Atmos. Chem. Phys. Discuss., 9, 59-80, 2009
© Author(s) 2009. This work is distributed
under the Creative Commons Attribution 3.0 License.
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This discussion paper has been under review for the journal Atmospheric Chemistry and Physics (ACP). Please refer to the corresponding final paper in ACP.
Light-absorbing secondary organic material formed by glyoxal in aqueous aerosol mimics
E. L. Shapiro, J. Szprengiel, N. Sareen, C. N. Jen, M. R. Giordano, and V. F. McNeill
Department of Chemical Engineering, Columbia University, NY, 10027, USA

Abstract. Light-absorbing and high-molecular-weight secondary organic products were observed to result from the reaction of glyoxal in mildly acidic (pH=4) aqueous inorganic salt solutions mimicking aqueous tropospheric aerosol particles. High-molecular-weight (500–600 amu) products were observed when ammonium sulfate ((NH4)2SO4) or sodium chloride (NaCl) was present in the aqueous phase. The products formed in the (NH4)2SO4 solutions absorb light at UV and visible wavelengths. Substantial absorption at 300–400 nm develops within two hours, and absorption between 400–600 nm develops within days. Pendant drop tensiometry measurements show that the products are not surface-active. The experimental results along with ab initio predictions of the UV/Vis absorption of potential products suggest that an aldol condensation mechanism is active in the glyoxal-(NH4)2SO4system, resulting in the formation of pi-conjugated products. If similar products are formed in atmospheric aerosol particles, they could change the optical properties of the seed aerosol over its lifetime.

Citation: Shapiro, E. L., Szprengiel, J., Sareen, N., Jen, C. N., Giordano, M. R., and McNeill, V. F.: Light-absorbing secondary organic material formed by glyoxal in aqueous aerosol mimics, Atmos. Chem. Phys. Discuss., 9, 59-80, doi:10.5194/acpd-9-59-2009, 2009.
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