Title: background concentration
Long Title: IUPAC Gold Book - background concentration
DOI: 10.1351/goldbook.B00578
Status: current

Definition
The concentration of a given species in a pristine air mass in which anthropogenic impurities of a relatively short lifetime are not present. The background concentrations of relatively long-lived molecules, methane, carbon dioxide, halocarbons ($\ce{CF3Cl}$, $\ce{CF2Cl2}$, etc.) and some other species continue to rise due to anthropogenic input, so the composition of background air is undergoing continual change. Background concentration of a given species is sometimes considered to be the concentration of that impurity in a given air mass when the contribution from anthropogenic sources under study is absent. Synonymous with baseline concentration.

Related Term
- lifetime: https://goldbook.iupac.org//terms/view/L03515

Source
- PAC, 1990, 62, 2167. 'Glossary of atmospheric chemistry terms (Recommendations 1990)' on page 2175 (https://doi.org/10.1351/pac199062112167)

Other Outputs
- html: https://goldbook.iupac.org/terms/view/B00578/html
- json: https://goldbook.iupac.org/terms/view/B00578/json
- xml: https://goldbook.iupac.org/terms/view/B00578/xml

Citation: Citation: 'background concentration' in IUPAC Compendium of Chemical Terminology, 5th ed. International Union of Pure and Applied Chemistry; 2025. Online version 5.0.0, 2025. 10.1351/goldbook.B00578
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Accessed: 2026-05-27T14:51:34+00:00