Environmental Chemistry Commons^™

The Influence Of Hydrogen Peroxide On The Enrichment Of Fe(Iii) Reducing Bacteria From Acid Mine Drainage, Susami Seth

Williams Honors College, Honors Research Projects

It is hypothesized that the ocean of Europa, a Jupiter moon, hosts bacteria on its oceanic floor. Understanding how Fe(III) reducing bacteria (FeRB) from AMD utilize organic materials within its surrounding environment outlines how FeRB could thrive and tolerate extreme conditions. FeRB are known to tolerate metals and highly reactive oxidants species (ROS), but in this experiment, H₂O₂ was the experimental factor to further test FeRB tolerance. H₂O₂ is a common ROS and is damaging to living material such as proteins, DNA, and RNA. A range of H₂O₂ concentrations were fed …

On The Stratospheric Chemistry Of Midlatitude Wildfire Smoke, Susan Soloman, Kimberlee Dube, Kane Stone, Pengfei Yu, Doug Kinnison, Owen B. Toon, Susan E. Strahan, Karen H. Rosenlof, Robert Portmann, Sean Davis, William Randel, Peter Bernath, Chris Boone, Charles G. Bardeen, Adam Bourassa, Daniel Zawada, Doug Degenstein

Chemistry & Biochemistry Faculty Publications

Massive Australian wildfires lofted smoke directly into the stratosphere in the austral summer of 2019/20. The smoke led to increases in optical extinction throughout the midlatitudes of the southern hemisphere that rivalled substantial volcanic perturbations. Previous studies have assumed that the smoke became coated with sulfuric acid and water and would deplete the ozone layer through heterogeneous chemistry on those surfaces, as is routinely observed following volcanic enhancements of the stratospheric sulfate layer. Here, observations of extinction and reactive nitrogen species from multiple independent satellites that sampled the smoke region are compared to one another and to model calculations. The …

Calcification, Dissolution And Test Properties Of Modern Planktonic Foraminifera From The Central Atlantic Ocean, Stergios D. Zarkogiannis, Shinya Iwasaki, James William Buchanan Rae, Matthew W. Schmidt, P. Graham Mortyn, George Kontakiotis, Jennifer E. Hertzberg, Rosalind E.M. Rickaby

OES Faculty Publications

The mass of well-preserved calcite in planktonic foraminifera shells provides an indication of the calcification potential of the surface ocean. Here we report the shell weight of 8 different abundant planktonic foraminifera species from a set of core-top sediments along the Mid-Atlantic Ridge. The analyses showed that near the equator, foraminifera shells of equivalent size weigh on average 1/3 less than those from the middle latitudes. The carbonate preservation state of the samples was assessed by high resolution X-ray microcomputed tomographic analyses of Globigerinoides ruber and Globorotalia truncatulinoides specimens. The specimen preservation was deemed good and does not overall explain …

Unintended Consequences Of Air Cleaning Chemistry, Douglas B. Collins, Delphine K. Farmer

Faculty Journal Articles

Amplified interest in maintaining clean indoor air associated with the airborne transmission risks of SARS-CoV-2 have led to an expansion in the market for commercially available air cleaning systems. While the optimal way to mitigate indoor air pollutants or contaminants is to control (remove) the source, air cleaners are a tool for use when absolute source control is not possible. Interventions for indoor air quality management include physical removal of pollutants through ventilation or collection on filters and sorbent materials, along with chemically reactive processes that transform pollutants or seek to deactivate biological entities. This perspective intends to highlight the …

High Altitude Ballooning As A Platform For Measuring Ozone Uptake Over Agricultural Landscapes, Thomas Sykora, Mark Potosnak

DePaul Discoveries

Measuring plant health is a key aspect in maximizing crop outputs. One often overlooked risk to crop fields is damage caused by stomatal ozone uptake; measuring this uptake is an important tool in understanding crop losses. Traditional methods for measuring plant ozone uptake are prohibitively expensive and rely on equipment that cannot easily be moved. Here, we propose high-altitude weather ballooning as a cost-effective alternative for measuring ozone uptake on a regional (~10 km) spatial scale. Ozonesounde data was obtained with weather balloons launched from the National Oceanic and Atmospheric Administration research station in Boulder, Colorado. This data was then …

