From Canopies to Creeks: Chasing Dissolved Organic Matter Through the Storm with High Resolution Mass Spectrometry

Throughfall dissolved organic matter (DOM) is an important, yet understudied, component of forest organic matter dynamics. Previous studies have focused primarily on bulk DOM characteristics, such as DOM concentrations and optical properties, with few studies exploring the detailed chemical composition of throughfall DOM. Moreover, previous researchers have often limited their scope to bulk precipitation samples on a per storm basis. No known research has examined intra-storm variations in throughfall DOM composition at the molecular level. To address this gap, the presented study analyzes intra-storm variations in throughfall DOM via high-frequency sampling during a precipitation event. Stream and throughfall samples were collected over 36 hours at the Arbutus Pond inlet, a long-term ecological monitoring site in the Adirondack region of New York State. Dissolved organic carbon and total nitrogen concentrations were obtained for each sample, along with excitation-emission matrix spectra, and single and tandem mass spectrometry analyses using HPLC-Orbitrap. The resulting analysis yielded molecular formula assignments for thousands of masses in both stream and throughfall DOM. Temporal dynamics in DOM composition highlight the importance of intra-storm analyses of throughfall DOM. Additionally, the presence of throughfall DOM in streams was examined to identify potential tracers for DOM transport from canopies to streams during precipitation events. This work lays the foundation for future intra-storm molecular characterization studies of throughfall DOM.

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Primary Presenter: Hollis Harrington, SUNY ESF (hcharrin@syr.edu)

Authors:

Hollis Harrington, SUNY College of Environmental Science and Forestry  (hcharrin@syr.edu)

John Hassett, SUNY College of Environmental Science and Forestry  (jphasset@esf.edu)

Leanne Powers, SUNY College of Environmental Science and Forestry  (lcpowers@esf.edu)