Chemistry Commons^™

Unraveling Sources Of Cyanate In The Marine Environment: Insights From Cyanate Distributions And Production During The Photochemical Degradation Of Dissolved Organic Matter, Rui Wang, Jihua Liu, Yongle Xu, Li Liu, Kenneth Mopper

Chemistry & Biochemistry Faculty Publications

Cyanate is a nitrogen and energy source for diverse marine microorganisms, playing important roles in the nitrogen cycle. Despite the extensive research on cyanate utilization, the sources of this nitrogen compound remain largely enigmatic. To unravel the sources of cyanate, distributions and production of cyanate during photochemical degradation of natural dissolved organic matter (DOM) were investigated across various environments, including freshwater, estuarine, coastal areas in Florida, and the continental and slope regions of the North American mid-Atlantic Ocean (NATL). Cyanate production was also examined during the photochemical degradation of exudates from a typical strain of Synechococcus, an important phytoplankton …

The Photo-Transformation Of Free Methionine In The Presence Of Surrogate And Standard Isolate Dissolved Organic Matter Under Sunlit Irradiation, Benjamin J. Mohrhardt

Dissertations, Master's Theses and Master's Reports

Sulfur (S)-containing amino acids are key sources of carbon, nitrogen, and sulfur involved in protein synthesis, protein function, and providing energy for microbial growth. Dissolved free and combined methionine is one of two S-containing amino acids incorporated into proteins and has been attributed to their stability and function. The oxidation of methionine has received considerable attention given its ubiquitous presence in most biological systems and has been associated with losses in protein function and pathological disorders. In natural waters, methionine is rapidly and selectively taken up by microorganisms to achieve cellular requirements of carbon, nitrogen, and sulfur. The abiotic transformation …

Influence Of Dissolved Organic Matter On Phosphate Interactions With Hydrous Ferric Oxides, Alaa Hasan Alsherbi

Theses and Dissertations (Comprehensive)

Phosphorus, iron oxides, and dissolved organic matter (DOM) are components present in all aquatic systems. Excess amounts of phosphorus in aquatic systems have the potential for toxic effects, in particular, contributing to eutrophication. Most of the previous studies performed looked at the surface complexation of inorganic phosphate anions (P) to mineral surfaces such as hydrous ferric oxide (HFO). However, the role of DOM on the interactions between HFO and P is unknown. This study investigates the influence of DOM on the surface complexation of P onto HFO surfaces. Moreover, this study looks at the possibility of cation bridging formation (Ca …

High-Resolution Molecular Characterization Of Complex Environmental Mixtures: Aquatic Dissolved Organic Matter And Wildfire-Influenced Aerosol, Amna Ijaz

Dissertations, Master's Theses and Master's Reports

The natural environment is replete with organic matter of varying complexities. Whether it is particulate material in the atmosphere, decades old organic matter trapped within glaciers, or biological debris flowing with rivers and streams, natural organic matter (NOM) is exquisitely complex. High-resolution mass spectrometry allows us to have a glimpse of the molecular composition of NOM and delineate the elemental compositions of thousands of chemical species that form it. In this dissertation, the overarching aim was to explore the molecular diversity of complex mixtures from two sources: Surface water and atmospheric organic aerosol. The first objective of this dissertation was …

Mercury Sulfide Dissolution In Environmental Conditions: Thermodynamic And Kinetic Approaches, Ping Jiang

FIU Electronic Theses and Dissertations

Mercury (Hg) is a global contaminant of ecosystems and human health risk, with complicated biogeochemical processes. Mercury sulfide (HgS) dissolution has been suggested as a key process in Hg cycling, as it could potentially increase the pool of inorganic Hg (iHg) for the production of methylmercury (MeHg). Despite previous sporadic observations of enhanced HgS dissolution under certain conditions, much remains unclear on mechanisms of HgS dissolution. The objective of my research was to advance the mechanistic understanding of HgS dissolution, concerning re-adsorption of released Hg, effects of thiol-ligands, and Hg speciation.