The Variability Of Seawater Carbonate Chemistry In Two Florida Urban Mangrove Ecosystems, Alexandrina R. Rangel

All HCAS Student Capstones, Theses, and Dissertations

Anthropogenic carbon dioxide (CO₂) emissions into the atmosphere are yielding serious impacts across the world’s ocean, including ocean acidification, sea level rise, and increasing seawater temperature. However, these changes are not occurring uniformly across all marine ecosystems. Coastal ecosystems, such as mangroves, already experience extreme and variable environmental conditions due to natural biogeochemical and physical processes. The goal of this study was to document small-scale variability in two urban mangrove ecosystems to gain insight into how ocean acidification will manifest within these systems. Using a stand-up paddleboard, a suite of sensors, and traditional bottle sampling techniques, we measured …

Isolated Point Discharges Into Coastal Swashes As Nutrient Sources To Coastal Waters, Mary E. Olsen

Honors Theses

Coastal water quality in the Grand Strand of South Carolina is directly influenced by human activities. Nutrient-rich runoff, stemming from numerous anthropogenic sources, finds its way into coastal waters through freshwater inputs often through tidal creeks, termed swashes. In order to better describe the amount of nutrient inputs into Singleton Swash and White Point Swash, we examine anthropogenic runoff from isolated identifiable point discharges and their nutrient concentrations. We report concentrations of dissolved inorganic nitrogen (DIN, as the sum of nitrate, nitrite and ammonium) and phosphate in discharge and creek water. We hypothesize that nutrient concentrations of isolated, minor point …

Characterization Of Uranium, Lead, And Rare Earth Element Pollution In Natural Soils And Sediments, Hope Rasmussen

Civil and Environmental Engineering Theses and Dissertations

Heavy metals in the environment add to the global burden of pollution, negatively impacting public health and ecosystem resilience. This study included projects regarding uranium (U), lead (Pb), and rare earth elements (REE) in natural samples, due to their known toxicity, ubiquity, and relevance in context to recent pollution trends. The first project focused on testing the potential of using a hydroxyapatite product as a remediation solution for U-contaminated groundwater and soil at an EPA Superfund site. The results showed that the U was sequestered in a highly crystalline mineral form within the solids, guiding the EPA to specify the …

Representing Methane Emissions From Wet Tropical Forest Soils Using Microbial Functional Groups Constrained By Soil Diffusivity, Debjani Sihi, Xiaofeng Xu, Mónica Salazar Ortiz, Christine S. O'Connell, Whendee L. Silver, Carla López-Lloreda, Julia M. Brenner, Ryan K. Quinn, Jana R. Phillips, Brent D. Newman, Melanie A. Mayes

Biology, Chemistry, and Environmental Sciences Faculty Articles and Research

Tropical ecosystems contribute significantly to global emissions of methane (CH₄), and landscape topography influences the rate of CH₄ emissions from wet tropical forest soils. However, extreme events such as drought can alter normal topographic patterns of emissions. Here we explain the dynamics of CH₄ emissions during normal and drought conditions across a catena in the Luquillo Experimental Forest, Puerto Rico. Valley soils served as the major source of CH₄ emissions in a normal precipitation year (2016), but drought recovery in 2015 resulted in dramatic pulses in CH₄ emissions from all topographic positions. Geochemical parameters …

Coastal Watershed Monitoring And Management: Geomorphology, Geochemistry, And Hydrologic Modeling Of Los Peñasquitos Creek, Ca, Ravleen Khalsa-Basra

Theses

Rivers in semi-arid climates are directly influenced by local geographic and hydrologic conditions and impacted by modifications to hydrology via urbanization. Changes can influence erosion, morphology, habitat sustainability, and watershed health. In highly urbanized southern California coastal regions, these rare open spaces provide vital ecosystem services. Los Peñasquitos Creek in San Diego County is one such watershed. Using stream surveying and laboratory methods we quantified channel characteristics, grain size distribution, total metal concentration [M], organic carbon (%OC), and phosphate to longitudinally characterize the creek for improved management. Results identified three distinct reaches in the watershed (upper, middle, lower). Downstream, depth …

Carbon Dioxide And Particulate Matter Concentration On Hampton Roads Air Quality, Gregory Hubbard

