5
1 Eutrophication: Challenges and Solutions
1.3.2.2 Financial Boom
Increasing economic growth and per capita income indirectly contributes the nutrient pollution in developing parts of
the world. Increasing incomes will lead to changes in dietary
choices, increasing energy use, and increasing consumption
of consumer goods. Worldwide increase in purchasing power
is moving dietary trends toward greater meat consumption
especially in the case of lower to middle income populations
(FAO 2002). The increased livestock production that will be
necessary to meet growing global demand for meat is expected to have significant implications for the severity of nutrient pollution worldwide. It is estimated that only 20 % of
the nitrogen used in swine production is actually consumed
by humans, the remainder is excreted as manure or lost to the
environment during the production of animal feed (UNEP
and WHRC 2007). On the contrary, one study of the Mississippi River Basin estimated that if feed cultivation for meat
production were switched to crops that would support a lacto-ovo-vegetarian diet, nitrate exports to the Gulf of Mexico
would decrease by 50 % (Donner 2006).
1.3.2.3 Agricultural Extension
In order to fulfill the food demand of increasing population
across the globe, the way in which we grow food has changed
dramatically. Significant advances in agriculture production have been made, the widespread use of agrochemicals
such as synthetic fertilizers and pesticides to improve crop
yields. These chemicals and modern machinery allowed the
intensification of agriculture, which has led to significant
unintended environmental impacts such as nutrient pollution. In fact, agriculture (including livestock agriculture)
is the largest source of water pollution. Fertilizer leaching,
runoff from agricultural fields, manure from concentrated
livestock operations, and aquaculture are the largest agricultural nutrient sources. Between 1960 and 1990, global use
of synthetic nitrogen fertilizer increased more than sevenfold, while phosphorus use more than tripled (MA 2005).
The excess nutrients are lost through volatilization, surface
runoff, and leaching to groundwater. On average, about 20 %
of nitrogen fertilizer is lost through surface runoff or leaching into groundwater (MA 2005). Synthetic nitrogen fertilizer and nitrogen in manure that is spread on fields is also
subject to volatilization. Volatilization is where nitrogen in
the form of ammonia (NH 3 ) is lost to the atmosphere. Under
some conditions, up to 60 % of the nitrogen applied to crops
can be lost to the atmosphere by volatilization (University
of Delaware Cooperative Extension 2009); more commonly,
volatilization losses are 40 % or less (MA 2005). A portion of
the volatilized ammonia is redeposited in waterways through
atmospheric deposition. Phosphorus, which binds to the soil,
is generally lost through sheet and rill erosion from agricultural lands.
1.4 Impacts of Fertilizers on Eutrophication
It is evident that eutrophication is related with a number of
anthropogenic activities in urban and rural areas including
agricultural practices. Phosphorus and nitrogen input owing
to excessive use in agricultural practices, their cycling in the
water bodies and seasonal variabilities (temperature, water
level, depth, irradiance, and winds) are the main causes of
eutrophication (Khan and Ansari 2005). Nonpoint sources
of nutrients are often of greater concern than point sources
because they are larger and more difficult to control. Fertilizer application on land remains a major contributor to
nonpoint nutrient pollution, and this source is still increasing
at an alarming rate in many geographic regions (Vitousek
et al. 1997). Both industrial and developing nations are
using significantly higher loadings of fertilizer in agriculture with global N and P fertilizer usage increasing eightfold
and threefold, respectively, since the early 1960s (Constant
and Sheldrick 1992; Caraco 1995; Matson et al. 1997; Smil
2001). In addition to compost, several brands of chemical
fertilizers containing macro and micronutrients are being
excessively used. The fertilizer industry recognizes its crucial role in meeting basic human needs. It stands to meet
the challenge of adopting new practices and technologies for
greater efficiency and optimum crop productivity to sustain
better quality of life (Fixen and West 2002).
The fluxes in nutrient concentration of a water body are
the result of synergistic action of population development
and fertilizer applications (Caraco 1995; Smil 2001). When
these nutrients get to lower rivers, estuaries, and coastal waters, they are available for phytoplankton uptake and growth.
The nitrate component of fertilizers can travel long distances.
A significant relationship between traveling distance of nitrate and increased phytoplankton productivity was recorded
by Mallin et al. (1993). A dramatic trend in world fertilizer
production is the increased proportion of urea in world N
production, especially in Third-World countries. Urea now
comprises roughly 40 % of all N fertilizers produced (Constant and Sheldrick 1992). This is significant because data
indicate that in some areas this shift in fertilizer composition
has resulted in a shift in the nutrient composition of runoff,
potentially favoring some harmful algal bloom species.
In situ experiment of nutrient enrichment in a temperate
region reservoir in Seoul (South Korea) revealed that algal
response on P treatments were greater than on treatments
with P + NH 4 − N or P + NO 3 − N. The response was greater
during summer monsoon than in any other season (An 2003).
