Numerical modelling for the prediction of sedimentary improvement by sand capping over a contaminated seabed

Abstract

An ecological system dynamics model is developed for the prediction of the seabed change after the placement of a sand layer over the contaminated seabed. The model simulates the cycling of materials among seawater, seabed sediments, and marine natures such as benthos, bottom fish and oyster in the coastal seas. Special attention is paid to the modelling of the interaction between the aquatic system and the sedimentary one, such as settling and the release of nutrient salts. The computation domain is divided into ten boxes with eleven layers in the water zone and seven layers in the sediment zone. The degree of seabed improvement is evaluated with the decrease of benthonic mortality and the decrease of dissolved oxygen consumption in the bottom layer. A field experiment of seabed capping was carried out in Kure Bay, Japan. The model predicted quite well the seasonal variations of the dissolved oxygen, zooplankton, and benthos, which were observed in the field. The model developed here enables to evaluate ...