OUR Journal: ODU Undergraduate Research Journal

Hampton Roads has been a maritime crossroads for the last 400 years. Industrialization has impacted the coastal region for the last 250 years. The expansion of the Port of Virginia in 2019 has created dense traffic in the region resulting in impacts to air quality. Two waste products that affect humans are particulate matter and carbon dioxide. Both respective emissions can cause adverse effects on humans, such as asthma, some lung cancers, and other respiratory distress. Scientists and health practitioners are studying the effects of particulate matter on human health. Hampton Roads, in particular, because of its unique location on …

The Quantitative Assessment Of Pond Scum: An Examination Of The Biogeochemistry Of Phosphorus Cycling In The Belgrade Lakes, Abbey M. Sykes

Honors Theses

The internal recycling phosphorus in freshwater lake bottom sediments represents a significant source of hypolimnetic phosphorus (P) release for many of Maine’s lakes. In summer months, Maine lakes often thermally stratify and the lake hypolimnion develops anoxia, leading to a reduction in redox potential at the sediment-water interface. These reducing conditions facilitate the reductive dissolution of ferric iron, and, since phosphorus is often present in freshwater lake sediments as solid FeOOH-PO₄ complexes, results in release of soluble phosphorus into the water column. Our current study presents field and laboratory data from sediment fractionation extractions designed to quantify concentrations of …

Fifteen Years Of Hfc-134a Satellite Observations: Comparisons With Slimcat Calculations, Jeremy J. Harrison, Martyn P. Chipperfield, Christopher D. Boone, Sandip S. Dhomse, Peter F. Bernath

Chemistry & Biochemistry Faculty Publications

The phase out of anthropogenic ozone-depleting substances such as chlorofluorocarbons under the terms of the Montreal Protocol led to the development and worldwide use of hydrofluorocarbons (HFCs) in refrigeration, air conditioning, and as blowing agents and propellants. Consequently, over recent years, the atmospheric abundances of HFCs have dramatically increased. HFCs are powerful greenhouse gases and are now controlled under the terms of the 2016 Kigali Amendment to the Montreal Protocol. HFC-134a is currently the most abundant HFC in the atmosphere, breaking the 100 ppt barrier in 2018, and can be measured in the Earth's atmosphere by the satellite remote-sensing instrument …

Line-Of-Sight Winds And Doppler Effect Smearing In Ace-Fts Solar Occultation Measurements, Chris D. Boone, Johnathen Steffen, Jeff Crouse, Peter F. Bernath

Chemistry & Biochemistry Faculty Publications

Line-of-sight wind profiles are derived from Doppler shifts in infrared solar occultation measurements from the Atmospheric Chemistry Experiment Fourier transform spectrometers (ACE-FTS), the primary instrument on SCISAT, a satellite-based mission for monitoring the Earth’s atmosphere. Comparisons suggest a possible eastward bias from 20 m/s to 30 m/s in ACE-FTS results above 80 km relative to some datasets but no persistent bias relative to other datasets. For instruments operating in a limb geometry, looking through a wide range of altitudes, smearing of the Doppler effect along the line of sight can impact the measured signal, particularly for saturated absorption lines. Implications …

Stratospheric Fluorine As A Tracer Of Circulation Changes: Comparison Between Infrared Remote-Sensing Observations And Simulations With Five Modern Reanalyses, M. Prignon, S. Chabrillat, M. Friedrich, D. Smale, S. E. Strahan, Peter F. Bernath, M. P. Chipperfield, S. S. Dhomse, W. Feng, D. Minganti, C. Servais, E. Mahieu

Chemistry & Biochemistry Faculty Publications

Using multidecadal time series of ground-based and satellite Fourier transform infrared measurements of inorganic fluorine (i.e., total fluorine resident in stratospheric fluorine reservoirs), we investigate stratospheric circulation changes over the past 20 years. The representation of these changes in five modern reanalyses is further analyzed through chemical-transport model (CTM) simulations. From the observations but also from all reanalyses, we show that the inorganic fluorine is accumulating less rapidly in the Southern Hemisphere than in the Northern Hemisphere during the 21st century. Comparisons with a study evaluating the age-of-air of these reanalyses using the same CTM allow us to link this …

