Total Ozone Reactivity Measurements Reveal Knowledge Gap in Volatile Organic Compound Emissions and Their Reactions

Total ozone (O 3 ) reactivity monitors (TORMs) were used to investigate biogenic volatile organic compound (BVOC) emissions from several ecosystems. Measurements were conducted in temperate deciduous North American forests, during the CABINEX and SOAS campaigns, on tundra vegetation emissions at Toolik lake field station (TFS) in Alaska, and in a boreal fen in Finland. Deciduous tree emissions produced up to six times higher O 3 loss than emissions from conifers. Emissions from the fen resulted in maximum O 3 loss values comparable to deciduous tree emissions, whereas emissions from Arctic tundra ground vegetation generated the smallest signals. Across all ecosystems, the O 3 loss expected from the reactions with identified BVOCs was consistently lower than the directly measured O 3 loss rate measured with TORM during midday emission peaks. On average, calculated losses from identified BVOCs accounted for 10–60% of the directly measured O 3 loss, depending on vegetation type and time of day. Measurement uncertainties explain only part of this discrepancy, leaving a substantial fraction of the observed signal unaccounted for. Additional uncertainty may arise from oxidation chemistry not captured by the BVOC‐O 3 reaction rate constants. These findings highlight the need for further research on O 3 ‐BVOC reactivity across ecosystems to better characterize emissions, their impacts on atmospheric chemistry, and especially their chemical diversity that is rarely captured exhaustively due to limitations of analytical methods.