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Evaluation of Regional Model Predictions of Secondary Organic Aerosol from Aromatic Compounds and Monoterpenes with Precursor-Specific Tracers
JIE ZHANG, Xiao He, Yaqin Gao, Shuhui Zhu, Shenggao Jing, Hongli Wang, Jian Zhen Yu, Qi Ying, Texas A&M University
Abstract Number: 287
Working Group: Carbonaceous Aerosol
Abstract
The Community Multiscale Air Quality (CMAQ), with modifications to track precursor-specific SOA, was applied to model SOA formation from aromatic compounds and monoterpenes in Shanghai in November 2018. The modeled aromatic SOA showed a moderate correlation with measured 2,3-dihydroxy-4-oxopentanoic acid (DHOPA) concentrations in the ambient aerosols (R~0.4 for hourly data and R~0.5 for daily average data). The ratios of DHOPA and modeled aromatic SOA using robust regression are approximately 1-3×10-3 when SOA from aromatic glyoxal (GLY) and methylglyoxal (MGLY) is excluded, which is comparable to the average tracer-to-aromatics SOA ratio of 2.3±1.2×10-3 determined in the chamber studies. This indicates that the model can reasonably predict aromatic SOA. The ratio is around 0.5-1×10-3 with GLY and MGLY SOA included, suggesting that tracer-based aromatics SOA estimations need to be ad-justed to account for the SOA from the secondary GLY and MGLY. The predicted monoterpene SOA shows a stronger correlation with the sum of two α-pinene tracers (α-pinT), pinic acid and 3-MBTCA, with R=0.5 and 0.6 for hourly and daily data, respectively. The α-pinT to modeled monoterpene SOA ratios are 0.11-0.16, which generally match the ratio of 0.168±0.081 reported in chamber studies. However, since the current model does not treat α-pinene and its SOA explicitly, future modeling studies should include a more detailed treatment of monoterpene emis-sions and reactions so that the predicted SOA from these important precursors can be directly compared with the ambient precursor-specific SOA-tracers.