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 PM_2.5 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 > 70 ppb 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 PM_2.5 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 ± 9 ppb, 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.