Seawater Analysis by Ambient Mass Spectrometry-Based Seaomics

A transmission mode-direct analysis in real time-quadrupole time of flight-mass spectrometry (TM-DART-QTOF-MS)-based analytical method coupled to multivariate statistical analysis was developed to interrogate lipophilic compounds in seawater samples without the need of desalinization. An untargeted metabolomics approach addressed here as seaomics was successfully implemented to discriminate sea surface microlayer (SML) from underlying water (ULW) samples (n=22, 10 paired samples) collected during a field campaign at the Cape Verde islands in September-October 2017. A panel of 11 ionic species detected in all samples allowed sample class discrimination by means of supervised multivariate statistical models. Tentative identification of species enriched at SML samples suggests that fatty alcohols, halogenated compounds, and oxygenated boron-containing organic compounds are available at the surface for water-air transfer processes. A subset of SML samples (n=5) were subject to on-site experiments during the campaign using a lab-to-the-field approach to test their secondary organic aerosol (SOA) formation potency. Results from these experiments and the analytical seaomics strategy provide a proof of concept for an approach to identifying organic molecules involved in aerosol formation processes at the water/air interface.