Toward Resolving Disparate Accounts Of The Extent And Magnitude Of Nitrogen Fixation In The Eastern Tropical South Pacific Oxygen Deficient Zone, Corday R. Selden, Margaret R. Mulholland, Brittany Widner, Peter Bernhardt, Amal Jayakumar

OES Faculty Publications

Examination of dinitrogen (N₂) fixation in the Eastern Tropical South Pacific oxygen deficient zone has raised questions about the range of diazotrophs in the deep sea and their quantitative importance as a source of new nitrogen globally. However, technical considerations in the deployment of stable isotopes in quantifying N₂ fixation rates have complicated interpretation of this research. Here, we report the findings of a comprehensive survey of N₂ fixation within, above and below the Eastern Tropical South Pacific oxygen deficient zone. N₂ fixation rates were measured using a robust ¹⁵N tracer method (bubble removal) …

Pore Water Exchange-Driven Inorganic Carbon Export From Intertidal Salt Marshes, Joeseph J. Tamborski, Meagan Eagle, Barret L. Kurylyk, Kevin D. Kroeger, Zhaoihui Aleck Wang, Paul Henderson, Matthew A. Charette

OES Faculty Publications

Respiration in intertidal salt marshes generates dissolved inorganic carbon (DIC) that is exported to the coastal ocean by tidal exchange with the marsh platform. Understanding the link between physical drivers of water exchange and chemical flux is a key to constraining coastal wetland contributions to regional carbon budgets. The spatial and temporal (seasonal, annual) variability of marsh pore water exchange and DIC export was assessed from a microtidal salt marsh (Sage Lot Pond, Massachusetts). Spatial variability was constrained from ²²⁴Ra : ²²⁸Th disequilibria across two hydrologic units within the marsh sediments. Disequilibrium between the more soluble ²²⁴Ra …

The Role Of Oxygen In Stimulating Methane Production In Wetlands, Jared L. Wilmoth, Jeffra K. Schaefer, Danielle R. Schlesinger, Spencer W. Roth, Patrick G. Hatcher, Julie K. Shoemaker, Xinning Zhang

Chemistry & Biochemistry Faculty Publications

Methane (CH₄), a potent greenhouse gas, is the second most important greenhouse gas contributor to climate change after carbon dioxide (CO₂). The biological emissions of CH₄ from wetlands are a major uncertainty in CH₄ budgets. Microbial methanogenesis by Archaea is an anaerobic process accounting for most biological CH₄ production in nature, yet recent observations indicate that large emissions can originate from oxygenated or frequently oxygenated wetland soil layers. To determine how oxygen (O₂) can stimulate CH₄ emissions, we used incubations of Sphagnum peat to demonstrate that the temporary exposure of …

The Aging And Impacts Of Atmospheric Soot: Closing The Gap Between Experiments And Models, Ogochukwu Yvonne Enekwizu

Dissertations

The main goal of this dissertation is to generate data and parameterizations to accurately represent soot aerosols in atmospheric models. Soot from incomplete combustion of fossil fuels and biomass burning is a major air pollutant and a significant contributor to climate warming. The environmental impacts of soot are strongly dependent on the particle morphology and mixing state, which evolve continuously during atmospheric transport via a process known as aging. To make predictions of soot impacts on the environment, most atmospheric models adopt simplifications of particle structure and mixing state, which lead to substantial uncertainties. Using an experimentally constrained modeling approach, …

