The Anthropogenic Impact on Indoor Radon Concentrations for Secunda, Mpumalanga Province, South Africa

Abstract

Secunda is a town built amid the coalfields of the Mpumalanga province of South Africa. Surrounding the town are 11 coal-fired plants (CFPs) contributing around 59% of the country’s energy needs. It is also home to Sasol Synfuels, which produces synthetic gas through coal gasification and natural gas reforming. Coal, like most materials found in nature, contains trace elements of the naturally occurring primordial radionuclides 40K, 238U, 232Th, and their decay products. The milling and combustion of coal in a CFP increases the mass concentration of these trace elements, and the residuals end up on ash heaps as fly ash, bottom ash, and boiler slag. A small percentage of fly ash also ends up in the atmosphere. This paper sets out to determine the anthropogenic impact of the industrial activity on indoor radon in the town of Secunda in the Mpumalanga region of South Africa. Measurements were done in 37 homes during July when higher indoor radon levels are expected due to homes typically being closed due to the low temperatures. The average indoor radon concentration was found to be 76.4 Bq m−3. This indicates that the fallout from the industrial activity surrounding Secunda does not enhance the emanation of radon. This may be due to the type of activity or the climate and prevailing winds mitigating its indoor build-up. Measurements during the warmer months and in neighboring towns with different industrial activities are required to confirm the trends established by this research.

The Effect of the Coal Industry on Indoor Radon Concentrations in eMalahleni, Mpumalanga Province of South Africa

“…In the figure, the natural logarithm is compared to a normalized normal distribution with a mean of 4.72 and a standard deviation of 0.42. Comparing these findings to the results Le Roux (2021) obtained for Secunda, it can be seen that despite both towns being surrounded by similar coal-centric anthropogenic activities, the indoor radon concentrations for eMalahleni are 60% higher. Fig.…”

“…Le Roux (2021) recorded an average indoor radon concentration of 76.4 ± 7.6 Bq m −3 for Secunda, which was less than expected. This was attributed to the prevailing wind depositing the radionuclide fallout in neighboring towns, such as eMalahleni.…”

“…The uranium content of the ash generated by pulverization and combustion is therefore expected to be approximately 9.00 ± 0.09 mg kg −1 . In fact, Le Roux et al (2021) determined this to be 9.46 ± 0.09 mg kg -1 . Despite this high uranium content indicating potentially high indoor radon levels, the levels measured were lower than expected, with an arithmetic mean of 76.4 ± 7.6 Bq m −3 .…”

“…As a result, many countries embarked on radon surveys in an attempt to identify potential radon hotspots. Le Roux et al (2021) identified the Mpumalanga province of South Africa as a potential hotspot due to its coalfields and aimed to prove that the fly ash, pollution, and radioactive progeny generated by the coal industry generates radioactive fallout that could artificially increase indoor radon concentrations.…”

“…As a result, many countries embarked on radon surveys in an attempt to identify potential radon hotspots. Le Roux et al (2021) identified the Mpumalanga province of South Africa as a potential hotspot due to its coalfields and aimed to prove that the fly ash, pollution, and radioactive progeny generated by the coal industry generates radioactive fallout that could artificially increase indoor radon concentrations. The town of Secunda was identified as a high radon risk due to its close proximity to 11 coal-fired power stations (CFPs), six coal mines, and Sasol Synfuels (Pty) Ltd., the world’s largest coal-to-liquid (CTL) operation.…”