Atmospheric nitrogen deposition to Barnegat Bay

To characterize atmospheric nitrogen deposition to Barnegat Bay, measurements of nitrate and ammonium were made, both in precipitation and in aerosol particulate matter, at coastal Tuckerton in southern New Jersey from February 1999 to February 2001. Results show that the concentrations of nitrate and ammonium in the ambient air exhibit strong temporal variation. The concentrations in precipitation ranged from 2.26 to 84.6 μmol l−1 (mean: 29.1 μmol l−1) for nitrate and from 0.625 to 107 μmol l−1 (mean: 18.3 μmol l−1) for ammonium. Most of the pH values in precipitation fall below 4.5, suggesting an acidic nature for precipitation. The low spring-time mean δ15N values in rain for both ammonium (−4.6‰) and nitrate (−6.03‰) indicate that increased agricultural and soil emissions as well as anthropogenic emissions contribute to atmospheric nitrate and ammonium. The average concentrations in the aerosol phase were 2.04 μg m−3 for nitrate and 0.497 μg m−3 for ammonium. High concentrations of aerosol nitrate were associated with both submicrometer and supermicrometer particles, while aerosol ammonium was primarily concentrated on particles of 0.5 μm in diameter. High wet deposition rates of nitrate and ammonium were observed during the summer in both 1999 and 2000, with average summer-time rates of 4.12 mmol m−2 month−1 for nitrate and 3.18 mmol m−2 month−1 for ammonium. On an annual basis, the total atmospheric deposition rates were 32.9 mmol m−2 yr−1 for nitrate and 20.3 mmol m−2 yr−1 for ammonium, and wet deposition accounted for >88% of the total deposition. The annual atmospheric input to the Barnegat Bay ecosystem is estimated to be 9.2×106 mol yr−1 for nitrate and 5.7×106 mol yr−1 for ammonium.