Characterization of CHOS compounds in rainwater from continental and coastal storms by ultrahigh resolution mass spectrometry

Rainwater from four continental and three coastal storms was collected and analyzed by (−) ESI Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). This study presents a comprehensive comparison of the CHOS molecular formulas of rainwater dissolved organic matter from these two different storm trajectories. There were 899 and 695 total molecular formula assignments in the continental and coastal storms respectively. Of these, 33% and 15% were unique to continental and coastal storms. Kendrick mass analysis of methylene units highlighted oligomers present in both storm types illustrating their ubiquitous occurrence in atmospheric waters. There was also evidence of organo-sulfate containing molecular formulas as well as highly condensed aromatic structures containing one sulfur and one oxygen. These condensed aromatic sulfur containing structures likely originate from fossil fuel sources and were only detected in continental derived rainwater.