Southern Hemisphere 2014 Year Report
The good news at present is that background levels here have stabilized. We still occasionally get significant peaks, but these events are not now as common as in 2011, 2012, and 2013.
For four years before Fukushima a GammaScout Geiger counter logged once a week local background radiation levels. The averaged over that time was ~ 0.1 uSv/hour. This data has allowed a comparison of background levels before, and after Fukushima.
Pre-Fukushima 2007 to 2011 local background level chart
The peak in the pre-Fukushima background level chart around September 2008, was probably an experiment being carried out at the time. Since 2012 local background radiation level data has been logged every 60 seconds.
The four years before Fukushima recorded data doesn't show much seasonal variation in background levels. After Fukushima, a seasonal variation showed up in the year average charts. Northerly winds tend to come from the equator here in the warmer months. In the cooler months, it tends to come from the Southern Ocean. The station location is on a headland, so there can be significant changes in background levels as the wind changes from North to South.
After you average out the season differences here, the yearly increase since Fukushima has averaged around 21%.
The 2012 year average was 21% above the pre-Fukushima 4 year average.
The 2013 year average was 22% above the pre-Fukushima 4 year average.
The 2014 year average was 20% above the pre-Fukushima 4 year average.
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Dynamic swings in the in 24 hour background charts where common in late 2011, 2012, and 2012. (The blue line is the day average)
Example 1:
http://sccc.org.au/wp-content/uploads/2012/01/24-hour-background-radiation-chart-27012012.jpg
Example 2:
They show significant waves of radiation coming through. When wind came from a Northerly direction, background went up. When wind direction came from the Southern Ocean, background tended to go down.
Now the increases showing on the 24 hour charts are much more averaged, and no where near as dynamic. This suggests that what ever was in the air in 2011, 2012, and 2013 that crossed the equatorial barrier, has had time become more evenly distributed into the southern hemisphere air mass.
It would be nice if other locations had pre and post Fukushima long term publicly available background data. This would
make it a lot easier to see accurately, what is happening worldwide.
As radiation fallout does not fall evenly, there will be areas that have seen significant background increases, and other areas that have only seen small increases.
Local Background Level and Detection Events Overview 2013
Detections have been made all over the world, these reports are local detections for Australia and New Zealand. "Is then, the whole of Australia also contaminated with radiation?" No!
A lot of these detections reported for Australia are very localized. Even with a recent record day average of 0.213 uSv/hr, which is 113% above our average local background, is still lower than a lot of places in the world. It much lower than the USA national average of 0.34 uSv/hr, and lower than the world average of 0.23 uSv/hr. Our traditional lower levels lets us detect small changes.
So far most of the increases here, seem to be manly increased Radon-222 levels in the atmosphere. Read the October 2012 monthly report here, for a couple theories on why Radon levels may be increasing.
Here is a theory put forward by the people running the Nimbin monitoring Station, for the large Radon washout events detected in the Nimbin and Mullumbimby areas in late January 2013.
The area had been in a dry period, and the underground aquifers were low. A flooding rain event came through and quickly forced a large amount of radioactive Radon gas into the atmosphere, that had built up during the dry period, in the aquifer layers.
The Radon daughter isotopes were then washed out of the atmosphere during the rain event, and detected on the rain swabs. It is not uncommon to get large radon washout events happening anywhere in the world during rain events. Radon gas is in the air we breath all the time, in small amounts. Radon-222 decays to its isotope daughters, radioactive Lead Pb-214, Bismuth Bi-214, and Polonium Po-214. Radon daughter isotopes decay very quickly to Lead Pb-210. In an event like this, with such high multi uSv/hr levels of detection, it would be advisable to stay out of the rain. We haven't seen any studies on the heath effects of being exposed to large Radon washout events. It is only a suggestion to take this precaution.
Rain Water Tests Overview for 2013
A lot of rain water and car bonnet swabs were conducted during the year. Test results
At the beginning of the year, these Geiger counter and scintillator tests manly detected Radon-222 decay daughter isotope washouts, plus traces of Beryllium Be-7, Lead Pb-210, Iodine I-129 and Uranium U-235. In July, traces of Thorium Th-234 were detected, plus in September, Radon-220 decay daughter isotopes were also detected for the first time.
If traces of U-235 were detected, it means a lot more Uranium U-238 was in the atmosphere. The detection of I-129 is also of concern, even if it is in trace amounts. Even though the amounts detected maybe below Government set risk levels, it is suggested that those who are using tank water should have very good water filters in place, and those on town water use a good reverse osmosis water filter. Also wash your fruit and vegetables well before cooking and eating.
