Estimation of source-receptor matrices for deposition of NO_x-N

Abstract

The contributions of the anthropogenic sources of NO_x from various combinations of contiguous U.S. states or Canadian provinces to integrated deposition across selected states or provinces are estimated with the Advanced Statistical Trajectory Regional Air Pollution (ASTRAP) model. The model assumes linearity between emissions and deposition, and uses the same parameterization methods, although with different rates, as in simulations of transport and deposition of SO_X. Vertical distributions of emissions for the two classes of pollutants are substantially different in the gridded inventories used in simulations, with a weighted mean effective emission height of 160 m for NO_X and 310 m for SO_X. This might be expected to lead to an effective transport distance before deposition shorter for NO_X than for SO_X. However, the calculated fraction of NO_X emissions deposited within the contiguous United States and Canada south of 60 deg N (57%) is not greatly different from the fraction calculated for SOX emissions (54%). This suggests that there may be compensating factors in the horizontal distribution of NO_X emissions, and in the lower dry deposition velocities for NO/NO₂ than for SO₂ in ASTRAP.