Contributions of Kansas rangeland burning to ambient O3: Analysis of data from 2001 to 2016.

Prescribed range/pasture burning is a common practice in Kansas to enhance the nutritional value of native grasses and control invading weeds, trees, and brush. A major concern associated with the burning is the contribution of smoke to elevated ground level ambient ozone (O3). The objective of this study is to estimate contributions of Kansas rangeland burning to ambient O3 mixing ratios through regression analysis (1) between observed O3 data and available satellite burn activity data from 2001 to 2016; and (2) between observed O3 data and the smoke contributions to PM2.5 which were resolved from receptor modeling. Positive correlations were observed between ambient O3 levels and the acres burned each year estimated from satellite imagery. When burned acres in April were larger than or equal to 1.9 million, O3>70ppb occurred at least at one of the ten monitoring sites in Kansas. Statistical regression models of daily maximum 8-hour O3 mixing ratios were developed at each of the ten monitoring sites using meteorological predictors. The O3 model residuals that were not explained by the meteorological effect models were affected by PM2.5 contributors including sulfate/industrial sources and emissions that generated secondary organic particles, such as rangeland burning, which were derived from receptor modeling. The average O3 model residual on the high O3 days in April was 21±9ppb, which was likely associated with smoke emissions from burning. Research will continue to obtain daily satellite burn activity data and to correlate burn data with daily O3 data, so that modeling of O3 levels can be improved under influences of daily burn activities. Less frequency of high O3 days was observed in April since 2011, which may be partly due to implementation of the Flint Hills Smoke Management Plan which promoted better timing of burns.