Accurate Determination of Chlorine, Bromine, and Iodine in Sedimentary Rock Reference Samples by Radiochemical Neutron Activation Analysis and a Detailed Comparison with Inductively Coupled Plasma Mass Spectrometry Literature Data

Trace amounts of three halogens (chlorine, bromine, and iodine) were determined using radiochemical neutron activation analysis (RNAA) for nine sedimentary rocks and three rhyolite samples. To obtain high-quality analytical data, the radiochemical procedure of RNAA was improved by lowering the background in gamma-ray spectrometry and completing the chemical procedure more rapidly than in conventional procedures. A comparison of the RNAA data of Br and I with corresponding inductively coupled plasma mass spectrometry (ICPMS) literature data revealed that the values obtained by ICPMS coupled with pyrohydrolysis preconcentration were systematically lower than the RNAA data for some reference samples, suggesting that the quantitative collection of Br and I cannot always be achieved by the pyrohydrolysis for some solid samples. The RNAA data of three halogens can classify sedimentary rock reference samples into two groups (the samples from inland water and those from seawater), implying the geochemical significance of halogen data

Technique for estimating the charge number of individual radioactive particles using Kelvin probe force microscopy

The Fukushima Daiichi Nuclear Power Plant accident in Japan resulted in the emission of many radioactive cesium (Cs)-containing particles that have charges on the surface due to self-charging. Charged aerosol particles are efficiently deposited inside human airways, leading to adverse health effects. To evaluate these effects, we developed a technique for estimating the charge number (np) of radioactive particles by measuring the surface potentials (Vp) of individual radioactive particles using Kelvin probe force microscopy. The Vp values of the individual CsCl particles were highly correlated with the surface np, indicating that Vp is a measure of the charged aerosol state. To further examine the Vp–np relationship, a simplified capacitance model was developed to estimate the ratio of Vp to np per unit area of particles. Although the calculated Vp was proportional to the np, consistent with our experiment, the calculated ratio was higher than those determined experimentally. The magnitude of this ratio may depend on the conductivity, microphysical properties and chemical composition of the particles. Despite these uncertainties, the experimentally determined Vp–np relationship of the CsCl particles was used to estimate the np of the radioactive and non-radioactive particles from the measurement of the Vp of these particles. It was demonstrated that the np of the radioactive particles was much higher than that of the non-radioactive particles, suggesting that radioactive particles are efficiently charged by self-charging. These charged radioactive particles may strongly cause adverse human health effects owing to their efficient deposition in human airways.</p