Physical Sciences and Mathematics Commons^™

Comparison Of A Simplified Cupric Oxide Oxidation Hplc Method With The Traditional Gc-Ms Method For Characterization Of Lignin Phenolics In Environmental Samples (Vol 13, Pg 1, 2015), Luni Sun, Robert G. M. Spencer, Peter J. Hernes, Rachael Y. Dyda, Kenneth Mopper

Chemistry & Biochemistry Faculty Publications

In our article entitled “Comparison of a simplified cupric oxide oxidation HPLC method with the traditional GC-MS method for characterization of lignin phenolics in environmental samples” (Limnol. Oceanogr.: Methods 13, 2015, 1–52), doi: 10.1002/lom3.10001, we would like to correct the errors in Fig. 2 and Table 2 as mentioned below. The label to Fig. 2(a) needs to be transposed as indicated in the corrected Fig. 2 image below.

Characterization And Photodegradation Of Dissolved Organic Matter (Dom) From A Tropical Lake And Its Dominant Primary Producer, The Cyanobacteria Microcystis Aeruginosa, Thais B. Bittar, Aron Stubbins, Armando A. H. Vieira, Kenneth Mopper

Chemistry & Biochemistry Faculty Publications

This study investigates optical and high-resolution molecular signatures and photochemical degradation of DOM from the Barra Bonita Reservoir (BB-DOM), a tropical eutrophic lake, as well as from its dominant phytoplankton species, the cyanobacteria Microcystis aeruginosa (Microcystis-DOM). Consistent with a predominantly autotrophic source, BB-DOM and Microcystis-DOM exhibited high protein-like fluorescence and contained a large number of aliphatics. Microcystis-DOM was enriched in peptide-like formulae, while BB-DOM had higher chromophoric and fluorescent DOM(CDOM and FDOM) and was enriched in moderately unsaturated formulae, indicating additions of terrigenous DOM and/or in situ processing of autochthonous material in the lake. Consistent with …

Spectroscopic Characterization Of Oceanic Dissolved Organic Matter Isolated By Reverse Osmosis Coupled With Electrodialysis, John R. Helms, Jingdong Mao, Hongmei Chen, E. Michael Perdue, Nelson W. Green, Patrick G. Hatcher, Kenneth Mopper, Aron Stubbins

Chemistry & Biochemistry Faculty Publications

Oceanic dissolved organic matter (DOM) is one of the largest pools of reduced carbon on Earth, yet DOM remains poorly chemically characterized. Studies to determine the chemical nature of oceanic DOM have been impeded by the lack of efficient and non-fractioning methods to recover oceanic DOM. Here, a DOM fraction (~40 to 86% recovery) was isolated using reverse osmosis/electrodialysis (RO/ED) and analyzed by solid-state ¹³C nuclear magnetic resonance (NMR) spectroscopy. Samples were obtained from biogeochemically distinct environments: photobleached surface gyre, productive coastal upwelling zone, oxygen minimum, North Atlantic Deep Water, and North Pacific Deep Water. A ubiquitous ‘background’ refractory …

Production Mechanisms, Number Concentration, Size Distribution, Chemical Composition, And Optical Properties Of Sea Spray Aerosols, Nicholas Meskhidze, Markus D. Petters, Kostas Tsigaridis, Tim Bates, Colin O'Dowd, Jeff Reid, Ernie R. Lewis, Brett Gantt, Magdalena D. Anguelova, Prakash V. Bhave, Andrew Wozniak

Chemistry & Biochemistry Faculty Publications

(First paragraph)

The impact of sea spray aerosols on global climate remains one of the most uncertain components of the aerosol–radiation–climate problem, but has received less attention than the impacts of terrestrial and anthropogenic aerosols. The last decade has produced a large body of information regarding the sources and composition of marine aerosols, resulting in a reassessment of the complex role that sea spray particles play in climate and various geophysical phenomena. As sea spray aerosol contributes substantially to the preindustrial, natural background which provides the baseline on top of which anthropogenic forcing should be quantified, and because the ocean …

A Preliminary Examination Of An In Situ Dual Dye Approach To Measuring Light Fluxes In Lotic Systems, Elizabeth C. Minor, Elizabeth James, Jay A. Austin, Veronica Nelson, Ryan Lusk, Kenneth Mopper

