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Impact of Clean Air Act Regulations on Nitrogen Fate and Transport in Neuse River Basin
Citation:
Gabriel, M., C. Knightes, R. Dennis, AND E. Cooter. Impact of Clean Air Act Regulations on Nitrogen Fate and Transport in Neuse River Basin. Presented at 2012 American Geophysical Union Conference, San Francisco, CA, December 03 - 07, 2012.
Impact/Purpose:
Presentation for 2012 AGU Fall Meeting.
Description:
This study investigated impacts of Clean Air Act Amendment (CAAA) NOx emissions regulations on the fate and transport of nitrogen for two watersheds in the Neuse River Basin, North Carolina, USA from 1990 to 2020. The Soil and Water Assessment Tool (SWAT) and the Community Multi-scale Air Quality (CMAQ) modeling system were used. CMAQ simulated atmospheric chemical transport and nitrogen deposition. This data was entered into SWAT which simulated watershed hydrology and water quality. Two cases were investigated: one that incorporates CAAA regulatory emissions controls in CMAQ simulation (with) and a second case that does not (without). SWAT model results forecasted a 70% decrease in inorganic nitrogen discharge from the Little River watershed and a 50% decrease for the Nahunta watershed by 2020 under the emission control (with) scenario. Denitrification and plant nitrogen uptake played important roles in nitrogen discharge from each watershed. The nitrogen discharge response time following a change in atmospheric nitrogen deposition was 4 years for the Nahunta watershed and 2 years for the Little River watershed. The longer response time for Nahunta is primarily due to a higher percentage of soybean land cover (22.5% [Nahunta]; 1.6% [Little River]). Agricultural land covers had varied nitrogen response times to changes in atmospheric deposition, particularly for soybean, hay and corn. The studied watersheds retained >80% of all nitrogen delivered by agriculture fertilization, biological fixation and atmospheric deposition.
