cometadata/datacite-titles-descriptions-related-identifiers huggingface dataset:
DOI: 10.6075/j0zk5dwh
title: Data from: Collapse Mechanisms of Nascent and Aged Sea Spray Aerosol Proxy Films. In Center for Aerosol Impacts on Chemistry of the Environment (CAICE)

description: Publication abstract: Sea spray aerosol (SSA) is highly enriched in marine-derived organic compounds during seasons of high biological productivity, and saturated fatty acids comprise one of the most abundant classes of molecules. Fatty acids and other organic compounds form a film on SSA surfaces, and SSA particle surface-area-to-volume ratios are altered during aging in the marine boundary layer (MBL). To understand SSA surface organization and its role during dynamic atmospheric conditions, an SSA proxy fatty acid film and its individual components stearic acid (SA), palmitic acid (PA), and myristic acid (MA) are studied separately using surface pressure – area isotherms and Brewster angle microscopy (BAM). The films were spread on an aqueous NaCl subphase at pH 8.2, 5.6, and 2.0 to mimic nascent to aged SSA aqueous core composition in the MBL, respectively. We show that the individual fatty acid behavior differs from that of the SSA proxy film, and at nascent SSA pH the mixture yields a monolayer with intermediate rigidity that folds upon film compression to the collapse state. Acidification causes the SSA proxy film to become more rigid and form 3D nuclei. Our results reveal film morphology alterations, which are related to SSA reflectivity, throughout various stages of SSA aging and provide a better understanding of SSA impacts on climate.
DOI: 10.6075/j04m932f
title: Data from: The Impact of pH and NaCl and CaCl2 Salts on the Speciation and Photochemistry of Pyruvic Acid in the Aqueous Phase. In Center for Aerosol Impacts on Chemistry of the Environment (CAICE)

description: Publication abstract: Recent studies have shown that pyruvic acid can produce higher-molecular-weight compounds upon irradiation in the aqueous phase. These compounds can contribute to the formation of secondary organic aerosols. There have been several previous studies on the effect of ionic strength on the photochemistry of pyruvic acid, however; few of them investigated the effects of marine relevant salts such as NaCl and CaCl2. In this study, we examine the effect of NaCl and CaCl2, namely the containing coordinating cations Na+ and Ca2+, on the speciation, absorption properties and photoreactivity of pyruvic acid in aqueous solutions of varying pH. NMR shows that both Ca2+ and Na+ further deprotonate pyruvic acid and decrease the diol to ketone ratio of pyruvic acid than in pure water at the same pH, especially at more acidic pH (pH less than 4). The absorption spectrum shows a strong red shift in the peak maxima for the n → π* transition of pyruvic acid in NaCl/CaCl2 solutions. This dependence is much more pronounced for divalent cations (Ca2+) compared to monovalent cations (Na+). Vertical excitation energy calculations of the anionic ketone form of pyruvic acid confirm the same red shift on the n → π* transition peak in the presence of Ca2+. In addition, the presence of NaCl/CaCl2 suppress the photolysis rate of pyruvic acid, which could be due to the deprotonation of pyruvic acid by the cations and the lower photochemical reactivity for pyruvate, the deprotonated form.
DOI: 10.6075/j02b8w60
title: Data from: Linking variations in sea spray aerosol particle hygroscopicity to composition during two microcosm experiments. In Center for Aerosol Impacts on Chemistry of the Environment (CAICE)

