About

Cort Anastasio is a Professor of Tropospheric Chemistry at the University of California, Davis, within the Department of Land, Air and Water Resources. He holds a Sc.B. in Chemistry from Brown University and a Ph.D. in Atmospheric Chemistry from Duke University. His research focuses on atmospheric pollution, atmospheric chemistry, and modern climate change. He is a member of the Atmospheric Science Graduate Group and the Agricultural and Environmental Chemistry Graduate Group. Professor Anastasio teaches courses including Fundamentals of Atmospheric Pollution, Atmospheric Chemistry, Modern Climate Change, and Introduction to Atmospheric Chemistry. He serves on the Executive Committee and the Admissions Committee of the Atmospheric and Environmental Chemistry Graduate Group, and participates in the selection of the Crosby Graduate Fellowship in Environmental Chemistry.

Research topics

• Chemistry
• Organic chemistry
• Environmental chemistry
• Photochemistry
• Atmospheric sciences
• Waste management
• Engineering
• Pulp and paper industry
• Environmental science
• Ecology
• Geology
• Environmental engineering
• Composite material
• Inorganic chemistry
• Materials science
• Biology

Selected publications

• Aqueous Oxidation of Biomass-Burning Furans by Singlet Molecular Oxygen (^<b>1</b>O_<b>2</b>*)

  Environmental Science & Technology · 2025-05-22 · 4 citations

  articleSenior authorCorresponding

  Furans are abundant emissions from biomass burning that can react with gas-phase oxidants to produce secondary organic aerosol (SOA). Furans might also react with aqueous photooxidants, such as singlet molecular oxygen (1O2*), to form aqueous SOA (aqSOA), but this has not been studied. To investigate the aqueous reactivities of furans and their potential to make low-volatility products, we first measured the reaction kinetics for singlet oxygen with 17 furans. The resulting second-order rate constants vary widely with chemical substitution, ranging from 105 to nearly 109 M–1 s–1. Inorganic salts can decrease or enhance the first-order loss of furans by singlet oxygen. To investigate whether furan-1O2* reactions might produce particulate matter, we measured SOA mass yields for three furans: furoic acid, furfuryl alcohol, and 2-methylfuran-3,4-dicarboxylic acid (MFDCA). The resulting mass yields span a huge range, with values of ∼0, 51, and 125%, respectively. Finally, we estimated rates of gas- and aqueous-SOA formation from reactions of MFDCA over a range of conditions, from cloud and fog drops to aerosol liquid water. Results suggest that aqueous reactions of highly substituted furans with 1O2* could be a significant source of aqSOA in biomass-burning plumes but that aqueous reactions of triplet excited states with phenols are more important.

  PublisherDOI

• Revealing the photochemical pathways of nitrate in water through first-principles simulations

  The Journal of Chemical Physics · 2025-04-14 · 1 citations

  article

  The nitrate anion (NO3-) is abundant in environmental aqueous phases, including aerosols, surface waters, and snow, where its photolysis releases nitrogen oxides back into the atmosphere. Nitrate photolysis occurs via two channels: (1) the formation of NO2 and O- and (2) the formation of NO2- and O(3P). The occurrence of two reaction channels with very low quantum yield (∼1%) highlights the critical role of the solvation environment and spin-forbidden electronic transitions, which remain unexplained at the molecular level. We investigate the two photolysis channels in water using quantum chemical calculations and first-principles molecular dynamics simulations with hybrid density functional theory and enhanced sampling. We find that spin-forbidden absorption to the triplet state (T1) is possible but occurs at a rate ∼15 times weaker than the spin-allowed transition to the singlet state (S1). A metastable solvation cage complex requires additional thermal energy to dissociate the N-O bond, allowing for recombination or non-radiative deactivation. Our results explain the temperature dependence of photolysis, linked to hydrogen bond rearrangement in the solvation shell. This work provides new molecular insights into nitrate photolysis and its low quantum yield under environmental conditions.

