Levy II, H., J. J. Yienger, W. J. Moxim, P. S. Kasibhatla, and W. L. Chameides, 1995: The increase of pollutants (nitrogen oxides and ozone) in the summertime Midwest. In Preparing for Global Change: A Midwestern Perspective, Amsterdam; The Netherlands: SPB Academic Publishing, 11-19.

Abstract: We use the Geophysical Fluid Dynamics Laboratory (GFDL) Global Chemical Transport Model, with the six known sources for tropospheric NO_x and off-line calculations of daytime gas-phase nitrogen photochemistry and night-time heterogeneous chemistry, to simulate the summertime concentrations of reactive nitrogen compounds for pre-industrial, current and future emission scenarios. The simulated levels are less than 0.5 ppbv throughout the Midwest during the pre-industrial period. For present conditions, the simulated NO_x levels range from [1.5 - 2 ppbv] in the west to [5-10 ppbv] in the east and are in reasonable agreement with summertime measurements in Bondville, Illinois. We predict that NO_x levels will increase another 30% by 2020.

Using a simple relationship that relates NO_y and NO_x concentrations to the net chemical production of ozone at rural sites (Trainer et al. 1993), we estimate, conservatively, that the ozone, which was at relatively harmless levels in the pre-industrial period, is now at the crop-damage threshold of 50-70 ppbv in parts of Illinois, Indiana and Ohio. Furthermore, we estimate that this threshold will be reached throughout most of the Midwest east of the Mississippi River and even exceeded in parts of Illinois, Indiana, and Ohio by the year 2020, unless the continued increase in midwestern nitrogen fertilizer application and fossil fuel combustion ceases.