Kelp Watch 2014 is a joint initiative between Dr. Steven Manley (Department of Biological Sciences, California State University- Long Beach) and Dr. Kai Vetter (UC Berkeley and Lawrence Berkeley National Laboratory). The program involves the analysis of kelp samples collected by citizen-scientists along the Pacific coast for Fukushima derived radioisotopes. Because of their sedentary existences and propensity to concentrate isotopes in their tissues kelp are useful sentinel organisms with which to monitor the timing and extent of the Fukushima impacted plume of seawater as it progressively affects more of the North American west coast.
Samples were collected over February and March of this year at various sampling locations along the coast with some kelp obtained from Chile (where little Fukushima impact is expected) to serve as a reference location.
Stations where samples of kelp were obtained for Kelp Watch 2014
While 137-Cs was detected in North Pacific kelp at activities in the range 0.08-0.44 Bq/kg, 134-Cs, diagnostic of the presence of Fukushima derived radioisotopes, was below the detection limit of ~0.04 Bq/kg (all data available here in table
). Given analytical conditions of the study there was no Fukushima sourced Cs present in kelp. The Chilean kelp contained no 137-Cs and no 134-Cs as the impact of weapons testing and other human sources of these isotopes was felt primarily in the northern hemisphere.
The activities of human produced isotopes in these kelp were dwarfed by the presence of naturally occurring radioisotopes like 40-K and 210-Po by a factor of at least 10,000 times. Calculated radiation doses for human of marine biota consumers of kelp would primarily reflect the presence of these naturally occurring isotopes.
More results from Kelp Watch 2014 can be expected in the future to add to the growing body of scientific studies by the international community aimed at determining the impact of the Fukushima disaster on the North Pacific.
Update with Figure
Given some comments, that are unrelated to the diary, I include the following figure documenting the activity of 137-Cs in seawater in coastal waters at the Fukushima Dai-ichi site in Japan. The measurements were taken by TEPCO at sites called T1 (30 m north of discharge channel for units 5 and 6 ) and T2 (Around South discharge channel (around 330 m south of Discharge channel for units 1 - 4). The figure documents how the activity of 137-Cs has been diminishing from maximum values in the weeks following the disaster to much lower and relatively stable levels through 2013 until the present. All of the data used to make the figure below can be found online (here). The axes for the plot are log scale 137-Cs (Bq/L) versus time. The range of 137-Cs activity is 0.1 - 100,000 Bq/L.
Activity in Bq/L of 137-Cs detected in coastal seawater off the Fukushima NPP site from 2011-2014
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