  PublisherDOI

• Atmospheric Singlet Molecular Oxygen Generation: Complementary Experimental and Theoretical DFT Approaches

  2025-01-10

  preprintOpen access
  PublisherOA PDFDOI

• Revealing the Photochemical Pathways of Nitrate in Water through First-Principles Simulations

  ChemRxiv · 2025-01-03

  preprintOpen access

  Nitrate anion (NO3-) is a ubiquitous species in aqueous phases in the environment, including atmospheric particles, aerosol droplets, surface waters, and snow. The photolysis of nitrate is a 'renoxification' process, which converts \nitrate solvated in water or deposited on surfaces back into NOx to the atmosphere. Nitrate photolysis under environmental conditions can follow two channels: (1) NO2 and O-; (2) nitrite and O. Despite the well-studied macroscopic kinetics of the two channels, the microscopic picture of the photolysis still needs to be explored. Furthermore, previous experiments have shown that nitrate photolysis in aqueous solutions has a low quantum yield of ~1% leading to a solvation cage effect hypothesis. A previous theoretical study has indicated that the low quantum yield may be due to the direct spin-forbidden absorption of \nitrate to its triplet state. Here, we employ first-principles molecular dynamics simulations at the level of hybrid DFT with enhanced sampling to explore the two channels in an aqueous solution to unravel the atomistic and electronic structure details of the photolysis, as well as investigate the causes of its low quantum yield under a solvation environment. The direct spin-forbidden absorption to T1 state is viable through spin-orbit coupling and is ~15 times weaker than the spin-allowed absorption to S1 state. A solvation cage complex is identified as a metastable state that requires additional thermal energy to complete the dissociation of the N-O bond at the triplet state. This metastable state allows the photo fragments to recombine or deactivate through non-radiative processes. Our simulations also qualitatively explain the temperature dependence of the two channels observed in experiments based on the rearrangement of H-bonds. This work provides a novel molecular picture illustrating the significantly low quantum yield and temperature dependence of nitrate photolysis under environmental conditions and a starting point for future studies of environmental nitrate photochemistry.

  PublisherOA PDFDOI

• Direct Determination of Absolute Radical Quantum Yields in Hydroxyl and Sulfate Radical-Based Treatment Processes

  Environmental Science & Technology · 2024-05-09 · 18 citations

  article

  The absolute radical quantum yield (Φ) is a critical parameter to evaluate the efficiency of radical-based processes in engineered water treatment. However, measuring Φ is fraught with challenges, as current quantification methods lack selectivity, specificity, and anti-interference capabilities, resulting in significant error propagation. Herein, we report a direct and reliable time-resolved technique to determine Φ at pH 7.0 for commonly used radical precursors in advanced oxidation processes. For H2O2 and peroxydisulfate (PDS), the values of Φ•OH and ΦSO4•− at 266 nm were measured to be 1.10 ± 0.01 and 1.46 ± 0.05, respectively. For peroxymonosulfate (PMS), we developed a new approach to determine Φ•OHPMS with terephthalic acid as a trap-and-trigger probe in the nonsteady state system. For the first time, the Φ•OHPMS value was measured to be 0.56 by the direct method, which is stoichiometrically equal to ΦSO4•−PMS (0.57 ± 0.02). Additionally, radical formation mechanisms were elucidated by density functional theory (DFT) calculations. The theoretical results showed that the highest occupied molecular orbitals of the radical precursors are O–O antibonding orbitals, facilitating the destabilization of the peroxy bond for radical formation. Electronic structures of these precursors were compared, aiming to rationalize the tendency of the Φ values we observed. Overall, this time-resolved technique with specific probes can be used as a reliable tool to determine Φ, serving as a scientific basis for the accurate performance evaluation of diverse radical-based treatment processes.

  PublisherDOI

• Modeling Novel Aqueous Particle and Cloud Chemistry Processes of Biomass Burning Phenols and Their Potential to Form Secondary Organic Aerosols

