Direct measurement of dissolved organic nitrogen concentration and 15N/14N ratio

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Dissolved organic nitrogen (DON) plays a significant role in terrestrial, marine, and atmospheric environments, but is a poorly understood part of the earth's nitrogen cycle. The concentration and isotopic composition of DON can be measured accurately in waters where minimal concentrations of inorganic nitrogen exist; however, there are currently no methods that can directly measure the concentration or isotopic composition of DON in aqueous samples where dissolved inorganic forms of nitrogen are present. Traditionally, the concentration of DON is estimated from the measurement of total dissolved nitrogen, but when DON makes up only a small fraction of the total dissolved nitrogen, it is difficult to accurately estimate the DON concentration with certainty. To address this issue, scientists from the University of Miami Rosenstiel School of Marine and Atmospheric Science are developing a new and potentially transformative method for studying organic nitrogen in the ocean. By developing such a technique scientists will be able to directly measure dissolved organic nitrogen, as well as the nitrogen isotopic composition, which will provide scientists with a better understanding of the global nitrogen cycle. Upon successful development of this new method of measuring oceanic nitrogen, scientists will be able to differentiate between natural and anthropogenic sources and sinks of DON, which will enhance our understanding of the controls on the fertility of the ocean, as well as its potential to sequester CO2 from the atmosphere. This research will also provide support for a postdoctoral researcher and a graduate student.