cometadata/datacite-titles-descriptions-related-identifiers huggingface dataset:
DOI: 10.6075/j0kk995z
title: Data from: Sodium Drives Interfacial Equilibria for Semi-Soluble Phosphoric and Phosphonic Acids of Model Sea Spray Aerosol Surfaces. In Center for Aerosol Impacts on Chemistry of the Environment (CAICE)

description: Publication abstract: Organic phosphates and phosphonates represent important yet understudied constituents in our molecular understanding of the ocean. Herein, we determined the critical concentration of sodium relating to the onset of surface activity of alkyl phosphates and phosphonates at the air-water interface to further understand the interfacial environment of sea spray aerosols emitted from the ocean’s surface. A low pH range (1 to 5.6) was chosen to represent a model system for aged, acidic marine aerosols. The protonation state and sodium binding properties of C16‒C18 alkyl phosphoric and phosphonic acids were explored using surface pressure‒area isotherms and infrared reflection‒absorption spectroscopy. We found that increasing pH and headgroup charge led to significant desorption of these semi-soluble phosphor-containing acids into bulk solution while the neutral, fully protonated and sodium complexed species were favored at the interface. For the phosphonate species, the competition between sodium complexation and protonation reveals a critical sodium chloride concentration of ≥2 M at pH 2 necessary to outcompete the acid‒base equilibrium. The onset of this equilibrium shift begins at concentrations as low as 0.1 M NaCl at pH 2 which demonstrates that ion pairing mediated surface activity is highly relevant in sea spray aerosol systems. We also show that competitive interfacial equilibria between speciation and binding cannot be modeled by known bulk processes for the fully soluble methylphosphonic acid or through theoretical predictions from the Gouy Chapman model.
DOI: 10.6075/j05x2934
title: Data from: Hydration and Hydrogen Bond Disorder of Octadecanoic Acid and Octadecanol Films on Water at 21 ᵒC and 1 ᵒC. In Center for Aerosol Impacts on Chemistry of the Environment (CAICE)

description: Publication abstract: The temperature-dependent hydration structure of long-chain fatty acids and alcohols at air-water interfaces has great significance in the fundamental interactions underlying ice nucleation in the atmosphere. We present an integrated theoretical and experimental study of the temperature-dependent vibrational structure and electric field character of the immediate hydration shells of fatty alcohol and acid headgroups. We use a combination of surface-sensitive spectroscopy, surface potentiometry, and ab initio molecular dynamics simulations to elucidate detailed molecular structures of the octadecanoic acid and octadecanol (stearic acid and stearyl alcohol) headgroup hydration shells at room temperature and near freezing. Results reveal that the hydration shells for both compounds screen their polar headgroup dipole moments reducing the surface potential at low surface coverages; at higher surface coverage, the polar headgroups become dehydrated, which reduces the screening, correlating to higher observed surface potential values. Lowering the temperature promotes tighter chain packing and an increase in surface potential. The chain packing correlates with stronger intermolecular interactions between the fatty compound headgroup and its hydration shell as shown by infrared reflection absorption spectroscopy (IRRAS). This in turn disrupts the water-water hydrogen bonds at near freezing temperatures. Using ab initio molecular dynamics (AIMD) calculations on cluster systems of propanol + 6 H2O and propionic acid + 10 H2O, a spectral decomposition scheme was developed to correlate the OH stretching motion with the IRRAS spectral features. These findings challenge assumptions that point to ice templating as the preferred mechanism for ice nucleation at aqueous surfaces.
DOI: 10.6075/j0gq6w2z
title: Data from: Cultivable, halotolerant ice nucleating bacteria and fungi in coastal precipitation. In Center for Aerosol Impacts on Chemistry of the Environment (CAICE)

