Sensitivity of fine particulate matter concentrations in South Korea to regional ammonia emissions in Northeast Asia
2021
Kim, Eunhye | Kim, Byeong-Uk | Kim, Hyun Cheol | Kim, Soontae
Ammonia (NH₃) is an important precursor for forming PM₂.₅. In this study, we estimated the impact of upwind transboundary and local downwind NH₃ emissions on PM₂.₅ and its inorganic components via photochemical grid model simulations. Nine sensitivity scenarios with ±50% perturbations of upwind (China) and/or downwind (South Korea) NH₃ emissions were simulated for the year 2016 over Northeast Asia. The annual mean PM₂.₅ concentrations in the downwind area were predicted to change from −3.3 (−18%) to 2.4 μg/m3(13%) when the NH₃ emissions in the upwind and downwind areas were perturbed by -50% to +50%. The change in PM₂.₅ concentrations in the downwind area depending on the change in NH₃ emissions in the upwind area was the highest in spring, followed by winter. This was mainly attributed to the change in nitrate (NO₃⁻), a secondary inorganic aerosol (SIA) that is a predominant constituent of PM₂.₅. Since NH₃ is mainly emitted near the surface and vertical mixing is limited during the night, it was modeled that the aloft nitric acid (HNO₃)-to-NO₃⁻ conversion in the morning hours was increased when the NH₃ accumulated near the surface during nighttime begins to mix up within the Planetary Boundary Layer (PBL) as it develops after sunrise. This implies that the control of upwind and/or downwind NH₃ emissions is effective at reducing PM₂.₅ concentrations in the downwind area even under NH₃ rich conditions in Northeast Asia.
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