The aeolian transport of aerosols (mineral dust from desert areas, smoke and ash from biomass burning, and from anthropogenic emissions) is an important process for introducing bioactive trace elements to the surface ocean and can have a large impact on marine primary production. All material that enters the ocean from the atmosphere must pass through the air-sea interface, or sea surface microlayer. The microlayer is the physical link between the sea surface and lower atmosphere and is therefore tied to the global biogeochemical cycling of trace elements. The microlayer (50 – 200 µm thickness) is a unique environment with different physical, chemical, and biological properties compared to the underlying water column. The microlayer is dynamic in nature due to numerous non-equilibrium processes such as temperature fluctuations, salinity gradients, irradiance, and wind and wave actions that influence its biogeochemical properties. However, the microlayer is mechanically more stable than the underlying water column due to the higher concentration of surface-active organic compounds; creating a more rigid film-like layer over the surface of the ocean. It is an important, yet often ignored component in the biogeochemical cycling of trace elements in the marine environment due to the lack of trace element clean sampling and analysis methods. A novel technique, a hollow cylinder of ultra-pure SiO₂ (quartz glass) with a plastic handle, was developed to sample the microlayer for trace elements. This research also developed and optimized clean trace element techniques to accurately measure nine trace metals (Al, Mn, Fe, Co, Ni, Cu, Zn, Cd, and Pb) in the dissolved and particulate fractions of the microlayer and underlying water column. Initially, our research focused on the behavior of dissolved and particulate Al, Mn, Fe, Co, Cu, Zn, Cd, and Pb in the microlayer in a controlled tank experiment using a Saharan dust source. The residence times of the dissolved trace elements ranged from 1.8 hours for Fe to 15 hours for Cd. The residence times for the particulate trace elements ranged from 1.0 minutes for Al and Fe to 1.4 minutes for Mn. There was an initial release of dissolved trace elements to the microlayer from the Saharan dust. However, the reactive fraction of the suspended particles increased over time, indicative of scavenging. Based on the artificial dust deposition experiment, aerosols should be retained in the sea surface microlayer long enough to undergo chemical and physical alteration that affects the bioavailability of trace elements. Opportunistic bacteria (example: Vibrio spp.) have been shown to experience rapid growth during dust deposition events. Aerosols and microlayer samples were collected in the Florida Keys over the course of two years for analysis of dissolved and particulate Al, Mn, Fe, Co, Ni, Cu, Zn, and Pb. Trace element concentrations increased by factors of 2 to 5 in the microlayer during significant Saharan dust events. Residence times of dissolved trace elements ranged from 0.12 hours for Mn to 2.4 hours for Cu. Residence times of particulate trace elements ranged from 1.1 minutes for Co to 2.4 minutes for Mn. The particulate residence times were comparable between the artificial deposition experiment and the natural deposition event observed in the Florida Keys. The relatively short residence times for dissolved trace elements compared to the artificial deposition event suggest external forces, such as wind and wave actions, mixed the dissolved metals faster than by simple molecular diffusion. Despite the short residence times, Vibrio spp. in the microlayer increased by factors of 2 to 10 after the passage of a Saharan dust event, which suggests that there was an initial pulse of bioavailable trace elements and other nutrients to the system. These findings demonstrate the dynamic nature of the sea surface microlayer and the large role atmospheric deposition can play when introducing trace elements to the surface oceans. It also sheds light on the need for more interdisciplinary research to deconvolute and quantify the processes occurring in the microlayer. / A Dissertation submitted to the Department of Earth, Ocean and Atmospheric Science in partial fulfillment of the Doctor of Philosophy. / Fall Semester 2016. / December 9, 2016. / atmospheric deposition, sea surface microlayer, trace elements / Includes bibliographical references. / William M. Landing, Professor Directing Dissertation; Albert E. Stiegman, University Representative; Angela N. Knapp, Committee Member; Sven A. Kranz, Committee Member; Vincent J. M. Salters, Committee Member.
| Identifer | oai:union.ndltd.org:fsu.edu/oai:fsu.digital.flvc.org:fsu_510039 |
| Contributors | Ebling, Alina M. (Alina Marie) (authoraut), Landing, William M. (professor directing dissertation), Stiegman, Albert E. (university representative), Knapp, Angela N., 1976- (committee member), Kranz, Sven Alexander (committee member), Salters, Vincent J. M. (committee member), Florida State University (degree granting institution), College of Arts and Sciences (degree granting college), Department of Earth, Ocean and Atmospheric Science (degree granting departmentdgg) |
| Publisher | Florida State University, Florida State University |
| Source Sets | Florida State University |
| Language | English, English |
| Detected Language | English |
| Type | Text, text, doctoral thesis |
| Format | 1 online resource (106 pages), computer, application/pdf |
| Rights | This Item is protected by copyright and/or related rights. You are free to use this Item in any way that is permitted by the copyright and related rights legislation that applies to your use. For other uses you need to obtain permission from the rights-holder(s). The copyright in theses and dissertations completed at Florida State University is held by the students who author them. |
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