Considering the lack of feasible techniques to differentiate dissolution …

Studies On Hydroxyl Radical Formation And Correlated Photoflocculation Process Using Degraded Wood Leachate As A Cdom Source, Luni Sun, Kenneth Mopper

Chemistry & Biochemistry Faculty Publications

In this study, we examined hydroxyl radical (•OH) formation with respect to photoreactivity of colored dissolved organic matter (CDOM), the Fenton reaction, and photoflocculation using leachate from decaying wood. The relationship between •OH photoproduction rate and leachate optical properties (UV-visible absorption and fluorescence excitation-emission matrices (EEMS)) was studied during irradiation using a UV solar simulator. The results showed that the •OH photochemical formation rate is strongly related to humic-like fluorescence as characterized by parallel factor analysis (PARAFAC), and that these fluorescence components are more photolabile than most of the other CDOM components. Fourier transform infrared spectroscopy (FT-IR) indicated the photodegradation …

Black Carbon: Sources, Mobility And Fate In Freshwater Systems, Sasha Wagner

FIU Electronic Theses and Dissertations

Black carbon (BC) is a complex mixture of polycondensed aromatic compounds produced by the incomplete combustion of biomass during events such as wildfires and the burning of fossil fuels. Black carbon was initially considered to be a refractory form of organic matter. However, recent studies have shown that BC can be quite mobile and reactive in the terrestrial environment. Black carbon can be translocated from soils and sediments in the form of dissolved BC (DBC). A global correlation between DBC and bulk dissolved organic carbon (DOC) has been established for fluvial systems where DBC comprises approximately 10% of the total …

Characterization Of Terrestrial Dissolved Organic Matter Fractionated By Ph And Polarity And Their Biological Effects On Plant Growth, Rachel L. Sleighter, Paolo Caricasole, Kristen M. Richards, Terry Hanson, Patrick G. Hatcher

Chemistry & Biochemistry Faculty Publications

Background: Humic substances are ubiquitous in the environment, complex mixtures, and known to be beneficial to plant growth. To better understand and identify components responsible for plant growth stimulation, a terrestrial aquatic DOM sample was fractionated according to pH and polarity, obtaining acid-soluble and acid-insoluble portions, as well as acid-soluble hydrophobic and hydrophilic fractions using C18. The various fractions were characterized then evaluated for their biological effects on plant growth using bioassays with corn at two carbon rates.

Results: Approximately 43% and 57% of the carbon, and 31% and 69% of the iron, was found in the acid-insoluble and acid-soluble …

Optical Characterization And Distribution Of Chromophoric Dissolved Organic Matter (Cdom) In Soil Porewater From A Salt Marsh Ecosystem, Catherine D. Clark, Paige Aiona, Jason K. Keller, Warren J. De Bruyn

Biology, Chemistry, and Environmental Sciences Faculty Articles and Research

To characterize chromophoric dissolved organic matter (CDOM) in marsh porewaters and its contribution as a carbon source, optical properties (absorbance, fluorescence indices, 3-dimensional excitation-emission matrices [EEMs]) of soil porewater and surface water were measured in a southern Californian salt marsh. Absorption coefficients and fluorescence intensities were higher in porewater than in overlying surface waters, consistent with higher CDOM concentration at depth. Humic-type peaks A and C were observed in EEMs in all samples, and peak M was observed in surface waters and shallow porewater to -5 cm depth. Fluorescence:absorbance (flu:abs) ratios and spectral slopes (S) decreased across the surface interface, …

Compositions And Constituents Of Freshwater Dissolved Organic Matter Isolated By Reverse Osmosis, Yulong Zhang, Wen Huang, Jingdong Mao

