Science Serving Maryland's Coasts
Ronald Siefert, Ph.D.
Chesapeake Biological Laboratory
Ammonia Flux Measurements at the Air-Water Interface on the Chesapeake Bay
Atmospheric deposition represents approximately 25% of the total nitrogen loading to the Chesapeake Bay, and ammonia(um) represents about 1/3 of this flux. In this study, ammonia(um) fluxes across the air-water interface were calculated using hourly atmospheric and surface-water measurements to investigate the temporal variability of ammonia(um) deposition directly to the Chesapeake Bay. A two-channel mist chamber collection system was used to collect hourly gas-phase ammonia and particulate ammonium concentrations at an over-water site on the Patuxent River with concurrent water measurements to calculate hourly air-water fluxes of ammonia and ammonium. Measurements were made on two separate dates in the summer of 2004. On July 29th, the net flux into the bay ranged from 74 to 440 ug NH3-N m-2 day -1 over an 8 hour time period, and on August 4th the net flux into the bay ranged from 119 to 1210ug NH3-N m-2 day -1 over a 6 hour time period. Gas-phase deposition dominated the overall deposition although particulate ammonium concentrations were usually larger by an average of 89%. The dominant factors for the large variability in the fluxes were the variation in gas-phase NH3 and its larger gas-phase exchange coefficient.
The results of this work were presented at the American Society of Limnology and Oceanography (ASLO) 2005 Aquatic Sciences meeting. Download the poster (pdf, ~500kb).
The REU students are indicated with an asterisk (*).
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