Contribution of Kansas pasture burning to ambient ozone: a combination of receptor modeling, time series and regression analysis

Abstract. Prescribed pasture burning is a long-standing practice in the Flint Hills region of eastern Kansas used to maintain the tallgrass prairie ecosystem, and most burning occur in April. The smoke plumes originating from these fires increases ambient PM_2.5 concentrations and potentially contributed to ozone (O₃) exceedances in downwind communities. Our source apportionment research using Unmix modeling has successfully unraveled the source profiles of Kansas pasture burning and demonstrated that burning activities contributed 39% of the average PM_2.5 concentration in April. The objective of this work is to investigate the potential correlations between O₃ and various sources of PM_2.5 that are derived from the Unmix modeling, and to specifically estimate contributions of Kansas pasture burning to ambient O₃ concentrations. The study utilized data from routine monitoring networks that provide long-term observations (2002-2014) of ambient concentrations of PM_2.5 (including chemical speciation) and O₃. 8-h daily maximum O₃ concentration data was . Multiple linear regression models were then be used to correlate the deseasonalized O₃ concentrations to the daily source contributions of PM_2.5 as well as weather conditions. The final O₃ regression model had an r² of 0.75 between measured and modeled O₃ concentrations. The O₃ concentrations were significantly affected by total solar radiation, precipitation, and air temperature. And they were partially correlated with the S3-secondary organic aerosol and S4-sulfate/industrial of the PM_2.5 sources. It can be estimated that prescribed rangeland burning contributed about 2.3 ppb or 4.5% of the average 8-h daily maximum O₃ concentration in April (51.3ppb).