description: Publication abstract: The extent to which water uptake influences the light scattering ability of marine sea spray aerosol (SSA) particles depends critically on SSA chemical composition. The organic fraction of SSA can increase during phytoplankton blooms, decreasing the salt content and therefore the hygroscopicity of the particles. In this study, subsaturated hygroscopic growth factors at 85% relative humidity (GF(85 %)) of predominately submicron SSA particles were quantified during two induced phytoplankton blooms in marine aerosol reference tanks (MARTs). One MART was illuminated with fluorescent lights and the other was illuminated with sunlight, referred to as the “indoor” and “outdoor” MARTs, respectively. Optically weighted GF(85%) values for SSA particles were derived from measurements of light scattering and particle size distributions. The mean optically weighted SSA diameters were 530 and 570nm for the indoor and outdoor MARTs, respectively. The GF(85%) measurements were made concurrently with online particle composition measurements, including bulk composition (using an Aerodyne high-resolution aerosol mass spectrometer) and single particle (using an aerosol time-of-flight mass spectrometer) measurement, and a variety of water-composition measurements. During both microcosm experiments, the observed optically weighted GF(85%) values were depressed substantially relative to pure inorganic sea salt by 5 to 15 %. There was also a time lag between GF(85%) depression and the peak chlorophyll a (Chl a) concentrations by either 1 (indoor MART) or 3-to-6 (outdoor MART) days. The fraction of organic matter in the SSA particles generally increased after the Chl a peaked, also with a time lag, and ranged from about 0.25 to 0.5 by volume. The observed depression in the GF(85%) values (relative to pure sea salt) is consistent with the large observed volume fractions of nonrefractory organic matter (NR-OM) comprising the SSA. The GF(85%) values exhibited a reasonable negative correlation with the SSA NR-OM volume fractions after the peak of the blooms (i.e., Chl a maxima); i.e., the GF(85%) values generally decreased when the NR-OM volume fractions in- creased. The GF(85%) vs. NR-OM volume fraction relation- ship was interpreted using the Zdanovskii–Stokes–Robinson (ZSR) mixing rule and used to estimate the GF(85%) of the organic matter in the nascent SSA. The estimated pure NR-OM GF(85%) values were 1.16±0.09 and 1.23±0.10 for the indoor and outdoor MARTS, respectively. These measurements demonstrate a clear relationship between SSA particle composition and the sensitivity of light scattering to variations in relative humidity. The implications of these observations to the direct climate effects of SSA particles are discussed.
DOI: 10.6075/j0zs2tpq
title: Data from: Let There be Light: Stability of Palmitic Acid Monolayers at the Air/Salt Water Interface in the Presence and Absence of Solar Light and a Photosensitizer. In Center for Aerosol Impacts on Chemistry of the Environment (CAICE)

description: Publication abstract: Fatty acid monolayers are known surfactants present at air/water interfaces. However, little is known about the stability of these fatty acid monolayers in the presence of solar irradiation. Here we have investigated for the first time, a study of palmitic acid monolayers on salt water interfaces in the presence and absence of simulated solar light with a photosensitizer in the underlying salt sub-phase. Using surface sensitive probes to measure changes in the properties of these monolayers upon irradiation with solar wavelengths, we find that the monolayers become less stable in the presence of light and a photosensitizer, in this case humic acid, present in the salt solution. The mechanism for this loss of stability is due to interfacial photochemistry involving excited humic acid and molecular oxygen leading to increased formation of less surface active species and therefore partitioning into the underlying solution as determined by surface pressure measurements.
DOI: 10.6075/j0f47mbf
title: Data from: Lab on a Tip: Atomic Force Microscopy - Photothermal Infrared Spectroscopy of Atmospherically Relevant Organic/Inorganic Aerosol Particles in the Nanometer to Micrometer Size Range. In Center for Aerosol Impacts on Chemistry of the Environment (CAICE)

description: Publication abstract: New developments in oscale analytical techniques have paved the way for detailed spectroscopic and microscopic measurements of substrate-deposited aerosol particles on a single particle basis. Atomic force microscopy based photothermal infrared (AFM-PTIR) spectroscopy is a technique that combines the ometer spatial resolution of AFM with the chemical analysis capabilities of vibrational spectroscopy. Herein we demonstrate the capability of AFM-PTIR to investigate single and multi-component systems comprised of inorganic salts and organic compounds relevant to the atmosphere. Chemical and microscopic characterization of particles as small as 50 nm in diameter is shown. Moreover, single particle data as a function of relative humidity using this technique is shown for the first time. These new measurements as a function of relative humidity allow for the simultaneous and independent acquisition of photothermal IR spectra, contact resoce frequency shifts, and water uptake growth factors, providing insight on changes in the composition, stiffness, and size of the particles, respectively. These results lay the foundation for more detailed AFM-PTIR studies of multicomponent aerosol particles under a range of environmental conditions.
DOI: 10.6075/j0639mx9
title: Data from: Enrichment of Saccharides and Divalent Cations in Sea Spray Aerosol during Two Phytoplankton Blooms. In Center for Aerosol Impacts on Chemistry of the Environment (CAICE)

