Which of the following parameters is not used as a pollution indicator in…

CONCEPT

Water-quality indicators are measurable physical, chemical, or biological quantities whose changes reveal contamination or its effects. An indicator must have an interpretable connection to pollutant load, sanitary contamination, or ecological stress.

APPLICATION

Classify each proposed parameter by what it measures and whether that measurement is routinely interpreted as evidence of water pollution.

CONTRAST

• Total dissolved solids measure the dissolved mineral and salt load in water; unusually high values can indicate contamination or poor water quality.

• Coliform count estimates indicator bacteria in a water sample and is used to assess possible faecal contamination.

• Dissolved oxygen measures oxygen available in water; organic pollution can reduce it when microorganisms consume oxygen during decomposition.

• Density is mass per unit volume. Although it varies with temperature and dissolved substances, it is not ordinarily used as a direct pollution indicator in routine water-quality assessment.

CROSS-CHECK

Standard water-quality monitoring commonly reports TDS, microbiological indicators such as coliforms, and dissolved oxygen because each has a direct interpretive link to water quality. Density is a general physical property and does not provide that routine diagnostic link by itself.

RESULT

Therefore, the parameter not used as a routine pollution indicator in water is Density.