Controls on the chemical composition of the surface microlayer of Delaware Bay
| Author(s) | Coffey, Nicole R. | |
| Date Accessioned | 2021-02-04T13:19:10Z | |
| Date Available | 2021-02-04T13:19:10Z | |
| Publication Date | 2020 | |
| SWORD Update | 2020-10-12T19:03:27Z | |
| Abstract | The surface microlayer (SML) is a thin (10s-100s μm) layer at the top of the water column which serves as a boundary between bodies of water and the atmosphere that mediates fluxes across the air-sea interface. The SML’s enrichment in organic matter (OM) is well-documented, and is thought to contribute to the SML’s physical properties and mediation of exchanges. Mechanisms behind material enrichments and their relationship to SML properties in space and time are still debated though, which complicates prediction of air-sea exchange rates. By sampling both the SML and subsurface (SUB, 8-15 cm) water at four stations throughout Delaware Bay to encompass different influences (marine, terrestrial/fluvial, salt marsh) on the system, this study aims to deconvolute relationships between SML and SUB OM composition, microbial community composition, and air-sea exchange relevant physical parameters, specifically surface tension. SML samples collected between December 2018 and October 2019 show consistent enrichments of dissolved organic carbon (DOC) as high as 4.42 times the SUB concentration and as low as 0.87 times the SUB concentration. Compositional assessment, using Fourier-transform ion cyclotron resonance mass spectrometry (FTICR-MS), reveals marine site samples to be compositionally distinct from the three inner-bay sites. This separation is due to an abundance of CHON compounds found in marine samples. Principal component analyses performed on individual sites reveal a consistent difference in the OM composition in the samples from the SML relative to their corresponding SUB sample. OM in the SML is characterized by higher abundances of compounds with H/C ratios above 1.7 and formulas with O/C ratios below 0.2, including an abundance of sulfur-containing compounds, CHO3S compounds, in particular. These traits are indicative of surfactant-like molecules, which can change the physical properties of the air-sea interface. Unsaturated aliphatic compounds, identified from FTICR data, significantly (p < 0.05) correlate with surface tension depression (SUB surface tension – SML surface tension) across the dataset. The sources and structures of these candidate surfactant molecules should be a focus of future work. Assessments of DOC concentration or enrichments in the microlayer alone showed no association with surface tension. The lack of relationship between DOC and surface tension speaks to the need for a compositional approach to estimating properties of the SML and the exchanges it regulates. | en_US |
| Advisor | Wozniak, Andrew S. | |
| Degree | M.S. | |
| Department | University of Delaware, School of Marine Science and Policy | |
| DOI | https://doi.org/10.58088/tdz5-5n50 | |
| Unique Identifier | 1236096246 | |
| URL | https://udspace.udel.edu/handle/19716/28576 | |
| Language | en | |
| Publisher | University of Delaware | en_US |
| URI | https://login.udel.idm.oclc.org/login?url=https://www.proquest.com/dissertations-theses/controls-on-chemical-composition-surface/docview/2455758511/se-2?accountid=10457 | |
| Keywords | Carbon | en_US |
| Keywords | FTICR-MS | en_US |
| Keywords | Microlayer | en_US |
| Keywords | Organic | en_US |
| Title | Controls on the chemical composition of the surface microlayer of Delaware Bay | en_US |
| Type | Thesis | en_US |