Institute of Ecosystem Studies

2007 BES Annual Meeting Presentation and Poster Abstracts


Testing Hypotheses Regarding Nitrate Deposition Patterns and NOx Sources to Landscapes Using Stable Isotope Techniques
 
Elliott, Emily M.
Co-Authors: Kendall, Doug A. Burns, Elizabeth W. Boyer, Karen Harlin
 
Abstract: While contemporary global inputs of NOx are dominated by fossil fuel combustion from stationary and vehicular sources, the fate of these emission remains ambiguous. Most often, deposition estimates from national deposition networks, including the NADP NTN, are assumed to reflect the combination of nitrogen deposition from stationary and mobile sources. We present results from a regional-scale study of nitrogen isotopes (d15N) in wet nitrate deposition across 33 sites in the Midwestern and Northeastern USA. We demonstrate that spatial variations in d15N are strongly correlated with NOx emissions from surrounding stationary sources, and further that d15N is more strongly correlated with surrounding stationary source NOx emissions than pH, SO42- or NO3- concentrations. Although emission inventories indicate that vehicle emissions are the dominant NOx source in the eastern USA, our results suggest that wet NO3- deposition at the study sites is strongly associated with NOx emissions from stationary sources. These findings indicate that spatial and temporal patterns in d15N can be a robust indicator of the influence of stationary source NOx emissions and a strong complement to existing tools for assessing relationships between NO3- deposition and regional emission inventories. Moreover, these findings have important implications for urban areas. In particular, our results suggest that deposition to urban areas may be significantly underestimated and highlight the need for atmospheric deposition in urban areas to be further characterized.