Date of Award

Winter 2018

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Ocean & Earth Sciences

Committee Director

Peter N. Sedwick

Committee Member

Margaret R. Mulholland

Committee Member

Dreaux P. Chappell

Abstract

Atmospheric deposition provides a significant source of nutrients and bioactive trace metals to the surface ocean, including the seasonally oligotrophic waters of the Mid-Atlantic Bight. These atmospherically derived nutrients and trace metals enter the surface ocean via dry deposition of aerosols and wet deposition in rain. To estimate the aeolian input of nutrients and trace metals to coastal waters east of the Delmarva Peninsula, wet and dry atmospheric deposition samples were collected over a one-year time series at the Anheuser-Busch Coastal Research Center, Oyster, Virginia. Weekly composite samples were collected from May 2014 through June 2015. Nutrient species examined were nitrate, ammonium and phosphate, and trace metals included aluminum, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, cadmium, antimony, and lead. Aerosol samples were leached with deionized water to estimate the fluxes of soluble nutrients and trace metals, and acid digestions of aerosol samples were performed to estimate the total fluxes of trace metals and their fractional solubility. Wet deposition was the dominant deposition mode for nutrients accounting for 47 %, 78 %, and 80 % of the total (wet+dry) deposition of soluble nitrate, ammonium and phosphate, respectively. The average fractional solubility of the aerosol iron fine fraction ranged from 5.5-7.3 %, whereas that of the coarse fraction ranged from 1.5-2.5 %. These values were higher than typically reported for mineral dust and suggest anthropogenic aerosol inputs. Wet deposition was the dominant deposition mode for chromium, nickel, and cadmium, whereas dry deposition was the dominant deposition mode for all other trace metals.

Wet and dry deposition samples were also collected during a cruise in the Mid-Atlantic Bight during summer 2014. Results obtained from shipboard aerosol and rain samples suggest that atmospheric deposition of trace metals at the land-based station is generally comparable to that of adjacent coastal waters. However, nutrient data for shipboard aerosol samples reveal major differences from the land-based station, as the mean dry deposition of nitrate was three times greater than that for ammonium, whereas the dry deposition of nitrate and ammonium were roughly equal at the land-based station.

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DOI

10.25777/ds48-rr53

ISBN

9780438989542

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Oceanography Commons

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