Environmental Chemistry Commons^™

Oxidation Camouflages Terrestrial Organic Matter To Appear Marine-Like, Aleksandar I. Goranov, Susan J. Carter, Ann Pearson, Patrick G. Hatcher

Chemistry & Biochemistry Faculty Publications

The export of terrestrial organic matter (TOM) to the ocean has been traditionally viewed to be minimal or only of significance in near-coastal continental margins. The broadly accepted explanation for the widespread loss of terrestrial lignin biomarkers and apparent disappearance of the <-25‰ stable carbon isotopic signature (δ¹³C) of TOM is that TOM is almost fully degraded before reaching the open ocean. Oceanic carbon (δ¹³C value ≥ -22‰) is therefore thought to be derived primarily from algae. However, an alternative explanation for the different molecular and δ¹³C signatures in terrestrial and marine environments may be that oxidative processing transforms TOM to appear marine-like. To test this hypothesis, we subjected eight TOM samples to a strong oxidation gradient. At carbon losses typical of TOM degradation during transport and sedimentation (above 60%), the differentiators of provenance disappeared, leaving a residue that was marine-like both chemically (aliphatic- and nitrogen-rich) and isotopically (δ¹³C enrichment of 4 to 9‰). This challenges the validity of conventional two-endmember mixing models, suggesting that a much larger fraction than previously estimated of the organic matter found in the ocean may originate from terrestrial sources, impacting global models of carbon cycling and sequestration.

Potentially Massive And Global Non-Pyrogenic Production Of Condensed "Black" Carbon Through Biomass Oxidation, Aleksandar I. Goranov, Hongmei Chen, Jianshu Duan, Satish C. B. Myneni, Patrick G. Hatcher

Chemistry & Biochemistry Faculty Publications

With the increased occurrences of wildfires worldwide, there has been an increase in scientific interest surrounding the chemistry of fire-derived "black" carbon (BC). Traditionally, wildfire research has assumed that condensed aromatic carbon (ConAC) is exclusively produced via combustion, and thus, ConAC is equated to BC. However, the lack of correlations between ConAC in soils or rivers and wildfire history suggests that ConAC may be produced non-pyrogenically. Here, we show quantitative evidence that this occurs during the oxidation of biomass with environmentally ubiquitous hydroxyl radicals. Pine wood boards exposed to iron nails and natural weather conditions for 12 years yielded a …

Deposited Cigarette Smoke As A Driver Of Oxidation And Partitioning Processes On Indoor Surfaces, April Hurlock

Honors Theses

Despite the large amount of time that individuals spend indoors during their lives, very little attention was paid to the chemistry that occurs on indoor surfaces until recently. Although not visible to the naked eye, physical and chemical processes, such as partitioning and oxidation, are occurring on virtually every indoor surface in a typical household. Indoor pollutants, ranging from skin oils to environmental cigarette smoke, drive a lot of these processes. The transformation of indoor surfaces by indoor pollutants can increase chemical exposure risks as new irritants or carcinogens can be introduced to the surfaces. In this thesis, I describe …

Brown Carbon Production By Aqueous-Phase Interactions Of Glyoxal And So2, David O. De Haan, Kevin Jansen, Alec D. Rynaski, W. Ryan P. Sueme, Ashley K. Torkelson, Eric T. Czer, Alexander K. Kim, Michael A. Rafla, Audrey C. De Haan, Margaret A. Tolbert

Chemistry and Biochemistry: Faculty Scholarship

Oxalic acid and sulfate salts are major components of aerosol particles. Here, we explore the potential for their respective precursor species, glyoxal and SO₂, to form atmospheric brown carbon via aqueous-phase reactions in a series of bulk aqueous and flow chamber aerosol experiments. In bulk aqueous solutions, UV- and visible-light-absorbing products are observed at pH 3–4 and 5–6, respectively, with small but detectable yields of hydroxyquinone and polyketone products formed, especially at pH 6. Hydroxymethanesulfonate (HMS), C₂, and C₃ sulfonates are major products detected by electrospray ionization mass spectrometry (ESI-MS) at pH 5. Past studies …

Green Chemistry: The Oxidation Of Benzaldehyde Using Atmospheric Oxygen And N-Heterocyclic Carbenes As Catalysts, Alex Brody, John Morgan

