Reduced Gas-Phase Kinetic Mechanism for Atmospheric Plume Chemistry

The subgrid-scale simulation of plume chemistry in three-dimensional air quality models can be computationally demanding. To minimize this computational burden, reduced kinetic mechanism for the gas-phase chemistry of power plant plumes is developed and validated against a full chemical kinetic mechanism. This reduced mechanism simulates plume chemistry according to three stages of the plume evolution: (1) A first stage where plume radical concentrations are negligible and plume chemistry is limited to four major reactions during the day and two at night. (2) A second stage where plume concentrations of OH and NO 3 radicals are sufficiently high to lead to significant formation of HNO 3 and H 2 SO 4 and which can be simulated with 30 reactions (or, alternatively, two different sets of 19 and 18 reactions for daytime and nighttime, respectively). (3) A third and final stage where VOC oxidation and O 3 formation become important, and the full chemical mechanism is required. For 10% accuracy in simulated plume concentrations, the reduced mechanism led to reductions in computational time of up to a factor of 3.