description: Publication abstract: Sea spray aerosol (SSA) is a globally important source of particulate matter. A mesocosm study was performed to determine the relative enrichment of saccharides and inorganic ions in nascent fine (PM<sub>2.5</sub>) and coarse (PM<sub>10-2.5</sub>) SSA and the sea surface microlayer (SSML) relative to bulk seawater. Saccharides comprise a significant fraction of organic matter in fine and coarse SSA (11 and 27%, respectively). Relative to sodium, individual saccharides were enriched 14− 1314-fold in fine SSA, 3−138-fold in coarse SSA, but only up to 1.0−16.2-fold in SSML. Enrichments in SSML were attributed to rising bubbles that scavenge surface-active species from seawater, while further enrichment in fine SSA likely derives from bubble films. Mean enrichment factors for major ions demonstrated significant enrichment in fine SSA for potassium (1.3), magnesium (1.4), and calcium (1.7), likely because of their interactions with organic matter. Consequently, fine SSA develops a salt profile significantly different from that of seawater. Maximal enrichments of saccharides and ions coincided with the second of two phytoplankton blooms, signifying the influence of ocean biology on selective mass transfer across the ocean−air interface.
DOI: 10.6075/j0j964k2
title: Data from: Coordination-Dependent Spectroscopic Signatures of Divalent Metal Ion Binding to Carboxylate Head Groups: H<sub>2</sub>- and He-Tagged Vibrational Spectra of M<sup>2+</sup>·RCO<sub>2</sub><sup>-</sup> (M = Mg and Ca, R = −CD<sub>3</sub>, −CD<sub>2</sub>CD<sub>3</sub>) Complexes. In Center for Aerosol Impacts on Chemistry of the Environment (CAICE)

description: Publication abstract: We explore the intramolecular distortions present in divalent metal ion−carboxylate ion pairs using vibrational spectroscopy of the cryogenically cooled, mass-selected species isolated in the gas phase. The spectral signatures of the C−O stretching modes are identified using the perdeutero isotopologues of the acetate and propionate anions to avoid congestion arising from the CH2 fundamentals. Both Ca<sup>2+</sup> and Mg<sup>2+</sup> are observed to bind in a symmetrical, so-called “bidentate” arrangement to the −CO<sub>2</sub><sup>-</sup> group. The very strong deformations of the head groups displayed by the binary complexes dramatically relax when either neutral water molecules or counterions are attached to the Mg<sup>2+</sup>RCO<sub>2</sub><sup>-</sup> cation. These results emphasize the critical role that local coordination plays when using the RCO<sub>2</sub><sup>-</sup> bands to deduce the metal ion complexation motif in condensed media.
DOI: 10.6075/j02805tn
title: Data from: Control of Interfacial Cl2 and N2O5 Reactivity by a Zwitterionic Phospholipid in Comparison with Ionic and Uncharged Surfactants. In Center for Aerosol Impacts on Chemistry of the Environment (CAICE)

description: Publication abstract: Gas–liquid scattering experiments reveal that charge-separated but neutral (zwitterionic) surfactants catalyze the oxidation of dissolved Br– to Br2 by gaseous Cl2 at the surface of a 0.3 M NaBr/glycerol solution. Solutions of NaBr dissolved in glycerol with no surfactant were compared with solutions coated with zwitterionic, cationic, and anionic surfactants at dilute surface concentrations of 1.1 to 1.5 × 1014 cm–2 (less than 65% of maximum chain packing). The zwitterionic phospholipid enhances Cl2 conversion of Br– to Br2 by a factor of 1.61 ± 0.15, in comparison with a 14-fold enhancement by a cationic surfactant (tetrahexylammonium) and a five-fold suppression by an anionic surfactant (dodecyl sulfate). Further studies indicate that even an uncharged surfactant, monododecanoylglycerol, enhances Cl2 → Br2 production. Similar behavior is observed for the oxidation of Br– to Br2 by N2O5; it is just slightly suppressed by the phospholipid and strongly enhanced by the cationic surfactant. Collectively, these results suggest that attractions and repulsions between the negative Br– ions and the positive and negative charges of the surfactant headgroups draw Br– ions to the surface or repel them away. At low coverages, ion-induced dipole and dispersion interactions between the CH2 groups and Br– or Cl2 may also enhance reactivity. These results demonstrate that the hydrocarbon chains of loosely packed surfactants do not necessarily block gas–liquid reactions but that positively charged, and even uncharged, groups can instead facilitate reactions by bringing gas-phase and solution-phase reagents together in the interfacial region.
DOI: 10.6075/j0p26w9d
title: Data from: Cation effects on phosphatidic acid monolayers at various pH conditions. In Center for Aerosol Impacts on Chemistry of the Environment (CAICE)

