Simulation of regional deposition patterns for N, S, and Hg species in the Pacific Northwest using the automated AIRPACT-3 air quality forecast system

In the Pacific Northwest, nitrogen and sulfur oxide emissions from anthropogenic sources exceed biogenic or natural emissions by more than a factor of five. Further, since the anthropogenic emissions are concentrated in the metropolitan areas, there is a clear chemical footprint that extends downwind from each major urban center. Along the I-5 corridor, these urban chemical footprints extend into the wilderness areas of the Cascade Mountains and into the Scenic River area of the Columbia Gorge. For mercury, a special situation exists in southern Idaho. A cluster of gold mining operations in Nevada represent a significant source of mercury emissions. These mines are generally upwind of southern Idaho. Limited monitoring data suggest that excessive levels of mercury occur in southern Idaho ecosystems, including several large reservoirs.

In this paper, the MM5/SMOKE/CMAQ modeling system implemented as the AIRPACT-3 air quality forecast system is used to provide preliminary analyses of deposition patterns for N, S, and Hg species within the Pacific Northwest. The analysis of the modeling products is being conducted in collaboration with the various groups involved in deposition measurement programs so that measurements can be used to help evaluate the accuracy of model output and, in turn, the model output can be used to help interpret measurements and enhance the use of measurements to explain local and regional deposition patterns.