Development of a Numerical Model for Calculating Exposure to Toxic and Nontoxic Stressors in the Water Column and Sediment from Drilling Discharges

• Published in: Integrated environmental assessment and management Vol. 4; no. 2; pp. 194 - 203
• Main Authors: Rye, Henrik, Reed, Mark, Frost, Tone Karin, Smit, Mathijs G. D, Durgut, Ismail, Johansen, Øistein, Ditlevsen, May Kristin
• Format: Journal Article
• Language: English
• Published: Hoboken Society of Environmental Toxicology and Chemistry 01-04-2008; Wiley Periodicals, Inc; Blackwell Publishing Ltd
• Subjects: Assessments; Atoms & subatomic particles; Biodegradation; Bioturbation; Chemicals; Discharge; Drilling; Drilling discharges; Environmental Exposure; Environmental fate; Environmental risk; ERMS; Extraction and Processing Industry; Geologic Sediments; Grain size; Hypoxia; IMARES; Lead; Mathematical models; Models, Theoretical; Ocean currents; Ocean floor; Oceanic turbulence; Organic matter; Oxygen depletion; Petroleum; Risk assessment; Risk Assessment - methods; Risk management; Seawater; Sediments; Special Section—Environmental Risk Management Systems; Wageningen Marine Research; Water column; Water currents; Water Pollutants - toxicity
• ISSN: 1551-3777; 1551-3793; 1551-3793
• DOI: 10.1897/IEAM_2007-039.1

EDITOR'S NOTE: This is 1 of 5 papers reporting on the results of a 4-year project to develop an environmental risk-based decision support tool, to assist the oil industry in establishing cost-effective measures for reducing risk to the marine environment from drilling discharges. Drilling discharges are complex mixtures of chemical components and particles which might lead to toxic and nontoxic stress in the environment. In order to be able to evaluate the potential environmental consequences of such discharges in the water column and in sediments, a numerical model was developed. The model includes water column stratification, ocean currents and turbulence, natural burial, bioturbation, and biodegradation of organic matter in the sediment. Accounting for these processes, the fate of the discharge is modeled for the water column, including near-field mixing and plume motion, far-field mixing, and transport. The fate of the discharge is also modeled for the sediment, including sea floor deposition, and mixing due to bioturbation. Formulas are provided for the calculation of suspended matter and chemical concentrations in the water column, and burial, change in grain size, oxygen depletion, and chemical concentrations in the sediment. The model is fully 3-dimensional and time dependent. It uses a Lagrangian approach for the water column based on moving particles that represent the properties of the release and an Eulerian approach for the sediment based on calculation of the properties of matter in a grid. The model will be used to calculate the environmental risk, both in the water column and in sediments, from drilling discharges. It can serve as a tool to define risk mitigating measures, and as such it provides guidance towards the “zero harm” goal.