A reaction diffusion model of C-N-S-O species in some arctic sediments

Abstract

A reaction diffusion model was used to simulate the mineralization processes in an Arctic sediment. The simulation and the actual sediment were compared in relation to profiles of O2, NO3 and NH4+. The site of particulate organic matter (POM) degradation was the single most important factor in fitting the simulation profiles to those of the sediment. It was deduced that most POM degradation occurred close to the sediment surface. When a reasonably good simulation had been obtained, the sensitivity of the model to changes in other parameters was investigated. Increases in POM degradation in the upper sediment resulted in increases in concentration of NH4+ and NO3−, but further increases in POM degradation created anoxic conditions below 3 mm, resulting in decreases in NO3− concentrations. The model was relatively intensive to changes in POM degradation in the lower sediment layers; increases led to more anoxic conditions and to less NO3−. Increases in the C/N ratio of the POM in the lower sediment layers had little effect; increases in C/N in the upper layers led to a decrease in NH4+ and NO3−. The model was sensitive to changes in the first order rate constant for nitrification, but not for denitrification. Decreases in the Km for O2 of the nitrifying bacteria had no effect on the profiles.