Spatial variations in the molecular diversity of dissolved organic matter in water moving through a boreal forest in eastern Finland

Abstract

Dissolved organic matter (DOM) strongly affects water quality within boreal forest ecosystems. However, how the quality of DOM itself changes spatially is not well understood. In this study, to examine how the diversity of DOM molecules varies in water moving through a boreal forest, the number of DOM molecules in different water samples, i.e., rainwater, throughfall, soil water, groundwater, and stream water was determined using Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) in Norway spruce and Scots pine stands in eastern Finland during May and June 2010. The number of molecular compounds identified by FT-ICR MS (molecular diversity) ranged from 865 to 2,194, revealing large DOM molecular diversity in the water samples. Additionally, some of the molecular compounds were shared between different water samples. The DOM molecular diversity linearly correlated with the number of low-biodegradable molecules, such as, lignin-like molecules (lignins), but not with dissolved organic carbon concentration. The number of lignins shared between different sampling locations was larger than that of any other biomolecular class. Our results suggest that low-biodegradable molecules, especially lignins, regulate spatial variations in DOM molecular diversity in boreal forests.

UltraMassExplorer: a browser‐based application for the evaluation of high‐resolution mass spectrometric data

“…Vice versa, this relationship has been used to assign molecular formulas from NOM to specific compound groups based on element and element ratio limits (e.g. Rossel et al and Ide et al). For NOM analysis, however, an assignment of formulas to compound groups based solely on regions in the van Krevelen plot involves the risk of over‐interpretation of mass spectrometric data.…”

The Contribution of Coniferous Canopy to the Molecular Diversity of Dissolved Organic Matter in Rainfall

“…1.0, NHMFL, Tallahassee, FL, USA, 1998,). The target m/z values ranged from 180 to 500, based on Ide et al [26] and Reemtsma [33], and the following conditions were adopted for formula assignment: C = 0-∞; H = 0-∞; O = 0-∞; N = 0-5; S = 0-3; P = 0-3; DBE ≥ 0 [34]. Subsequently, a van Krevelen diagram was used based on the elemental ratios of the expected molecular formulas, i.e., the oxygen-to-carbon (O/C) and hydrogen-to-carbon ratios (H/C), to identify which biomolecular class each molecular species belonged to.…”

“…Subsequently, a van Krevelen diagram was used based on the elemental ratios of the expected molecular formulas, i.e., the oxygen-to-carbon (O/C) and hydrogen-to-carbon ratios (H/C), to identify which biomolecular class each molecular species belonged to. Each molecular species was divided into seven biomolecular classes, i.e., lipids, proteins, aminosugars/carbohydrates (As/Ch), unsaturated hydrocarbons (UH), lignin-like molecules (lignins), tannin-like molecules (tannins), and condensed aromatic structures (CAS), based on the same protocol as in Ide et al [26].…”

“…Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) is an ultrahigh-resolution mass spectrometry technique that allows for the detection of hundreds or thousands of DOM molecular species in river and lake water [24,25]. It also can be used to trace changes in molecular composition in rainwater moving through a forest [26]. Additionally, molecular species detected can be classified into seven biomolecular classes, such as, lipids, proteins, and lignin-like molecules, using a van Krevelen diagram [25,27].…”

Linking Organic Matter Dynamics to Management, Restoration, and Climate in the Florida Everglades

“…However, high molecular diversity and gradients of reactivity, from ephemeral to refractory (Ide et al 2017), make characterizing the DOM pool a significant challenge. As a result, a variety of analytical approaches have been used to describe the composition of natural DOM, ranging from determination of individual molecules using mass spectrometry and nuclear magnetic resonance to classifying general compositional features via fluorescence spectroscopy (Minor et al 2014 and references therein).…”