Cosore: A Community Database For Continuous Soil Respiration And Other Soil-Atmosphere Greenhouse Gas Flux Data, Ben Bond-Lamberty, Danielle S. Christianson, Avni Malhotra, Stephanie C. Pennington, Debjani Sihi, Amir Aghakouchak, Hassan Anjileli, M. Altaf Arain, Juan J. Armesto, Samaneh Ashraf, Mioko Ataka, Dennis Baldocchi, Thomas Andrew Black, Nina Buchmann, Mariah S. Carbone, Shih-Chieh Chang, Patrick Crill, Peter S. Curtis, Eric A. Davidson, Ankur R. Desai, John E. Drake, Tarek S. El-Madany, Michael Gavazzi, Carolyn-Monika Görres, Christopher M. Gough, Michael Goulden, Jillian Gregg, Omar Gutiérrez Del Arroyo, Jin-Sheng He, Takashi Hirano, Anya Hopple, Holly Hughes, Järvi Järveoja, Rachhpal Jassal, Jinshi Jian, Haiming Kan, Jason Kaye, Yuji Kominami, Naishen Liang, David Lipson, Catriona A. Macdonald, Kadmiel Maseyk, Kayla Mathes, Marguerite Mauritz, Melanie A. Mayes, Steve Mcnulty, Guofang Miao, Mirco Migliavacca, Scott Miller, Chelcy F. Miniat, Jennifer G. Nietz, Mats B. Nilsson, Asko Noormets, Hamidreza Norouzi, Christine S. O'Connell, Bruce Osborne, Cecilio Oyonarte, Zhuo Pang, Matthias Peichl, Elise Pendall, Jorge F. Perez-Quezada, Claire L. Phillips, Richard P. Phillips, James W. Raich, Alexandre A. Renchon, Nadine K. Ruehr, Enrique P. Sánchez-Cañete, Matthew Saunders, Kathleen E. Savage, Marion Schrumpf, Russell L. Scott, Ulli Seibt, Whendee L. Silver, Wu Sun, Daphne Szutu, Kentaro Takagi, Masahiro Takagi, Munemasa Teramoto, Mark G. Tjoelker, Susan Trumbore, Masahito Ueyama, Rodrigo Vargas, Ruth K. Varner, Joseph Verfaillie, Christoph Vogel, Jinsong Wang, Greg Winston, Tana E. Wood, Juying Wu, Thomas Wutzler, Jiye Zeng, Tianshan Zha, Quan Zhang, Junliang Zou

Biology, Chemistry, and Environmental Sciences Faculty Articles and Research

Globally, soils store two to three times as much carbon as currently resides in the atmosphere, and it is critical to understand how soil greenhouse gas (GHG) emissions and uptake will respond to ongoing climate change. In particular, the soil-to-atmosphere CO₂ flux, commonly though imprecisely termed soil respiration (R_S), is one of the largest carbon fluxes in the Earth system. An increasing number of high-frequency R_S measurements (typically, from an automated system with hourly sampling) have been made over the last two decades; an increasing number of methane measurements are being made with such systems …

Iron Speciation In Pm2.5 From Urban, Agriculture, And Mixed Environments In Colorado, Usa, Joseph R. Salazar, David J. Pfotenhauer, Frank Leresche, Fernando L. Rosario-Ortiz, Michael P. Hannigan, Sirine C. Fakra, Brian Majestic

Chemistry and Biochemistry: Faculty Scholarship

Atmospheric iron solubility varies depending on whether the particles are collected in rural or urban areas, with urban areas showing increased iron solubility. In this study, we investigate if the iron species present in different environments affects its ultimate solubility. Field data are presented from the Platte River Air Pollution and Photochemistry Experiment (PRAPPE), aimed at understanding the interactions between organic carbon and trace elements in atmospheric particulate matter (PM). 24-hr PM2.5 samples were collected during the summer and winter (2016–2017), at three different sites on the Eastern Colorado plains: an urban, agricultural, and a mixed site. Downtown Denver had …

Algal Biomarkers As A Proxy For Pco2: Constraints From Late Quaternary Sapropels In The Eastern Mediterranean, Caitlyn R. Witkowski, Marcel T.J. Van Der Meer, Brian Blais, Jaap S. Sinninghe Damsté, Stefan Schouten

Science and Technology Department Faculty Journal Articles

Records of carbon dioxide concentrations (partial pressure expressed as pCO2) over Earth’s history provide trends that are critical to understand our changing world. To better constrain pCO2 estimations, here we test organic pCO2 proxies against the direct measurements of pCO2 recorded in ice cores. Based on the concept of stable carbon isotopic fractionation due to photosynthetic CO2 fixation (Ɛp), we use the stable carbon isotopic composition (δ13C) of the recently proposed biomarker phytol (from all photoautotrophs), as well as the conventionally used alkenone biomarkers (from specific species) for comparison, to reconstruct pCO2 over several Quaternary …

Annual Concentration And Flux Of Non-Sea-Salt Sulfate In The Wais Divide Ice Core (Wdc) For The Last 11,000 Years, Jihong Cole-Dai

Ice Core and Environmental Chemistry Lab Datasets and Publications

Annual concentration and flux of non-sea-slat sulfate in the WAIS Divide ice core (WDC) for the last 11,000 years.

