Atmospheric input of nitrogen to the coastal region of southeastern Texas

Abstract

inorganic nitrogen (DIN; NH4+, N03-), and dissolved organic nitrogen (DON) were measured in rainwater collected at three sampling sites (College Station, Houston, and Galveston, Texas). Dry deposition rate of nitrogen species was also measured in College Station. Concentrations of major ions, DIN, and DON in wet deposition samples collected in College Station depended on surface wind direction. High concentrations of most major ions in wet deposition correlated with winds from the northwest. In contrast, concentrations of DIN and DON from southern wind sectors (SE, S, SW, and W) were higher than those from northern wind sectors (NW, N, NE, and E). Anthropogenic sources significantly contributed to atmospheric nitrogen over Houston and this enhanced nitrogen affected the concentration of nitrogen species in College Station rain when the air mass came from the southern direction. In the coastal region (Galveston), concentrations of DIN and DON were significantly affected by marine sources, which diluted atmospheric nitrogen with sea-salt aerosol particles. Mean concentration and flux of DIN in College Station were 32.16︢3.4 limol I-I and II 81︢13 @Mol M-2 day-1, respectively. The mean concentration and flux of DON in College Station were 35.31︢04.7 gmol 1-1 and 1312︢47 IIMOI M-2 day-', respectively. These values were similar for DIN and DON. The isotopic data of rain nitrate and ammonium showed that the surface wind direction was a significant factor influencing