Spectrophotometric titrations to characterize and monitor chromophoric dissolved organic matter (CDOM) in natural waters

Academic Research Topics in Environmental Measurement and Monitoring
Oral Presentation

Prepared by , N. Blough

Contact Information: ccarti2@umd.edu; 845-978-1814


Chromophoric dissolved organic matter (CDOM) is an important natural component found ubiquitously throughout aquatic environments. However, it can cause aesthetic problems including an unpleasant odor, taste and a yellow to brown color. Therefore having methods for its characterization and monitoring is critical. In the past, spectrophotometric pH titrations have been conducted on humic and fulvic acid reference materials and on concentrated samples of extracted CDOM, but there has been little examination of the changes in optical properties with pH for open ocean waters due to the low CDOM content, thus low absorption. The World Precision Instrument (WPI) UltraPath spectrometer vastly increases the detection of low concentrations of absorbing species due to its increased pathlength (~200 cm). Thus, this system can allow investigation of the pH dependence of absorption on low absorbing open ocean samples. Direct titrations on natural waters instead of on extracts could also provide far more information on the whole CDOM in the ocean without extraction biases or concentrating factors that could impact the sample’s overall properties. This approach can be extended to other water constituents or contaminants difficult to monitor due to the low concentrations in aquatic environments.