Spatial autocorrelation and hotspot analysis of natural radionuclides to study sediment transport.

Tracking sediment movement is typically done with artificial radionuclides. However, this can be environmentally harmful and does not allow for sediment classification. Naturally occurring radionuclides are consequently offered as an alternative. In this study, a mobile Delta Underwater Gamma System (DUGS) capable of measuring low levels of natural radionuclides in sediment was deployed in an estuary, and a radiometric map of the sediment was constructed. Spatial autocorrelation using the Moran's I statistic was used to investigate the spatial distribution patterns of natural radionuclides in the sediments. Hotspot analysis using Getis-Ord* was used to validate and map areas that had been identified as clustered by the Moran's I statistic. The Moran's I analysis indicated that 40K displayed a positive spatial autocorrelation with a value of 0.4 and a standardized Z score of 16, thus indicating that the clustering was significant. 238U and 232Th displayed a low Moran's I value but a strong positive correlation, hence indicating some spots of clustering in the river channel. Further analysis of hotspots confirmed that the identified clusters were areas with relatively high radionuclide concentrations. This proved that the hotspot areas identified have a high deposition of sediment. In situ radiometric measurements of sediment, as well as spatial analysis, are consequently useful tools to model and study spatial structure and sediment.

Estimating geothermal and background radiation hotspots from primordial radionuclide concentrations in geology of South Africa.

Naturally occurring radionuclides are the main generator of geothermal energy in the Earth's crust and mantle. The generated energy is consequently directly proportional to the concentrations of the three main naturally occurring radionuclides (uranium, thorium and potassium), which are primordial in origin. Concentrations of these naturally occurring radionuclides were extracted for all the different geological rock units in South Africa. The radionuclide concentrations were then mapped and integrated by using QGIS. The results were used to estimate and map the geothermal energy production rates for the rock units. The radionuclide concentrations in the rock units were also used to identify regions with high radiation background. These radiation hotspots were plotted and investigated. The estimated geothermal energy and background radiation hotspots were compared to measurements and projections of other studies and good corelations were found.

Indoor Radon Levels in Homes and Schools in the Western Cape, South Africa-Results from a Schools Science Outreach Initiative and Corresponding Model Predictions.

We describe a school science outreach initiative that introduced learners to applied nuclear physics research by means of a two-day workshop that involved learners and teachers from 5 schools in the Western Cape province of South Africa. During this workshop, the participants were introduced to the naturally occurring, inert, colorless, and tasteless radioactive gas radon (222Rn). During the first day of the workshop, the participants were informed about the detrimental health impacts of inhaling radon and its daughter radionuclides and were shown how indoor radon activity concentrations can be measured using the electret ion chamber (EIC) technology. The learners were then each supplied with a short-term electret (E-PERM, Radelec, Frederick, MD, USA) and associated ion chamber to enable them to make radon measurements in their homes. The teachers in turn were supplied with EICs to enable them make radon measurements in their schools. The participants returned the EICs on the second day of the workshop, one week later. Here, the drop in the potential difference across each electret was measured in order to calculate the average indoor radon activity concentration. A total of 49 indoor radon concentrations were measured. The average indoor radon concentrations were 36 ± 26 Bqm-3 in homes and 41 ± 36 Bqm-3 in schools, while the highest concentration was found to be 144 Bqm-3. These levels were compared to predictions from a model that uses input information about the uranium content associated with the surface geology at each measurement location. The predictions compared well with the measured values.

Effect of the Elemental Content of Shells of the Bivalve Mollusks (Mytilus galloprovincialis) from Saldanha Bay (South Africa) on Their Crystallographic Texture.

A both wild and farmed mussels in natural conditions, anthropogenic inputs are usually reflected in the increase of the content of specific elements. To determine the possible effect of the elemental patterns of farmed and wild mussels (Mytilus galloprovincialis) collected in the Saldanha Bay area (South Africa) on the crystallographic texture of the shells, the content of 20 elements in shells and 24 in the soft tissue of mussels was determined by neutron activation analysis. The crystallographic texture of mussel shells was analyzed using time-of-flight neutron diffraction. The wild mussels from open ocean site live in stressful natural conditions and contain higher amounts of the majority of determined elements in comparison with mussels farmed in closed water areas with anthropogenic loadings. The changes between the maximums of the same pole figures of the three samples are in the range of variability identified for the genus Mytilus. The content of Cl, Sr, and I was the highest in mussels from the open ocean site, which is reflected by the lowest mass/length ratio. The determined crystallographic textures of mussels are relatively stable as shown in the analyzed pole figures despite the concentrations of Na, Mg, Cl, Br, Sr, and I in shells, which significantly differ for wild and farmed mussels. The stability of the crystallographic texture that we observed suggests that it can be used as a reference model, where if a very different texture is determined, increased attention to the ecological situation should be paid.

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.

Associations of Pretreatment Physical Status Parameters with Tolerance of Concurrent Chemoradiation and Survival in Patients with Non-small Cell Lung Cancer.

