An Investigation on NH3 Emissions and Particulate NH4+ - NO3- Formation in East Asia

In this study, the accuracy of NH3 emissions in East Asia is evaluated by comparing measured and predicted NH4NO3 concentrations. For the predictions of particulate NH4NO3 concentrations, USEPA Models-3/CMAQ (Models-3/ Community Multi-scale Air Quality) model is used in this study. The measurement data are collected from 4 ground-based stations (Beijing, Shanghai, Qingdao, and Kangwha) and ACE-ASIA C130 Flights #6, #7, and #10. The 4 ground-based stations and air flight tracks are located in and around Yellow Sea in East Asia. According to the results, the predicted fine-mode NH4+concentrations are 1.2-3.8 times overestimated compared to measured fine-mode NH4+ concentrations, and fine-mode NO3- concentrations are 1.9-7.6 times overestimated. Since the fine-mode NO3- concentration can be a good proxy concentration of gas-phase NH3, it can be estimated that the gas-phase NH3 concentrations and the NH3 emissions are likely 1.9-7.6 times overestimated in East Asia. Based on the conclusion of this study, it is recommended that approximately 50-80% reduced NH3 emission fields should be used in the future modeling studies for East Asia.