AAAR 31st Annual Conference
October 8-12, 2012
Hyatt Regency Minneapolis
Minneapolis, Minnesota, USA
Abstract View
New Information on Cr Speciation in the Presence of Ozone and Reactive Oxygen Species during Atmospheric and Sampling Aging
Mehdi Amouei Torkmahalleh, Lin Lin, Thomas M. Holsen, Don H. Rasmussen, PHILIP K. HOPKE, Clarkson University
Abstract Number: 225 Working Group: Aerosol Chemistry
Abstract Cr(III) and Cr(VI) are the two stable oxidation states of chromium in the environment. Cr(VI) was found to be toxic for human body such that exposure to Cr(VI) may lead to cancer, nasal damage, asthma, bronchitis, pneumonitis, inflammation, dermatitis and skin allergies. On the other hand, Cr(III) is a trace element essential for the proper function of living organisms. Little is known about chromium chemistry in the atmosphere as well as during sampling and storage. Exposure of chromium to ozone at 24oC and 10% RH showed approximately 40 ± 8% and 17.1 ± 1.7% loss of Cr(VI), at pH 4 and 9, respectively. Compared with control experiments, ozone added to the conversion of Cr(III) to Cr(VI) at pH 4 and 9. The aging of chromium in the presence of ozone at pH 4 and12oC after 2 hours, showed a statistically significant (P = 0.002) reduction in Cr(III) conversion from 7.1 % to 0.7% compared with aging at 24oC. ROS exposure resulted in 15.4 ± 5.7% loss of Cr(VI) at 24oC, pH 9 and 10% RH during chromium aging. Overall, ROS and ozone added to the conversion of Cr(III) to Cr(VI) during sampling of chromium in airborne PM and atmospheric aging such that aging at a lower temperature reduced the Cr(III) conversion fraction compared to a higher temperature. All of the reactions were complete in less than 1 to 2 hours.