The
specific contaminants leading to pollution in water include a wide spectrum of
chemicals, pathogens, and physical or sensory changes such as elevated temperature
and discoloration. While many of the chemicals and substances that are
regulated may be naturally occurring (calcium, sodium, iron, manganese, etc.) the
concentration is often the key in determining what is a natural component of water,
and what is a contaminant. High concentrations of naturally occurring substances
can have negative impacts on aquatic flora and fauna.
Oxygen-depleting
substances may be natural materials, such as plant matter (e.g. leaves
and grass) as well as man-made chemicals. Other natural and anthropogenic
substances may cause turbidity (cloudiness) which blocks light and disrupts plant
growth, and clogs the gills of some fish species.
Many
of the chemical substances are toxic. Pathogens can produce waterborne diseases
in either human or animal hosts. Alteration of water's physical chemistry includes
acidity (change in pH), electrical conductivity, temperature, and eutrophication.
Eutrophication is an increase in the concentration of chemical nutrients in an
ecosystem to an extent that increases in the primary productivity of the
ecosystem. Depending on the degree of eutrophication, subsequent negative environmental
effects such as anoxia (oxygen depletion) and severe reductions in water
quality may occur, affecting fish and other animal populations.
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