Modeling Environmental Impact On Sediment Caused By Discharges Deposited On The Sea Floor
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319 - 327
A model has been developed that is able to model various types of impact on the sea floor caused by the deposition of particle matter and chemicals (attached to the particle matter). Particle matter may also contain heavy metals. The sediment is assumed to be represented by natural grains and porewater. The concentrations of dissolved chemicals in the pore water are assumed to be bioavailable, and the concentrations (toxicity) in the pore water are then given by partition of the chemicals (and heavy metals) between the pore water and the sediment. Other stressors caused by the discharges deposited are oxygen depletion (caused by the biodegradation of the chemicals deposited), generation of \“exotic” sediment (caused by the particle size distribution of the particle matter deposited, which may have another distribution than the original sediment) and burial. All these factors are embedded into a numerical model that is able to simulate these stressors as a function of sediment location and time. Keywords: sediment, environmental impact, numerical simulation, partitioning. 1 Introduction This paper will focus on impacts on the sea floor caused by offshore discharges of drilling debris. Activities associated with offshore drilling operations lead to a variety of discharges with different durations and behavior in the recipient. Examples of the types of drilling muds used include WBM (Water Based Mud), SBM (Synthetic Based Mud) and OBM (Oil Based Mud). The discharges can take place from the drilling rig (when drilling deeper well sections) or directly to the sea floor (when drilling top well sections). Some constituents of the discharge are water-soluble chemical additives, which dissolve into the water column whilst others are particulates (cuttings and weight material like barite) or
sediment, environmental impact, numerical simulation, partitioning.