  Environmental Science & Technology · 2024-02-12 · 27 citations

  articleOpen access

  Phenols emitted from biomass burning contribute significantly to secondary organic aerosol (SOA) formation through the partitioning of semivolatile products formed from gas-phase chemistry and multiphase chemistry in aerosol liquid water and clouds. The aqueous-phase SOA (aqSOA) formed via hydroxyl radical (•OH), singlet molecular oxygen (1O2*), and triplet excited states of organic compounds (3C*), which oxidize dissolved phenols in the aqueous phase, might play a significant role in the evolution of organic aerosol (OA). However, a quantitative and predictive understanding of aqSOA has been challenging. Here, we develop a stand-alone box model to investigate the formation of SOA from gas-phase •OH chemistry and aqSOA formed by the dissolution of phenols followed by their aqueous-phase reactions with •OH, 1O2*, and 3C* in cloud droplets and aerosol liquid water. We investigate four phenolic compounds, i.e., phenol, guaiacol, syringol, and guaiacyl acetone (GA), which represent some of the key potential sources of aqSOA from biomass burning in clouds. For the same initial precursor organic gas that dissolves in aerosol/cloud liquid water and subsequently reacts with aqueous phase oxidants, we predict that the aqSOA formation potential (defined as aqSOA formed per unit dissolved organic gas concentration) of these phenols is higher than that of isoprene-epoxydiol (IEPOX), a well-known aqSOA precursor. Cloud droplets can dissolve a broader range of soluble phenols compared to aqueous aerosols, since the liquid water contents of aerosols are orders of magnitude smaller than cloud droplets. Our simulations suggest that highly soluble and reactive multifunctional phenols like GA would predominantly undergo cloud chemistry within cloud layers, while gas-phase chemistry is likely to be more important for less soluble phenols. But in the absence of clouds, the condensation of low-volatility products from gas-phase oxidation followed by their reversible partitioning to organic aerosols dominates SOA formation, while the SOA formed through aqueous aerosol chemistry increases with relative humidity (RH), approaching 40% of the sum of gas and aqueous aerosol chemistry at 95% RH for GA. Our model developments of biomass-burning phenols and their aqueous chemistry can be readily implemented in regional and global atmospheric chemistry models to investigate the aqueous aerosol and cloud chemistry of biomass-burning organic gases in the atmosphere.

  PublisherOA PDFDOI

• Aq_Ox_Biomass-Burning_Furans_by_Singlet_Oxygen

  ioChem-BD Computational Chemistry Datasets · 2024-10-08

  datasetOpen accessSenior author
  PublisherDOI

• Comment on egusphere-2023-2876

  2024-02-20

  peer-reviewOpen access1st authorCorresponding

  <strong class="journal-contentHeaderColor">Abstract.</strong> Nitrate photolysis is a potentially significant mechanism for &ldquo;renoxifying&rdquo; the atmosphere, i.e., converting nitrate into nitrogen oxides (nitrogen dioxide (NO₂) and nitric oxide (NO)) and nitrous acid (HONO). Nitrate photolysis in the environment occurs through two channels, which produce: (1) NO₂ and hydroxyl radical (^&bull;OH) and (2) nitrite (NO₂^&ndash;) and an oxygen atom (O(³<em>P</em>)). Although the aqueous quantum yields and photolysis rate constants of both channels have been established, field observations suggest that nitrate photolysis is enhanced in the environment. Laboratory studies investigating these enhancements typically only measure one of the two photo-channels, since measuring both channels generally requires separate analytical methods and instrumentation. However, measuring only one channel makes it difficult to assess whether secondary chemistry is enhancing one channel at the expense of the other, or if there is an overall enhancement of nitrate photochemistry. Here, we show that the addition of S(IV), i.e., bisulfite and sulfite, can convert NO₂ to NO₂^&ndash;, allowing measurement of both nitrate photolysis channels with the same equipment. By varying the concentration of S(IV) and exploring method parameters, we determine the experimental conditions that quantitatively convert NO₂ and accurately quantify the resulting NO₂^&ndash;. We then apply the method to a test case, showing how an ^&bull;OH scavenger in solution prevents the oxidation of NO₂^&ndash; to NO₂ but does not enhance the overall photolysis efficiency of nitrate.

