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  1. Maria Villa Alfageme on March 6, 2021 at 3:55 pm

    Dear Jen,
    First, I would like to thank you for the role you took as organizer of this fantastic event, wonderfully organized! It’s been great to attend.
    And also thank you for the audio! It was very descriptive.
    Now, question about the poster, I agree with you 129I/137Cs and 129 I/90Sr activity ratios are less likely to be effective oceanographic tracers, because there is very little 129I and it is difficult to distinguish from global fallout ratio. And that is strictly true for 2015 samples. However, when I look to your figure III, for year 2016 in red most of the samples are distinctly over the fall out 129I/137Cs ratio. Maybe that is not so true for the samples with lower 129I concentration, but there are a few points with really high ratios. And, to me, it looks that the general trend is that ratios are higher than fallout. That is also supported by the average ratio you show for 2016.
    First question is, why 129I/137Cs and 129I concentrations are higher in 2016 than in 2015? Second question is, are you disregarding 2016 results with high and distinct ratios and suggest that it is not possible to use it as tracer? In that case, why?
    Thank you!

  2. Jennifer Kenyon on March 6, 2021 at 7:42 pm

    Thank you for your question, Maria! I hope you are doing well.

    I think I can answer both of your questions at once: we think that the cause of the elevated 129I/137Cs ratio in 2016 is likely a sporadic or one-off event (we discuss the possibility of these in the paper), that is why the high ratio is not seen in 2015 and indeed, not observed for all of the 2016 samples. If we were able to go back and sample in subsequent years (indeed, our lab was supposed to do so before the pandemic) and find those same elevated ratios, we would probably review our stance on not using it as a tracer. However, with only a handful of samples showing elevated ratios, and a still unclear source for the increase in 129I, it is difficult for us to say with certainty that the observed 2016 129I/137Cs ratio is a reliable tracer.