International Journal of PIXE

To achieve the elemental characterization of particles emitted from the aircraft, we performed elemental analysis using micro-PIXE for those emitted from carbon disc brakes and tires in addition to the turbine blade particles and engine reverser particles of the exhaust produced by jet engines, and identified the characteristics of individual particles from the elemental maps. As for the elemental characteristics of aircraft source particles, the turbine blade particles contained 16 elements (Na, Mg, Al, Si, S, K, Ca, Se, Ti, Cr, Mn, Fe, Co, Ni, Cu and W), and were considered to be those of the same origin. In the case of the engine reverser particles, in addition to turbine blade particles and turbine blade wear particles (nickel alloy), atmospheric particles were found. As one hypothesis, particles containing Ti–V, Mn–W and Cu–Zn may have got altered or aggregated in the process of particles moving from the turbine blade to the engine reverser. Clumps of particles were exhibited only in the elemental maps of tire particles. These clumps of particles were shaped like they had been scraped away, and were believed to have been caused by friction between the tire and the runway. These results aid in determining the component features of particles emitted from an aircraft.

After the conclusion of the Minamata Convention on Mercury, the use of mercury (Hg) has been prohibited worldwide, except in some developing countries. The Republic of the Philippines is one of the 128 signatories of the Convention. There are many artisanal and small-scale gold mining (ASGM) operations in the Philippines that still use Hg to amalgamate gold. In order to know the direct effect of exposure to Hg on women’s hair, we performed the proton-induced X-ray emission analysis of Hg concentrations in the hair samples collected from women at risk of Hg contamination, in both ASGM and non-ASGM areas in Camarines Norte, Philippines. At the same time of the hair sampling, we also conducted interviews with the women about their lives. From the analysis results, we found that the range of Hg concentrations in the hair samples was at a safe level, with no significant difference between the ASGM and non-ASGM areas. An analysis of the effect of diet on Hg concentrations in the hair samples showed a tendency toward higher Hg concentrations in women who ate more fish. Our results through hair analysis did not show a direct effect of exposure to atmospheric Hg, but further survey of local people should be necessary to reduce the risk of Hg contamination in women even after the use of Hg in ASGM eventually comes to an end.

Here, we apply 20 MeV particle-induced X-ray emission (PIXE) to elemental analysis of microplastic samples with a diameter of approximately 2 mm, collected from the seashores of the northeastern area of Honshu in Japan. The samples were in a grain form with unwanted elements adhering to their surfaces. The PIXE measurements were conducted in a helium atmosphere. For normalization, the number of K X-rays of the residual gas argon was used instead of the directly measured beam irradiation, and the number of continuous X-rays in the PIXE spectrum was used instead of the mass of each sample. Thirteen elements were identified on the microplastics, among which were toxic chromium and lead. Thus, PIXE analysis is useful for analyzing microplastic samples.

Soil polluted by the Fukushima Daiichi nuclear power plant accident was collected and reduced in volume. We explored whether clay particles adsorbed radioactive cesium. Soil was sampled in a highly contaminated zone 16 km northwest of the power plant; soil particles 0.15–200 $\mu$m in diameter were obtained by sieving and centrifugation, and specific activity was analyzed using a high-powered Ge detector. Vermiculite contents were quantified by X-ray diffraction. For soil particles$<10\mu$m in diameter, the specific activity was constant, at about 381 kBq/kg, which is close to the 350 kBq/kg reported previously. For particles 10–200 $\mu$m in diameter, the specific activity decreased by approximately the square root of the surface/entire volume ratio. The vermiculite content was identical for all soil particles $<$2.5 $\mu$m in diameter, but decreased in particles 2.5–200 $\mu$m in diameter. Thus, the specific activity and vermiculite content were approximately proportionate. Vermiculite adhered to soil particles $<$10 $\mu$m in diameter, and radioactive cesium was uniformly distributed within the vermiculite.

We evaluated the spatial distributions of cesium and strontium in tea leaves using micro particle-induced X-ray emission (micro-PIXE) analysis to explore the characteristics of the concentrations and translocations of these elements in tea leaves, and the similarities and differences between cesium and potassium and between strontium and calcium. We examined samples of tea [Camellia sinensis (L.) Kuntze] leaves that took up cesium and strontium via foliar absorption. We confirmed that calcium and strontium accumulated in many narrow areas of the leaves, while cesium and potassium were distributed throughout the leaf samples. Almost all of the strontium and calcium accumulated in the same narrow locations in the leaf samples 30 days after foliar absorption.