Spurengasen

Spurengasen, or trace gases, are atmospheric constituents that occur in much smaller amounts than the major components nitrogen (N2) and oxygen (O2). Despite their low abundances, they collectively influence climate, air quality, and atmospheric chemistry. Trace gases include carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), ozone (O3), carbon monoxide (CO), sulfur dioxide (SO2), and numerous halogenated and organic compounds. Mixing ratios are typically expressed in parts per billion or parts per million, with CO2 around 400 parts per million and CH4 around 1–2 parts per million in recent years, and many other gases in the ppb–ppt range.

Origin and sinks: Spurengasen originate from natural processes such as volcanic activity, wildfires, microbial metabolism in soils and oceans, and plant and animal respiration, as well as from human activities including fossil-fuel combustion, agriculture, waste management, and industrial production. They are removed from the atmosphere through chemical reactions, uptake by oceans and terrestrial ecosystems, and deposition to surfaces. Lifetimes span days to centuries, making many trace gases useful tracers of specific sources and processes.

Role in climate and chemistry: Some spurengasen are greenhouse gases that trap infrared radiation and contribute to radiative forcing. Others participate in catalytic cycles that create or destroy ozone; for example, NOx and certain volatile organic compounds influence tropospheric ozone formation, while halogenated compounds affect stratospheric ozone. The hydroxyl radical budget, which governs the atmospheric lifetime of many gases, is sensitive to trace gas concentrations and shapes overall atmospheric chemistry.

Measurement and use: Trace gas concentrations are monitored by ground-based networks, airborne campaigns, flask sampling, and satellite remote sensing. Units include ppm, ppb, and ppt, with calibration and intercomparison coordinated by international programs such as the WMO Global Atmosphere Watch. Data on spurengasen support climate research, pollution tracking, and policy decisions on emissions.