Testing N2/Ar Ratios for Measuring Sedimentary Denitrification in Continental Shelves

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ABSTRACT OCE-9617960 Denitrification rates in continental shelf sediments are globally significant in that they affect nutrient availability in surface waters of the ocean, modulate oceanic productivity and influence atmospheric carbon dioxide concentrations. Classical approaches to determine these rates are limited, since nitrogen fluxes cannot be accurately estimated from wide areas of the coastal ocean where rates are moderate or low, and these regions may be more important globally than those areas already identified with high rates. The objective of this proposal is to expand our ability to measure denitrification rates in areas of low or moderate nitrogen fluxes. The approach to be employed by the principal investigator is to use a more precise mass spectrometric technique, where not only nitrogen, but nitrogen/argon ratios are measured in order to determine more accurately nitrogen fluxes in sediment cores collected from test sites in the Gulf of Maine region. The principal investigator is a leading pioneer in studies of the global nitrogen cycle, and advances based upon this new method should expand significantly our ability to identify and quantify global sources and sinks of nitrogen in marine systems. Christensen (OCE-9617960)