Comparison of the Vertical PM2.5 Distributions according to Atmospheric Stability Using a Drone during Open Burning Events

초록

Biomass burning in rural areas is one of the major particulate matter (PM) emission sources. Open burning events frequently occur during post- and pre-agricultural activities in early and late winter, resulting in high PM2.5 concentration episodes immediately near emission sources. We have investigated the wintertime vertical PM2.5 distribution on three open burning days and three non burning days in the morning in the lower atmospheric boundary layer according to atmospheric stabilities. A drone has been utilized to measure the vertical distributions of air temperature, PM2.5, BC (black carbon), and O-3 concentrations at 40, 80, 120, 160, 200, and 250 m heights in a rural area near an industrial complex. On open burning days, ground PM2.5 concentrations increased up to 169 mu g m(-3) at 9 AM while the closest urban PM2.5 concentration was only 33 mu g m(-3). On non burning days, the difference in ground PM2.5 concentrations at most 23 mu g m(-3). The PM2.5 on open burning days was accumulated in the stable boundary layer (below 80 m above ground level) at 8 and 9 AM in the morning due to the suppressed vertical mixing of emitted PM2.5. The vertical gradients of PM2.5 concentration, then, became reduced after solar heating on ground activates atmospheric mixing. Consequently, the atmospheric stability in the early morning plays an important role in vertical mixing of emitted PM2.5 and increasing ground PM2.5 concentrations during open burning events.

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