Depositional fluxes and residence time of atmospheric radioiodine (131I) from the Fukushima accident

► Concurrent 131I peak and anomalous 210Po/210Pb ratios were observed in the Southern United States after the Fukushima nuclear accident. ► Cumulative 131I depositional flux was 4.6 ± 0.2 Bq m−2 during the fallout. ► Wet precipitation was the main removal pathway, resulting in detectable 131I activities in surface waters. ► The residence time of atmospheric 131I was estimated to be 12 ± 3 days.