Meteorological Conditions And Transport Of Air Pollutants At Bachok Marine Research Station (Bmrs) In Peninsular Malaysia, Mohyeddin Noraini

Student Works (2020-2029)

This study is focused at relatively new regional Global Atmospheric Watch (GAW) station at Peninsular Malaysia – Bachok Marine Research Station (BMRS) using the observational and remote sensing data. The study consists of three main objectives. Firstly, to investigate the meteorological conditions during two major Southeast Asia monsoon – NE and SW monsoon. Secondly, to determine the potential sources of air pollution at BMRS during the monsoon periods. Thirdly, to examine the relations of carbon dioxide (CO2), methane (CH4) and particulate matters (PM10, and PM2.5) with the meteorological conditions during intensive case study periods. The first case study (CS1) was …

Long Term Air Quality Analysis In Reference To Thermal Power Plants Using Satellite Data In Singrauli Region, India, H. K. Romana, Ramesh P. Singh, D. P. Shukla

Biology, Chemistry, and Environmental Sciences Faculty Articles and Research

The exponentially growing population and related anthropogenic activities have led to modifications in local environment. The change in local environment, evolving pattern of land use, concentrations of greenhouse gases and aerosols alter the energy balance of our climate system. This alteration in climate is leading to pre-mature deaths worldwide. This study analyses the air quality of Singrauli region, Madhya Pradesh, India for the past 15 years. Otherwise known as Urjanchal “the energy capital” of India has been declared as critically polluted by CPCB. The study provides an updated list of thermal power plants in the study area and their emission …

Freshwater Endmembers Impacting Carbonate Chemistry In The Mississippi Sound, Allison Savoie

Master's Theses

Coastal ecosystems are highly dynamic areas for carbon cycling and are likely to be negatively impacted by increasing ocean acidification. This research focused on dissolved inorganic carbon (DIC) and total alkalinity (TA) in the Mississippi Sound in order to understand the influence of local rivers that supply alkalinity to the area and buffer against ocean acidification. This area receives large fluxes of freshwater from local rivers, in addition to episodic inputs from the Mississippi River through a human-built diversion, the Bonnet Carré Spillway. Sites in the Mississippi Sound were sampled monthly during August 2018 to November 2019 and at weekly …

Global Atmospheric Budget Of Acetone: Air-Sea Exchange And The Contribution To Hydroxyl Radicals, Siyuan Wang, Eric C. Apel, Rebecca H. Schwantes, Kelvin H. Bates, Daniel J. Jacob, Emily V. Fischer, Rebecca S. Hornbrook, Alan J. Hills, Louisa K. Emmons, Laura L. Pan, Shawn Honomichl, Simone Tilmes, Jean‐François Lamarque, Mingxi Yang, Christa A. Marandino, E. S. Saltzman, Warren J. De Bruyn, Sohiko Kameyama, Hiroshi Tanimoto, Yuko Omori, Samuel R. Hall, Kirk Ullmann, Thomas B. Ryerson, Chelsea R. Thompson, Jeff Peischl, Bruce C. Daube, Róisín Commane, Kathryn Mckain, Colm Sweeney, Alexander B. Thames, David O. Miller, William H. Brune, Glenn S. Diskin, Joshua P. Digangi, Steven C. Wofsy

Biology, Chemistry, and Environmental Sciences Faculty Articles and Research

Acetone is one of the most abundant oxygenated volatile organic compounds (VOCs) in the atmosphere. The oceans impose a strong control on atmospheric acetone, yet the oceanic fluxes of acetone remain poorly constrained. In this work, the global budget of acetone is evaluated using two global models: CAM‐chem and GEOS‐Chem. CAM‐chem uses an online air‐sea exchange framework to calculate the bidirectional oceanic acetone fluxes, which is coupled to a data‐oriented machine‐learning approach. The machine‐learning algorithm is trained using a global suite of seawater acetone measurements. GEOS‐Chem uses a fixed surface seawater concentration of acetone to calculate the oceanic fluxes. Both …

