AAAR 35th Annual Conference October 17 - October 21, 2016 Oregon Convention Center Portland, Oregon, USA
Abstract View
A Molecular Dynamics Simulation based Analysis of Atmospheric Droplets Containing Chromium
MEHDI AMOUEI TORKMAHALLEH, Bekbol Aldamzharov, Assel Bukayeva, Dhawal Shah, Nazarbayev University
Abstract Number: 542 Working Group: Single Aerosol Particle Studies - Fundamentals
Abstract Two most stable chromium’s oxidation states in the environment are trivalent and hexavalent states. Hexavalent chromium, Cr (VI), is human carcinogen, while trivalent chromium, Cr (III) is essential micronutrient. Possible reductants for conversion of Cr(VI) to Cr(III) in atmospheric droplets are ionic forms of As, V and Fe while Mn was found to be an oxidant for the conversion of Cr(III) to Cr(VI). In addition to the ionic reductants and oxidants, chromium may react with dissolved gaseous compounds such as volatile organic compounds (VOCs) and ozone. The availability of the Cr for the reactions may change whether Cr presents on the surface of the atmospheric droplets or at the interior parts of the particles. If Cr presents inside the particles, then diffusion of the dissolved gases within the atmospheric droplets towards the Cr ions could be important. Nonetheless, no study is found in the literature investigating the physical properties of Cr containing atmospheric particles, in particular in the presence of dissolved gases. Experimental measurements of such properties could be hard or even impossible. However, molecular dynamics simulation is a suitable tool to investigate physical interactions of molecules in such complex systems. The aim of this study was to estimate some physical properties of soluble Cr+3 in a single droplet in the presence of dissolved gases such as ozone and VOCs using molecular dynamics simulation. The preliminary results showed that the presence of ozone, increased diffusion coefficient of chromium in water from 0.5092×10-5 to 0.6147×10-5 cm2/s. Dissolved methane increased the diffusion of chromium, while benzene slightly decreased. It is concluded that the presence of the Cr(III) in atmospheric droplets changes the solubility level of the gases compounds such as VOCs and ozone and this change then affects the availability of the atmospheric reductants oxidants to reacts with chromium species.