Application of trajectory analysis to the assessment of local and long-range contributions to acidic deposition

Abstract.

Two methods of back trajectories have been applied for 14 precipitation events. One method consisted of a combination of isentropic and constant level trajectories. The second method consisted only of the constant level trajectory. For each method a long range and a local contribution to the chemistry of the precipitation was calculated. The long range contribution was calculated by taking into account the SO₂ an NO_x emissions in the areas of the mixed layers traversed by the trajectories, the diffusion, and the dry and wet depositions along the trajectories path. For the local contribution, local emissions and the dry deposition were taken into account. From these contributions expected values of sulfate and nitrate in the precipitation were calculated and these values compared with the observed ones. Results indicate that: a) the isentropic-constant level model is much better in estimating the measured concentrations of sulfate and nitrate in precipitation than the constant level mode, and b) the long range transport of precursors contributed more to the total concentration than the local emissions.