Amines are likely to enhance neutral and ion-induced sulfuric acid-water nucleation in the atmosphere more effectively than ammonia

We have studied the structure and formation thermodynamics of dimer clusters containing H<sub>2</sub>SO<sub>4</sub> or HSO<sub>4</sub><sup>−</sup> together with ammonia and seven different amines possibly present in the atmosphere, using the high-level ab initio methods RI-MP2 and RI-CC2. As expected from e.g. proton affinity data, the binding of all studied amine-H<sub>2</sub>SO<sub>4</sub> complexes is significantly stronger than that of NH<sub>3</sub>•H<sub>2</sub>SO<sub>4</sub>, while most amine-HSO<sub>4</sub><sup>−</sup> complexes are only somewhat more strongly bound than NH<sub>3</sub>•HSO<sub>4</sub><sup>−</sup>. Further calculations on larger cluster structures containing dimethylamine or ammonia together with two H<sub>2</sub>SO<sub>4</sub> molecules or one H<sub>2</sub>SO<sub>4</sub> molecule and one HSO<sub>4</sub><sup>−</sup> ion demonstrate that amines, unlike ammonia, significantly assist the growth of not only neutral but also ionic clusters along the H<sub>2</sub>SO<sub>4</sub> co-ordinate. A sensitivity analysis indicates that the difference in complexation free energies for amine- and ammonia-containing clusters is large enough to overcome the mass-balance effect caused by the fact that the concentration of amines in the atmosphere is probably 2 or 3 orders of magnitude lower than that of ammonia. This implies that amines might be more important than ammonia in enhancing neutral and especially ion-induced sulfuric acid-water nucleation in the atmosphere

The role of ammonia in sulfuric acid ion induced nucleation

We have developed a new multi-step strategy for quantum chemical calculations on atmospherically relevant cluster structures that makes calculation for large clusters affordable with a good accuracy-to-computational effort ratio. We have applied this strategy to evaluate the relevance of ternary ion induced nucleation; we have also performed calculations for neutral ternary nucleation for comparison. The results for neutral ternary nucleation agree with previous results, and confirm the important role of ammonia in enhancing the growth of sulfuric acid clusters. On the other hand, we have found that ammonia does not enhance the growth of ionic sulfuric acid clusters. The results also confirm that ion-induced nucleation is a barrierless process at high altitudes, but at ground level there exists a barrier due to the presence of a local minimum on the free energy surface

Proton affinities of candidates for positively charged ambient ions in boreal forests

The optimized structures and proton affinities of a total of 81 nitrogen-containing bases, chosen based on field measurements of ambient positive ions, were studied using the CBS-QB3 quantum chemical method. The results were compared to values given in the National Institute of Standards and Technology (NIST) Chemistry WebBook in cases where a value was listed. The computed values show good agreement with the values listed in NIST. Grouping the molecules based on their molecular formula, the largest calculated proton affinities for each group were also compared with experimentally observed ambient cation concentrations in a boreal forest. This comparison allows us to draw qualitative conclusions about the relative ambient concentrations of different nitrogen-containing organic base molecules

Highly oxygenated organic molecule cluster decomposition in atmospheric pressure interface time-of-flight mass spectrometers

Identification of atmospheric molecular clusters and measurement of their concentrations by atmospheric pressure interface time-of-flight (APi-TOF) mass spectrometers may be affected by systematic error due to possible decomposition of clusters inside the instrument. Here, we perform numerical simulations of decomposition in an APi-TOF mass spectrometers and formation in the atmosphere of a set of clusters which involve a representative kind of highly oxygenated organic molecule (HOM), with the molecular formula C10H16O8. This elemental composition corresponds to one of the most common mass peaks observed in experiments on ozone-initiated autoxidation of alpha-pinene. Our results show that decomposition is highly unlikely for the considered clusters, provided their bonding energy is large enough to allow formation in the atmosphere in the first place.Peer reviewe

Fatty acids on continental sulfate aerosol particles

Published 2005 American Geophysical Union. Reproduced by permission of American Geophysical Union.Surface analyses of atmospheric aerosols from different continental sources, such as forest fires and coal and straw burning, show that organic surfactants are found on such aerosols. The predominant organic species detected by time-of-flight secondary ion mass spectrometry on the sulfate aerosols are fatty acids of different carbon chain length up to the C32 acid. These observations are consistent with literature accounts of functional group analysis of bulk samples, but this is the first direct evidence of fatty acid films on the surface of sulfate aerosols. Surface analysis leads to the conclusion that fatty acid films on continental aerosols may be more common than has been previously suggested

