Smith Ellie N, Baker Kirk R, El-Sayed Marwa M H, Hennigan Christopher J, Rosanka Simon, Carlton Annmarie G
Department of Chemistry, University of California, Irvine, California 92617, United States.
Office of Research and Development, U.S. EPA, Research Triangle Park, North Carolina 27711, United States.
ACS Earth Space Chem. 2025 May 9;9(6):1501-1509. doi: 10.1021/acsearthspacechem.4c00379. eCollection 2025 Jun 19.
Prediction of gas-phase water-soluble organic carbon (WSOC), a precursor for secondary organic aerosol formed through processing in atmospheric waters (aqSOA), has not yet been evaluated in models. We pair the WSOC predictions from the U.S. EPA's Community Multiscale Air Quality (CMAQ) model with continuous mist chamber measurements during February-March 2015 and August 2016 in Baltimore County, MD. We simulate mist chamber collection of WSOC from CMAQ's atmosphere with application of compound-specific collection efficiencies as a function of Henry's law. CMAQ predictions of WSOC mass concentrations are highest in August, while measurements are highest during February-March. CMAQ does not replicate the average diurnal pattern of the measured WSOC in any month. The CMAQ prediction of directly emitted VOCs that oxidize to form WSOC is more reasonable, and the model skill for nitrogen dioxide (NO) and ozone (O) is relatively excellent in comparison ( = 0.5 and = 0.6, respectively; ≈ 0). These findings suggest that representation of organic gases and their chemistry in this CMAQ simulation is sufficient to accurately predict the criteria pollutants NO and O, but not necessarily the chemical transformations that produce WSOC, an important precursor for aqSOA.
气相水溶性有机碳（WSOC）是通过大气水相中反应生成二次有机气溶胶（aqSOA）的前体物，目前尚未在模型中对其预测进行评估。我们将美国环保署（U.S. EPA）社区多尺度空气质量（CMAQ）模型对WSOC的预测结果，与2015年2月至3月以及2016年8月在马里兰州巴尔的摩县进行的连续雾室测量结果进行了比对。我们利用特定化合物的收集效率作为亨利定律的函数，模拟了从CMAQ大气中收集WSOC的雾室实验。CMAQ对WSOC质量浓度的预测在8月最高，而测量值在2月至3月最高。CMAQ在任何月份都无法重现实测WSOC的平均日变化模式。CMAQ对氧化生成WSOC的直接排放挥发性有机化合物（VOCs）的预测较为合理，并且该模型对二氧化氮（NO）和臭氧（O）的模拟技能相对出色（分别为 = 0.5和 = 0.6； ≈ 0）。这些研究结果表明，在该CMAQ模拟中，有机气体及其化学过程的表征足以准确预测常规污染物NO和O，但不一定能预测产生WSOC（aqSOA的重要前体物）的化学转化过程。
