Geoscience Reference
In-Depth Information
Acids and alkalies. Most freshwater lakes, streams, and ponds have a natural pH
in the range of 6
8. Acid deposition has many harmful ecological effects when
the pH of most aquatic systems falls below 6 and especially below 5.
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Anions. The most toxic form of cyanide is free cyanide, which includes the
cyanide anion itself and hydrogen cyanide, HCN, either in a gaseous or aqueous
state. One teaspoon of a 2 % cyanide solution can kill a person.
Detergents. There are two kinds of detergents with different characteristics:
phosphate detergents and surfactant detergents. Detergents that contain phos-
phates are highly caustic, and surfactant detergents are very toxic.
Gases. Some gases that can harm aquatic freshwater life are gases such as
chlorine, ammonia and methane.
Heat. Respiration and growth rates may be changed and these may alter the
feeding rates of organisms. The reproduction period may be brought forward
and development may be speeded up. Parasites and diseases may also be
affected. An increase of temperature also means a decrease in oxygen solubility.
Heavy metals. The most common heavy metal pollutants are arsenic, cadmium,
chromium, copper, nickel, lead and mercury. Some metals, such as manganese,
iron, copper, and zinc are essential micronutrients. Each type of heavy metals in
its own way affects the water ecosystem
s biochemistry and can accumulate in
bottom deposits and in the biomass of living elements.
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Nutrients. Too many nutrients stimulate the rapid growth of plants and algae,
clogging waterways and sometimes creating blooms of toxic blue-green algae.
This process is called eutrophication.
Organic pollution. Organic pollution occurs when large quantities of organic
compounds, which act as substrates for microorganisms, are released into
watercourses. Organic pollutants consist of proteins, carbohydrates, fats and
nucleic acids in a multiplicity of combinations. Organic pollution affects the
organisms living in a stream by lowering the available oxygen in the water.
Pathogens. A pathogen is an organism that produces a disease.
The process of eutrophication is the most widespread phenomenon in the life of
water ecosystems. An excess amount of nitrogen and phosphorus leads to a rapid
growth of phytoplankton or algae biomass, and as a result, the content of oxygen in
the water decreases sharply, and the mortality of living organisms grows substan-
tially. The gas exchange with the atmosphere is violated. From available estimates,
the share of eutrophicated lakes on different continents constitutes: Asia
—
54 %,
Europe
—
53 %, North America
—
48 %, South America
—
41 %, and Africa
—
28 %.
In the present-day world, it is dif
cult to differentiate the anthropogenic process of
eutrophication from natural because of globalized biogeochemical cycles and dif-
ficult control of the
fl
fluxes of chemical elements through the atmosphere and river
run-off.
Stability of the biosphere as a global ecosystem and its self-regulating ability are
determined by the cyclic character of the processes of exchange with matter,
energy, and information taking place in it and realized due to the incoming solar
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