The chemical composition of ambient air has significant implications for human health and long-term weather. As we always breathe air, our fundamental curiosity to explore what is in the air justifies scientific investigations.  The NSF grant allowed us to evaluate an analytical technique to quantify the total amount of atmospheric reactive gases. The observable is called OH (hydroxyl radical) reactivity, notating the reciprocal of the atmospheric lifetime of OH.  Although these gases determine air quality as they are precursors in producing major air pollutants such as ozone and fine particles, it has long been speculated that we, as the scientific community, have yet to quantify the total amount completely. The laboratory characterization allows us to deploy the OH reactivity quantification system to the New York Metropolitan area as a part of the community field campaign.  The comparison with the observed trace gas dataset illustrates that the unmeasured reactive trace gas amount increases as ambient temperature increases. This is also when isoprene, a reactive biogenic volatile organic compound, and ozone concentrations were observed at elevated levels. The dataset provides a critical dataset to evaluate ozone photochemical production regimes in different temperature environments. The evaluation suggests that higher temperatures bring a physical and chemical environment with more efficient ozone production. We used a box model with detailed photochemical reaction mechanisms to predict ambient ozone levels in the area. Warmer weather will bring higher evaporative VOC emissions along with higher biogenic VOC emissions. At the same time, reactive nitrogen oxides (NO and NO2) emissions, mostly from combustion sources such as internal combustion engines, are expected to decrease. The detailed mechanistic analysis illustrates that the occurrence of high ozone episodes will most likely increase. This developed streamlined research framework, from experimental to computational methodologies, can be applied to other metropolitan areas, as our fundamental desire is to breathe cleaner air. 

Last Modified: 04/29/2025
Modified by: Saewung Kim