REDUCED GAS-PHASE KINETIC MECHANISMS FOR ATMOSPHERIC PLUME CHEMISTRY

The subgrid-scale simulation of plume chemistry in three-dimensional a ir quality models can be computationally demanding. To minimize this c omputational burden, a reduced kinetic mechanism for the gas-phase che mistry of power plant plumes is developed and validated against a full chemical kinetic mechanism. This reduced mechanism simulates plume ch emistry according to three stages of the plume evolution: (1) A first stage where plume radical concentrations are negligible and plume chem istry is limited to four major reactions during the day and two at nig ht. (2) A second stage where plume concentrations of OH and NO3 radica ls are sufficiently high to lead to significant formation of HNO3 and H2SO4 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 requir ed. For 10% accuracy in simulated plume concentrations, the reduced me chanism led to reductions in computational time of up to a factor of 3 .