Chemistry & Biochemistry Faculty Publications

Light is a critical parameter in aquatic ecosystems, affecting primary production and in situ photochemistry. However, measuring light exposure for suspended particles or dissolved components in a dynamic water column can be challenging with existing Eulerian approaches. Here, we assess the simultaneous deployment of two dyes differing in photolability (rhodamine WT and fluorescein) as a Lagrangian measure of sunlight exposure in a lotic system. Fluorescein is sensitive to light exposure; rhodamine WT is relatively photostable. We examined dye fluorescence at various pH, salinity, and temperature conditions. We also tested dye photolability as a function of pH and wavelength range. In …

Improved Method For Quantifying The Air-Sea Flux Of Volatile And Semi-Volatile Organic Carbon, Emily Hauser, Rebecca M. Dickhut, Renee Falconer, Andrew S. Wozniak

Chemistry & Biochemistry Faculty Publications

A method for quantifying the diffusive air-sea exchange of gaseous organic carbon (OC) was developed. OC compounds were separated into two operational pools-those that were kinetically air limited in diffusion across the air-sea interface and those that were water limited-during simultaneous air/water sampling. The method separates OC compounds into low Henry's law constant (low-H) semivolatile OC (SOC) and high Henry's law constant (high-H) volatile OC (VOC) pools that can be categorized by relating diffusion kinetic parameters to Henry's Law constant. Air limited (low-H; H << similar to 0.1 L atm mol(^-1)) compounds were collected in pure water traps and were quantified as dissolved OC, whereas …

Isotopic Characterization Of Aerosol Organic Carbon Components Over The Eastern United States, Andrew S. Wozniak, James E. Bauer, Rebecca M. Dickhut, Xu Li, Ann P. Mcnichol

Chemistry & Biochemistry Faculty Publications

Carbon isotopic signatures (δ¹³C, Δ¹⁴C) of aerosol particulate matter total organic carbon (TOC) and operationally defined organic carbon (OC) components were measured in samples from two background sites in the eastern U.S. TOC and water-soluble OC (WSOC)δ¹³C values (−27 to −24‰) indicated predominantly terrestrial C₃ plant and fossil derived sources. Total solvent extracts (TSE) and their aliphatic, aromatic, and polar OC components were depleted in δ¹³C (−30 to −26‰) relative to TOC and WSOC. Δ¹⁴C signatures of aerosol TOC and TSE (−476 to +25‰) suggest variable fossil contributions (∼5–50%) …

Characterization Of Heterogeneities And Domains In Aquatic And Sedimentary Organic Matter By 1 H Spin Diffusion: Potential For Elucidating The Formation Mechanisms, Jingdong Mao, Xiaoyan Cao

Chemistry & Biochemistry Faculty Publications

Although the information on domains and heterogeneities of natural organic matter (NOM) can provide insights into its formation mechanisms, the appropriate solid-state NMR technique for measuring them is still lacking. The traditional technique requires mobility differences in NOM whereas NOM components are primarily rigid. We introduced a new ¹H spin diffusion technique, ¹H-¹³C two-dimensional heteronuclear correlation (2D HETCOR) NMR with ¹H spin diffusion, for characterization of domains and heterogeneities in aquatic and sedimentary organic matter. It was achieved by collecting a series of 2D HETCOR spectra with a variable mixing time, t_m', and …

A Mini-Electrodialysis System For Desalting Small Volume Saline Samples For Fourier Transform Ion Cyclotron Resonance Mass Spectrometry, Hongmei Chen, Aron Stubbins, Patrick G. Hatcher

Chemistry & Biochemistry Faculty Publications

An affordable, commercially available mini-electrodialysis (mini-ED) system has been evaluated for the efficient desalting of small volume samples of seawater before analysis by electrospray Fourier transform ion cyclotron resonance mass spectrometry (ESI FT-ICR MS). Mini-ED FT-ICR mass spectra were compared with spectra for samples that were treated by C₁₈ solid phase extraction, a commonly used method for rapid sample preparation for this type of analysis. In this comparison, it is clear that mini-ED provides more representative molecular information, compared with C₁₈ isolation, and recovers the overwhelming majority of peaks from salt-free samples, indicating that it adequately represents the …

Electrospray And Photoionization Mass Spectrometry For The Characterization Of Organic Matter In Natural Waters: A Qualitative Assessment, William C. Hockaday, Jeremiah M. Pucell, Alan G. Marshall, Jeffery A. Baldock, Patrick G. Hatcher

