HR: 1340h
AN: B33A-1019    [Abstracts]
TI: Near-field Physical And Biological Impacts Of Direct Injection Of CO2 Into The Ocean
AU: * Chen, B
EM: b.chen@aist.go.jp
AF: National Institute of Advanced Industrial Science and Technology, Distributed Energy System Research Group, 1-2-1 Namiki, Tsukuba East, Tsukuba, 305-8564 Japan
AU: Nishio, M
EM: m.nishio@aist.go.jp
AF: National Institute of Advanced Industrial Science and Technology, Distributed Energy System Research Group, 1-2-1 Namiki, Tsukuba East, Tsukuba, 305-8564 Japan
AU: Akai, M
EM: m.akai@aist.go.jp
AF: National Institute of Advanced Industrial Science and Technology, Distributed Energy System Research Group, 1-2-1 Namiki, Tsukuba East, Tsukuba, 305-8564 Japan
AB: To assess the roles of injection technologies on CO2 ocean sequestration, a two-phase box model is applied to simulate the near-filed plume dynamics of CO2 droplets and CO2 enriched seawater. The physical impacts are measured by pH changes, while the biological impacts are examined by an injury degree. Zooplankton, a kind of floating animals at depth ocean, is considered as the target animal monitored. Zooplankton is injured by seawater pH reductions. The injury degree is defined as follows: At the background pH environments (no CO2 injected and pH changes is zero), the injury degree is set to be zero, while approached to unit when experienced large pH reductions for a long time. This injury degree model was developed on the basis of the libratory experimental data. CO2 is directly released into the ocean by a number of nozzles installed on the terminal of a towered pipe. CO2 injection rate of 100kg/sec and tower ship speed of 3m/sec are fixed in this study. We sampled the vertical pH changes due to dissolution of injected CO2 droplets with initial diameters (D0) of 5, 10, 15, 20, and 25 mm, respectively. We examined two injection technologies, vertical injection and horizontal injection. The vertical injection means that the injection nozzles are arranged vertically on two injection ports with vertical length of 10 meters and a horizontal interval of 3 meters. The horizontal injection means that the injection nozzles are arranged horizontally on two injection ports with horizontal length of 10 meters and a vertical interval of 3 meters. Simulation results shown that pH reductions and zooplankton injury degrees are both sensitive to the injection technologies. Up to the elapsed time of 180 minutes at injection depth of 2000 meters, the maximum pH reductions produced by horizontal injection are 0.72, 0.45, 0.37, 0.35, and 0.30 with respects to initial droplet diameters of 5, 10, 15, 20, and 25 mm, respectively. These maximum pH reductions increased to 1.42, 1.26, 1.16, 1.14, and 1.10 for vertical injection. Associated with the pH reductions, the zooplanktons could be injured slightly if CO2 was injected by horizontal injection technology. The maximum injury degrees of 0.83 at elapsed time of 10 minutes and D0 = 5mm. These injured zooplanktons then recovered back with the injury degrees all being less then 3.0E-3 for each initial droplet diameters at elapsed time of 180 minutes. The recovery is due to the dilute of CO2 enriched seawater by ocean turbulence. However, it seems to be difficult for the injured zooplanktons in case of vertical injection that the maximum injury degrees remain large range of 0.9 for D0 = 5mm to 0.7 for D0 = 25mm even the elapsed time had been up to 180 minutes. From this study, we suggested that direct injection of CO2 into the ocean by the horizontal injection technology and a middle size of droplet (D0=15mm) at depths ranging from 1500m to 2500m could produce a slight near-filed physical and biological impact.
DE: 0466 Modeling
DE: 1630 Impacts of global change (1225)
DE: 1635 Oceans (1616, 3305, 4215, 4513)
DE: 4890 Zooplankton
SC: Biogeosciences [B]
MN: Fall Meeting 2005