Philosophiae Doctor - PhD / This thesis characterises and discusses two continuous coastal Southern Hemispheric (SH) atmospheric radon (222Rn) signals. Large-scale atmospheric circulation patterns are important components of the climate system implicated in driving catastrophic events such as extreme droughts and mega-wildfires and radon measurements at coastal sites provide valuable information on interactions of terrestrial and oceanic air masses on regional to hemispheric scales. The main collaborating SH atmospheric observatories in this study are located at Cape Grim (CGO, Tasmania, 1992-2017) and Cape Point (CPO, South Africa, 1999-2017). The radon signal from a high-altitude remote island oceanic site in the Northern Hemisphere Mauna Loa Observatory (MLO, Hawaii, 2004-2015) is also incorporated for comparison purposes. The CGO radon signal is the longest and most sensitive in current existence. A variety of statistical, spectral, trend, back-trajectory and trajectory density methods are utilized in this study to illuminate features of the datasets on multiple scales. Strongly skewed radon distributions occur, with a large number of events falling into a compact range of low values (corresponding to marine air-masses) and a smaller number of events spread over a wide range of high-radon values (continental air-masses). Making use of Fast Fourier Transform power spectral analysis, prominent periodicities are identified on diurnal and annual scales. Inter-annual variations in seasonal and diurnal radon and meteorological characteristics, indicating changes in the continental/oceanic atmospheric mixing state, are evident especially during the period from 2012 to 2017, perhaps associated with the strong El-Niño southern oscillation centred on 2015. A slow but systematic decline in CGO and CPO radon levels is evident over the dataset, associated with fewer continental and more marine air-masses impacting the coastal stations. The long-term trends observed in the atmospheric radon signal may indicate changes in SH circulation patterns over time, perhaps associated with climate change effects.

As concentrações de urânio equivalente, tório equivalente, potássio e taxa de exposição foram determinadas em diferentes dias e horários para um mesmo local, a partir de dados gamaespectrométricos aerotransportados, medidos a uma altura média de 81 metros. Os perfis individuais foram então comparados com os perfis médios de todas as medidas. Os efeitos do radônio atmosférico e dos seus produtos de decaimento foram corrigidos com um pacote de cristais detectores extras voltados para cima, e os valores de calibração desses foram determinados a partir dos dados dos testes de radiação gama atmosférica: medidas acima de 760 metros de altura. A influência da radioatividade dos solos e rochas nos detectores voltados para cima foi corrigida de acordo com a técnica desenvolvida por Grasty e Hovgaard (1996) e discutida para as duas situações que elas são propostas. / The concentration of equivalent uranium, equivalent thorium, potassium and exposure rate were calculated on different days and hours for the same location, from airborne gamma ray spectrometric data, measured at an average height of 81 meters. The individual profiles were compared with mean profiles of all the measurements. The effects of atmospheric radon and its decay products were corrected using a pack of additional detectors crystals facing up (upward looking detector), and the calibration values these were determined from test data of atmospheric gamma radiation: measurements above 760 meters in height. The influence of radioactivity in soil and rocks in the upward looking detector was corrected according to the technique developed by Grasty and Hovgaard (1996) and discussed the two situations for which they are proposed.

As concentrações de urânio equivalente, tório equivalente, potássio e taxa de exposição foram determinadas em diferentes dias e horários para um mesmo local, a partir de dados gamaespectrométricos aerotransportados, medidos a uma altura média de 81 metros. Os perfis individuais foram então comparados com os perfis médios de todas as medidas. Os efeitos do radônio atmosférico e dos seus produtos de decaimento foram corrigidos com um pacote de cristais detectores extras voltados para cima, e os valores de calibração desses foram determinados a partir dos dados dos testes de radiação gama atmosférica: medidas acima de 760 metros de altura. A influência da radioatividade dos solos e rochas nos detectores voltados para cima foi corrigida de acordo com a técnica desenvolvida por Grasty e Hovgaard (1996) e discutida para as duas situações que elas são propostas. / The concentration of equivalent uranium, equivalent thorium, potassium and exposure rate were calculated on different days and hours for the same location, from airborne gamma ray spectrometric data, measured at an average height of 81 meters. The individual profiles were compared with mean profiles of all the measurements. The effects of atmospheric radon and its decay products were corrected using a pack of additional detectors crystals facing up (upward looking detector), and the calibration values these were determined from test data of atmospheric gamma radiation: measurements above 760 meters in height. The influence of radioactivity in soil and rocks in the upward looking detector was corrected according to the technique developed by Grasty and Hovgaard (1996) and discussed the two situations for which they are proposed.

