Which gases are commonly found in water?

Which gases are commonly found in water?

• A. Oxygen and Nitrogen
• B. Hydrogen sulfide (H2S), Carbon dioxide (CO2), Methane (CH4)
• C. Argon and Neon
• D. Ammonia and Chlorine

Answer: (B)

Dissolved gases in water come from two main sources: exchange with the atmosphere and biological/chemical processes in the water and sediments. Carbon dioxide is universally present because it readily dissolves from the air and forms carbonic acid, so CO2 is a very common dissolved gas in water. In environments without oxygen, microorganisms break down organic matter and produce gases like methane and hydrogen sulfide. Methane appears in anaerobic settings such as sediments or groundwater, while hydrogen sulfide forms where sulfate-reducing bacteria are active. So CO2, CH4, and H2S together reflect the typical range of gases you’d encounter dissolved in natural waters under different conditions. The other options aren’t as representative: noble gases like argon and neon occur only in trace amounts, not typically discussed as common dissolved gases; ammonia and chlorine may appear in water under certain conditions but aren’t as universally or routinely present as CO2, CH4, and H2S.

Dissolved gases in water come from two main sources: exchange with the atmosphere and biological/chemical processes in the water and sediments. Carbon dioxide is universally present because it readily dissolves from the air and forms carbonic acid, so CO2 is a very common dissolved gas in water. In environments without oxygen, microorganisms break down organic matter and produce gases like methane and hydrogen sulfide. Methane appears in anaerobic settings such as sediments or groundwater, while hydrogen sulfide forms where sulfate-reducing bacteria are active. So CO2, CH4, and H2S together reflect the typical range of gases you’d encounter dissolved in natural waters under different conditions.

The other options aren’t as representative: noble gases like argon and neon occur only in trace amounts, not typically discussed as common dissolved gases; ammonia and chlorine may appear in water under certain conditions but aren’t as universally or routinely present as CO2, CH4, and H2S.