Biogenic Volatile Organic Compounds in Tropospheric Ozone Formation: Mechanisms, Uncertainties, and Implications for Air Quality

Abstract

Biogenic Volatile Organic Compounds (BVOCs), which are estimated to release 1000 TgC annually on a global scale, play an essential yet little known role in the formation of tropospheric ozone (O₃). Isoprene is the most important Biogenic Volatile Organic Compound (BVOC) and accounts for around 50 percent of all BVOC emissions through its oxidation reaction, which forms ozone under varying NOx levels at efficiency values between 0.5 and 10 O₃ molecules for each oxidized isoprene molecule. It is evident from recent studies that BVOCs are responsible for the creation of 11 percent to 19 percent of summer ozone levels in locations with abundant vegetation coverage, even though they account for 38 percent of VOC reactivity. Significant difficulties arise for scientists when they attempt to measure the response of emissions to the existence of several environmental stressors that cause autoxidation, leading to high levels of oxygenation of organic molecules. With the increase of temperature between 2 and 4 degrees Celsius due to global warming, isoprene emissions would be up by 30% to 60%, thus forming positive feedback loops. Given that there is a reduction in anthropogenic emissions worldwide, the role of BVOCs in the creation of ozone will prove challenging to air pollution control strategies. As such, the integration concept of this review highlights that the biogenic precursors must be incorporated in future air quality management strategies.

Keywords: Biogenic VOCs (BVOCs); Tropospheric ozone; Isoprene oxidation; NOx chemistry; Secondary organic aerosols (SOA); Atmospheric chemistry; Air quality; Climate feedback