The relation between NO x emissions and precipitation NO 3− in the eastern USA

• Published in: Atmospheric environment (1994) Vol. 37; no. 15; pp. 2093 - 2104
• Main Authors: Butler, Thomas J, Likens, Gene E, Vermeylen, Francoise M, Stunder, Barbara J.B
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 2003
• Subjects: Acid deposition; Acid rain; Nitrogen deposition; Nitrogen oxide; Precipitation chemistry trends; Precipitation nitrate; Nitrogen oxide; Acid rain; Precipitation nitrate; Nitrogen deposition; Acid deposition; Precipitation chemistry trends
• ISSN: 1352-2310; 1873-2844
• DOI: 10.1016/S1352-2310(03)00103-1

Changes in total NO x emissions in the eastern USA have been relatively small through the 1990s, even with implementation of the Clean Air Act Amendments of 1990. The decreases in NO x emissions from the non-vehicle sectors have been significantly offset by increases from the vehicle sector. To quantify the impact of NO x emissions on precipitation NO 3 −, we used a random coefficient model. Regional NO x emission densities were regressed on NO 3 − concentrations in precipitation from 24 NADP/NTN and NADP/AIRMoN sites for precipitation chemistry in the northeastern and mid-Atlantic regions of the USA. These were areas where changes in NO x emissions have been the greatest. Total NO x , and non-vehicle NO x emissions have declined from 7% to 12% and 19% to 25%, respectively, from 1991 to 2000 in these regions. Different NO x source regions impacting particular sites were evaluated based on 12-, 24- and 36-h air mass back trajectories. A simple random coefficient model based on precipitation NO 3 − (dependent variable) and total NO x emissions (independent variable) showed a highly significant ( P-value<0.0001) relation for the source areas based on 12-h back trajectories. Using this model, a 50% decline in total NO x emissions from the appropriate source regions predicted an overall decline in precipitation NO 3 − concentration of 38%. A model based on non-vehicle NO x emissions as the independent variable predicted that a 50% decline in non-vehicle emissions, which is a 23% decline in total emissions impacting the area, results in a 19% decline in precipitation NO 3 − concentration. Similar results are found when source areas based on 24- and 36-h back trajectories are used. The several models evaluated, using the different-sized source regions and either total or non-vehicle NO x emissions, predict that reductions in NO x emissions should reduce NO 3 − concentrations (and deposition) with an efficiency ranging between 75% and 95%. It can be inferred that equivalent reductions (in terms of μeq l −1) in precipitation acidity will also occur.