Prab at 02:42, 2 October 2020

2020-10-02T02:42:21Z

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[[Image:TurbidityStandards.jpg|right|frame|Turbidity standards of 5, 50, and 500 NTU]]
'''Turbidity''' is a [[measurement|measure]] of how well light penetrates water. It is caused by [[particle]]s (total suspended or dissolved solids) that are generally invisible to the [[naked eye]]. The [[measurement]] of turbidity is a key test of [[water quality]].

[[Fluids]] can contain suspended particles of many different sizes. Some suspended material will be large enough and heavy enough to settle rapidly to the bottom if a liquid sample is left to stand. Very small particles settle very slowly or not at all if the sample is regularly [[Agitator (device)|agitated]] or the particles are [[colloid]]al. These small solid particles cause the liquid to appear turbid or murky.

== Causes ==

Turbidity in open [[water]] may be caused by growth of [[phytoplankton]].<ref>''Fundamentals of Aquacultural Engineering'', ed. Thomas B. Lawson (Norwell, MA; The Netherlands: Kluwer Publishers, 2002), p. 19</ref> Naturally occurring [[Algal bloom]]s can cause turbidity. Human activities that disturb land can lead to high [[sediment]] levels entering water bodies during rain storms due [[surface runoff|runoff]]. These can include [[construction]], [[mining]] and [[agriculture]]. [[water pollution|pollution]] from [[Pavement (material)|paved]] surfaces such as roads, bridges and parking lots is another source.<ref>U.S. Environmental Protection Agency (EPA). Washington, D.C. [http://www.epa.gov/owow/nps/urbanmm/index.html "National Management Measures to Control Nonpoint Source Pollution from Urban Areas."] Chapters 7 and 8. Document No. EPA 841-B-05-004. November 2005.</ref> Certain industries such as [[quarry]]ing, [[coal mine|mining]] and coal recovery can generate very high levels of turbidity from rock particles entering the water.

In drinking water, the higher the turbidity level, the higher the risk that people may develop [[disease]]s.<ref>A.G. Mann, C.C. Tam, C.D. Higgins, & L.C. Lodrigues. (2007). The association between drinking water turbidity and gastrointestinal illness: a systematic review. ''BMC Public Health''. 7(256): 1 - 7</ref> Contaminants like [[virus]]es or [[bacteria]] can become attached to the suspended solids. The suspended solids interfere with water disinfection with [[chlorine]] because the particles act as shields for the virus and bacteria. Similarly, suspended solids can protect bacteria from [[Ultraviolet germicidal irradiation|ultraviolet (UV) sterilization]] of water.{{citation needed|date=March 2011}}

In water bodies such as [[lake]]s, rivers and [[reservoirs]], high turbidity levels can reduce the amount of light reaching lower depths. This can limit growth of submerged [[aquatic plants]]. In turn this affects species which are dependent on them, such as [[fish]] and [[shellfish]]. High turbidity levels can also affect the ability of fish [[gill]]s to absorb [[Oxygen saturation|dissolved oxygen]]. This situation has been regularly observed throughout the [[Chesapeake Bay]] in the eastern [[United States]].<ref>U.S. Fish and Wildlife Service. Annapolis, MD. [http://www.fws.gov/chesapeakebay/savpage.htm "Decline of Submerged Plants in Chesapeake Bay."]</ref><ref>EPA. Chesapeake Bay Program. Annapolis, MD. [http://www.chesapeakebay.net/sediments.aspx "Sediments."]</ref>

== References ==
{{reflist}}

[[Category:Water pollution]]
{{pollution}}
[[Category:Pollution]]

Turbidity - Revision history

Prab at 02:42, 2 October 2020