description: Publication abstract: Ice nucleating particles (INPs) are a rare subset of aerosol particles that initiate cloud droplet freezing at temperatures above the homogenous freezing point of water (-38 °C). Considering that the ocean covers 70% of the earth’s surface and represent a large potential source of INPs, it is imperative that the uncertainties in the identities and emissions of ocean INP become better understood. However, the specific underlying drivers of marine INP emissions and their identities remain largely unknown due to limited observations and the challenge involved in isolating exceptionally rare IN forming particles. By generating nascent sea spray aerosol (SSA) over a range of biological conditions, mesocosm studies show that microbes can contribute to marine INPs. Here, we identify 14 (30%) cultivable halotolerant ice nucleating microbes and fungi among 47 total isolates recovered from precipitation and aerosol samples collected in coastal air in Southern California. IN isolates collected in coastal air were found to nucleate ice from extremely warm to moderate freezing temperatures (-2.3 to -18 °C). Air mass trajectory analyses, and cultivability in marine growth media indicate marine origins of these isolates. Further phylogenetic analysis confirmed that at least two of the 14 IN isolates were of marine origin. Moreover, results from cell washing experiments demonstrate that most IN isolates maintained freezing activity in the absence of nutrients and cell growth media. This study provides confirmation of previous studies’ findings that implicated microbes as a potential source of marine INPs and additionally demonstrates links between precipitation, marine aerosol and IN microbes.
description: Back-trajectory analysis completed with FLEXPART: https://www.flexpart.eu/ Cloud temperatures and altitude estimates retrieved from High-Resolution Rapid Refresh (HRRR): https://rapidrefresh.noaa.gov/hrrr/
DOI: 10.6075/j01836nn
title: Data from: Zinc–Carboxylate Binding in Mixed Octadecanoic Acid and Octadecanol Monolayers on Proxy Seawater Solution Surfaces. In Center for Aerosol Impacts on Chemistry of the Environment (CAICE)

description: Publication abstract: Organic coatings on sea spray aerosol are largely comprised of fatty acids in addition to a vast array of other organic molecules including fatty alcohols. The seawater from which sea spray aerosol originates contains metal ions that interact with the organic coating at the air-seawater interface, resulting in transport of these metals into the atmosphere. Metal binding within single-substance monolayers on aqueous solutions has been previously studied. However, such binding events within mixed monolayers, especially those of ocean relevant ratios, are not well explored. Here we examine four monolayer ratios of octadecanoic acid (stearic acid) to octadecanol (stearyl alcohol) on aqueous solutions with varying ZnCl2 concentrations and a seawater-relevant NaCl concentration of 0.465 M. Surface pressure–area (Π-A) isotherms and infrared reflection-absorption spectroscopy (IRRAS) are used to quantify the Zn2+–carboxylate surface binding affinities for each monolayer composition. We find that: Zn2+–carboxylate binding is enhanced by ~300 times at the surface when compared to the bulk solution. Addition of 10% octadecanol reduces the apparent surface binding affinity by over 50% from 3.6 × 103 to 1.4 × 103 M-1; this is significantly more than predicted from the slight reduction in viable 1:1 binding sites. Furthermore, 1:2 Zn2+–carboxylate binding is shown to only be viable for the 100% and 95% fatty acid film whereas 1:1 binding is observed for all film ratios investigated.
DOI: 10.6075/j02807rk
title: Data from: Role of Hydration in Magnesium versus Calcium Ion Pairing with Carboxylate Solution and the Aqueous Interface. In Center for Aerosol Impacts on Chemistry of the Environment (CAICE)

description: Publication abstract: The binding of group II metal cations such as Ca2+ and Mg2+ have been largely categorized as electrostatic or ionic using carboxylate symmetric and asymmetric stretching frequency assignments referenced from works of Tackett and Nakamoto.1,2 However, given the importance of these cations and their binding mechanisms related to biological function and in revealing surface enrichment factors for ocean to marine aerosol transfer, it is imperative that a deeper understanding be sought to include hydration effects. Here, infrared reflection-absorption and Raman spectra for surface and solution phase carboxylate binding information, respectively, are compared against bare (unbound) carboxylate and bi-dentate Zn2+ : carboxylate spectral signatures. Spectral non- coincidence effect analysis, temperature studies, and spectral and potential of mean force calculations result in a concise interpretation of binding motifs that include the role of mediating water molecules, that is, contact and solvent-shared ion pairs. Calcium directly binds to the carboxylate group in contact ion pairs where magnesium rarely does. Moreover, we reveal the dominance of the solvent-shared ion pair of magnesium with carboxylate at the air-water interface and in solution.
DOI: 10.6075/j0gm85tv
title: Data from: Importance of Supermicron Ice Nucleating Particles in Nascent Sea Spray. In Center for Aerosol Impacts on Chemistry of the Environment (CAICE)

