Gamma Spectrometry Forum

At the beginning of November and again on the 14th November, a 40%+ increase in day average backgrounds levels were detected at my location on the East Coast Of Australia, near Brisbane. Tests were conducted to try an establish the source of the elevated background.

http://sccc.org.au/wp-content/uploads/2 ... r-2015.jpg

There were evening storms on the 14th, during one of these elevated background events, so a car rain swab was collected on the morning of the 15th November. The rain had been sitting on the car overnight. A scintillator test of it was started on the afternoon of the15th. It was tested for ~24 hours.

Radon is formed in the normal radioactive decay of Thorium which produces Radon-220, and Uranium which produces Radon-222. Both of these different Radon isotopes decay slowly into lead.

In the test chart you will see isotope maker peaks for Lead Pb-212 and an X-ray at 77 keV. These are decay daughters of Radon-220. This suggests that Thorium-232 was the source. There are also traces of Lead Pb-210, and Potassium-40. Lead Pb-210 is the decay daughter of Radon-222. This means there was also some Radon-222 in the air at the time.

The test detected trace amounts of Th-232 decay daughters, so the rain swab test chart only shows the tops of the main Th-232 decay daughter and X-ray peaks. A Thorium gas mantle test shows the main Thorium Th-232 decay daughter peaks. I have provided it as a reference. As you can see from the gas mantel test, the equipment here can separate the combined X-ray daughter peak around 89/90 keV, from the main 77 KeV peak.

November 15th Rain Swab Chart.

http://sccc.org.au/wp-content/uploads/2 ... 5854-B.png

Thorium Mantel Chart for Comparison

http://sccc.org.au/wp-content/uploads/2 ... 5-3000.jpg

Where is the Thorium-232 coming from?

Sources of atmospheric releases of Thorium-232 could be the recent Indonesian, New Zealand or South American volcanic eruptions, or a mining operation somewhere? There is a lot of volcanic activity in the Southern Hemisphere at present.

On the Emergency and Disaster Information Service map, you can see the locations of erupting volcanoes in South America, New Zealand and Indonesia.

http://hisz.rsoe.hu/alertmap/index2.php

http://hisz.rsoe.hu/alertmap/index2.php

Because the elevated detections where detected along the entire Eastern Coast of Australia, by numerous private monitoring stations, I am leaning towards volcanic activity, rather than a mining operation.

If you have a different analysis, or other suggestion, let us know.

Peter,

Thanks for sharing. Note for future posting there is no need to add html coding to your URL's simply select the URL string and click the [URL] formatting button above the text editor.

The local November month average background radiation for November 2014, 2013, and 2012, works out to 0.130 uSv. The volcanic activity, or whatever source created the increase, appears to have increased the November 2015 month average local background to 0.137 uSv.

These measurements are recorded by a GammaScout Alert Geiger counter, logging every 60 seconds. The data is downloaded and turned into a day average chart, and eventually a month average chart.

Monitoring Station Location




Here are month day average charts for November 2015, 2014, 2013, and 2012, local background radiation levels.


Day Average Chart November 2015




Day Average Chart November 2014




Day Average Chart November 2013




Day Average Chart November 2012

Peter,

It would be interesting to see an overlay on your chart with daily temperature in Caloundra. The gammascout is a geiger tube and would be sensitive to pressure changes. Maybe the effect is less than you are measuring.

http://www.bom.gov.au/jsp/ncc/cdio/weat ... tYear=2015
And here is the bureau chart overlay on your november chart.
These temperatures were rexcorded 22 km from Coloundra and show a fair correlation to your radiation chart, with the trend at the beginning matching the trend at the end.

More data is available for the other months at the bureau site.

Steven

Hi Peter,

in addition to effects on the geiger tube, you will often find elevated background radiation after heavy Rain due to the washout of Radon daughters from the atmosphere. The Radon concentration in the air also varies depending on meteorological conditions, see for example http://journals.ametsoc.org/doi/pdf/10. ... 2.0.CO%3B2

I think it is quite possible that Volcano eruptions release Radon to the atmosphere, but to show that you will have to compare your data with older records taken under similar conditions, or with measurements taken near the site of the eruption.

Valentin

Most of these background increases detected in November where on clear find days. We also have a live Radon monitor here at Caloundra, to keep track of local Radon levels. A number of private live monitoring stations down the east coast of Australia, from Cairns to Tasmania detected an increase in background in November. Here is a Cairns and Caloundra background level comparison chart, kindly provided by the operator of a live monitoring station near Cairns.

Cairns November 2015 Report - "After several months of very flat readings, last month had a number of peaks, with the increase starting the last week in October. It appears, the peaks coincide with higher altitude wind coming from the inland and usually very hot days."

As you can see from the comparison chart below, Cairns had much more dynamic swings in background than Caloundra for November.


Cairns is red in this chart and Caloundra is yellow.




Over many years of recording local background levels, the conclusion is that wind direction causes the greatest changes in background levels here. When the 24 hour data charts show a dramatic change it is when the wind changes direction. This is very noticeable even on clear fine days. Here in the cooler months, the winds mainly come from a Southerly direction, and in the warmer months they come from a Northerly direction. A seasonal variation now shows up in the month average year charts. Hotter tropical air seems to be the main source for these background increases.

Here are year charts showing month averages for 2015, 2014, 2013, and 2012.

2015 so far,




2014




2013




2012



Here are year averages from 2007 to 2014, recorded here in Caloundra