Regional comparison between continuous emission monitoring (CEM) SO2 emissions and ambient SO4 concentrations from the US.
Time series are based on national IMPROVE network and CSN sites. Regions include the Far West, Southeast and Great Plains as examples. Numbers over the trend lines are the number of sampling sites included in the annual concentrations. Emissions data from EPA’s National Emissions Inventory (NEI) for states in a designated region. From Hand et al. (2012a), reprinted with permission.