description: Publication Abstract: The impact of pH and cations on phase behavior, stability, and surface morphology for dipalmitoyl- phosphatidic acid (DPPA) monolayers was investigated. At pH &lt; 10, DPPA monolayers on water are predomitly populated by neutral species and display the highest packing density. Cations are found to expand and stabilize the monolayer in the following order of increasing magnitude at pH 5.6: Na<sup>+</sup> &gt; K<sup>+</sup> ≈ Mg<sup>2+</sup> &gt; Ca<sup>2+</sup>. Additionally, cation complexation is tied to the pH and protonation state of DPPA, which are the primary factors controlling the monolayer surface behavior. The binding affinity of cations to the headgroup and thus deprotonation capability of the cation, ranked in the order of Ca<sup>2+</sup> &gt; Mg<sup>2+</sup> &gt; Na<sup>+</sup>&gt; K<sup>+</sup>, is found to be well explained by the law of matching water affinities. Nucleation of surface 3D lipid structures is observed from Ca<sup>2+</sup>, Mg<sup>2+</sup>, and Na<sup>+</sup>, but not from K<sup>+</sup>, consistent with the lowest binding affinity of K<sup>+</sup>. Unraveling cation and pH effects on DPPA monolayers is useful in further understanding the surface properties of complex systems such as organic-coated marine aerosols where organic films are directly influenced by the pH and ionic composition of the underlying aqueous phase.
DOI: 10.6075/j08c9tfw
title: Data from: Bulk Contributions Modulate the Sum-Frequency Generation Spectra of Interfacial Water on Model Sea-Spray Aerosols. In Center for Aerosol Impacts on Chemistry of the Environment (CAICE)

description: Publication abstract: Vibrational sum-frequency generation (vSFG) spectroscopy is used to determine the molecular structure of water at the interface of palmitic acid monolayers. Both measured and calculated spectra display specific features due to third-order contributions to the vSFG response which are associated with finite interfacial electric potentials. We demonstrate that theoretical modeling enables to separate the third-order contributions, thus allowing for a systematic analysis of the strictly surface-sensitive, second-order component of the vSFG response. This study provides fundamental, molecular-level insights into the interfacial structure of water in a neutral surfactant system with relevance to single layer bio-membranes and environmentally relevant sea-spray aerosols. Our results emphasize the key role that computer simulations can play in interpreting vSFG spectra and revealing microscopic details of water at complex interfaces, which can be difficult to extract from experiments due to the mixing of second-order, surface-sensitive and third-order, bulk-dependent contributions to the vSFG response.
description: Softwares: 1. LAMMPS: An open-source molecular dynamics package http://lammps.sandia.gov/ 2. DLPOLY_2.0: A open-source molecular dynamics package which is modified to include MB-pol water model. It can be downloaded for free using the below link, http://paesanigroup.ucsd.edu/software/mbpol_ipi.html 3. SFG spectrum: It is calculated with in-house software which is provided along with the data (filename: dipole_polarizability.zip). Instructions on how to compile the code are also provided in the zipped file.
DOI: 10.6075/j0n58jkb
title: Data from: Impacts of Lipase Enzyme on the Surface Properties of Marine Aerosols. In Center for Aerosol Impacts on Chemistry of the Environment (CAICE)

description: Publication abstract: Triacylglycerol lipases have recently been shown to be transferred from the ocean to the atmosphere in atmospheric sea spray aerosol (SSA). Lipases have the potential to alter the composition of SSA; however, the structure and properties of enzymes in the high salt, high ionic strength, and low pH conditions found in SSA have never been explored. Here, we study the dynamics of Burkholderia cepacia triacylglycerol lipase (BCL) at SSA model surfaces comprised of palmitic acid and dipalmitoylphosphatidic acid (DPPA), two commonly found lipids at SSA surfaces. Surface adsorption Langmuir isotherm experiments and all-atom explicit solvent molecular dynamics simulations together illuminate how and why BCL expands the ordering of lipids at palmitic acid surfaces the most at pH &lt; 4 and the least in DPPA surfaces at pH 6. Taken together, these results represent a first glimpse into the complex interplay between lipid surface structure and protein dynamics within enzyme-containing aerosols.
description: All-atom explicit solvent molecular dynamics simulations were performed with AMBER and CHARMM Force fields. Analyses were performed in Jupyter notebooks.
DOI: 10.6075/j0st7n0c
title: Data from: Heterogeneous Chemistry of Lipopolysaccharides with Gas-Phase Nitric Acid: Reactive Sites and Reaction Pathways. In Center for Aerosol Impacts on Chemistry of the Environment (CAICE)

