Abstract
In this study, we examined how modeled ozone concentrations respond to changes in anthropogenic emissions when different modeled emissions of biogenic volatile organic compounds (BVOCs) are used. With biogenic emissions estimated by the Model of Emissions of Gases and Aerosols from Nature (MEGAN) and the Biogenic Emissions Inventory System Version 3 (BEIS3), the Community Multi-scale Air Quality with the High-order Direct Decouple Method (CMAQ-HDDM) simulations were conducted to acquire sensitivity coefficients. For the case study, we chose 17–26 August 2007, when the Southern Korean peninsula experienced region-wide ozone standard exceedances. The results show that modeled local sensitivities of ozone to anthropogenic emissions in certain NOx-saturated places can differ significantly depending on the method used to estimate BVOC emission, with an opposite trend of ozone changes alongside NOx reductions often shown in model runs using MEGAN and BEIS3. Findings of increased ozone concentrations with one model and decreased ozone concentrations with the other model implies that estimating BVOCs emissions is an important element in predicting variability in ozone concentration and determining the responses of ozone concentrations to emission changes, a discovery that may lead to different policy decisions related to air quality improvement. Quantitatively, areas in the 3-km modeling domain that experienced daily maximum one-hour ozone concentrations greater than 120 ppb (MDA1O3) showed differences of over 20 ppb in MDA1O3 values between model runs with MEGAN and BEIS3. For selected monitoring sites, the maximum difference in relative daily maximum eight-hour ozone concentrations (MDA8O3) response between the methods to model BVOCs was 4.2 ppb in MDA8O3 when we adopted a method similar to the Relative Reduction Factor used by the US Environmental Protection Agency (EPA).
Highlights
Ozone, a persistent and prevalent urban air pollutant, imposes significant health burdens around the world, including respiratory diseases [1,2,3]
We used the Community Multi-scale Air Quality (CMAQ) model, and compared two sets of simulated ozone concentrations and sensitivities to changes in anthropogenic emissions, using biogenic emissions estimated with MEGAN and Biogenic Emissions Inventory System Version 3 (BEIS3)
30% reduction in anthropogenic nitrogen oxides (NOx) across the 3-km domain would result in a slight decrease in ozone in Gwangju at 5 PM on 17 August 2007 while CMAQ-BEIS3 estimated that the same reduction (A) contrasting sensitivities of ozone in high NOx would lead to about a 5 ppb increase in ozone
Summary
A persistent and prevalent urban air pollutant, imposes significant health burdens around the world, including respiratory diseases [1,2,3]. The uncertainties in estimated isoprene emissions can be large enough to change the modeled response of ozone to reductions in anthropogenic emissions, both quantitatively and directionally [11,23,24,25]. It remains unclear which model is generally the best, in Northeast Asia. We used the Community Multi-scale Air Quality (CMAQ) model, and compared two sets of simulated ozone concentrations and sensitivities to changes in anthropogenic emissions, using biogenic emissions estimated with MEGAN and BEIS3. For the response of ozone concentrations to changes in anthropogenic precursors, we examined absolute changes in ozone concentration as well as relative response, following an approach similar to the US EPA’s Relative Reduction Factor (RRF) method to project design values for regulatory modeling
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