Nucleation barrier reconstruction via the seeding method in a lattice model with competing nucleation pathways

We study a three-species analogue of the Potts lattice gas model of nucleation from solution in a regime where partially disordered solute is a viable thermodynamic phase. Using a multicanonical sampling protocol, we compute phase diagrams for the system, from which we determine a parameter regime where the partially disordered phase is metastable almost everywhere in the temperature–fugacity plane. The resulting model shows non-trivial nucleation and growth behaviour, which we examine via multidimensional free energy calculations. We consider the applicability of the model in capturing the multi-stage nucleation mechanisms of polymorphic biominerals (e.g., CaCO3). We then quantitatively explore the kinetics of nucleation in our model using the increasingly popular “seeding” method. We compare the resulting free energy barrier heights to those obtained via explicit free energy calculations over a wide range of temperatures and fugacities, carefully considering the propagation of statistical error. We find that the ability of the “seeding” method to reproduce accurate free energy barriers is dependent on the degree of supersaturation, and severely limited by the use of a nucleation driving force ∆µ computed for bulk phases. We discuss possible reasons for this in terms of underlying kinetic assumptions, and those of classical nucleation theory. C 2016 Author(s

Changes in background aerosol composition in Finland during polluted and clean periods studied by TEM/EDX individual particle analysis

