Investigating the dynamics of organic matter in the hudson river catchment across spatial, temporal, and hydrologic regimes
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Authors
Collins, Alexander, Charles
Issue Date
2025-08
Type
Electronic thesis
Thesis
Thesis
Language
en_US
Keywords
Geology
Alternative Title
Abstract
Organic matter plays a critical role in the transfer of carbon between terrestrial, aquatic, and atmospheric reservoirs. As such, constraining the behavior and fluxes of organic matter in the environment is necessary to predict both short- and long-term exchange of carbon between these reservoirs. Environmental perturbations such as climate change and land use alterations have affected the production, mobilization, and fate of organic matter. However, many foundational studies have been performed on idealized, smaller scale systems leaving significant gaps in our understanding of organic matter sources and transport pathways. As the predictions of organic carbon fluxes between reservoirs are only as robust as our understanding of organic matter dynamics, there is a need to investigate previously unconstrained or understudied systems. This dissertation aims to improve our understanding of how historic and ongoing environmental perturbations influence the transport and storage of organic matter, and to identify previously overlooked source-inputs. In Chapter 1, I introduce the dynamics of organic matter, its role in global carbon budgets, and how its transport and fate can be altered by environmental perturbations. In Chapter 2, I assess the effects of hydrologic management, land use, and storm events on the quality of dissolved organic matter exported by the Hudson River. Given the region’s intensive hydrologic management and the anticipated increase in storm event frequency and intensity, this study provides insights into processes affecting similarly managed watersheds. I found that impoundments preferentially retain and degrade organic matter upstream, fundamentally changing the location and degree of organic matter processing. In Chapter 3, I assess whether the optical character of water extractable organic matter sequestered in the sediments of Brant Lake, NY effectively reflects historical environmental perturbations (e.g., logging, damming, and acid rain). Unlike rivers, which act as a conduit of organic matter transfer, lakes primarily serve as locations of carbon processing and storage. As such, understanding how environmental changes influence organic matter within lakes enhances our ability to interpret both past and future carbon dynamics in aquatic environments. In Chapter 4, I utilize compound-specific isotopic analysis to quantify shale-derived condensed aromatic compounds and estimate shale-derived bulk organic carbon inputs to the Hudson River. Although lithogenic sources have previously been excluded from short-term carbon cycling budgets, recent evidence suggests that rock-derived organic carbon may play more of an active role than previously assumed. By measuring this environmentally resistant fraction of organic matter, I estimated the contribution of petrogenic organic carbon and compared it to existing geochemical data. My findings indicate that shale-derived organic carbon is a plausible source of the aged organic carbon exported in the modern-day Mohawk and Hudson Rivers. While centered on the Hudson River system, the findings in this dissertation contribute to a growing understanding of how natural and anthropogenic forces shape the export and processing of organic carbon in aquatic systems.
Description
August2025
School of Science
School of Science
Full Citation
Publisher
Rensselaer Polytechnic Institute, Troy, NY