description: Publication abstract: With oceans covering 71% of the Earth’s surface, sea spray aerosols (SSA) play an important role in the global radiative budget by acting as cloud condensation nuclei and ice nucleating particles. By acting as ice nucleating particles (INPs), SSA can affect the structure and properties of mixed-phase clouds by inducing freezing at warmer temperatures than the homogeneous freezing temperature. Climate models that incorporate marine INPs often assume that submicron SSA particles form INPs due to the fact they contain a higher fraction of organic mass. Here we show that supermicron SSA, produced using a natural breaking wave analogue, are the major source of INPs throughout the lifecycle of a phytoplankton bloom. Additionally, supermicron SSA are shown to be more efficient INPs than submicron SSA, suggesting ice active components are contained in these larger sea spray particles.
DOI: 10.6075/j0g15z7r
title: Data from: Microscopic Mechanisms of N2O5 Hydrolysis on the Surface of Water Droplets. In Center for Aerosol Impacts on Chemistry of the Environment (CAICE)

description: Publication abstract: Reactions of N2O5, in particular heterogeneous hydrolysis, play a vital role in determining the chemistry of the atmosphere. The N2O5 heterogeneous hydrolysis reaction has been the subject of extensive research for decades, yet the physicochemical details of the mechanism have not been established. In this study, we show that this reaction can occur on the surface of a pure water droplet. We compute a relevant transition state for a nano-size model system and follow its evolution in time by means of ab initio molecular dynamics. This transition state, where N2O5 has a strong ion-pair character, leads directly to HNO3. Both electrophilic and nucleophilic mechanisms take place. It is suggested that corresponding simulations for hydrolysis in the bulk are desirable.
DOI: 10.6075/j0s46qg6
title: Data from: Probing the Water Uptake and Phase State of Individual Sucrose Nanoparticles using Atomic Force Microscopy. In Center for Aerosol Impacts on Chemistry of the Environment (CAICE)

description: Publication abstract: Atmospheric aerosols’ effects on the Earth’s climate and atmosphere can vary significantly depending on their properties including size, morphology, and phase state, all of which are influenced by varying relative humidity (RH) in the atmosphere. Furthermore, a significant fraction of atmospheric aerosols is below 100 nm in size (i.e., nanoparticles). However, due to size limitations of conventional experimental techniques, the atmospheric role of sub-100 nm aerosols and how the particle-to-particle variability of the phase state affects atmospheric processes are poorly understood. To address this issue, the atomic force microscopy (AFM) methodology that was previously established for submicrometer aerosols is extended to measure the water uptake and identify the phase state of individual sucrose nanoparticles. Quantified 3D hygroscopic growth factors of individual sucrose nanoparticles at 60% RH were lower than expected values observed on the submicrometer sucrose particles. Specifically, the growth factor of sucrose nanoparticle (height of 50 nm) was 0.89, which is approximately 18% lower than the expected value of 1.08. The effect was attributed to the nanoparticle restructuring on a solid substrate. Despite this however, the identified phase states of the nanoparticles were comparable to their submicrometer counterparts. The identified phase transition between solid to semisolid, and semisolid to liquid were at ~18% and 60% RH, which would be equivalent to viscosities of 1011.2 Pa s and 102.5 Pa s, respectively. This work demonstrates that measurements of the phase state using AFM is applicable to nanosized particles, even when the substrate alters the shape of semisolid nanoparticles at elevated RH.
DOI: 10.6075/j0m32t8b
title: Data from: Best practices for precipitation sample storage for offline studies of ice nucleation. In Center for Aerosol Impacts on Chemistry of the Environment (CAICE)

