The Chesapeake Bay has water inputs from more than 100,000 different rivers and streams, yielding a dynamic mixture of water varying in quality and composition. Due to the diversity of water inputs and the importance of water constituents to biogeochemical processes, understanding the variability of these waters on both spatial and temporal scales is of great interest. Chromophoric dissolved organic matter (CDOM), a major constituent within estuaries, plays numerous important roles in these aquatic ecosystems, not only significantly affecting the aquatic light field but also undergoing important photochemical reactions. CDOM is a chemically complex material which is not completely characterized nor understood. We are pursuing an in-depth optical analysis of CDOM variability in the Chesapeake Bay using UV-Visible absorption and fluorescence spectroscopies. Additionally, pH titrations, borohydride reduction and size exclusion chromatography are being employed and their effects on the optical properties studied. These chemical tests provide insight into the molecular moieties contributing to the optical and photochemical properties and how they vary from source to source. To date, water has been collected and CDOM extracted from more than a dozen inputs into the Bay and their corresponding optical properties collected. Examining the temporal and spatial molecular variations should aid in elucidating the role that CDOM plays in the optical, photochemical and biogeochemical properties of the estuarine waters. This extensive optical and chemical characterization of Chesapeake Bay CDOM should further aid in the calibration and validation of satellite remote sensing water quality products.

Detailed optical analysis of chromophoric dissolved organic matter in the Chesapeake Bay using pH titration, borohydride reduction and size exclusion chromatography

ACS Spring 2022

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