Meteorological effects on PM2.5 change over a receptor region in regional transport of air pollutants: observational study of recent year emission reduction in central China.

As an important issue in atmospheric environment, the contributions of anthropogenic emissions and meteorological conditions to air pollution have been few assessed over the receptor region in regional transport of air pollutants. In this study on observations of environment and meteorology over 2015-2019, the Kolmogorov-Zurbenko (KZ) filter was performed to decompose the PM_2.5 variations into multi-time scale components over the Twain-Hu Basin (THB), a receptor region in regional transport of air pollutants in central China, where the short-term, seasonal and long-term components accounted for respectively 47.5%, 41.4% and 3.7% to daily PM_2.5 changes. The short-term and seasonal components dominated the day-to-day PM_2.5 variations with long-term component determining the change trend of PM_2.5 concentrations over recent years. The emission- and meteorology-related long-term PM[sub 2.5] components over the THB were identified. The meteorological contribution to PM_2.5 declining trend presented the distinct spatial pattern over the THB with northern positive rates up to 61.92% and southern negative rates down to -24.93%. The opposite effects of meteorology on PM_2.5 pollution could accelerate and offset the effects of emission reductions in the northern and southern THB, which is attributed to the upwind diffusion and downward accumulation of air pollutants over the receptor region in regional PM[sub 2.5] transport. It is noteworthy that the increasing conversion efficiencies of SO₂ and NO₂ to sulfate and nitrate for secondary PM_2.5 could offset the effects of PM_2.5 emission reduction on air pollution in the THB during recent years, revealing the enhancing contribution of gaseous precursor emissions to PM_2.5 concentrations with controlling anthropogenic emissions of PM_2.5 and the gaseous precursors over the receptor region in regional transport of air pollutants. [ABSTRACT FROM AUTHOR]