Radon gas may be a major air quality hazard issue inside the home. Radon (222Rn) comes from the natural breakdown of radioactive uranium (238U) via radium (226Ra) in soil, rocks, and water. Radon and its progeny contribute more than 50% of the total radiation dose to the human population due to inhalation; it can result in severe and fatal lung disease. This investigation has determined the radon concentrations in seventy-seven domestic houses in a mountainous area of Hamadan in Iran which were monitored using track-etch detectors of type CR-39 exposed for three month periods. The arithmetic mean radon concentration in Hamadan buildings was determined to be 80 Bqm-3 and also an average indoor annual effective dose equivalent for the Hamadan city population was calculated as 1.5 mSv. Maximum radon concentrations were noted during the winter and spring season. In addition to this, 28 water wells were monitored by utilizing a Sarad Doseman detector at hourly intervals over extended periods. Radon measurements were also carried out in the nearby Alisadr show cave, using Solid State Nuclear Track etch Detectors (SSNTDs) during the winter and the spring periods. In the cave, the average annual effective geometric and arithmetic mean dose for guides was 28.1 and 34.2 mSv respectively. The dose received by visitors was very low. Hamadan city is built on alluvial fan deposits which are the source of the local water supply. The data from the wells shows that the groundwater in these alluvial deposits influences the flux of radon. The atmospheric radon concentration measurement in wells above the water surface ranged from 1,000 Bqm-3 to 36,600 Bqm-3. There is evidence that radon-rich ground waters play a significant role in the transport of radon through the alluvial fan system. There is evidence that the radon concentrations in homes in Hamadan are greatly influenced by the porous nature of the underlying geology and the movement of groundwater within the alluvial fan.

Radon gas may be a major air quality hazard issue inside the home. Radon (222Rn) comes from the natural breakdown of radioactive uranium (238U) via radium (226Ra) in soil, rocks, and water. Radon and its progeny contribute more than 50% of the total radiation dose to the human population due to inhalation; it can result in severe and fatal lung disease. This investigation has determined the radon concentrations in seventy-seven domestic houses in a mountainous area of Hamadan in Iran which were monitored using track-etch detectors of type CR-39 exposed for three month periods. The arithmetic mean radon concentration in Hamadan buildings was determined to be 80 Bqm-3 and also an average indoor annual effective dose equivalent for the Hamadan city population was calculated as 1.5 mSv. Maximum radon concentrations were noted during the winter and spring season. In addition to this, 28 water wells were monitored by utilizing a Sarad Doseman detector at hourly intervals over extended periods. Radon measurements were also carried out in the nearby Alisadr show cave, using Solid State Nuclear Track etch Detectors (SSNTDs) during the winter and the spring periods. In the cave, the average annual effective geometric and arithmetic mean dose for guides was 28.1 and 34.2 mSv respectively. The dose received by visitors was very low. Hamadan city is built on alluvial fan deposits which are the source of the local water supply. The data from the wells shows that the groundwater in these alluvial deposits influences the flux of radon. The atmospheric radon concentration measurement in wells above the water surface ranged from 1,000 Bqm-3 to 36,600 Bqm-3. There is evidence that radon-rich ground waters play a significant role in the transport of radon through the alluvial fan system. There is evidence that the radon concentrations in homes in Hamadan are greatly influenced by the porous nature of the underlying geology and the movement of groundwater within the alluvial fan. / The Ministry of Health and Education; the University of Hamadan in Iran: University of Bradford: University of Kingston