Which gas is responsible for the distinct "rotten egg" odor in many water sources?

The gas responsible for the distinct "rotten egg" odor in many water sources is hydrogen sulfide. This compound, which is produced by the anaerobic breakdown of organic material by bacteria, is characterized by its characteristic smell that is often likened to that of rotten eggs. In nature, hydrogen sulfide can be found in various environments, including sulfide-rich water sources and certain geothermal areas.

When it comes to drinking water, the presence of hydrogen sulfide can indicate the presence of certain types of bacteria that thrive in low-oxygen conditions, and it can be a sign of decaying organic matter. Additionally, high levels of hydrogen sulfide in water are not only unpleasant but can be indicative of deeper contamination issues, making it a critical focus in water quality assessments.

In contrast, carbon dioxide does not have any odor and is a naturally occurring gas involved in various biological processes. Chlorine gas is used as a disinfectant in water treatment processes and has a sharp, pungent odor, but it does not resemble the smell associated with hydrogen sulfide. Hydrogen carbonate, or bicarbonate, is anionic and plays a role in buffering systems in water, but it does not have a significant odor. Therefore, hydrogen sulfide is distinctly recognized for