Marginal PM: Nonlinear Aerosol Mass Response to Sulfate Reductions in the Eastern United States.

Reductions in airborne sulfate concentration may cause inorganic fine particulate matter (PM) to respond nonlinearly, as nitric acid gas may transfer to the aerosol phase. Where this occurs, reductions in sulfur dioxide (SO) emissions will be much less effective than expected at reducing PM. As a measure of the efficacy of reductions in sulfate concentration on PM , we define marginal PM as the local change in PM resulting from a small change in sulfate concentration.