Updating the SAPRC Maximum Incremental Reactivity (MIR) scale for the United States from 1988 to 2010

Abstract

Ozone reactivity scales play an important role in selecting which chemical compounds are used in products ranging from gasoline to pesticides to hairspray in California, across the United States and around the world. The California Statewide Air Pollution Research Center (SAPRC) box model that calculates ozone reactivity uses a representative urban atmosphere to predict how much additional ozone forms for each kilogram of compound emission. This representative urban atmosphere has remained constant since 1988, even though more than 25 years of emissions controls have greatly reduced ambient ozone concentrations across the United States during this time period. Here we explore the effects of updating the representative urban atmosphere used for ozone reactivity calculations from 1988 to 2010 conditions by updating the meteorology, emission rates, concentration of initial conditions, concentration of background species, and composition of volatile organic compound (VOC) profiles. Box model scenarios are explored for 39 cities across the United States to calculate the Maximum Incremental Reactivity (MIR) scale for 1,233 individual compounds and compound-mixtures. Median MIR values across the cities decreased by approximately 20.3% when model conditions were updated. The decrease is primarily due to changes in atmospheric composition ultimately attributable to emissions control programs between 1998 and 2010. Further effects were caused by changes in meteorological variables stemming from shifting seasons for peak ozone events (summer versus early fall). Lumped model species with the highest MIR values in 1988 experienced the greatest decrease in MIR values when conditions were updated to 2010. Despite the reduction in the absolute reactivity in the updated 2010 atmosphere, the relative ranking of the VOCs according to their reactivity did not change strongly compared to the original 1988 atmosphere. These findings indicate that past decisions about ozone control programs remain valid today, and the ozone reactivity scale continues to provide relevant guidance for future policy decisions even as new products are developed. Implications: Updating the representative urban atmosphere used for the Maximum Incremental Reactivity (MIR) scale from 1988 to 2010 conditions caused the reactivity of 1223 individual compounds and combined mixtures to decrease by an average of 20.3% but the relative ranking of the VOCs was not strongly affected. This means that previous guidance about preferred chemical formulations to reduce ozone formation in cities across the United States remain valid today, and the MIR scale continues to provide relevant guidance for future policy decisions even as new products are developed.

Predicted ultrafine particulate matter source contribution across the continental United States during summertime air pollution events

“…1). These cities have been used to characterize atmospheric reactivity across the US in previous air pollution studies (Carter, 1994(Carter, , 2010Venecek et al, 2018a, b). Simulations within each target city were carried out during peak summer air pollution events in 2010.…”

Traffic, transport, and vegetation drive VOC concentrations in a major urban area in Texas

“…Several studies have used chamber experiments, mathematical models, and parameters such as the maximum incremental reactivity to investigate the O 3 production potential of select VOCs (Hakami et al, 2004;Huang et al, 2008;Kansal, 2009). These studies have shown that the contribution of a specific VOC to O 3 formation depends both on its intrinsic reactivity and its abundance and emission strength J o u r n a l P r e -p r o o f Journal Pre-proof (Kansal, 2009;Venecek et al, 2018). The O 3 production model based on inorganic trace gas and VOCs, including those discussed in detail herein, showed that the OH reactivity of formaldehyde, isoprene and alkenes were amongst the highest in San Antonio (Guo et al, 2021).…”

VOCs Fugitive Emission Characteristics and Health Risk Assessment from Typical Plywood Industry in the Yangtze River Delta Region, China

“…The fugitive emission of VOCs in workshops can release into the outdoor air, which could impact the secondary formation of ambient ozone. The OFP values for individual VOC species are calculated as the product of their concentration and maximum incremental reactivity (MIR) reported from the literature [29]. Figure 4a shows the OFP values and chemical composition of VOCs emitted from the adhesive-making, adhesive-coating, and hot-pressing processes in the plywood manufacturing industry.…”