Formation of binary ion clusters from polar vapours: effect of the dipole-charge interaction

Formation of binary cluster ions from polar vapours is considered. The effect of vapour polarity on the size and composition of the critical clusters is investigated theoretically and a corrected version of classical Kelvin-Thomson theory of binary ion-induced nucleation is derived. The model predictions of the derived theory are compared to the results given by classical binary homogeneous nucleation theory and ion-induced nucleation theory. The calculations are performed in wide range of the ambient conditions for a system composed of sulfuric acid and water vapour. It is shown that dipole-charge interaction significantly decreases the size of the critical clusters, especially under the atmospheric conditions when the size of critical clusters is predicted to be small

Ammonia in positively charged pre-nucleation clusters: a quantum-chemical study and atmospheric implications

The quantum-chemical treatment of pre-nucleation clusters consisting of atmospheric nucleation precursors is critically important for the understanding of the molecular nature of atmospheric nucleation. In the present study, the influence of ammonia on the thermochemical stability of positively charged pre-nucleation clusters has been studied using the Density Functional Theory (DFT). The formation of binary (NH<sub>4</sub><sup>+</sup>)(H<sub>2</sub>O)<sub><i>n</i></sub> and ternary (NH<sub>4</sub><sup>+</sup>)(H<sub>2</sub>SO<sub>4</sub>)(H<sub>2</sub>O)<sub><i>n</i></sub> ionic clusters and the conversion of (H<sub>3</sub>O<sup>+</sup>)(H<sub>2</sub>O)<sub><i>n</i>−1</sub> into (NH<sub>4</sub><sup>+</sup>)(H<sub>2</sub>O)<sub><i>n</i></sub> and (H<sub>3</sub>O<sup>+</sup>) (H<sub>2</sub>SO<sub>4</sub>)(H<sub>2</sub>O)<sub><i>n</i>−1</sub> into (NH<sub>4</sub><sup>+</sup>)(H<sub>2</sub>SO<sub>4</sub>)(H<sub>2</sub>O)<sub><i>n</i></sub> have been investigated. The thermochemical analysis carried out in the present study shows both (H<sub>3</sub>O<sup>+</sup>)(H<sub>2</sub>O)<sub><i>n</i>−1</sub>→(NH<sub>4</sub><sup>+</sup>) (H<sub>2</sub>O)<sub><i>n</i></sub> and (H<sub>2</sub>SO<sub>4</sub>)(H<sub>3</sub>O<sup>+</sup>)(H<sub>2</sub>O)<sub><i>n</i>−1</sub>→(NH<sub>4</sub><sup>+</sup>)(H<sub>2</sub>SO<sub>4</sub>) (H<sub>2</sub>O)<sub><i>n</i></sub> transformations to be favorable thermodynamically and gives us a clear indication of the important role of ammonia in the conversion of positively charged clusters containing hydronium (H<sub>3</sub>O<sup>+</sup>) into those containing protonated ammonia. Under typical continental boundary layer condition, a large fraction of small positive ions may contain ammonia, but most of neutral and negative hydrated sulfuric acid monomers do not contain ammonia. In term of absolute concentrations, around 1000 cm<sup>−3</sup> out of 10<sup>7</sup> cm<sup>−3</sup> of sulfuric acid momoners contain ammonia. (NH<sub>4</sub>)<sup>+</sup>(H<sub>2</sub>O)<sub><i>n</i></sub> clusters appear to dominate the concentrations of small positive ions. Because of the weak affinity of sulfuric acid molecules to (H<sub>3</sub>O<sup>+</sup>)(H<sub>2</sub>O)<sub><i>n</i></sub> and (NH<sub>4</sub><sup>+</sup>)(H<sub>2</sub>O)<sub><i>n</i></sub> ions (<i>n</i>≤6), the concentrations of both ammoniated and un-ammoniated sulfuric acid water proton clusters are quite low. The atmospheric implications of the obtained results are discussed

Impact of temperature dependence on the possible contribution of organics to new particle formation in the atmosphere

