Date of Award

12-2010

Document Type

Campus Access Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Environmental Sciences/Environmental, Earth & Ocean Sciences

First Advisor

Robert F. Chen

Second Advisor

George B. Gardner

Third Advisor

Curtis R. Olsen

Abstract

Chromophoric dissolved organic matter (CDOM), as a sizable fraction of total dissolved organic matter (DOM) pool, plays an important role in natural water biogeochemical processes and remote sensing of coastal waters. The major source of CDOM in coastal waters is often terrestrial DOM originating in coastal watersheds and delivered to the ocean by rivers or streams. Due to differences in hydrological environments as CDOM is transported from land to ocean, three different ecosystems are described: watersheds, estuaries and coastal ocean. The Neponset watershed, the Hudson Estuary and the Hudson River plume were chosen as study sites.

In the Neponset watershed, monthly samples were taken at five land-cover endmembers for 22 months, and the results indicated that variability in watershed CDOM could be explained by a model that used land-cover types, seasons, freshwater discharge and precipitation as inputs. Different spectral characteristics were observed for different land-cover sources of CDOM.

This watershed CDOM model was successfully applied to the Hudson Watershed including its tributary watersheds, and CDOM spectral characteristics could be used to trace estuarine CDOM sources. Three cruises were conducted in the Hudson Estuary and its tributaries, covering the dry season, the wet season and a flood event. CDOM budgets in the lower Hudson Bay were estimated based on discrete sample data, incubation results and literature values.

Research cruises were conducted during times of high freshwater discharge and average discharge in the Hudson River plume. Dissolved organic carbon (DOC) production and CDOM photo-degradation dominated in the plume, but CDOM production in coastal water was observed. These observations can explain the conservative CDOM-Salinity mixing curve often observed in coastal waters, while few terrestrial optical signals are observed in marine CDOM. CDOM in the Hudson River plume was modeled based on incubation degradation rate and a plume dynamic model which was controlled by freshwater discharge, wind speed and wind direction.

The main objective of my work is to predict CDOM sources and transport from land to ocean. Further model development and increased understanding will provide valuable information to global carbon cycling studies as well as have application in coastal water remote sensing observations.

Comments

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