PNNL

Abstract

Advancing our understanding of dissolved organic matter (DOM) chemistry in aquatic systems necessitates the integration of data streams derived from multiple analytical platforms. Some measurements, however, require pretreatment with solid phase extraction (SPE) while others can be performed directly on whole water samples. Evidence suggests that SPE will bias against select DOM fractions, leading to concerns over the ability to derive linkages and interpretations that rely on multiple data streams with variable need for SPE pretreatment, such as those from optical measurements and those that provide high-resolution molecular information. Here, we directly addressed this concern by assessing the impact of SPE on DOM optical properties through excitation-emission matrices with parallel factor analysis (PARAFAC), and by further pairing with molecular information obtained by Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS) across a stream network reflective of variable DOM sources. A comparison of PARAFAC models first revealed no systematic qualitative differences in major components between whole water DOM and DOM isolated by SPE (SPE-DOM); however, quantitative biases against select components were observed. Further linkages with FTICR-MS data revealed that the molecular fingerprint associated with each PARAFAC component was consistent between whole water DOM and SPE-DOM, which suggests that broad scale linkages across these analytical platforms can be inferred irrespective of some of the select quantitative biases observed as a result of SPE. This work represents a key step toward the systematic evaluation of linkages between optical and high-resolution mass spectrometry datasets in diverse environmental contexts.