description: Publication abstract: Ice nucleating particles (INPs) are efficiently removed from clouds through precipitation, a convenience of nature for the study of the rare particles (1 in 106 in the free troposphere) that influence multiple climate-relevant cloud properties including ice crystal concentrations, size distributions, and formation processes. INPs suspended in precipitation have been considered a basis for estimating in-cloud INP concentrations and for inferring their original composition. Offline droplet assays are commonly used to measure INP concentrations in precipitation samples. Heat and filtration “treatments” are used to probe INP composition and size ranges. Many previous studies report storing samples prior to INP analyses, but little is known about the effects of storage on INP concentration or their sensitivity to treatments. Here, through a study of 15 precipitation samples collected at a coastal location in La Jolla, CA, USA between 9/22/2016 and 11/22/2019, we bound enhancements and losses of INPs with warm to moderate freezing temperatures (-7 to -19 ºC) due to storage under 4 conditions: 1.) storage at room temperature (+ 21-23 ºC) , 2.) storage at +4 ºC 3.) storage at -20 ºC, and 4.) flash freezing samples with liquid nitrogen prior to storage at -20 ºC. Results demonstrate that storage can lead to both enhancements and losses of greater than one order of magnitude, non-heat-labile INPs are generally less sensitive to storage, and significant losses of INPs below 0.45 μm are exhibited across all tested storage protocols. No correlation between total storage time (1-166 days) and changes in INP concentration was found. We provide the following recommendations for precipitation samples from coastal environments intended for INP analysis: that samples be stored at -20 ºC to minimize storage artifacts, that potential changes due to storage are considered to be additional uncertainty in measurement of INP concentration (e.g. a loss of 25% on average, for samples stored at -20 ºC,), and that filtration treatments are applied only to fresh samples. Finally, correction factors are provided so that INP measurements obtained from stored samples may be used to estimate concentrations present in the fresh sample.
DOI: 10.6075/j03j3d4s
title: Data from: Preparation and Characterization of the Halogen Bonding Motif in the Isolated Cl−∙IOH Complex with Cryogenic Ion Vibrational Spectroscopy. In Center for Aerosol Impacts on Chemistry of the Environment (CAICE)

description: Publication Abstract: In the presence of a halide ion, hypohalous acids can adopt two binding motifs upon formation of the ion-molecule complexes [XHOY]−, (X, Y = Cl, Br, I): a hydrogen (HB) bond to the acid OH group and a halogen (XB) bond between the anion and the acid halogen. Here we isolate the X-bonded Cl−∙IOH ion-molecule complex by collisions of I−∙(H2O)n clusters with HOCl vapor and measure its vibrational spectrum by IR photodissociation of the H2-tagged complex. Anharmonic analysis of its vibrational band pattern reveals that formation of the XB complex results in dramatic lowering of the HOI bending fundamental frequency and elongation of the O-I bond (by 168 cm−1 and 0.13 Å, respectively, relative to isolated HOI). The frequency of the O-I stretch (estimated 436 cm−1) is also encoded in the spectrum by the weak v = 0 → 2 overtone transition at 872 cm−1.
DOI: 10.6075/j0jq0z7c
title: Data from: Molecular-level Origin of the Carboxylate Head Group Response to Divalent Metal Ion Complexation at the Air-water Interface. In Center for Aerosol Impacts on Chemistry of the Environment (CAICE)

description: Publication abstract: We exploit gas-phase cluster ion techniques to provide insight into the local interactions underlying divalent metal ion-driven changes in the spectra of carboxylic acids at the air-water interface. This information is used to clarify the experimental findings that the CO stretching bands of long chain acids appear at very similar energies when the head group is deprotonated by high sub-phase pH or is exposed to relatively high concentrations of Ca2+ metal ions. To this end, we report the evolution of the vibrational spectra of size-selected [Ca2+·RCO2¯]+·(H2O)n=0-12 and RCO2¯·(H2O)n=0-14 cluster ions toward the features observed at the air-water interface. Surprisingly, not only does stepwise hydration of the RCO2¯ anion and the [Ca2+·RCO2¯]+ contact ion pair yield solvatochromic responses in opposite directions, but in both cases, the responses of the two (symmetric and asymmetric stretching) CO bands to hydration are opposite to each other. The result is that the two CO bands evolve toward their interfacial asymptotes from opposite directions. Simulations of the [Ca2+·RCO2¯]+·(H2O)n clusters indicate that the metal ion remains directly bound to the head group in a contact ion pair motif as the asymmetric CO stretch converges at the interfacial value by n = 12. This establishes that direct metal complexation or deprotonation can account for the interfacial behavior. We discuss these effects in the context of a model that invokes the water network-dependent local electric field along the C-C bond that connects the head group to the hydrocarbon tail as the key parameter that is correlated with the observed trends.
DOI: 10.6075/j0df6rdd
title: Data from: Characterization of Oxidation Products from HOCl Uptake by Microhydrated Methionine Anions using Cryogenic Ion Vibrational Spectroscopy. In Center for Aerosol Impacts on Chemistry of the Environment (CAICE)

