Based on the statistics of surface drifter data of 1979-2011 and the simulation of nuclear pollutant particulate move- merits simulated using high quality ocean reanalysis surface current dataset, the transport pathwa...Based on the statistics of surface drifter data of 1979-2011 and the simulation of nuclear pollutant particulate move- merits simulated using high quality ocean reanalysis surface current dataset, the transport pathways and impact strength of Fuku-shima nuclear pollutants in the North Pacific have been estimated. The particulates are used to increase the sampling size and en- hance the representativeness of statistical results. The trajectories of the drifters and particulates are first examined to identify typical drifting pathways. The results show that there are three types of transport paths for nuclear pollutants at the surface： 1） most pollutant particles move eastward and are carried by the Kuroshio and Kuroshio-extension currents and reach the east side of the North Pacific after about 3.2-3.9 years; 2） some particles travel with the subtropical circulation branch and reach the east coast of China after about 1.6 years according to one drifter trajectory and about 3.6 years according to particulate trajectories; 3） a little of them travel with local, small scale circulations and reach the east coast of China after about 1.3-1.8 years. Based on the par-tieulates, the impact strength of nuclear pollutants at these time scales can be estimated according to the temporal variations of relative concentration combined with the radioactive decay rate. For example, Cesium-137, carried by the strong North Pacific current, mainly accumulates in the eastern North Pacific and its impact strength is 4% of the initial level at the originating Fuku- shima area after 4 years. Due to local eddies, Cesium-137 in the western North Pacific is 1% of the initial pollutant level after 1.5 years and continuously increases to 3% after 4 years. The vertical movement of radioactive pollutants is not taken into account in the present study, and the estimation accuracy would be improved by considering three-dimensional flows.展开更多
基金supported by the National Basic Research Program (Grant No.2013CB430304)the National Natural Science Foundation of China (Nos.41206178, 41030854, 41106005, 41176003 and 41306006)the National High-Tech R&D Program of China (No.2013 AA09A505)
文摘Based on the statistics of surface drifter data of 1979-2011 and the simulation of nuclear pollutant particulate move- merits simulated using high quality ocean reanalysis surface current dataset, the transport pathways and impact strength of Fuku-shima nuclear pollutants in the North Pacific have been estimated. The particulates are used to increase the sampling size and en- hance the representativeness of statistical results. The trajectories of the drifters and particulates are first examined to identify typical drifting pathways. The results show that there are three types of transport paths for nuclear pollutants at the surface： 1） most pollutant particles move eastward and are carried by the Kuroshio and Kuroshio-extension currents and reach the east side of the North Pacific after about 3.2-3.9 years; 2） some particles travel with the subtropical circulation branch and reach the east coast of China after about 1.6 years according to one drifter trajectory and about 3.6 years according to particulate trajectories; 3） a little of them travel with local, small scale circulations and reach the east coast of China after about 1.3-1.8 years. Based on the par-tieulates, the impact strength of nuclear pollutants at these time scales can be estimated according to the temporal variations of relative concentration combined with the radioactive decay rate. For example, Cesium-137, carried by the strong North Pacific current, mainly accumulates in the eastern North Pacific and its impact strength is 4% of the initial level at the originating Fuku- shima area after 4 years. Due to local eddies, Cesium-137 in the western North Pacific is 1% of the initial pollutant level after 1.5 years and continuously increases to 3% after 4 years. The vertical movement of radioactive pollutants is not taken into account in the present study, and the estimation accuracy would be improved by considering three-dimensional flows.
