Modeling denitrification in aquatic sediments

Author Posting. © The Author(s), 2008. This is the author's version of the work. It is posted here by permission of Springer for personal use, not for redistribution. The definitive version was published in Biogeochemistry 93 (2009): 159-178, doi:10.1007/s10533-008-9270-z.Sediment denitrification is a major pathway of fixed nitrogen loss from aquatic systems. Due to technical difficulties in measuring this process and its spatial and temporal variability, estimates of local, regional and global denitrification have to rely on a combination of measurements and models. Here we review approaches to describing denitrification in aquatic sediments, ranging from mechanistic diagenetic models to empirical parameterizations of nitrogen fluxes across the sediment-water interface. We also present a compilation of denitrification measurements and ancillary data for different aquatic systems, ranging from freshwater to marine. Based on this data compilation we reevaluate published parameterizations of denitrification. We recommend that future models of denitrification use (1) a combination of mechanistic diagenetic models and measurements where bottom waters are temporally hypoxic or anoxic, and (2) the much simpler correlations between denitrification and sediment oxygen consumption for oxic bottom waters. For our data set, inclusion of bottom water oxygen and nitrate concentrations in a multivariate regression did not improve the statistical fit.Financial support for AEG to work on the manuscript came from NSF NSF-DEB-0423565. KF, DB and DDT acknowledge support from NOAA CHRP grant NA07NOS4780191

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The Chesapeake Bay Model development project has as it goal the development of a comprehensive model of eutrophication in the estuary. It is a mass balance model that relates the inputs of nutrients to the growth and death of hytoplankton and the resulting extent and duration of the hypoxia and anoxia. The aim is to identify and quantify the causal chain that begins with nutrient inputs and ends with the dissolved oxygen distributions in space and time. The modeling framework is based on a mass balance of the carbon, nitrogen, phosphorus, silica, and dissolved oxygen in the bay. It requires a detailed specification of the transport that affects all these components and the kinetics that describe the growth and death of phytoplankton biomass, the nutrient cycling, and the resulting dissolved oxygen distribution in the bay and estuaries. A critical component of the model is the role of sediments in recycling nutrients and consuming oxygen. This report presents the formulation and calibration of a sediment model which quantifies these processes within the context of mass balances in the sediment compartment.Cheasapeake Bay Program Office, U.S. Enviromental Protection Agency, U.S. Army Engineer Distric