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ARS Home » Northeast Area » University Park, Pennsylvania » Pasture Systems & Watershed Management Research » Research » Publications at this Location » Publication #232583
Title: Using atmospheric chemistry and storm tracks to explain nitrate stable isotope variations in precipitation at a site in central Pennsylvania, USA

Author
item Buda, Anthony
item DEWALLE, DAVID - PENN STATE UNIV

Submitted to: Atmospheric Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/15/2009
Publication Date: 9/20/2009
Citation: Buda, A.R., DeWalle, D.R. 2009. Using atmospheric chemistry and storm track information to explain the variations of nitrate stable isotopes in precipitation at a site in central Pennsylvania, USA. Atmospheric Environment. 43(29):4453-4464.

Interpretive Summary: Atmospheric nitrogen deposition continues to threaten the integrity of sensitive terrestrial and aquatic ecosystems throughout the United States. We studied nitrate stable isotopes in precipitation at a site in central Pennsylvania in order to assess their utility as tracers of nitrogen from the atmosphere. Results showed considerable variation in nitrate isotope signatures during different seasons and within individual storm events. Findings demonstrate the importance of understanding nitrate isotope variability in wet deposition in order to improve efforts to track the fate of atmospheric nitrogen in the landscape.

Technical Abstract: Stable isotopes of NO3- (delta15N-NO3- and delta18O-NO3-) were monitored in precipitation at a central Pennsylvania site during six storm events in 2005 to determine whether information on atmospheric oxidants (e.g. O3, NO2, and NOx), and storm-tracks were capable of explaining observed seasonal and within-storm isotopic variations. Results showed that delta15N-NO3- and delta18O-NO3- in precipitation varied significantly during individual storm events. Seasonally, delta15N-NO3- and delta18O-NO3- in precipitation followed a pattern of depletion during the summer months and enrichment during the winter months. NO3- precursor concentrations and atmospheric oxidants were useful for explaining seasonal and within-storm variations of delta15N-NO3- for all six storm events as evidenced by negative relationships with NO2:NOx ratios and ozone (O3). In comparison, delta18O-NO3- was positively related to O3 in three dormant season storms, which suggested that the O3 oxidation pathway was important for producing the high delta18O-NO3- observed in wintertime precipitation. Storm track information was especially useful for describing differences in delta15N-NO3-. Cool-sector storms originating from the E/NE produced low delta15N-NO3- characteristic of automobile emissions, whereas warm-sector storms with tracks from the SW/S/SE produced high delta15N-NO3- characteristic of coal-fired emissions. Lightning also may have been an important source of atmospheric NO3- during two warm-sector thunderstorms. This study showed that (1) information about oxidant levels can be useful to predict seasonal and within-storm variations of NO3- stable isotopes in precipitation, and (2) knowledge of storm tracks (warm-sector versus cool-sector) may be important for determining sources of NO3- in wet deposition.