Chemistry & Biochemistry Faculty Publications

Fourier-transform ion cyclotron resonance mass spectrometry (MS) has demonstrated potential to revolutionize the fields of limnology and chemical oceanography by identifying the individual molecular components of organic matter in natural waters. The use of MS for this purpose is made possible by the electrospray technique which successfully ionizes polar, nonvolatile organic molecules. Another recently developed ion source, atmospheric pressure photoionization (APPI), extends MS capabilities to less polar molecules. This article presents early results on the application of APPI MS to natural organic matter. We compare APPI MS and electrospray MS data for dissolved organic matter from Lake Drummond (Virginia, USA). …

Determination Of Photochemically Produced Carbon Dioxide In Seawater, Emily M. White, David J. Kieber, Kenneth Mopper

Chemistry & Biochemistry Faculty Publications

An analytical system was developed to determine photochemically produced carbon dioxide in marine waters. Our system was designed to measure low levels of carbon dioxide by maintaining a closed system to prevent atmospheric contamination during sample preparation, irradiation, and analysis. To detect low levels of photoproduced carbon dioxide in seawater, background dissolved inorganic carbon (DIC) was removed before irradiation. To strip out DIC, samples were acidified to pH 3.0 (converting DIC to carbon dioxide) and bubbled with low carbon dioxide air. The pH was then readjusted back to the original value, and the resulting low-DIC seawater samples were transferred pneumatically …

Naturally Present Fatty Acids As Internal Calibrants For Fourier Transform Mass Spectra Of Dissolved Organic Matter, Rachel L. Sleighter, Georgina A. Mckee, Zhanfei Liu, Patrick G. Hatcher

Chemistry & Biochemistry Faculty Publications

The analysis of dissolved organic matter ( DOM) by Fourier transform ion cyclotron resonance mass spectrometry ( FTICR- MS) has gained wide interest recently, driven primarily by its ultrahigh resolving power and mass accuracy. Accurate calibration of mass spectra is a key step to successfully decipher the DOM components. We propose a simple and accurate method to internally calibrate the peaks in the complex spectra without the need to add a calibrant. Mass spectra of DOM samples from the Dismal Swamp, Virginia, and the lower Chesapeake Bay display the presence of naturally occurring fatty acids which can be readily recognized …

Absorption Spectral Slopes And Slope Ratios As Indicators Of Molecular Weight, Source, And Photobleaching Of Chromophoric Dissolved Organic Matter, John R. Helms, Aron Stubbins, Jason D. Ritchie, Elizabeth C. Minor, David J. Kieber, Kenneth Mopper

Chemistry & Biochemistry Faculty Publications

A new approach for parameterizing dissolved organic matter ( DOM) ultraviolet-visible absorption spectra is presented. Two distinct spectral slope regions ( 275-295 nm and 350-400 nm) within log-transformed absorption spectra were used to compare DOM from contrasting water types, ranging from wetlands (Great Dismal Swamp and Suwannee River) to photobleached oceanic water ( Atlantic Ocean). On the basis of DOM size-fractionation studies ( ultrafiltration and gel filtration chromatography), the slope of the 275-295- nm region and the ratio of these slopes (S_R; 275-295- nm slope : 350-400- nm slope) were related to DOM molecular weight ( MW) and …

Effects Of Salinity Changes On The Photodegradation And Ultraviolet-Visible Absorbance Of Terrestrial Dissolved Organic Matter, E. C. Minor, J. Pothen, B. J. Dalzell, H. Abdulla, K. Mopper

Chemistry & Biochemistry Faculty Publications

We performed laboratory studies to determine the effects of salinity on the photodegradation of dissolved organic matter (DOM) from the Great Dismal Swamp, Virginia, an important source of terrestrial DOM to the lower Chesapeake Bay. Samples were created by mixing Great Dismal Swamp water (ionic strength approximate to 0 mol L^-1) with modified artificial seawater solutions of differing salinities while keeping the final dissolved organic carbon (DOC) concentration constant. These samples were then irradiated for 24 h in a light box providing ultraviolet (UV) light similar to that of natural sunlight. Light absorbance and DOC concentrations decreased after …

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. …

Permanganate Colorimetric Rapid Method For Chemical Oxygen Demand In Seawater, Myung Zoon Czae, Taekee Hong, Myung Hoon Kim

Chemistry & Biochemistry Faculty Publications

No abstract provided.