Phosphorus Variability In The Area Of Influence Of The Mid-Barataria Sediment Diversion, Peter Mates

LSU Master's Theses

Man-made levees along the lower Mississippi River prevent delivery of sediment from building and maintaining Louisiana’s coastal wetlands. The Mid-Barataria sediment diversions is designed to reintroduce Mississippi River water, sediment, and nutrients into the sediment-starved Barataria Basin. Phosphorus (P) is an important macronutrient for regulating primary production in coastal marine ecosystems. Wetlands can serve as a sink or source for phosphorus to the overlying water column through various retention and release processes, dependent on concentration. Louisiana coastal systems can be phosphorus limited due to much higher concentrations of bioavailable Nitrogen in river water. The high soluble molar N:P ( >50:1) …

Glyoxal’S Impact On Dry Ammonium Salts: Fast And Reversible Surface Aerosol Browning, David O. De Haan Phd, Lelia N. Hawkins Phd, Kevin Jansen, Hannah G. Welsh, Raunak Pednekar, Alexia De Loera, Natalie G. Jimenez, Margaret A. Tolbert Phd, Mathieu Cazaunau Phd, Aline Gratien, Antonin Bergé, Edouard Pangui, Paola Formenti, Jean-François Doussin

Chemistry and Biochemistry: Faculty Scholarship

Alpha-dicarbonyl compounds are believed to form brown carbon in the atmosphere via reactions with ammonium sulfate (AS) in cloud droplets and aqueous aerosol particles. In this work, brown carbon formation in AS and other aerosol particles was quantified as a function of relative humidity (RH) during exposure to gas-phase glyoxal (GX) in chamber experiments. Under dry conditions (RH < 5%), solid AS, AS/glycine, and methylammonium sulfate aerosol particles brown within minutes upon exposure to GX, while sodium sulfate particles do not. When GX concentrations decline, browning goes away, demonstrating that this dry browning process is reversible. Declines in aerosol albedo are found to be a function of [GX]², and are consistent between AS and AS/glycine aerosol. Dry methylammonium sulfate aerosol browns 4´ more than dry AS aerosol, but deliquesced AS aerosol browns much less than dry AS aerosol. Optical measurements at 405, 450, and 530 nm provide an …

Glyoxal’S Impact On Dry Ammonium Salts: Fast And Reversible Surface Aerosol Browning (Raw Data), David O. De Haan Phd, Lelia N. Hawkins Phd, Margaret A. Tolbert Phd, Jean-François Doussin

Chemistry and Biochemistry: Faculty Scholarship

Alpha-dicarbonyl compounds are believed to form brown carbon in the atmosphere via reactions with ammonium sulfate (AS) in cloud droplets and aqueous aerosol particles. In this work, brown carbon formation in AS and other aerosol particles was quantified as a function of relative humidity (RH) during exposure to gas-phase glyoxal (GX) in chamber experiments. Under dry conditions (RH < 5%), solid AS, AS/glycine, and methylammonium sulfate aerosol particles brown within minutes upon exposure to GX, while sodium sulfate particles do not. When GX concentrations decline, browning goes away, demonstrating that this dry browning process is reversible. Declines in aerosol albedo are found to be a function of [GX]2, and are consistent between AS and AS/glycine aerosol. Dry methylammonium sulfate aerosol browns 4´ more than dry AS aerosol, but deliquesced AS aerosol browns much less than dry AS aerosol. Optical measurements at 405, 450, and 530 nm provide an estimated Ångstrom absorbance coefficient of -16 ±4. This coefficient and the empirical relationship between GX and albedo are used to estimate an upper limit to global radiative forcing by brown carbon formed by 70 ppt GX reacting with AS (+7.6 ´10-5 W/m2). This quantity is < 1% of the total radiative forcing by secondary brown carbon, but occurs almost entirely in the ultraviolet range.

The zipped data files are in the following formats: Igor experiments (.pxp), Word documents (.docx), Excel spreadsheets (.xlsx), organized by experiment number. “Optical” files contain cavity attenuated phase shift (CAPS) extinction, scattering and albedo data; PILS/waveguide data (experiments 1,2, and 5 only); …