A modelling study of the contribution of riverine and anthropogenic inputs of ammonium to a North Sea coastal area

A random-walk model has been set up to predict the concentration of ammonium in an area of the North Sea off Tees Bay. The model takes into consideration the inputs of ammonium from the rivers Tees, Tyne and Wear, production by sediments and an anthropogenic input. The latter is from waste produced by the manufacture of methyl methacrylate which is discharged, into a designated disposal ground, from a moving ship. The model also includes the effect of assimilation of ammonium by phytoplankton. The model has been used to assess the environmental impact of the waste discharge with the predictions indicating that there would be no build-up of ammonium within the disposal ground. Approximately 20 km from the disposal ground the ammonium levels are reduced to the predicted background so no impact of the ammonium, due to the waste disposal, outside of this region is likely. Additionally the model has been used to estimate the ammonium used by the phytoplankton over a given time period in a given volume and this has been related to the expected biomass that would be produced. It is unlikely that the biomass generated, due to the additional available ammonium, would be of the concentration associated with algal blooms.