Mineralization in a northeastern Greenland sediment: Mathematical modelling, measured sediment pore water profiles and actual activities

Abstract

A mathematical computer model describing mineralization processes and transport of solutes within sediments was developed based on the degradation of organic matter, stoichiometrically coupled to the consumption of O2 in the oxic layers, and to NO3- and SO42- in the anoxic layers. The reaction rates obey Michaelis-Menten type kinetics and all transport of solutes is assumed to take place by diffusion. The model was tested on a northeastern Greenland sediment and gave accurate simulations of the measured concentration profiles. In addition, measured processes of nitrification, coupled nitrification-denitrification, denitrification of water column NO3-, NH4+ mineralization and the fluxes of NH4+ and NO3- across the sediment-water interface were predicted with great accuracy. Since the model is based on Michaelis-Menten type kinetics and diffusional transport mechanisms, it is of general use and provides an important tool to evaluate the regulation of biogeochemical cycling in sediments. This is shown in a series of simulations predicting the effect of various concentrations in the water column of O2 and NO3- on the rates of nitrification and denitrification. The results are in good agreement with previously published measurements.