No abstract

No abstract

No abstract

[1] The deposition of atmospheric nitrogen contributes significantly to total nitrogen (TN) entering U.S. coastal water bodies. Nitrogen inputs via wet deposition are well quantified but dry-deposition fluxes are uncertain. In this study, dry fluxes of major atmospheric nitrogen species (including gaseous NH 3 and HNO 3 and particulate NH 4 + , NO 3 À , NO 2 À , and organic nitrogen (ON)) were quantified during a 2-week summer sampling period at Lewes, Delaware, on the mid-Atlantic U.S. coast. Results indicate that dry deposition contributed approximately 43% to total atmospheric nitrogen deposition. Under all flow conditions, NH 3(g) accounted for the largest fraction of TN dry deposition (averaging 60%); HNO 3(g) and NO 3 À also contributed considerably (averaging 25 and 8%, respectively). During onshore flow, scavenging of HNO 3(g) by sea-salt aerosols shifted the phase partitioning and relative dry fluxes of total NO 3 (HNO 3(g) + NO 3 À ) toward particulate NO 3 À . The mass-weighted deposition velocities for particulate NO 3 À (associated primarily with sea-salt size fractions) were similar to those of HNO 3(g) . Consequently, phase changes did not substantially alter the dry-deposition fluxes of total NO 3 . In light of these results, dry-deposition monitoring programs at coastal locations should (1) quantify NH 3(g) deposition; (2) reliably sample supermicron particles (with which most particulate NO 3 À is associated); and (3) apply deposition models for particulate nitrogen that are consistent with corresponding size distributions.

No abstract