Assessing Near-Field and Downwind Impacts of Reactivity-Based Substitutions

摘要

Three-dimensional chemical transport modeling of sixdifferent solvent substitution test scenarios was used toinvestigate possible transport effects of using volatile or-ganic compound (VOC) reactivity scales for air qualitymanagement purposes with a particular focus on thenortheastern United States. The primary issues analyzedare whether uses of reactivity-based substitutions ad-versely affect ozone concentrations downwind of the areain which they are applied and which reactivity scalesappear most appropriate for areas where ozone transportbetween multiple cities is significant. VOC substitutionscenarios were designed to assess biases in ozone metricsassociated with substituting relatively highly reactiveVOCs (as defined by the Maximum Incremental Reactiv-ity MIR scale) associated with solvent use with less reac-tive VOCs that might be considered as possible substi-tutes. Aiming to balance industrially realistic andscientifically relevant constraints, the set of solvent emis-sions to be substituted included toluene, isomers of xy-lene, 2-butoxyethanol by the surrogate, and lower reac-tivity compounds 2-methylheptane and n-butyl acetate.For a 14-day episode in August 2002, seven scenarios weremodeled including base-case emissions, removal of theselected higher reactivity solvent compounds, and substi-tution tests using the equivalent mass or equivalent reac-tivity-adjusted emissions based on the MIR and Maxi-mum Ozone Incremental Reactivity (MOIR) reactivityscales. Results show that downwind increases in ozoneconcentrations are noticeable for the MIR-based substitu-tion test scenarios although sensitivities demonstrate thatthese could be used to complement oxides of nitrogen (N0x) controls. However, using the MOIR-scaled substi-tution test scenario led to results that were less biased, andthe population-weighted metric showed little bias com-pared with the base case. Temporally and spatially exten-sive decreases are evident with the solvent mass substitu-tion and the selected emissions removal test scenarios,supporting the conclusion that reactivity-based controlcan be used to regionally reduce ozone.