fertilizer is converted into nitric
acid which combined with the minerals in the soil, such as
calcium and potassium, rendering them soluble and subject
to leaching.
6) Industrial Wastes—The nutrient content of indus-
trial waste effluents is variable and depends
entirely upon the nature, location and size of the
industry. In some cases the effluents are totally
free of nitrogen and phosphorus.
The meat packing industry is one of the chief producers of
nitrogen-bearing wastes. The greatest producer of phosphate-
bearing wastes is most likely the phosphate-manufacturing
industry itself. Most phosphate production in the United States
is concentrated in Florida and as a result many severe local-
ized problems of eutrophication have resulted in that state.
Fuel processing industries and petroleum refi neries dis-
charge vast quantities of nitrogen into the atmosphere both
in the gaseous state and solid state as particulate matter. This
nitrogen is then washed from the atmosphere by the rain and
carried back to earth. In 1964, the 500 billion tons of coal
used in the United States released about 7.5 million tons of
nitrogen into the atmosphere, most of which has returned to
be combined with the soil. This greatly exceeds the use of
nitrogen in the form of fertilizers which, as previously stated,
amounted to 4.4 million tons for that year. Thus, through the
atmosphere we are bringing more nitrogen into the soil thanC005_012_r03.indd 394C005_012_r03.indd 394 11/18/2005 10:26:02 AM11/18/2005 10:26:02 AM