ATMOSPHERIC NITROGEN DEPOSITION TO THE NEW JERSEY COASTAL WATERS AND ITS IMPLICATIONS

Abstract

In situ measurements of atmospheric NO3− and NH4+ at Sandy Hook on the northern New Jersey (USA) coast and at Tuckerton on the southern New Jersey coast reveal significant temporal and spatial variations of these inorganic N constituents. The mean concentration of NO3− in precipitation was higher at Sandy Hook (44.6 μmol/L) than at Tuckerton (29.1 μmol/L). The mean concentration of NH4+ in precipitation exhibited a similar pattern, being higher at Sandy Hook (26.3 μmol/L) than at Tuckerton (18.3 μmol/L). Aerosol NO3− and NH4+ concentrations at Sandy Hook were also higher than those at Tuckerton. On an annual basis, the total atmospheric deposition of NO3− was estimated to be 51.1 mmol·m−2·yr−1 at Sandy Hook and 32.9 mmol·m−2·yr−1 at Tuckerton. For NH4+, the total atmospheric deposition was 32.8 mmol·m−2·yr−1 at Sandy Hook and 20.3 mmol·m−2·yr−1 at Tuckerton. Wet deposition accounted for up to 89% of the total NO3− deposition and 76–91% of the total NH4+ deposition on the New Jersey coast.By comparison, NO3− and NH4+ concentrations are relatively low in estuarine waters of New Jersey. The annual mean NO3− concentrations recorded in surface waters of the Mullica River–Great Bay Estuary near the Tuckerton atmospheric site during the 2002–2004 period were as follows: 12.1 μmol/L for the upper estuary, 4.5 μmol/L for the mid‐estuary, 2.5 μmol/L for the lower estuary, and 1.2 μmol/L for the bay inlet area. The annual mean NH4+ concentrations in these waters were as follows: 1.5 μmol/L for the upper estuary, 3.8 μmol/L for the mid‐estuary, 3.8 μmol/L for the lower estuary, and 2.4 μmol/L for the bay inlet area. In the Barnegat Bay–Little Egg Harbor Estuary, the mean concentrations of NO3− plus NO2− were <4 μmol/L. In this system, atmospheric deposition accounts for ∼39% of the total N load. These results suggest that atmospheric deposition appears to be an important pathway of new N inputs to New Jersey coastal waters and a potentially significant N enrichment source for biotic production.