AAAR 33rd Annual Conference
October 20 - October 24, 2014
Rosen Shingle Creek
Orlando, Florida, USA
Abstract View
Enhancement in the Production of Nucleating Clusters Due to Dimethylamine and Large Uncertainties in the Thermochemistry of Amine-enhanced Nucleation
ALEXEY NADYKTO, Jason Herb, Fangqun Yu, Yisheng Xu, Moscow State University of Technology; SUNY at Albany
Abstract Number: 416 Working Group: Advances in the Physics and Chemistry of New Particle Formation and Growth
Abstract The enhancing effect of dimethylamine (DMA) on the production of stable ternary clusters have been studied using the Density Functional Theory (DFT) and large uncertainties in the thermochemistry of amine-enhanced nucleation have been pointed out and discussed [1]. It has been pointed out that the DMA concentrations of 1-10 ppt are needed in order to achieve a considerable enhancement in production of sulfuric acid-water clusters under typical atmospheric conditions and that the relative humidity (RH) plays a significant role at the early stages of the gas-to-cluster conversion. The present study leads us to conclude that: (a) At RH typical for the atmosphere most of the small DMA-containing clusters are hydrated; (b) Thermodynamics of ternary homogeneous nucleation (THN) involving ammonia and amines is similar in terms of both composition dependencies of base and acid affinities and hydration; (c) The uncertainties in the effect of DMA on nucleation thermochemistry are very large and largely associated with the description of interactions of the sulfuric acid, the key atmospheric nucleation precursor, with nucleating clusters. It has been pointed out that conventional ab initio RI-MP2/CBS and present PW91PW91/6-311++G(3df,3pd) methods are in much better agreement with experiments than the locally developed multi-step BLRIMPP2 and B3RICC2 methods [2-3], on which the current conclusions about the THN involving amines are based; (d) The uncertainties in the catalytic effect of the DMA on production of stable sulfuric acid clusters are very large and may affect conclusions about the importance of amine-enhanced nucleation in the Earth’s atmosphere.
[1] A.B. Nadykto, J. Herb, F. Yu, Y. Xu. (2014) Chem. Phys. Lett, in press. [2] Loukonen, V et al. (2010), Atmos. Chem. Phys. 10: 4961-4974. [3] Paasonen, P. et al. (2012) Atmos. Chem. Phys., 12, 9113-9133.