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USING THE REGIONAL ACID DEPOSITION MODEL TO DETERMINE THE NITROGEN DEPOSITION AIRSHED OF THE CHESAPEAKE BAY WATERSHED
Citation:
Dennis, R. USING THE REGIONAL ACID DEPOSITION MODEL TO DETERMINE THE NITROGEN DEPOSITION AIRSHED OF THE CHESAPEAKE BAY WATERSHED. U.S. Environmental Protection Agency, Washington, D.C., EPA/600/A-95/120 (NTIS PB96116819).
Description:
The Regional Acid Deposition Model, RADM, an advanced Eulerian model, is used to develop an estimate of the primary airshed of nitrogen oxide (NOx) emissions that is contributing nitrogen deposition to the Chesapeake Bay watershed. rief description of RADM together with a summary of the aggregation method used to develop annual average deposition is given. he evaluation background of RADM is summarized. he transport range of the nitrogen affecting deposition, principally the termination product nitric acid, is first established in the model. his range is compared to that determined for sulfur. urprisingly, the two are comparable. odel evaluation results and literature comparisons suggest the range of nitrogen influence computed for different source regions and a decision rule that diminishing returns start at distances where 50 to 70% of the deposition has fallen, the main airshed affecting the Chesapeake Bay watershed was defined. he shape of the airshed is irregular, stretched towards the Ohio River Valley, because of the influence of the prevailing winds. he size of the airshed is roughly 5.5 times larger than the watershed. ith 3096 of the eastern North American NOx emissions, the airshed explains 70% of the nitrogen deposition to the watershed. n addition, RADM is used to show that the main deposition influence of utility and mobile source Nox emissions are geographically separate.