Which substance is an indicator of water quality related to organic pollution?

The correct choice focuses on nitrogen as an indicator of water quality related to organic pollution. Nitrogen, particularly in the form of ammonium or nitrate, often indicates the presence of organic material because it is derived from the breakdown of organic matter. High levels of nitrogen in water bodies typically suggest that there is an influx of organic waste, such as sewage or runoff from agricultural activities, where fertilizers are used.

Assessing nitrogen levels helps in monitoring the effects of organic pollution because these compounds can lead to eutrophication, a process where excessive nutrients stimulate algal blooms, subsequently harming aquatic life. Understanding nitrogen levels is crucial in wastewater treatment and water quality assessment because managing organic pollutants often focuses on controlling nutrient loading to protect aquatic ecosystems.

Other substances like chlorine are often used as a disinfectant in water treatment and do not directly relate to organic pollution levels. Ammonia can indicate organic pollution as well, but nitrogen as a broader category encompasses various forms and their impacts. Phosphorus is also related to water quality but is more directly associated with algal growth rather than organic pollution specifically. Therefore, nitrogen serves as a more comprehensive indicator of overall water quality concerning organic pollution.