Water-soluble organic carbon (WSOC) is a complex mixture of thousands of organic compounds, which may have significant influence on the climate-relevant properties of atmospheric aerosols. An improved understanding of the molecular composition of WSOC is needed to evaluate the effect of aerosol composition upon aerosol physical properties. Products of gas, aqueous and particle phase reactions contribute to the aerosol organic mass. Thus, ambient aerosols carry a complex array of WSOC components with variable chemical signatures depending upon its origin and aerosol life-cycle processes. In this work, ultrahigh-resolution Fourier transform-ion cyclotron resonance mass spectrometry (FT-ICR MS) was used to characterize ambient aerosol WSOC collected during the summer of 2010 at the Storm Peak Laboratory (3210 m a.s.l.) near Steamboat Springs, CO. Thousands of molecular formulas were assigned in the mass range of m/z 100�800 after negative-ion electrospray ionization. The observed trends indicate significant non-oxidative accretion reaction pathways for the formation of high molecular weight WSOC components. The aerosol WSOC was further characterized using ultrahigh resolution tandem MS analysis with infrared multiphoton dissociation to determine the functional groups and structural properties of the WSOC species up to m/z 600. Multiple neutral losses clearly indicate a multifunctional nature of the studied aerosol WSOC. Analysis of the fragment ions indicates an overall aliphatic terpene-like structure. Specifically, fragment ions associated with a-pinene ozonolysis such as C8H12O, C8H14O2, C9H12O3 and C9H14O4 were observed in 85% or more of the MS2 spectra. The patterns observed in the low molecular weight fragment ion spectra are very consistent over all of the fragmented precursors (up to m/z 600) thus providing further evidence for the significance of the non-oxidative accretion formation pathways.

Structural insights of water-soluble organic carbon from ultrahigh resolution FT-ICR tandem mass spectrometry

248th National Meeting (2014)

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