Process Study on Numerical Simulation for Persistent Organic Pollutants in the East China Sea

A three-dimensional/high-resolution transport model for persistent organic pollutants (POPs) has been developed to investigate the dynamics of POPs in the East China Sea. The POPs model includes four compartments: POPs in air, water, phytoplankton, and detritus. Biochemical processes considered in this study are diffusive air-water exchange, phytoplankton uptake of POPs, vertical sinking of phytoplankton, detritus from phytoplankton, and vertical sinking and decomposition of detritus. The POPs model is coupled with an ocean circulation model that successfully reproduces the velocity fields to include processes of advection and diffusion. We have conducted numerical simulation for the PCB153 from the atmosphere and river. The model showed the remarkable seasonal variability in PCB153. Concentrations of dissolved and particulate PCB153 were higher in winter (January–March) and lower in summer (July–September). In coastal regions where chlorophyll a concentrations are higher, horizontal and vertical distributions of dissolved and particulate PCB153 concentrations were strongly affected by the effect of phytoplankton uptake. The sensitivity experiments on the dynamics of PCB153 suggested that the seasonal variability in PCB153 was mainly caused by water temperature fields. From the yearly mass balance of PCB153, most of the atmospheric input by diffusive air-water exchange were removed by horizontal advection and were accumulated to the sea bottom by vertical sinking. Massive amounts of the dissolved PCB153 from river influenced air-water and water-phytoplankton exchange processes but its impacts were confined to regions near the mouth of river.