Pollution of river water is measured by dissolved amount of?

Pollution of river water is often measured by the dissolved amount of **oxygen**. Specifically, the parameter used is called Biological Oxygen Demand (BOD), which measures the amount of dissolved oxygen consumed by microorganisms in the water while they decompose organic matter. High BOD levels indicate that there is a high amount of organic material in the water, which can lead to oxygen depletion as microorganisms break it down, potentially harming aquatic life that depends on oxygen levels for survival. Therefore, BOD is an important indicator of water quality and the extent of organic pollution in rivers and other water bodies.