Draft:Wendell Walters

Wendell W. Walters is an Assistant Professor of Chemistry at the University of South Carolina. His focus is in analytical and environmental chemistry involving reactive nitrogen and sulfur in the atmosphere.

Education and Career
Walters earned his B.S. in Chemistry from the University of Maryland, College Park in 2012 followed by earning his Ph.D. in Earth, Atmospheric, and Planetary Sciences at Purdue University in 2016. He then completed postdoctoral research at Brown University for the Department of Earth, Environmental, and Planetary Sciences in 2018.

Walters started his career as an assistant professor at Brown University in 2018 following his completion of postdoctoral research. From 2022 to 2023, he was a visiting assistant professor at the US EPA Office of Research and Development. He then became an Assistant Professor of Chemistry at the University of South Carolina in 2023.

Research
The Walters research group interests are the connections between atmospheric chemistry, the environment, and climate. Natural and anthropogenic activities have changed the environment from emissions and the chemistry involving trace gases and aerosols. Examples of these activities are volcanic emissions, wildfires, fossil fuel combustion, and agriculture. The goal of the research is to quantify the impacts of both natural and anthropogenic effects on atmospheric chemistry and composition, while also examining the consequences it has on the environment, climate, and human health. The research includes different environment and conditions, such as urban and polar regions.

Research Themes:


 * Changes in atmospheric reactive nitrogen, sulfur, and carbon
 * Evaluation of paleo- and remote atmospheric chemistry and how it connects to climate
 * Development of models and analytical techniques in atmospheric chemistry

This research involves stable isotope measurements and advanced instrumentation of high resolution and/or high-density concentration measurements. Their approach include field measurements, experiments, theoretical considerations, instrumentation development, and modeling utilizing both concentration and stable isotopes.

Some of the group projects include:

Emission and Regulation Feedbacks on Atmospheric Chemistry - Nitrate and sulfate aerosols have not decreased as much as expected, even with the NOx and SOx reductions. The Walters research group wants to examine the sulfate and nitrate aerosol production mechanisms and how the rates have changes with emission regulations.

Development of New Instrumentation for Air Quality Studies - The research group is currently developing instrumentation for high-resolution measurements of stable isotopes of reactive nitrogen, sulfur, and carbon gases. The new instrumentation will be used for field and aircraft air quality and climate campaigns, such as a controlled biomass burn and marine atmospheric chemistry.



Chemistry/Climate Interactions Inferred from Ice Cores - The interaction between nitrogen oxides and climate forcings is not well understood, but they could be helpful for returning the atmosphere to its natural state. The Walters research group wants to examine the connections between climate change and atmospheric chemistry. They are aiming to create a new method to automate the decontamination of ice cores to evaluate paleoatmospheric chemistry.

New Stable Isotope Measurements Using High Resolution Mass Spectrometry - To examine the isotope measurements, the Walters research group uses two mass spectrometers. A magnetic sector (GC/IRMS) is the traditional oxyanion stable isotope measurements and isotope ratio mass spectrometer. The next generation of oxyanion stable isotope measurements is a HPLC/Orbitrap mass spectrometer.

Awards and Honors
During his career, he earned many awards, including;
 * Atmospheric Chemistry Colloquium for Emerging Senior Scientists (ACCESS XIV), Selected Participant, Brookhaven National Lab, 2017
 * NSF Atmospheric and Geospace Sciences (AGS) Postdoctoral Fellowship, 2016
 * Bisland Dissertation Fellowship, 2016
 * Purdue Earth, Atmospheric, and Planetary Sciences Outstanding Graduate Student of the Year, 2016
 * Henry Silver Environmental Science Graduate Student of the Year, 2015
 * Purdue University Earth, Atmospheric, and Planetary Sciences Expo Outstanding Student Presentation Award, 2014
 * NSF Graduate Research Fellowship, 2013

Selected Publications
His publications include;
 * Kim, H.; Walters, W.W.; Bekker, C.; Murray, L.T.; Hastings, M.G. Nitrate chemistry in the Northeast US Part II: Oxygen Isotopes Reveal Differences in Particulate and Gas Phase Formation. Chem. Phys., 23(7), 4203-4219, 2023.
 * Walters, W.W., Wilcock, E.; Baek, B.H.; Karod, M.; Blum, D.E.; Hastings, M.G. Quantifying the importance of vehicle ammonia emissions in an urban area of the northeastern US utilizing nitrogen isotopes. Chem. Phys., 22(20), 13431-13448, 2022.
 * Blum, D. E.; Walters, W.W.; Hastings, M.G. Collection Methods of Simultaneously Speciated Nitric Acid and Fine Particulate Matter for Determination of Nitrogen and Oxygen Stable Isotopic Composition, Anal Chem, 92, 16079-16088, 2020.
 * Walters, W.W.; Song, L.; Fang, Y.; Colombi, N.; Chai, J.; Hastings, M.G. Characterizing the spatiotemporal nitrogen stable isotopic composition of ammonia in vehicle plumes Chem. Phys., 20, 11551-11567, 2020.
 * Walters, W.W.; Michalski, G.; Böhlke, J. K.; Alexander, B.; Savarino, J.; Thiemens, M. H. Assessing the seasonal dynamics of nitrate and sulfate aerosols at the South Pole utilizing stable isotopes. J Geophys Res-Atmos. 124(14), 8161-8177, 2019.
 * Walters, W.W.; Chai, J.; Hastings, M.G. Theoretical phase resolved ammonia- ammonium nitrogen equilibrium isotope exchange fractionations: Applications for tracking atmospheric ammonia gas-to-particle conversion. ACS Earth Space Chem., 3(1), 79-89, 2018.
 * Walters, W.W.; Fang, H.; Michalski, G. Summertime diurnal variations in the isotopic composition of atmospheric nitrogen dioxide at a small midwestern United States city. Atmospheric Environ. 179, 1-11, 2016.
 * Walters, W.W.; Michalski, G. Ab initio study of nitrogen and position-specific oxygen kinetic isotope effects in the NO + O3 J. Chem. Phys. 145(22), 224311, 2016.
 * Walters, W.W.; Tharp, B. D.; Fang, H.; Kozak, B. J.; Michalski, G. Nitrogen isotope composition of thermally produced NOx from various fossil-fuel combustion sources. Sci. Techn., 49(19), 11363-11371, 2015.

Group Members
P.I. Dr. Wendell W. Walters

Postdoctoral Students: Huan Fang

Graduate Students: Adam Baer, Olivia Steinbeck, Meghan Weatherly

Undergraduate Students: Mia Goedken

Grants Received

 * NSF Atmospheric Chemistry program for the project “Quantifying Natural and Anthropogenic Influences on Nitrogen Oxides Emissions and Chemistry.”, 2024
 * NSF Atmospheric Chemistry program for the project “Evaluating the Atmospheric Dynamics of Nitrate and Sulfate in Southern New England in Response to Emission Regulations.”, 2024
 * NSF Atmospheric Chemistry program for the project “Assessment of Multiscale Air Quality Model (CMAQ) Representation of Spatiotemporal Atmospheric Nitrate Chemical Production in New England.”, 2024