OBJECTIVE: The aim of this study was to evaluate associations between pretreatment physical status parameters and tolerance of concurrent chemoradiation (cCHRT) and survival among patients with stage III non-small cell lung cancer (NSCLC). METHODS: A retrospective cohort study was conducted among patients with stage III NSCLC who had received cCHRT between 2006 and 2015. Multivariate independent associations were analysed between the pretreatment parameters age, Charlson comorbidity index, World Health Organization performance status (WHO performance status), body mass index (BMI), fat-free mass index (FFMI), maximal handgrip strength, forced expiratory volume in one second and carbon monoxide lung diffusion capacity on the one hand with tolerance of cCHRT (defined as a received radiation dose at least equal to the prescribed radiation dose) and survival on the other hand. RESULTS: 527 of 577 patients (91.3%) tolerated cCHRT. A WHO performance status ≥ 2 (odds ratio (OR) 0.43) and BMI < 18.5 kg/m2 (OR 0.36) were associated with poorer tolerance of cCHRT. In the total group, a WHO performance status ≥ 2 (hazard ratio (HR) 1.73), low FFMI (HR 1.23) and intolerance of cCHRT (HR 1.55) were associated with poorer survival. CONCLUSION: In patients with stage III NSCLC receiving cCHRT, poor WHO performance status and BMI < 18.5 kg/m2 were independently associated with tolerance of cCHRT. Physical status parameters and intolerance of cCHRT were independently associated with poorer survival. Besides using this information for treatment decisions, optimizing physical status in patients at risk for intolerance of cCHRT might be a next step for improving treatment outcomes.

INDOOR RADON MEASUREMENTS FOR THE SOUTH AFRICAN WEST COAST PENINSULA.

Granite commonly contains high concentrations of uranium, with consequent high exhalation of radon. The geology of the West Coast peninsula of South Africa is dominated by granite, and a recent article predicted potentially high indoor radon concentrations in this region's two largest towns, Vredenburg and Saldanha. This research aimed to measure indoor radon levels in these towns. Measurements were first done for a minimum of 3 d during warmer months, with houses typically being more ventilated. Thirty-four homes in Vredenburg and 27 in Saldanha were measured, and the average indoor radon determined to be 40 and 58 Bq m-3, respectively. The measurements were then repeated during the colder months, and an increase in average radon concentration of 173 Bq m-3 for Saldanha and 153 Bq m-3 for Vredenburg was found. The granite geology and lifestyle of occupants during the colder months seem to contribute towards elevated levels of indoor radon concentrations.

Handgrip weakness, low fat-free mass, and overall survival in non-small cell lung cancer treated with curative-intent radiotherapy.

BACKGROUND: Assessment of handgrip strength and fat-free mass provides quick and objective information on muscle performance and mass that might complement subjective World Health Organization Performance Status (WHO PS). We investigated to what extent the presence of pre-treatment handgrip weakness and low fat-free mass index (FFMI) provides additional prognostic information on top of well-established prognostic factors (including WHO PS) in non-small cell lung cancer (NSCLC) patients selected for curative-intent (chemo)radiation. METHODS: Prospectively, patients with early and locally advanced NSCLC (stages I-III) treated with (chemo)radiation were enrolled. Handgrip weakness and low FFMI, derived from bioelectrical impedance analysis, were defined using normative values and were correlated with overall survival (OS). RESULTS: We included 936 patients (age 68 ± 10 years; 64% male; 19% stage I, 9% stage II, and 72% stage III disease; 26% handgrip weakness; 27% low FFMI). In patients with good performance status (WHO PS 0 or 1), handgrip weakness and low FFMI were significant prognostic factors for OS, after adjustment for age, gender, disease stage, and co-morbidities. The combined presence of handgrip weakness and low FFMI was a strong prognostic factor for OS when compared with patients with normal handgrip strength and FFMI (hazard ratio: 1.79, 95% confidence interval: 1.34-2.40, P < 0.0001). In patients with impaired performance status (WHO PS ≥ 2, 19% of sample), handgrip weakness and low FFMI were not related to OS. CONCLUSIONS: In early and locally advanced NSCLC patients treated with curative-intent (chemo)radiation who have good WHO PS, patients with combined handgrip weakness and low FFMI have the worst prognosis.

In situ gamma ray measurements of radionuclides at a disused phosphate mine on the West Coast of South Africa.

High levels of uranium and its radioactive progeny like radium is normally associated with phosphate mining. In Situ gamma ray spectroscopy as a survey tool has been successfully applied to assess radionuclide concentrations in various geographical environments. A transportable and robust gamma ray detection system (GISPI) was therefore employed to determine the concentrations of naturally occurring radionuclides at a disused phosphate mine on the West Coast of South Africa. The concentrations of radium, thorium and potassium were measured and plotted. The measurements showed fairly high concentrations with medians of 320 Bq/kg for (226)Ra, 64 Bq/kg for (232)Th and 390 Bq/kg for (40)K. The highest concentrations were however confined to specific areas of the mine. The effective dose due to gamma irradiation for the various areas of the mine was also estimated and the highest estimated level was 0.45 mSv/y. The article finally draws conclusions as to the origins and impact of the radiation.