<p> To investigate how biogeochemical processes affect the concentrations and fluxes of dissolved organic matter (DOM) in forested watersheds, I studied the quantity and quality of DOM at the Arbutus Lake Watershed, Adirondack Park (NY, USA). First, to understand the biogeochemical changes of DOM for surface waters in the watershed, I studied spatial and temporal patterns of the quantity (bioavailable/refractory concentrations) and quality (δ<sup>13</sup>C, aromaticity, and low (LMW; < 1kDa) and high molecular weight (HMW; > 1kDa) of dissolved organic carbon (DOC), nitrogen (DON), and sulfur (DOS). DOC and DON constituents passing through a wetland were composed of highly refractory, aromatic HMW components compared to upland streams. DOS was dominated by the refractory, LMW form. I developed a “bioavailability-molecular size model” showing the refractoriness of the LMW DOS compared to the HMW DOC and DON. </p><p> Second, to evaluate how a lake nested in a forested watershed affects the dynamics of DOC and DON, I analyzed a mass balance of DOC, DON and dissolved inorganic nitrogen (DIN) from 2000 to 2009. Annual DOC and DON mass balances were strikingly uncoupled, and Arbutus Lake generally acted as a sink for DOC. But a periodic source for DON was observed, indicating that internal recycling between DIN and DON might be important in affecting DON concentrations in this oligo-mesotrophic lake. </p><p> Third, isotopic signatures of DOS in the inlet catchment of the Watershed revealed that the incorporation of reduced S (e.g., SH-) derived from bacterial dissimilatory sulfate reduction contributed to generating DOS in ground and surface waters. These results provide new information on mechanisms for geochemical DOS formation in forested catchments. </p><p> Last, to better understand isotopic changes in DOS, three isotopic pretreatment methods for sulfate widely used were compared. I found an excellent agreement of the δ<sup>34</sup>S-sulfate values among the three methods. However, some differences were observed in the δ<sup>18</sup>O-sulfate values associated with possible O contamination before isotopic measurements. </p><p> Overall, my studies highlighted novel approaches comparing sources and transformation of three elemental DOM fractions of DOC, DON, and DOS along various watershed components and a lake nested forested watersheds.</p>
| Identifer | oai:union.ndltd.org:PROQUEST/oai:pqdtoai.proquest.com:10117985 |
| Date | 13 July 2016 |
| Creators | Kang, Phil-Goo |
| Publisher | State University of New York Col. of Environmental Science & Forestry |
| Source Sets | ProQuest.com |
| Language | English |
| Detected Language | English |
| Type | thesis |
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