Agriculture Reference
In-Depth Information
act only on solutes that are not adsorbed. Degradation of organic compounds likely
occurs mainly, or even exclusively, in the liquid phase. On the other side, radioactive
decay takes place equally in the solution and adsorbed phases, while other reactions
or transformations may occur only or primarily in the sorbed phase.
Pollution of surface water from storm runoff and its management has been
described in Chapter 3 ( Wa t e r ), Volume. 1.
7.3.5 Hazard of Nitrate (NO 3 -N) Pollution
There is sufficient evidence that high nitrate contamination in drinking water can
cause serious health problems. Thus, acute and chronic health effects of contami-
nated water due to agricultural activities are serious threats to human beings. Nitrate
may cause methemoglobinemia (blue baby syndrome) in infants (Stone et al., 1997 )
when it is above the maximum contamination level of 10 mg/l. Additionally, nitrate
interaction with other dietary substances may cause health problems in humans
(Maidson and Brunett, 1985 ) .
7.3.6 Impact of Agricultural Pollutants on Surface Water
Body and Ecosystem
7.3.6.1 Impact of Eutrophication
The process of nutrient over-enrichment of natural water - “eutrophication” is a
threat for sustainable water resource management. Modern agriculture is dependent
on irrigation, chemical fertilizers and pesticides. Irrigated agriculture accounts for
over two-thirds of the world's current freshwater use. In some cases excessive fer-
tilizer is used, i.e., more than the plant's absorbing capacity. As a consequence, the
river water and lakes have become enriched with nitrogen and phosphorous nutrients
which in turn degraded the water environment.
The eutrophication has devastating impacts on fisheries, biodiversity, and other
activities in the aquatic ecosystem. Generally the growth of floating algae in the
aquatic ecosystem depends on the availability of light, nutrients, and densities of
grazing species, but they start to grow very fast in the nutrient enriched water.
Subsequently, the huge biomass of algal bloom produced due to their rapid growth
requires enormous amount of oxygen from the water column to be decomposed and
consequently the oxygen concentration becomes too low for fish and invertebrates
to survive. Fisheries resources may be increased to a certain level of eutrophication
but low oxygen concentration reduces fish stock. High phosphorus concentration in
river water may harm the plant communities and modifies the biological balance.
Food chains in the aquatic ecosystem may be altered.
Eutrophication can be minimized by planting vegetation at the river bank for
reduction of erosion and nutrient effluent, managing the amount and timing of
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