The Identification of Deposition “Hotspots,” an Enhancement to the Critical Loads Approach

Bruce B. Hicks
Earth Resources Technology, Inc.
10810 Guilford Road, Suite 105
Annapolis Junction, MD 20701

Critical loads are a product of Eulerian modeling. They apply to grid cell averages. Given sufficient computer power, these grid cells can be made as small as one likes. However, weather forecasting and mesoscale meteorological experience indicates that there is a lower limit, below which increasingly fine detail does not improve the predictions. In fact, and depending on the circumstances, the consequences may be in the opposite direction. The net result is that critical loads for areas less than about 10 km2 will be hard to defend. An alternative approach that shows considerable initial promise is to employ Lagrangian methods. Instead of using grid size averages to describe average exposure regimes, consider instead those areas most likely to be adversely affected by deposition. Such areas can be identified using existing data bases in a GIS framework. Once such “hotspots” are identified, straightforward Lagrangian methods can be used to assess the relative contributions due to potentially offending sources, such as power plants or other industrial complexes. The methods involved have been tested for the case of western Maryland – Garratt and Alleghany Counties. Maps showing expected hotspots have been constructed. A related question appears well worth consideration: Does the ability to identify such hotspots permit a new monitoring focus on those biomes most at risk?

This work was supported by the Maryland Department of Natural Resources through a contract with Environmental Resources Management, Inc.

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