description: Publication Abstract: The oxidation of the amino acid methionine (Met) by hypochlorous acid (HOCl) to yield methionine sulfoxide (MetO) has been implicated in both the interfacial chemistry of tropospheric sea spray aerosols as well as the destruction of pathogens in the immune system. Here, we investigate the reaction of deprotonated methionine water clusters Met‾‧(H2O)n with HOCl and characterize the resulting products using cryogenic ion vibrational spectroscopy and electronic structure calculations. Capture of the MetO− oxidation product in the gas phase requires the presence of water molecules attached to the reactant anion. Analysis of its vibrational band pattern confirms that the sulfide group of Met‾ has indeed been oxidized. Additionally, the vibrational spectrum of the anion corresponding to uptake of HOCl by Met‾‧(H2O)n indicates that it exists as an “exit-channel” complex, in which the Cl– product ion is bound to the COOH group following formation of the S=O motif.
DOI: 10.6075/j05q4w83
title: Data from: Reduction and Photoreduction of NO2 in Humic Acid Films as a Source of HONO, ClNO, N2O, NOX, and Organic Nitrogen. In Center for Aerosol Impacts on Chemistry of the Environment (CAICE)

description: Publication Abstract: Atmospheric nitrous acid (HONO), a trace atmospheric gas, is often underestimated in global atmospheric models due to the poor understanding of its daytime sources and sinks. HONO is known to accumulate during nighttime and undergo rapid photodissociation during the day to form NO and highly reactive OH radical, making it important to have accurate atmospheric HONO estimations. Despite its rapid photolysis, recent field observations have found quasi-steady-state concentrations of HONO at midday, suggesting photolytic HONO formation pathways to replenish daytime atmospheric HONO. Recent studies suggest that the presence of complex organic photosensitizers in atmospheric aerosols converts atmospheric NO2 into HONO. To better understand the effect of environmental photosensitizers in daytime mechanisms of HONO formation, we present here laboratory studies on the heterogeneous photolytic reduction of NO2 by humic acid films, a proxy for organic chromophoric compounds. The effect of pH and Cl− in the photosensitized formation of HONO and other nitrogen-containing gases is also investigated. A dual Fourier transform infrared (FTIR) system is utilized to simultaneously perform in situ analysis of condensed-phase reactants and gas-phase products. We find that the rate of HONO formation is faster at lower pHs. Nitrogen incorporation in the complex organic chromophore is observed, suggesting a competing pathway that results in suppressed daytime formation of nitrogenous gases. Significantly, the presence of chloride ions also leads to the organic-mediated photolytic formation of nitrosyl chloride (ClNO), a known precursor of HONO. Overall, this work shows that organic acid photosensitizers can reduce adsorbed NO2 to form HONO, ClNO, and NO while simultaneously incorporating nitrogen into the organic chromophores present in aerosol.
DOI: 10.6075/j0416x7m
title: Data from: Isotopic Insights into Organic Composition Differences between Supermicron and Submicron Sea Spray Aerosol. In Center for Aerosol Impacts on Chemistry of the Environment (CAICE)

description: Publication abstract: To elucidate the seawater biological and physicochemical factors driving differences in organic composition between supermicron and submicron sea spray aerosol (SSAsuper and SSAsub), carbon isotopic composition (δ13C) measurements were performed on size segregated, nascent SSA collected during a phytoplankton bloom mesocosm experiment. The δ13C measurements indicate that SSAsuper organic composition resembles a mixture of particulate and dissolved organic material in the bulk seawater. After phytoplankton growth, a greater amount of freshly produced carbon was observed in SSAsuper with the proportional contribution being modulated by bacterial activity, emphasizing the importance of the microbial loop in controlling the organic composition of SSAsuper. Conversely, SSAsub exhibited no apparent relationship with biological activity, but correlated closely with surface tension measurements probing the topmost ~0.2 1.5 µm of the sea surface microlayer. This probing depth is similar to a bubble’s film thickness at the ocean surface, suggesting that SSAsub organic composition strongly depends on surfactants present at the air sea interface that are transferred into SSAsub by bubble bursting. Our findings illustrate the substantial impact of seawater dynamics on the pronounced organic compositional differences between SSAsuper and SSAsub, and demonstrate that these two SSA populations should be considered separately when assessing their contribution to marine aerosols and climate.