  PublisherDOI

• Chemical Differences between Phenolic Secondary Organic Aerosol Formed through Gas-Phase and Aqueous-Phase Reactions

  ACS Earth and Space Chemistry · 2024-10-10 · 11 citations

  articleOpen access

  Phenolic compounds, which are significant emissions from biomass burning (BB), undergo rapid photochemical reactions in both gas and aqueous phases to form secondary organic aerosol, namely, gasSOA and aqSOA, respectively. The formation of gasSOA and aqSOA involves different reaction mechanisms, leading to different product distributions. In this study, we investigate the gaseous and aqueous reactions of guaiacol-a representative BB phenol-to elucidate the compositional differences between phenolic aqSOA and gasSOA. Aqueous-phase reactions of guaiacol produce higher SOA yields than gas-phase reactions (e.g., roughly 60 vs 30% at one half-life of guaiacol). These aqueous reactions involve more complex reaction mechanisms and exhibit a more gradual SOA evolution than their gaseous counterparts. Initially, gasSOA forms with high oxidation levels (O/C > 0.82), while aqSOA starts with lower O/C (0.55-0.75). However, prolonged aqueous-phase reactions substantially increase the oxidation state of aqSOA, making its bulk chemical composition closer to that of gasSOA. Additionally, aqueous reactions form a greater abundance of oligomers and high-molecular-weight compounds, alongside a more sustained production of carboxylic acids. AMS spectral signatures representative of phenolic gasSOA have been identified, which, together with tracer ions of aqSOA, can aid in the interpretation of field observation data on aerosol aging within BB smoke. The notable chemical differences between phenolic gasSOA and aqSOA highlighted in this study also underscore the importance of accurately representing both pathways in atmospheric models to better predict the aerosol properties and their environmental impacts.

  PublisherDOI

• Overview of the Alaskan Layered Pollution and Chemical Analysis (ALPACA) Field Experiment

  ACS ES&T Air · 2024-02-21 · 36 citations

  articleOpen access

  The Alaskan Layered Pollution And Chemical Analysis (ALPACA) field experiment was a collaborative study designed to improve understanding of pollution sources and chemical processes during winter (cold climate and low-photochemical activity), to investigate indoor pollution, and to study dispersion of pollution as affected by frequent temperature inversions. A number of the research goals were motivated by questions raised by residents of Fairbanks, Alaska, where the study was held. This paper describes the measurement strategies and the conditions encountered during the January and February 2022 field experiment, and reports early examples of how the measurements addressed research goals, particularly those of interest to the residents. Outdoor air measurements showed high concentrations of particulate matter and pollutant gases including volatile organic carbon species. During pollution events, low winds and extremely stable atmospheric conditions trapped pollution below 73 m, an extremely shallow vertical scale. Tethered-balloon-based measurements intercepted plumes aloft, which were associated with power plant point sources through transport modeling. Because cold climate residents spend much of their time indoors, the study included an indoor air quality component, where measurements were made inside and outside a house to study infiltration and indoor sources. In the absence of indoor activities such as cooking and/or heating with a pellet stove, indoor particulate matter concentrations were lower than outdoors; however, cooking and pellet stove burns often caused higher indoor particulate matter concentrations than outdoors. The mass-normalized particulate matter oxidative potential, a health-relevant property measured here by the reactivity with dithiothreiol, of indoor particles varied by source, with cooking particles having less oxidative potential per mass than pellet stove particles.

  PublisherOA PDFDOI

Recent grants

• Photochemical Formation of Oxidants and Destruction of Organic Compounds in the Snowpack at Summit, Greenland

  NSF · $269k · 2005–2009

• Collaborative Research: Fog Drop Reactions of Green Leaf Volatiles as a Source of Secondary Organic Aerosols

  NSF · $230k · 2011–2016

• Physical, Chemical, and Optical Properties of Snow: Impacts on Ocean-Atmosphere-Sea Ice-Snowpack Interactions (OASIS) and Sensitivity to Climate Change

  NSF · $543k · 2008–2012

• Formation of photo-oxidants and processing of organic species in aerosol liquid water

  NSF · $816k · 2022–2027

• Collaborative Research: Multi-phase Sulfur and Nitrogen Chemistry in Air and Snow during Alaskan Layered Pollution and Chemical Analysis (ALPACA)

  NSF · $613k · 2021–2025

Frequent coauthors

• Qi Zhang

  36 shared

• Florent Dominé

  Makivik Corporation

  30 shared

• Ted Hullar

  University of California, Davis

  28 shared

• Manuel Barret

  Université Grenoble Alpes

  19 shared

• Wenqing Jiang

  19 shared

• H. J. Beine

  University of California, Davis

  18 shared

• Joël Savarino

  17 shared

• Chrystal Guzman

  16 shared