Volatility of Atmospherically Relevant Alkylaminium Carboxylate Salts

Carbonyl-amine condensation coupled ozonolysis of dipropylamine and styrene: Decay kinetics, reaction mechanism, secondary organic aerosol formation and cytotoxicity

Oxidation of organic amines (OAs) or aromatic hydrocarbons (AHs) produces carbonyls, which further react with OAs to form carbonyl-amine condensation products, threatening environmental quality and human health. However, there is still a lack of systematic understanding of the carbonyl-amine condensation reaction processes of OAs or between OAs and AHs, and subsequent environmental health impact. This work systematically investigated the carbonyl-amine condensation coupled ozonolysis kinetics, reaction mechanism, secondary organic aerosol (SOA) formation and cytotoxicity from the mixture of dipropylamine (DPA) and styrene (STY) by a combined method of product mass spectrometry identification, particle property analysis and cell exposure evaluation. The results from ozonolysis of DPA and STY mixture revealed that STY inhibited the ozonolysis of DPA to different degrees to accelerate its own decay rate. The barycenter of carbonyl-amine condensation reactions was shifted from inside of DPA to between DPA and STY, which accelerated STY ozonolysis, but slowed down DPA ozonolysis. For the first time, ozonolysis of DPA and STY mixture to complex carbonyl-amine condensation products through the reactions of DPA with its carbonyl products, DPA with STY's carbonyl products and DPA's bond breakage product with STY's carbonyl products was confirmed. These condensation products significantly contributed to the formation and growth of SOA. The SOA containing particulate carbonyl-amine condensation products showed definite cytotoxicity. These findings are helpful to deeply and comprehensively understand the transformation, fate and environmental health effects of mixed organics in atmospheric environment.

Thermal Stability of Particle-Phase Monoethanolamine Salts

The use of monoethanolamine (MEA, 2-hydroxyethanamine) for scrubbing of carbon dioxide from combustion flue gases may become the dominant technology for carbon capture in the near future. The widespread implementation of this technology will result in elevated emissions of MEA to the environment that may increase the loading and modify the properties of atmospheric aerosols. We have utilized experimental measurements together with aerosol microphysics calculations to derive thermodynamic properties of several MEA salts, potentially the dominant forms of MEA in atmospheric particles. The stability of the salts was found to depend strongly on the chemical nature of the acid counterpart. The saturation vapor pressures and vaporization enthalpies obtained in this study can be used to evaluate the role of MEA in the aerosol and haze formation, helping to assess impacts of the MEA-based carbon capture technology on air quality and climate change.

Chemical Characterization of Gas- and Particle-Phase Products from the Ozonolysis of α-Pinene in the Presence of Dimethylamine

Amines are recognized as key compounds in new particle formation (NPF) and secondary organic aerosol (SOA) formation. In addition, ozonolysis of α-pinene contributes substantially to the formation of biogenic SOAs in the atmosphere. In the present study, ozonolysis of α-pinene in the presence of dimethylamine (DMA) was investigated in a flow tube reactor. Effects of amines on SOA formation and chemical composition were examined. Enhancement of NPF and SOA formation was observed in the presence of DMA. Chemical characterization of gas- and particle-phase products by high-resolution mass spectrometric techniques revealed the formation of nitrogen containing compounds. Reactions between ozonolysis reaction products of α-pinene, such as pinonaldehyde or pinonic acid, and DMA were observed. Possible reaction pathways are suggested for the formation of the reaction products. Some of the compounds identified in the laboratory study were also observed in aerosol samples (PM₁) collected at the SMEAR II station (Hyytiälä, Finland) suggesting that DMA might affect the ozonolysis of α-pinene in ambient conditions.

Kinetics, mechanisms and ionic liquids in the uptake of n-butylamine onto low molecular weight dicarboxylic acids

Atmospheric particles adversely affect visibility, health, and climate, yet the kinetics and mechanisms of particle formation and growth are poorly understood. Multiphase reactions between amines and dicarboxylic acids (diacids) have been suggested to contribute. In this study, the reactions of n-butylamine (BA) with solid C3-C8 diacids were studied at 296 ± 1 K using a Knudsen cell interfaced to a quadrupole mass spectrometer. Uptake coefficients for amines on the diacids with known geometric surface areas were measured at initial amine concentrations from (3-50) × 10¹¹ cm^-3. Uptake coefficients ranged from 0.7 ± 0.1 (2σ) for malonic acid (C3) to <10^-6 for suberic acid (C8), show an odd-even carbon number effect, and decrease with increasing chain length within each series. Butylaminium salts formed from evaporation of aqueous solutions of BA with C3, C5 and C7 diacids (as well as C8) were viscous liquids, suggesting that ionic liquids (ILs) form on the surface during the reactions of gas phase amine with the odd carbon diacids. Predictions from the kinetic multi-layer model of aerosol surface and bulk chemistry (KM-SUB) were quantitatively consistent with uptake occurring via dissolution of the underlying diacid into the IL layer and reaction with amine taken up from the gas phase. The butylaminium salts formed from the C4 and C6 diacids were solids, and their uptake coefficients were smaller. These experiments and kinetic modeling demonstrate the unexpected formation of ILs in a gas-solid reaction, and suggest that ILs should be considered under some circumstances in atmospheric processes.

Knudsen cell studies of the uptake of gaseous ammonia and amines onto C3–C7 solid dicarboxylic acids

While atmospheric particles affect health, visibility and climate, the details governing their formation and growth are poorly understood on a molecular level.

Hygroscopic Characteristics of Alkylaminium Carboxylate Aerosols

The hygroscopic growth factor (HGF) and cloud condensation nuclei (CCN) activity for a series of alkylaminium carboxylate aerosols have been measured using a hygroscopicity tandem differential mobility analyzer coupled to a condensation particle counter and a CCN counter. The particles, consisting of the mixtures of mono- (acetic, propanoic, p-toluic, and cis-pinonic acid) and dicarboxylic (oxalic, succinic, malic, adipic, and azelaic acid) acid with alkylamine (mono-, di-, and trimethylamines), represent those commonly found under diverse environmental conditions. The hygroscopicity parameter (κ) of the alkylaminium carboxylate aerosols was derived from the HGF and CCN results and theoretically calculated. The HGF at 90% RH is in the range of 1.3 to 1.8 for alkylaminium monocarboxylates and 1.1 to 2.2 for alkylaminium dicarboxylates, dependent on the molecular functionality (i.e., the carboxylic or OH functional group in organic acids and methyl substitution in alkylamines). The κ value for all alkylaminium carboxylates is in the range of 0.06-1.37 derived from the HGF measurements at 90% RH, 0.05-0.49 derived from the CCN measurements, and 0.22-0.66 theoretically calculated. The measured hygroscopicity of the alkylaminium carboxylates increases with decreasing acid to base ratio. The deliquescence point is apparent for several of the alkylaminium dicarboxylates but not for the alkylaminium monocarboxylates. Our results reveal that alkylaminium carboxylate aerosols exhibit distinct hygroscopic and deliquescent characteristics that are dependent on their molecular functionality, hence regulating their impacts on human health, air quality, and direct and indirect radiative forcing on climate.