Chemistry & Biochemistry Faculty Publications

Dissolved organic matter (DOM) from riverine and lacustrine water was isolated using a reverse osmosis (RO) system. Solid-state ¹³C nuclear magnetic resonance (¹³C NMR) was used to quantitatively evaluate the compositions and constituents of DOM, which are compared with previous investigations on marine DOM. Results indicated that concentration factor (CF) was a key metric controlling yield and sorption of DOM on the RO system. The sorption was likely non-selective, based on the ¹³C NMR and δ¹³C analyses. Carbohydrates and lipids accounted for 25.0–41.5% and 30.2–46.3% of the identifiable DOM, followed by proteins (18.2–19.8%) and …

Advances In Understanding The Molecular Composition Of Dissolved Organic Matter And Its Reactivity In The Environment, Rajaa Mesfioui

Chemistry & Biochemistry Theses & Dissertations

Dissolved organic matter (DOM) is the ultimate product of Earth's systems dynamics. DOM chemical signature is strongly shaped by the interaction among Earth's spheres, such as the atmosphere, the geosphere, the biosphere, and the hydrosphere, but also life and human activity. DOM source, composition, photochemical alteration and availability affect freshwater ecosystems, their carbon and nitrogen fluxes and, thus, the global carbon and nitrogen cycles. The aim of this thesis was to gain an understanding of the molecular composition of DOM and its photochemical and biological reactivity in an environment impacted by anthropogenic disturbance. The York and James River systems within …

Dissolved Organic Matter Composition And Bioavailability Reflect Ecosystem Productivity In The Western Arctic Ocean, Yuan Shen, Cedric Fichot, Ronald Benner

Faculty Publications

Dissolved organic carbon (DOC) and total dissolved amino acids (TDAA) were measured in high (Chukchi Sea) and low (Beaufort Sea) productivity regions of the western Arctic Ocean to investigate the composition and bioavailability of dissolved organic matter (DOM). Concentrations and DOC-normalized yields of TDAA in Chukchi surface waters were relatively high, indicating an accumulation of bioavailable DOM. High concentrations and yields of TDAA were also observed in the upper halocline of slope and basin waters, indicating off-shelf transport of bioavailable DOM from the Chukchi Sea. In contrast, concentrations and yields of TDAA in Beaufort surface waters were relatively low, indicting …

Open-Ocean Carbon Monoxide Photoproduction, Aron Stubbins, Günther Uher, Cliff S. Law, Kenneth Mopper, Carol Robinson, Robert C. Upstill-Goddard

Chemistry & Biochemistry Faculty Publications

Sunlight-initiated photolysis of chromophoric dissolved organic matter (CDOM) is the dominant source of carbon monoxide (CO) in the open-ocean. A modelling study was conducted to constrain this source. Spectral solar irradiance was obtained from two models (GCSOLAR and SMARTS2). Water-column CDOM and total light absorption were modelled using spectra collected along a Meridional transect of the Atlantic ocean using a 200-cm pathlength liquid waveguide UV-visible spectrophotometer. Apparent quantum yields for the production of CO (AQY_CO) from CDOM were obtained from a parameterisation describing the relationship between CDOM light absorption coefficient and AQY_CO and the CDOM spectra collected. …

Effect Of Humic Substance Photodegradation On Bacterial Growth And Respiration In Lake Water, Alexandre M. Anesio, William Granéli, George R. Aiken, David J. Kieber, Kenneth Mopper

Chemistry & Biochemistry Faculty Publications

This study addresses how humic substance (HS) chemical composition and photoreactivity affect bacterial growth, respiration, and growth efficiency (BGE) in lake water. Aqueous solutions of HSs from diverse aquatic environments representing different dissolved organic matter sources (autochthonous and allochthonous) were exposed to artificial solar UV radiation. These solutions were added to lake water passed through a 0.7-μm pore-size filter (containing grazer-free lake bacteria) followed by dark incubation for 5, 43, and 65 h. For the 5-h incubation, several irradiated HSs inhibited bacterial carbon production (BCP) and this inhibition was highly correlated with H₂O₂ photoproduction. The H_{2 …}