Measurements of ~(129)I in the Pacific Ocean at Scripps Pier and Pacific Northwest sites: A search for effects from the 2011 Fukushima Daiichi Nuclear Power Plant accident and Hanford

摘要

Radionuclides from the Fukushima Daiichi Nuclear Power Plant were released directly into he ocean as a result of the Great East Japan Earthquake on March 11, 2011. This material became entrained in surface ocean currents and subsequently transported for great. distances. In June 2011, a few months alter the disaster, we began a surface ocean I-129 monitoring program, with samples from Scripps Pier, La Jolla, California, USA, with the expectation that surface currents originating off the east coast of Japan would eventually carry radionuclides to the La Jolla site. After 7 years of ocean transport, a distinct signal has not yet arrived at Scripps Pier. We have however, recorded an interesting systematic seasonal I-129 time series record that stems from surface circulation variations along the California coast To provide a more comprehensive picture of the I-129 budget in coastal surface waters off the west coast of the U.S., we also include I-129 data from the Columbia River, and offshore sites along the coast of Washington State. Anthropogenic nuclides are carried by the Columbia River into the Pacific Ocean from the vicinity of the decommissioned Hanford nuclear facility. We find highly elevated I-129/I-127 values in the Columbia River, downstream from the Hanford site, but this anthropogenic I-129 becomes significantly diluted once it reaches the Pacific Ocean. Nonetheless, its imprint persists in surface seawater off the west coast of the U.S. that has significantly higher I-129/I-127 levels than other surface sites in the Pacific Ocean. (C) 2019 The Authors. Published by Elsevier B.V.