The trace gases glyoxal (CHOCHO) and formaldehyde (HCHO) are formed during the oxidation of volatile organic compounds (VOC). They have short lifetimes so their distribution mainly resembles the source areas and can be used as indicators of tropospheric VOC emissions. In the presence of nitrogen oxides, the photochemical degradation of volatile organic compounds (VOC) leads to secondary gaseous and particulate products, such as ozone and secondary organic aerosols (SOA). Both are important contributors to air pollution with severe impacts on human health, ecosystems, and regional climate.

Sources of Formaldehyde include natural and Anthropogenic sources. Natural sources include: biomass combustion (forest and bush fires), biomass decomposition, through volcanic eruptions and more. Anthropogenic sources include on-site industrial emissions, fuel combustion from traffic, and other combustion processes e.g. power plants and incineration. Formaldehyde can also be found indoors as it is extensively produced industrially worldwide for use in the manufacture of resins, as a disinfectant and fixative, or as a preservative in consumer products, or released during combustion processes such as smoking, heating, cooking, or candle or incense burning. Formaldehyde can be an irritant of skin, eyes, nose, and throat and some authorities consider formaldehyde to increase the risks of certain types of cancer in people.

CHOCHO and HCHO can be measured with the TROPOMI sensor aboard Sentinel-5p and the first global measurements were taken with SCHIMACHY aboard Envisat in 2006.

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Featured Educator

• Dr Andreas Richter, Senior Scientist, University of Bremen