Figure 2

Average concentrations of NO2, PM2.5, and O3 over the Kansas state from 2000 to 2015 (from upper row to the lower row represent the average concentrations during 2000–2004, 2005–2009, 2010–2015 for three pollutants) as estimated by using spatiotemporal ensemble models, which utilized over one hundred predictors, integrated three machine learning algorithms, and achieved excellent model performance.