The water pollution in a river is not typically measured by the dissolved amount of chlorine, ozone, or nitrogen. Instead, the measurement commonly used to assess water pollution is the dissolved oxygen (DO) level in the water.

Dissolved oxygen refers to the amount of oxygen gas dissolved in water, which is essential for aquatic life and the overall health of the ecosystem. It is an important parameter to measure the quality of water and assess the level of pollution.

Low levels of dissolved oxygen in water indicate pollution and can lead to the degradation of aquatic habitats and harm to aquatic organisms. Various factors can contribute to the depletion of dissolved oxygen in water, including organic pollution, excessive nutrient input (such as nitrogen and phosphorus), and the presence of certain pollutants.

Monitoring dissolved oxygen levels helps in understanding the health of water bodies, identifying sources of pollution, and implementing appropriate measures to mitigate water pollution and protect the environment.