1.4.1 Effects of Nitrogen
The atmospheric reservoir of gaseous dinitrogen is the initial
source of nitrogen. It must be converted by nitrogen fixation
1 Eutrophication: Challenges and Solutions
1.3.2.2 Financial Boom
Increasing economic growth and per capita income indirectly contributes the nutrient pollution in developing parts of
the world. Increasing incomes will lead to changes in dietary
choices, increasing energy use, and increasing consumption
of consumer goods. Worldwide increase in purchasing power
is moving dietary trends toward greater meat consumption
especially in the case of lower to middle income populations
(FAO 2002). The increased livestock production that will be
necessary to meet growing global demand for meat is expected to have significant implications for the severity of nutrient pollution worldwide. It is estimated that only 20 % of
the nitrogen used in swine production is actually consumed
by humans, the remainder is excreted as manure or lost to the
environment during the production of animal feed (UNEP
and WHRC 2007). On the contrary, one study of the Mississippi River Basin estimated that if feed cultivation for meat
production were switched to crops that would support a lacto-ovo-vegetarian diet, nitrate exports to the Gulf of Mexico
would decrease by 50 % (Donner 2006).
1.3.2.3 Agricultural Extension
In order to fulfill the food demand of increasing population
across the globe, the way in which we grow food has changed
dramatically. Significant advances in agriculture production have been made, the widespread use of agrochemicals
such as synthetic fertilizers and pesticides to improve crop
yields. These chemicals and modern machinery allowed the
intensification of agriculture, which has led to significant
unintended environmental impacts such as nutrient pollution. In fact, agriculture (including livestock agriculture)
is the largest source of water pollution. Fertilizer leaching,
runoff from agricultural fields, manure from concentrated
livestock operations, and aquaculture are the largest agricultural nutrient sources. Between 1960 and 1990, global use
of synthetic nitrogen fertilizer increased more than sevenfold, while phosphorus use more than tripled (MA 2005).
The excess nutrients are lost through volatilization, surface
runoff, and leaching to groundwater. On average, about 20 %
of nitrogen fertilizer is lost through surface runoff or leaching into groundwater (MA 2005). Synthetic nitrogen fertilizer and nitrogen in manure that is spread on fields is also
subject to volatilization. Volatilization is where nitrogen in
the form of ammonia (NH 3 ) is lost to the atmosphere. Under
some conditions, up to 60 % of the nitrogen applied to crops
can be lost to the atmosphere by volatilization (University
of Delaware Cooperative Extension 2009); more commonly,
volatilization losses are 40 % or less (MA 2005). A portion of
the volatilized ammonia is redeposited in waterways through
atmospheric deposition. Phosphorus, which binds to the soil,
is generally lost through sheet and rill erosion from agricultural lands.
1.4 Impacts of Fertilizers on Eutrophication
It is evident that eutrophication is related with a number of
anthropogenic activities in urban and rural areas including
agricultural practices. Phosphorus and nitrogen input owing
to excessive use in agricultural practices, their cycling in the
water bodies and seasonal variabilities (temperature, water
level, depth, irradiance, and winds) are the main causes of
eutrophication (Khan and Ansari 2005). Nonpoint sources
of nutrients are often of greater concern than point sources
because they are larger and more difficult to control. Fertilizer application on land remains a major contributor to
nonpoint nutrient pollution, and this source is still increasing
at an alarming rate in many geographic regions (Vitousek
et al. 1997). Both industrial and developing nations are
using significantly higher loadings of fertilizer in agriculture with global N and P fertilizer usage increasing eightfold
and threefold, respectively, since the early 1960s (Constant
and Sheldrick 1992; Caraco 1995; Matson et al. 1997; Smil
2001). In addition to compost, several brands of chemical
fertilizers containing macro and micronutrients are being
excessively used. The fertilizer industry recognizes its crucial role in meeting basic human needs. It stands to meet
the challenge of adopting new practices and technologies for
greater efficiency and optimum crop productivity to sustain
better quality of life (Fixen and West 2002).
The fluxes in nutrient concentration of a water body are
the result of synergistic action of population development
and fertilizer applications (Caraco 1995; Smil 2001). When
these nutrients get to lower rivers, estuaries, and coastal waters, they are available for phytoplankton uptake and growth.
The nitrate component of fertilizers can travel long distances.
A significant relationship between traveling distance of nitrate and increased phytoplankton productivity was recorded
by Mallin et al. (1993). A dramatic trend in world fertilizer
production is the increased proportion of urea in world N
production, especially in Third-World countries. Urea now
comprises roughly 40 % of all N fertilizers produced (Constant and Sheldrick 1992). This is significant because data
indicate that in some areas this shift in fertilizer composition
has resulted in a shift in the nutrient composition of runoff,
potentially favoring some harmful algal bloom species.
In situ experiment of nutrient enrichment in a temperate
region reservoir in Seoul (South Korea) revealed that algal
response on P treatments were greater than on treatments
with P + NH 4 − N or P + NO 3 − N. The response was greater
during summer monsoon than in any other season (An 2003).
1.4.1 Effects of Nitrogen
The atmospheric reservoir of gaseous dinitrogen is the initial
source of nitrogen. It must be converted by nitrogen fixation