Basedonthestatisticsofsurfacedrifterdataof1979–2011andthesimulationofnuclearpollutantparticulatemovementssimulatedusinghighqualityoceanreanalysissurfacecurrentdataset,thetransportpathwaysandimpactstrengthofFukushimanuclearpollutantsintheNorthPacifichavebeenestimated.Theparticulatesareusedtoincreasethesamplingsizeandenhancetherepresentativenessofstatisticalresults.Thetrajectoriesofthedriftersandparticulatesarefirstexaminedtoidentifytypicaldriftingpathways.Theresultsshowthattherearethreetypesoftransportpathsfornuclearpollutantsatthesurface:1)mostpollutantparticlesmoveeastwardandarecarriedbytheKuroshioandKuroshio-extensioncurrentsandreachtheeastsideoftheNorthPacificafterabout3.2–3.9years;2)someparticlestravelwiththesubtropicalcirculationbranchandreachtheeastcoastofChinaafterabout1.6yearsaccordingtoonedriftertrajectoryandabout3.6yearsaccordingtoparticulatetrajectories;3)alittleofthemtravelwithlocal,smallscalecirculationsandreachtheeastcoastofChinaafterabout1.3–1.8years.Basedontheparticulates,theimpactstrengthofnuclearpollutantsatthesetimescalescanbeestimatedaccordingtothetemporalvariationsofrelativeconcentrationcombinedwiththeradioactivedecayrate.Forexample,Cesium-137,carriedbythestrongNorthPacificcurrent,mainlyaccumulatesintheeasternNorthPacificanditsimpactstrengthis4%oftheinitiallevelattheoriginatingFukushimaareaafter4years.Duetolocaleddies,Cesium-137inthewesternNorthPacificis1%oftheinitialpollutantlevelafter1.5yearsandcontinuouslyincreasesto3%after4years.Theverticalmovementofradioactivepollutantsisnottakenintoaccountinthepresentstudy,andtheestimationaccuracywouldbeimprovedbyconsideringthree-dimensionalflows.