description: Publication abstract: Recent studies have shown that sea spray aerosol (SSA) has a size-dependent, complex composition consisting of biomolecules and biologically derived organic compounds in addition to salts. This additional chemical complexity most likely influences the heterogeneous reactivity of SSA, as these other components will have different reactive sites and reaction pathways. In this study, we focus on the reactivity of a class of particles derived from some of the biological components of sea spray aerosol including lipopolysaccharides (LPS) that undergo heterogeneous chemistry within the reactive sites of the biological molecule. Examples of these reactions and the relevant reactive sites are proposed as follows: R−COONa(s) + HNO<sub>3</sub>(g) → NaNO<sub>3</sub> + R−COOH and R−HPO<sub>4</sub>Na(s) + HNO<sub>3</sub>(g) → NaNO<sub>3</sub> + R−H<sub>2</sub>PO<sub>4</sub>. These reactions may be a heterogeneous pathway not only for sea spray aerosol but also for a variety of other types of atmospheric aerosol as well.
DOI: 10.6075/j03r0r1h
title: Data from: Expanding Single Particle Mass Spectrometer Analyses for the Identification of Microbe Signatures in Sea Spray Aerosols. In Center for Aerosol Impacts on Chemistry of the Environment (CAICE)

description: Publication abstract: Ocean-derived microbes in sea spray aerosols (SSA) have the potential to influence climate and weather by acting as ice nucleating particles in clouds. Single particle mass spectrometers (SPMS), which generate in situ single particle composition data, are excellent tools for characterizing aerosols under changing environmental conditions as they can provide high temporal resolution and require no sample preparation. While SPMS have proven capable of detecting microbes, these instruments have never been utilized to definitively identify aerosolized microbes in ambient sea spray aerosols. In this study, an aerosol time-of-flight mass spectrometer was used to analyze laboratory generated SSA produced from natural seawater in a marine aerosol reference tank. We present the first description of a population of biological SSA mass spectra (BioSS), which closely match the ion signatures observed in previous terrestrial microbe studies. The fraction of BioSS dramatically increased in the largest supermicron particles, consistent with field and laboratory measurements of microbes ejected by bubble bursting, further supporting the assignment of BioSS mass spectra as microbes. Finally, as supported by analysis of inorganic ion signals, we propose that dry BioSS particles have heterogeneous structures, with microbes adhered to sodium chloride nodules surrounded by magnesium-enriched coatings. Consistent with this structure, chlorine-containing ion markers were ubiquitous in BioSS spectra and identified as possible tracers for distinguishing recently aerosolized marine from terrestrial microbes.
DOI: 10.6075/j0jq0z6x
title: Data from: Trace Metal Enrichment driven by Phosphate Functional Group Binding Selectivity. In Center for Aerosol Impacts on Chemistry of the Environment (CAICE)
DOI: 10.6075/j0xk8cqp
title: Data from: The i-TTM model for ab initio-based ion–water interaction potentials. II. Alkali metal ion–water potential energy functions. In Center for Aerosol Impacts on Chemistry of the Environment (CAICE)

description: Publication abstract: A new set of i-TTM potential energy functions describing the interactions between alkali metal ions and water molecules is reported. Following our previous study on halide ion–water interactions [J. Phys. Chem. B, 2016, 120, 1822], the new i-TTM potentials are derived from fits to CCSD(T) reference energies and, by construction, are compatible with the MB-pol many-body potential, which has been shown to accurately predict the properties of water from the gas to the condensed phase. Within the i-TTM formalism, two-body repulsion, electrostatic, and dispersion energies are treated explicitly, while many-body effects are represented by classical induction. The accuracy of the new i-TTM potentials is assessed through extensive comparisons with results obtained from different ab initio methods, including CCSD(T), CCSD(T)-F12b, DF-MP2, and several DFT models, as well as from polarizable force fields for M<sup>+</sup>(H<sub>2</sub>O)<sub>n</sub> clusters with M<sup>+</sup> =Li<sup>+</sup>,Na<sup>+</sup>,K<sup>+</sup>,Rb<sup>+</sup>, and Cs<sup>+</sup>, and n = 1–4.
description: All the MOLPRO and GAUSSIAN calculations were run using MOLPRO 2015.1 and GAUSSIAN 09. If you want to reproduce those calculations, please refer to the MOLPRO and GAUSSIAN user manuals, and use the same basis sets used in our manuscript. All these basis sets are available by default in both programs. For the MOLPRO calculations, please refer to the SI of the manuscript to follow the two-point extrapolation to the complete basis set.