Which is the most abundant hydrocarbon in the atmosphere?

Concept

A hydrocarbon is a compound made only of carbon and hydrogen. Atmospheric abundance is compared by the amount of each compound present in air, usually expressed as a mixing ratio.

This distinction is unrelated to a compound's toxicity, emission source, or physical state. A long-lived gas that is mixed nearly uniformly through the atmosphere can be more abundant than short-lived volatile organic compounds.

Application

Methane is a one-carbon hydrocarbon and a long-lived gas distributed globally through the atmosphere. Its concentration is on the parts-per-million scale; common non-methane hydrocarbons such as ethane and benzene occur at far lower trace levels.

Contrast

• Methane: a specific gaseous alkane that is globally distributed in the atmosphere.

• Benzene: a specific aromatic hydrocarbon found mainly as a much lower-level volatile pollutant.

• Ethane: a specific two-carbon alkane present as a lower-level non-methane hydrocarbon.

• Acetylene: a specific two-carbon unsaturated hydrocarbon that occurs at lower trace levels in the atmosphere.

Cross-check

Atmospheric monitoring treats methane as a major globally distributed gas, while benzene, ethane, and acetylene are measured among trace volatile or non-methane hydrocarbons. The comparison therefore identifies methane as the most abundant offered hydrocarbon.

Result

The most abundant hydrocarbon in the atmosphere is methane.