Secondary particles formed via new particle formation (NPF) dominate cloud condensation nuclei (CCN) abundance in most parts of the troposphere and are important for aerosol indirect radiative forcing (IRF). Laboratory measurements have shown that certain organic compounds can significantly enhance the binary nucleation of sulfuric acid and H2O. According to our recent study comparing particle size distributions measured in nine forest areas in North America with those predicted by a global size-resolved aerosol model, current H2SO4–organics nucleation parameterizations appear to significantly overpredict NPF and particle number concentrations in summer. The lack of temperature dependence in the current H2SO4–organics nucleation parameterization has been suggested to be a possible reason for the observed overprediction. In this work, H2SO4–organics clustering thermodynamics from quantum chemical studies has been employed to develop a scheme to incorporate temperature dependence into H2SO4–organics nucleation parameterization. We show that temperature has a strong impact on H2SO4–organics nucleation rates and may reduce the nucleation rate by  ∼  1 order of magnitude per 10 K of temperature increase. The particle number concentrations in summer over North America based on the revised scheme is a factor of more than 2 lower, which is in much better agreement with the observations. With the temperature-dependent H2SO4–organics nucleation parameterization, the summer CCN concentrations in the lower troposphere in the Northern Hemisphere are about 10–30 % lower compared to the temperature-independent parameterization. This study highlights the importance of the temperature effect and its impacts on NPF in the global modeling of aerosol number abundance

H₂SO₄–H₂O–NH₃ ternary ion-mediated nucleation (TIMN): kinetic-based model and comparison with CLOUD measurements

New particle formation (NPF) is known to be an important source of atmospheric particles that impacts air quality, hydrological cycle, and climate. Although laboratory measurements indicate that ammonia enhances NPF, the physicochemical processes underlying the observed effect of ammonia on NPF are yet to be understood. Here we present a comprehensive kinetically based H2SO4–H2O–NH3 ternary ion-mediated nucleation (TIMN) model that is based on the thermodynamic data derived from both quantum-chemical calculations and laboratory measurements. NH3 was found to reduce nucleation barriers for neutral, positively charged, and negatively charged clusters differently, due to large differences in the binding strength of NH3, H2O, and H2SO4 to small clusters of different charging states. The model reveals the general favor of nucleation of negative ions, followed by nucleation on positive ions and neutral nucleation, for which higher NH3 concentrations are needed, in excellent agreement with Cosmics Leaving OUtdoor Droplets (CLOUD) measurements. The TIMN model explicitly resolves dependences of nucleation rates on all the key controlling parameters and captures the absolute values of nucleation rates as well as the dependence of TIMN rates on concentrations of NH3 and H2SO4, ionization rates, temperature, and relative humidity observed in the well-controlled CLOUD measurements well. The kinetic model offers physicochemical insights into the ternary nucleation process and provides a physics-based approach to calculate TIMN rates under a wide range of atmospheric conditions.</p

Electromagnetic Radiation and Heat Transfer in Disperse Systems Consisting of Spherical and Cylindrical Particles

The article deals with the electromagnetic radiation transfer in systems of spherical disperse particles with different optical characteristics. A model of the electromagnetic radiation transfer in cylindrical particles containing a small volume of different chemical substance is developed. The substance differs substantially from that of the particle in a radiation absorption coefficient for the wavelength under study in the long wave approximation. The finite element method is used to calculate the temperature field for the system of spherical particles in a two-dimensional approximation. The configurations of particle packing is chosen on a random basis, which significantly complicated the calculations, the longitudinal and transverse diameters of particle clusters, the distance between centers of two largest particles, and similar natural geometric properties have been considered as characteristic system dimensions.The possibility of controlling heat transfer in such systems is studied. It follows from our model calculations that both electromagnetic and thermal interaction of dispersed particles can be noticeable at large distances between their centers; that near the boundary of the dispersed particle there is a thermal surface layer of the particle, where the temperature distribution is essentially heterogeneous. It is concluded that the thermal mechanism of destruction of a weakly absorbing particle due to a strong increase in temperature because of electromagnetic resonance in a neighboring particle with a strong absorption. It is established that the effect of collective influences in polydisperse system can change temperature by more than 1,5 times