Molecular correlations of dissolved organic matter with inorganic mercury and methylmercury in Canadian boreal streams

Abstract

The molecular composition of dissolved organic matter (DOM) is increasingly recognized as fundamentally important to mercury transport and transformations, with numerous approaches undertaken to examine DOM characteristics beyond dissolved organic carbon concentrations. In this study, we use a high-resolution mass spectrometry approach, Fourier-transform ion cyclotron resonance mass spectrometry, to characterize DOM compound classes, DOM aromaticity (AImod), and the nominal oxygenation state of carbon (NOSC) across thirteen small boreal forest streams in central Canada. We then relate the relative abundance of hundreds of different DOM molecules with inorganic mercury and methylmercury (MeHg) concentrations across late spring and fall seasons. The number of significant correlations and the classes of DOM compounds significantly correlating with inorganic mercury and MeHg …