Date of Award
5-12-2024
Degree Type
Thesis
Degree Name
Master of Science (MS)
Department
Civil and Environmental Engineering
Advisor(s)
Teng Zeng
Keywords
Adirondacks;Browning;Dissolved Organic Matter;Photoreactivity;Quantum Yield;Singlet Oxygen
Subject Categories
Civil and Environmental Engineering | Engineering | Environmental Engineering
Abstract
Many inland lakes in temperate and boreal regions, including those in the Adirondack region of New York, are experiencing browning due to increased terrestrial inputs of colored dissolved organic matter (DOM). This phenomenon results from watershed recovery following declines in atmospheric acid deposition and shifts in precipitation patterns. Close coupling of changes in dissolved organic carbon levels and DOM quality in Adirondack lakes has important implications for ecosystem services, ranging from aquatic food web functioning to drinking water production. However, comparatively little is known about the potential effects of lake browning on carbon cycling and contaminant attenuation driven by the photochemical production of reactive intermediates from DOM. To address this gap, I measured singlet oxygen production in 131 surface water samples collected from 38 drainage and seepage lakes in the Adirondack region over three sampling seasons. Furfuryl alcohol was applied as a chemical probe under simulated sunlight conditions to determine the apparent quantum yields of singlet oxygen, which were then paired with solar irradiance predicted by the Simple Model of the Atmospheric Radiative Transfer of Sunshine program to estimate the noontime steady-state concentrations of singlet oxygen in the epilimnion of Adirondack lakes on sampling dates. Overall, the apparent quantum yields of singlet oxygen for Adirondack lake water samples ranged from 0.3 to 5.3 × 10^-2 mol per mol-photons and were higher for samples from drainage lakes than from seepage lakes. The apparent quantum yields of singlet oxygen did not vary significantly across seasons at the observed scale despite spatial heterogeneity among individual lakes. The noontime, epilimnion-averaged steady-state concentrations of singlet oxygen in Adirondack lakes were estimated to range from 1.1 × 10^-15 to 3.6 × 10^-14 M, which were 11±6 times lower than those estimated for the near-surface layer. The noontime, epilimnion-averaged steady-state concentrations of singlet oxygen estimated for the fall-winter season were lower than those for the spring-summer and summer-fall seasons, although they did not differ between drainage and seepage lakes. The seasonal Mann-Kendall test confirmed statistically significant increases in DOC in most Adirondack lakes over the past 30 years (1992 – 2022), whereas generalized additive mixed modeling revealed that DOC trend directions were somewhat heterogeneous across lakes. The apparent quantum yields of singlet oxygen for samples from lakes with lower seasonal Theil-Sen’s slopes of DOC were higher than those from lakes experiencing higher rates in DOC increase; however, the noontime, epilimnion-averaged steady-state concentrations of singlet oxygen were lower in lakes featuring upward DOC trends compared to those estimated for lakes with stable or inconsistent DOC trend directions during the most recent decade (2012 – 2022). Overall, this work provided new insights into the spatiotemporal distribution of singlet oxygen production in Adirondack lakes and explored its relationship to long-term DOC trends, finding decreasing patterns of photoreactivity with increased DOC concentrations. This highlighted the need for continued research into the complex interplay between browning and photoreactivity in these and other similar surface water ecosystems, as it will impact the fate of organic contaminants, trace metals, and pathogens.
Access
Open Access
Recommended Citation
Oz, Birdem, "Exploring the Impact of Lake Browning on the Production of Singlet Oxygen in Adirondack Surface Waters" (2024). Theses - ALL. 891.
https://surface.syr.edu/thesis/891
