Geoscience Reference
In-Depth Information
Table 9.1 Some criteria and factors, the structure of substances and parameters that determine the
water quality
(a) Factors
Type of water
pollution
Factors
Biological
Microorganisms favouring the fermentation of organic substances
Chemical
Toxic substances or changing the composition of water
Physical
Heating, radioactivity
(b) Elements
Group of
characteristics
Elements
Basic ions
, sulphate SO 2 4 , hydrocarbon HCO 3 , carbon CO 2 3 ,
natrium Na + , potassium K + , magnesium Mg 2+ , calcium Ca 2+
Chloride Cl
Dissolved gases
Oxygen O 2 , carbon dioxide CO 2 , nitrogen N 2 , hydrogen sul de H 2 S
Biogenic elements
Nitrogen, phosphorus and silicon compounds
Microelements
Zn, Cu, Pb, Ni, Co, Li, Rb, Cs. Be, Br, I, F, etc.
Organic
substances
Content of carbon, oxidizability, biochemical consumption of oxygen
that assess the water quality with different criteria. Abbasi and Abbasi (2012)
describe water quality indices and show that only with the use of such indices is it
feasible to assess, express, communicate, and monitor the overall quality of any
water source. In general, the conditions of water quality include ( http://water.epa.
gov/type/rsl/monitoring/vms52.cfm )
￿
Stream
flow, or discharge, is the volume of water that moves
over a designated point over a
fl
ow. The stream
fl
fixed period of time. It is often expressed in cubic
meters per second (m 3 /s). The
flow is affected by weather, increasing during
rainstorms and decreasing during dry periods. It also changes during different
seasons of the year, decreasing during the summer months when evaporation
rates are high and shoreline vegetation is actively growing and removing water
from the ground. August and September are usually the months of lowest flow
for most streams and rivers in most of the country.
fl
Dissolved oxygen and biochemical oxygen demand. The stream system both
produces and consumes oxygen. It gains oxygen from the atmosphere and from
plants as a result of photosynthesis. Running water, because of its churning,
dissolves more oxygen than still water, such as that in a reservoir behind a dam.
Respiration by aquatic animals, decomposition, and various chemical reactions
consume oxygen.
￿
Temperature. The rates of biological and chemical processes depend on tem-
perature. Aquatic organisms from microbes to
￿
fish are dependent on certain
temperature ranges for their optimal health. Temperature affects the oxygen
content of the water (oxygen levels become lower as temperature increases); the
rate of photosynthesis by aquatic plants; the metabolic rates of aquatic organ-
isms; and the sensitivity of organisms to toxic wastes, parasites, and diseases.
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