Student Research Poster Presentations 2020

Oxidation is a vital process in organic and biochemical reactions. In particular, the oxidation of aromatic aldehydes to carboxylic acids and esters is a vital process used in many different environments. Benzaldehyde is one common subject of this type of reaction, used in the synthesis of benzoic acid and benzoate derivatives. Unfortunately, the industrial synthesis of these compounds uses harmful heavy metal oxidants such as Chromium(VI) and Manganese(VII), which are very harmful to the environment. We proposed to eliminate these pollutants by using atmospheric oxygen and an organic catalyst in a solvent free reaction. This reaction would then be microwaved …

Oxidative Depolymerization Of Lignin To Low Molecular Weight Aromatics, Yang Song

Theses and Dissertations--Chemistry

To date, most lignocellulosic biorefinery strategies have focused on optimizing conversion of cellulose to ethanol, leaving lignin as an underutilized biomass constituent. Lignin is engineered by nature with the intent to protect plants from chemical and biological attack; this leaves lignin with high structural irregularity and recalcitrance, rendering conversion of the lignin macromolecule to valuable products particularly challenging. Nevertheless, given that the economics of cellulosic ethanol production are strongly dependent on the value that can be obtained for the lignin co-product, the successful valorization of lignin is a crucial step in the transition towards a bio-based economy.

This thesis focuses …

The Investigation Of The Chlorine Initiated Oxidation Of 2-Phenylethanol And Stability Of Superalkali Lithium Substituted Silyls., Adam Otten

Master's Theses

This thesis investigates the combustion potential of 2-phenylethanol and the superalkali properties of small lithium substituted silicon compounds. All combustion experiments were performed at the Advanced Light Source of Lawrence Berkeley National Laboratory at the Chemical Dynamics Beamline 9.0.2. The chlorine initiated oxidation of 2PE was investigated at 298 and 550 K using a multiplex photoionization mass spectrometer, coupled with the tunable vacuum ultraviolet radiation. Reaction products were identified using kinetic time traces and photoionization spectra.

Additionally, the stability of small superalkali silicon-lithium compounds has also been investigated. All structures and energetics were calculated using the CBS-QB3 composite method.

The …

An Overview Of Dynamic Heterogeneous Oxidations In The Troposphere, Elizabeth A. Pillar-Little, Marcelo I. Guzman

Chemistry Faculty Publications

Due to the adverse effect of atmospheric aerosols on public health and their ability to affect climate, extensive research has been undertaken in recent decades to understand their sources and sinks, as well as to study their physical and chemical properties. Atmospheric aerosols are important players in the Earth’s radiative budget, affecting incoming and outgoing solar radiation through absorption and scattering by direct and indirect means. While the cooling properties of pure inorganic aerosols are relatively well understood, the impact of organic aerosols on the radiative budget is unclear. Additionally, organic aerosols are transformed through chemical reactions during atmospheric transport. …

Determination Of The Oxidative Capacity Of Soot Toward Gsh And Characterization Of Soot Physicochemical Properties, Kaylee Troth

All Master's Theses

Fine atmospheric particulate matter (PM_2.5) emitted during the combustion of fossil and biomass fuels is known to adversely affect human health. While the underlying mechanisms are thought to be driven by the generation of reactive oxygen species (ROS), specific particle characteristics responsible for this detrimental effect are not well understood. In this research, the quantitative determination of the biologically relevant antioxidant, glutathione (GSH), was optimized for use as an indicator of oxidative stress to shed light on relevant particle characteristics. This was accomplished via fluorescent spectroscopy for GSH determination by way of reaction with o-phthalaldehyde (OPA), a …

Homogeneous Ligand-Centered Hydrogen Evolution And Hydrogen Oxidation : Exploiting Redox Non-Innocence To Drive Catalysis., Andrew Z. Haddad

Electronic Theses and Dissertations

Hydrogen is a promising carbon-free fuel / energy carrier and is an essential building block for many industrial and agricultural processes. Rising energy demands have ignited interest in the development of carbon-free and carbon neutral energy sources. In this context, hydrogen is an attractive candidate—being energy-dense, carbon-free—and easily accessible through a two-electron reduction of water. Accordingly, many electrochemical homogeneous catalyst systems have been studied, with a focus on understanding the mechanism of hydrogen evolution proceeding through metal-hydride intermediates. However, there has been a renaissance in hydrogen evolution reaction (HER) catalyst design, with many groups implicating ligand redox non-innocence as a …

