Soil update (9/16/2011)
9/16 (3:10pm): We are in the process of testing several layers of soil from a yard in Oakland, CA. The first test of the top 2 cm has been performed and the results are posted on the Food Chain page. The soil has a smaller amount of Cs-134 than in any other soil sample we have tested, while the Cs-137 level is on par with the other older soils we have tested, yielding a 137/134 ratio of about 30. The yard is made of older soil, so the presence of higher levels of Cs-137 is expected from pre-Fukushima fallout depositions.
Our testing is continuing, but at a slower rate. We are sharing a room with a laboratory course and cannot count samples when they are doing their experiments, so that limits the time we have for testing. It will take several days to finish testing the remaining soil layers, which go down to a depth of 14 cm.
Mark [BRAWM Team Member]
Mark - Am i reading it
Mark - Am i reading it wrong, or is this sample the highest yet detected level of Cesium 137? Can you account for why it would be so high? Also, in another soil sample you have that was below a couple inches there was no cesium detected. Why would that be? If there is so much cesium from past weapons testing wouldn't it be down just a few inches below the surface?
Thanks for any light you can shed on this. I've been wondering why milk levels have been going up and I suspect it has something to do with grass growing out of very contaminated soil...
The Oakland sample
The Oakland sample (2.46±0.25 Bq/kg of Cs-137) is not the highest — the Sacramento soil has 2.59±0.26 Bq/kg. They are consistent within error bars. The Oakland sample does have the highest ratio of Cs-137 to Cs-134 (≈30), but that is partially because the Cs-134 level is especially low.
The Alameda and San Diego samples were from newer soils — they had not been exposed to rain during the 1950s and 1960s. In the case of the San Diego samples, that soil had been purchased very recently from a store and laid in the garden. That is why there is no extra Cesium-137 in them. On the other hand, the soils from farms (Sonoma and Sacramento) have been near the surface a long time, so they likely were exposed to some rain in the 1950s and 1960s.
Mark [BRAWM Team Member]
Thank you!
Thank you again to all the team for your continued work.
Mark- Thanks! The Cs-134
Mark-
Thanks!
The Cs-134 level is quite low compared to the Berkeley samples, and I would expect that Berkeley and Oakland would have very similar levels. Maybe a difference in the sample-taking methodology is the cause?
BC
The Alameda and Oakland
The Alameda and Oakland samples were collected in similar ways — both samples were collected from the top inch of soil. There could be a difference in the character of the soil — for example, the Oakland soil may be sandier and therefore the Cs-134 could be more spread out. Or maybe that small area where the soil was collected from just didn't receive as much rain as the area in Alameda.
I am interested in testing other soils from the Bay Area to get a wider survey, since two points don't tell us all that much.
Mark [BRAWM Team Member]
I would like to see more
I would like to see more samples from a wider geographical range. Is there anywhere I could send soil samples for testing? (like from my garden in SoCal?)
FYI - San Diego soil
FYI - San Diego soil already tested. Check main sampling page.