Aerosol samples were collected at a rural background site in southern Finland in May 2004 during pollution episode ( PM1 similar to 16 mu g m(-3), backward air mass trajectories from south-east), intermediate period (PM1 similar to 5 mu g m(-3), backtrajectories from north-east) and clean period (PM1 similar to 2 mu g m(-3), backtrajectories from northwest/ north). The elemental composition, morphology and mixing state of individual aerosol particles in three size fractions were studied using transmission electron microscopy (TEM) coupled with energy dispersive X-ray (EDX) microanalyses. The TEM/EDX results were complemented with the size-segregated bulk chemical measurements of selected ions and organic and elemental carbon. Many of the particles in PM0.2-1 and PM1-3.3 size fractions were strongly internally mixed with S, C and/or N. The major particle types in PM0.2-1 samples were 1) soot and 2) ( ammonium) sulphates and their mixtures with variable amounts of C, K, soot and/or other inclusions. Number proportions of those two particle groups in PM0.2-1 samples were 0 - 12% and 83 - 97%, respectively. During the pollution episode, the proportion of Ca-rich particles was very high ( 26 - 48%) in the PM1- 3.3 and PM3.3-11 samples, while the PM0.2-1 and PM1- 3.3 samples contained elevated proportions of silicates ( 22 - 33%), metal oxides/hydroxides ( 1 - 9%) and tar balls ( 1 - 4%). These aerosols originated mainly from polluted areas of Eastern Europe, and some open biomass burning smoke was also brought by long-range transport. During the clean period, when air masses arrived from the Arctic Ocean, PM1- 3.3 samples contained mainly sea salt particles ( 67 - 89%) with a variable rate of Cl substitution ( mainly by NO3-). During the intermediate period, the PM1- 3.3 sample contained porous (sponge-like) Na-rich particles (35%) with abundant S, K and O. They might originate from the burning of wood pulp wastes of paper industry. The proportion of biological particles and C-rich fragments ( probably also biological origin) were highest in the PM3.3-11 samples ( 0 - 81% and 0 - 22%, respectively). The origin of different particle types and the effect of aging processes on particle composition and their hygroscopic and optical properties are discussed.Aerosol samples were collected at a rural background site in southern Finland in May 2004 during pollution episode ( PM1 similar to 16 mu g m(-3), backward air mass trajectories from south-east), intermediate period (PM1 similar to 5 mu g m(-3), backtrajectories from north-east) and clean period (PM1 similar to 2 mu g m(-3), backtrajectories from northwest/ north). The elemental composition, morphology and mixing state of individual aerosol particles in three size fractions were studied using transmission electron microscopy (TEM) coupled with energy dispersive X-ray (EDX) microanalyses. The TEM/EDX results were complemented with the size-segregated bulk chemical measurements of selected ions and organic and elemental carbon. Many of the particles in PM0.2-1 and PM1-3.3 size fractions were strongly internally mixed with S, C and/or N. The major particle types in PM0.2-1 samples were 1) soot and 2) ( ammonium) sulphates and their mixtures with variable amounts of C, K, soot and/or other inclusions. Number proportions of those two particle groups in PM0.2-1 samples were 0 - 12% and 83 - 97%, respectively. During the pollution episode, the proportion of Ca-rich particles was very high ( 26 - 48%) in the PM1- 3.3 and PM3.3-11 samples, while the PM0.2-1 and PM1- 3.3 samples contained elevated proportions of silicates ( 22 - 33%), metal oxides/hydroxides ( 1 - 9%) and tar balls ( 1 - 4%). These aerosols originated mainly from polluted areas of Eastern Europe, and some open biomass burning smoke was also brought by long-range transport. During the clean period, when air masses arrived from the Arctic Ocean, PM1- 3.3 samples contained mainly sea salt particles ( 67 - 89%) with a variable rate of Cl substitution ( mainly by NO3-). During the intermediate period, the PM1- 3.3 sample contained porous (sponge-like) Na-rich particles (35%) with abundant S, K and O. They might originate from the burning of wood pulp wastes of paper industry. The proportion of biological particles and C-rich fragments ( probably also biological origin) were highest in the PM3.3-11 samples ( 0 - 81% and 0 - 22%, respectively). The origin of different particle types and the effect of aging processes on particle composition and their hygroscopic and optical properties are discussed.Aerosol samples were collected at a rural background site in southern Finland in May 2004 during pollution episode ( PM1 similar to 16 mu g m(-3), backward air mass trajectories from south-east), intermediate period (PM1 similar to 5 mu g m(-3), backtrajectories from north-east) and clean period (PM1 similar to 2 mu g m(-3), backtrajectories from northwest/ north). The elemental composition, morphology and mixing state of individual aerosol particles in three size fractions were studied using transmission electron microscopy (TEM) coupled with energy dispersive X-ray (EDX) microanalyses. The TEM/EDX results were complemented with the size-segregated bulk chemical measurements of selected ions and organic and elemental carbon. Many of the particles in PM0.2-1 and PM1-3.3 size fractions were strongly internally mixed with S, C and/or N. The major particle types in PM0.2-1 samples were 1) soot and 2) ( ammonium) sulphates and their mixtures with variable amounts of C, K, soot and/or other inclusions. Number proportions of those two particle groups in PM0.2-1 samples were 0 - 12% and 83 - 97%, respectively. During the pollution episode, the proportion of Ca-rich particles was very high ( 26 - 48%) in the PM1- 3.3 and PM3.3-11 samples, while the PM0.2-1 and PM1- 3.3 samples contained elevated proportions of silicates ( 22 - 33%), metal oxides/hydroxides ( 1 - 9%) and tar balls ( 1 - 4%). These aerosols originated mainly from polluted areas of Eastern Europe, and some open biomass burning smoke was also brought by long-range transport. During the clean period, when air masses arrived from the Arctic Ocean, PM1- 3.3 samples contained mainly sea salt particles ( 67 - 89%) with a variable rate of Cl substitution ( mainly by NO3-). During the intermediate period, the PM1- 3.3 sample contained porous (sponge-like) Na-rich particles (35%) with abundant S, K and O. They might originate from the burning of wood pulp wastes of paper industry. The proportion of biological particles and C-rich fragments ( probably also biological origin) were highest in the PM3.3-11 samples ( 0 - 81% and 0 - 22%, respectively). The origin of different particle types and the effect of aging processes on particle composition and their hygroscopic and optical properties are discussed.Peer reviewe

Communication: Tolman length and rigidity constants of water and their role in nucleation

A proper understanding of nucleation is crucial in several natural and industrial processes. However, accurate quantitative predictions of this phenomenon have not been possible. The most popular tool for calculating nucleation rates, classical nucleation theory (CNT), deviates by orders of magnitude from experiments for most substances. We investigate whether part of this discrepancy can be accounted for by the curvature-dependence of the surface tension. To that end, we evaluate the eading order corrections for water, the Tolman length and the rigidity constants, using square gradient theory coupled with the accurate cubic plus association equation of state. The Helfrich expansion is then used to incorporate them into the CNT-framework. For water condensation, the modified framework successfully corrects the erroneous temperature dependence of the nucleation rates given by the classical theory and reproduces experimental nucleation rates

Corrigendum to "The role of ammonia in sulfuric acid ion induced nucleation" published in Atmos. Chem. Phys., 8, 2859–2867, 2008

No abstract available