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Water clarity is a descriptive term for how deeply visible light penetrates through water. In addition to light penetration, the term water clarity is also often used to describe underwater visibility. Water clarity is one way that humans measure water quality, along with oxygen concentration and the presence or absence of pollutants and algal ...
According to the EPA, water quality laws generally specify protection of fisheries and recreational use and require, as a minimum, retention of current quality standards. [18] In some locations, desired water quality conditions include high dissolved oxygen concentrations, low chlorophyll-a concentrations, and high water clarity. [19]
The international definition of fog is a visibility of less than 1 km (3,300 ft); mist is a visibility of between 1 km (0.62 mi) and 2 km (1.2 mi) and haze from 2 km (1.2 mi) to 5 km (3.1 mi). Fog and mist are generally assumed to be composed principally of water droplets, haze and smoke can be of smaller particle size.
The standard measurement for underwater visibility is the distance at which a Secchi disc can be seen. The range of underwater vision is usually limited by turbidity. In very clear water visibility may extend as far as about 80m, [18] and a record Secchi depth of 79 m has been reported from a coastal polynya of the Eastern Weddell Sea ...
The disc is mounted on a pole or line and lowered slowly down in the water. The depth at which the disk is no longer visible is taken as a measure of the transparency of the water. This measure is known as the Secchi depth and is related to water turbidity. Since its invention, the disk has also been used in a modified, smaller 20 cm (8 in ...
Turbidity is the cloudiness or haziness of a fluid caused by large numbers of individual particles that are generally invisible to the naked eye, similar to smoke in air.The measurement of turbidity is a key test of both water clarity and water quality.
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Parts Per Million of standard substance, such as PPM/DE (Kieselguhr) "Trübungseinheit/Formazin" (TE/F) a German standard, now replaced by the FNU unit. diatomaceous earth ("ppm SiO 2") an older standard, now obsolete; A more popular term for this instrument in water quality testing is a turbidimeter.