IMPACTS OF REDUCED PH FROM OCEAN CO2 DISPOSAL - SENSITIVITY OF ZOOPLANKTON MORTALITY TO MODEL PARAMETERS

Our group has developed a methodology to quantify mortality suffered b y marine zooplankton passing through a CO2-enriched sea water plume. H ere we explore model sensitivity to some of the more important biologi cal, physical and engineering design parameters, with particular refer ence to CO2 injection as a buoyant droplet plume. Uncertainty in the d ose-response relationship, e.g. caused by the use of data for surface organisms, will affect predicted values of total mortality by less tha n a factor of two for a single point discharge from 10 standard 500 MW e coal-fired electric power plants and a factor of five for a single p oint discharge from one standard plant. The most important design vari able is the number of physically separated discharge points (diffuser ports or groups of ports) used to disperse the CO2. Predicted mortalit y drops to zero as the number of discharge points per standard plant e xceeds two. Finally, the most important physical parameters are ambien t current speed and turbulent diffusivity. As with the dose-response d ata, most physical oceanographic measurements have been conducted near the ocean surface. Model sensitivity suggests that a factor of 2.5 re duction in current speed or a factor of 3 reduction in ambient diffusi vity, relative to our base case, would require that the number of disc harge points per standard plant increase from 2 to 12 in order to avoi d mortality. Thus impacts can be strongly site-specific, and additiona l oceanographic measurements are needed at depths appropriate for CO2 sequestration. Nonetheless, it should be easy to design an environment ally conservative multi-point discharge system that can disperse CO2 a s a droplet plume without significant mortality, even under adverse en vironmental conditions. (C) 1998 Elsevier Science Ltd. All rights rese rved.