160 Ecology and Applied Environmental Science
Surface waters, i.e. rivers, lakes, springs, lagoons, enclosed marine bays
and open seas, are susceptible to pollution to a greater or lesser degree,
depending on their capacity for renewal. Here a decisive part is played by the
amount of oxygen dissolved in the water. As distinct from the atmosphere,
lution, water has low oxygen saturation concentrations. Under specific conditions, water is in danger of lacking the oxygen necessary for the respiration
of organisms; consequently, the phenomenon of oxygen depletion may occur.
The oxygen saturation concentration in water becomes lower as the temperature rises. When there is organic matter in the water, the dissolved oxygen is
consumed by aerobic respiration of the microorganisms that decompose it.
That is why organic compounds constitute a serious pollutant for water. The
consequences may be fatal for a number of aquatic organisms, which are in
danger of suffocating. Thus pollution with urban wastewater or other waste
containing an organic load may seriously degrade an aquatic ecosystem.
Pollution with inorganic salts containing either nitrogen in the form of
nitrates or ammonium salts or phosphorus in the form of phosphates may
also have adverse effects on surface water. Such pollutant loads are usually contained in urban wastewater (excrement, detergents, etc.), in certain
industrial waste and in agricultural runoff (excess fertilizers). The most
important problem created by nitrogen and phosphorus is eutrophication,
which consists of an excessive growth of algae (phytoplankton) in surface
waters due to an excessive supply of nutrients. This phenomenon constitutes a serious disturbance for an aquatic ecosystem with various adverse
consequences including greater turbidity and oxygen depletion.
Groundwater is very susceptible to pollution because of its limited ability
to self-purify. The main effect of agricultural runoff and urban wastewater
that end up in the underground water table is an increase in concentrations
of nitrates, causing groundwater to become toxic to humans and animal
organisms. Pollution of groundwater with industrial waste may bring about
increased concentrations of metals or other toxic substances.
Another form of pollution of surface and groundwater is contamination,
i.e. the presence of pathogenic microorganisms. This is usually a result of drainage of wastewater from cities and from stock-raising activities. Pathogenic
microorganisms are detected in water indirectly by measuring fecal coliform
bacteria, which are generally not pathogenic; their increased presence is an
indication of possible contamination of water with other pathogens.
We now examine in more detail some of the main pollutants of water,
their sources and their effects.
8.2 organic MattEr—oxygEn dEPlEtion
Dissolved oxygen is generally not abundant in water; therefore, organic
matter can cause serious pollution, since it can lead to oxygen depletion of
Surface waters, i.e. rivers, lakes, springs, lagoons, enclosed marine bays
and open seas, are susceptible to pollution to a greater or lesser degree,
depending on their capacity for renewal. Here a decisive part is played by the
amount of oxygen dissolved in the water. As distinct from the atmosphere,
lution, water has low oxygen saturation concentrations. Under specific conditions, water is in danger of lacking the oxygen necessary for the respiration
of organisms; consequently, the phenomenon of oxygen depletion may occur.
The oxygen saturation concentration in water becomes lower as the temperature rises. When there is organic matter in the water, the dissolved oxygen is
consumed by aerobic respiration of the microorganisms that decompose it.
That is why organic compounds constitute a serious pollutant for water. The
consequences may be fatal for a number of aquatic organisms, which are in
danger of suffocating. Thus pollution with urban wastewater or other waste
containing an organic load may seriously degrade an aquatic ecosystem.
Pollution with inorganic salts containing either nitrogen in the form of
nitrates or ammonium salts or phosphorus in the form of phosphates may
also have adverse effects on surface water. Such pollutant loads are usually contained in urban wastewater (excrement, detergents, etc.), in certain
industrial waste and in agricultural runoff (excess fertilizers). The most
important problem created by nitrogen and phosphorus is eutrophication,
which consists of an excessive growth of algae (phytoplankton) in surface
waters due to an excessive supply of nutrients. This phenomenon constitutes a serious disturbance for an aquatic ecosystem with various adverse
consequences including greater turbidity and oxygen depletion.
Groundwater is very susceptible to pollution because of its limited ability
to self-purify. The main effect of agricultural runoff and urban wastewater
that end up in the underground water table is an increase in concentrations
of nitrates, causing groundwater to become toxic to humans and animal
organisms. Pollution of groundwater with industrial waste may bring about
increased concentrations of metals or other toxic substances.
Another form of pollution of surface and groundwater is contamination,
i.e. the presence of pathogenic microorganisms. This is usually a result of drainage of wastewater from cities and from stock-raising activities. Pathogenic
microorganisms are detected in water indirectly by measuring fecal coliform
bacteria, which are generally not pathogenic; their increased presence is an
indication of possible contamination of water with other pathogens.
We now examine in more detail some of the main pollutants of water,
their sources and their effects.
8.2 organic MattEr—oxygEn dEPlEtion
Dissolved oxygen is generally not abundant in water; therefore, organic
matter can cause serious pollution, since it can lead to oxygen depletion of