Nitrate Radicals And Biogenic Volatile Organic Compounds: Oxidation, Mechanisms And Organic Aerosol, Nga Lee Ng, Steven S. Brown, Alexander T. Archibald, Elliot Atlas, Ronald C. Cohen, John N. Crowley, Douglas A. Day, Neil M. Donahue, Juliane L. Fry, Hendrik Fuchs, Robert J. Griffin, Marcelo I. Guzman, Hartmut Hermann, Alma Hodzic, Yoshiteru Iinuma, José L. Jimenez, Astrid Kiendler-Scharr, Ben H. Lee, Deborah J. Luecken, Jingqiu Mao, Robert Mclaren, Anke Mutzel, Hans D. Osthoff, Bin Ouyang, Benedicte Picquet-Varrault, Ulrich Platt, Havala O. T. Pye, Yinon Rudich, Rebecca H. Schwantes, Manabu Shiraiwa, Jochen Stutz, Joel A. Thornton, Andreas Tilgner, Brent J. Williams, Rahul A. Zaveri

Chemistry Faculty Publications

Oxidation of biogenic volatile organic compounds (BVOC) by the nitrate radical (NO₃) represents one of the important interactions between anthropogenic emissions related to combustion and natural emissions from the biosphere. This interaction has been recognized for more than 3 decades, during which time a large body of research has emerged from laboratory, field, and modeling studies. NO₃-BVOC reactions influence air quality, climate and visibility through regional and global budgets for reactive nitrogen (particularly organic nitrates), ozone, and organic aerosol. Despite its long history of research and the significance of this topic in atmospheric chemistry, a number …

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 …

Measurement Of Antioxidant Activity Toward Superoxide In Natural Waters, D. Whitney King, Emma Berger, Zachary Helm, Eleanor Irish, Kenneth Mopper

Chemistry & Biochemistry Faculty Publications

Antioxidants are a class of molecules that provide a protective function against reactive oxygen species (ROS) in biological systems by out competing physiologically important molecules for ROS oxidation. In natural waters, the reactivity of antioxidants gives an estimate of oxidative stress, and may determine the reactivity and distribution of reactive oxidants. We present an analytical method to measure antioxidant activity in natural waters through the competition between ascorbic acid, an antioxidant, and MCLA, a chemiluminescent probe for superoxide. A numerical kinetic model of the analytical method has been developed to optimize analytical performance. Measurements of antioxidant concentrations in pure and …

Characterization Of Organic Carbon In Sediments From Old Rifle, Co, A Former Uranium Mill, Francis Michael Tee, Morris Jones, Sharon Bone, Michael Schaefer, Scott Fendorf, John Bargar

STAR Program Research Presentations

Characterization of sediments from Old Rifle, CO, a former uranium mill

More than 34 million gallons (~129 million liters) of groundwater are contaminated with uranium at Old Rifle, Colorado – a former uranium-processing site that operated until 1958. The original Department of Energy strategy for remediation, involving natural flushing of U from the groundwater through mixing with surface water, has not been as successful as predicted. The uranium plume is replenished when insoluble U(IV) is oxidized to the more mobile U(VI). Relatively thin pockets of silt-, clay-, and organic-rich sediments contain reduced uranium, iron and sulfur and are referred to …

Effects Of Activated Carbon Surface Chemistry Modification On The Adsorption Of Mercury From Aqueous Solution, Emily K. Faulconer

Publications

Mercury (Hg), a naturally occurring element, is toxic and can lead to negative health impacts for humans and ecosystems. Activated carbon adsorption is effective in treating Hg-laden aqueous effluent for safe discharge. Two modifications of commercially available activated carbon were investigated: iron impregnation to allow for magnetic sorbent recapture and wet chemical oxidation to enhance aqueous Hg capture. The modified carbons were characterized by nitrogen adsorption-desorption, XRD, pHpzc, vibrating sample magnetometry, elemental analysis, and total acidity titration. The 3:1 C:Fe magnetic powdered activated carbon (MPAC) retained a high surface area of 790 m2 /g and was 95% magnetically recoverable, with …

Synthesis, Kinetic And Photocatalytic Studies Of Porphyrin-Ruthenium-Oxo Complexes, Yan Huang

Masters Theses & Specialist Projects

Macrocyclic ligand-complexed transition metal-oxo intermediates are the active oxidizing species in a variety of important biological and catalytic oxidation reactions. Many transition metal catalysts have been designed to mimic the predominant oxidation catalysts in Nature, namely the cytochrome P450 enzymes. Ruthenium porphyrin complexes have been the center of the research and have successfully been utilized, as catalysts, in major oxidation reactions such as the hydroxylation of alkanes. This study focuses on kinetic and photocatalytic studies of oxidation reactions with wellcharacterized high-valent ruthenium-oxo porphyrin complexes.
The trans-dioxoruthenium(VI) porphyrins have been among the best characterized metal-oxo intermediates and their involvement as …