We have been determinig atmospheric radioactive cesium (¹³⁴Cs and ¹³⁷Cs) concentrations in the early period after the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident in 2011 using suspended particulate matter (SPM) collected hourly on a filter tape at many automated SPM monitoring stations located widely in eastern Japan. The hourly atmospheric ¹³⁴Cs and ¹³⁷Cs concentrations just after the FDNPP accident in wide areas of eastern Japan were first revealed in our study. The determined ¹³⁴Cs and ¹³⁷Cs concentrations are expected to play an important role in reducing uncertainties of estimations of the internal radiation dose rates from inhalation and time-series radionuclides release rates from FDNPP, and an evaluation of the atmospheric transport models. There are four steps for the determination of radioactive cesium; i.e., identification of the date and time of SPM samples collected on filter-tapes, preparation of samples for gamma-ray measurement, measurement of gamma-rays, and calculation of concentrations and screening of their values. In this article, we introduced the technical methods to conduct the quality assurance through these four steps, based on our experience for about 7 years.

A river-water certified reference material (CRM), NMIJ CRM 7202-c was developed by National Metrology Institute of Japan (NMIJ). This CRM is intended for use in the quality control of analyses and the validation of analytical methods and instruments used for analyses of trace elements in river water. To avoid elemental contamination, laboratory wares, such as polypropylene bottles and pipette tip, and polyethylene bottles into which the CRM are filled were immersed in 3 mol L⁻¹ nitric acid for more than 1 week. At least three independent analytical methods were applied to characterize the certified value of each element. Twenty-one elements (i.e., Al, As, B, Ba, Ca, Cd, Cr, Cu, Fe, K, Mg, Mn, Mo, Ni, Na, Pb, Rb, Sb, Se, Sr, Zn) were certified. The certified value for each element was given as the property value±expanded uncertainty, with a coverage factor of 2 for the expanded uncertainty. The expanded uncertainties were estimated while considering the contribution of the analytical methods, the method-to-method variance, the sample homogeneity, and the concentrations of the standard solutions for calibration.

In solid-phase extraction (SPE), hydrophilic-lipophilic balance (HLB) type sorbents prepared by copolymerization with divinylbenzene (DVB) and polar monomers are widely used. The hydrophobicity of the HLB-type sorbents depends on DVB as the main component, and the extraction efficiency for polar compounds is enhanced by interaction with the polar groups introduced by polar monomers. On the other hand, high adsorption ability, due to the hydrophobicity of DVB, adversely affects the rapid elution of trapped compounds. In this study, the non-aromatic sorbents that has high adsorption ability for polar compounds, and can rapidly elute polar compounds including aromatic rings were developed. Porous polymer particles were prepared with trimethylolpropane trimethacrylate (TMPT), and the solid-phase extraction characteristics were evaluated. By optimizing the pore characteristics of TMPT-type sorbent, it was possible to effectively extract the nucleobases and nucleosides whose extraction efficiency was comparable to that of the commercial HLB-type sorbent. Furthermore, in order to improve the hydrophobicity of the TMPT-type sorbents, non-aromatic sorbents copolymerized with stearyl methacrylate (SMA) were prepared. However, the adsorption abilities of the TMPT-type sorbent could not be improved. The adsorption and desorption properties of the non-aromatic sorbents were evaluated using the TMPT-type sorbent. The aromatic polar compounds were able to be strongly sorbed to the TMPT-type sorbent, but they could be rapidly eluted by low concentration organic solvent as eluent. These results suggest that the TMPT-type sorbents are useful for a solid-phase extraction of the polar compounds and will solve the problem of the poor desorption in the HLB-type sorbents containing DVB.

A novel chemiluminescence analysis system using a polydimethylsiloxane (PDMS) microfluidic device and an organic photodiode (OPD) detector was developed. The sample and reagent solutions in the reservoir on the degassed PDMS microfluidic device were autonomously flowed into the microchannel in the PDMS microfluidic device, since the degassed PDMS resin absorbs the air in the microchannel. The OPD was fabricated by a spin-coating method using poly(3-hexylthiophene-2,5-diyl) and [6,6]-phenyl-C61 butyric acid methyl ester as a material of photoelectric conversion layer. The measurement of hydrogen peroxide was evaluated using the chemiluminescence analysis system. SuperSignal^TM ELISA Femto Substrate and Horseradish Peroxidase were used in the measurement. The calibration curve for hydrogen peroxide was linear for concentrations under 3.2 mM with a correlation coefficient of 0.9986. The limit of detection, defined as three-times the standard deviation of the blank signal, was estimated to be 4.4 μM. Compared to the hydrogen peroxide assay kit using a 96-well microtiter plate and a micro plate reader, the amount of sample and reagent consumption and the analysis time could be reduced to 1/5 and 1/10, respectively. The chemiluminescence analysis system was successfully used in the determination of hydrogen peroxide in a commercially available disinfectant, oxydol. The chemiluminescence analysis system would be useful for on-site environmental measurement, quality control of food, point-of-care testing etc. since a pump is unnecessary and the detector is very small and lightweight.

The inside of a tunnel was a semi-closed space, quite different from an outdoor environment, and had special environmental characteristics. In this study, we measured the radiation dose, dust, and wind speed for three tunnels (A, B, C), which penetrated the northern and southern regions in Kochi Prefecture, and attempted to specifically consider the factors for variations in the radiation dose. The results obtained showed that the radiation dose tended to be high inside the tunnel, but did not increase unilaterally away from the entrance. In addition to the radiation that came from soil to form mountains, it is believed that sediments present in leaked water and dust scattered in the air also contributed to this radiation source.

In order to clarify the impact of air pollution on the formation of sudden and locally distributed heavy rain in urban areas (hereafter UHR = urban-induced heavy rain), we analyzed inorganic ions concentration, dissolved and suspended fraction of trace metals, and stable isotope ratio of water (δD and δ¹⁸O) in rainwater samples collected from 2008 to 2016 in Tokyo. Acidic substance-derived components (H⁺, NH₄⁺, NO₃⁻, nss-SO₄²⁻) have high concentrations in UHR, and acidic deposition increased locally along with rainfall amount near urban centers when UHR occurs. In addition, UHR has stable isotopes of hydrogen and oxygen smaller than normal rainfall, indicating that the influence of marine-derived water vapor was small. The concentration of air pollutants before the UHR was high, and secondary reaction rapidly progressed just before the UHR. Based on these results, we proposed the following UHR formation mechanism: (1) Air pollutants accumulate from the surrounding area into the area with the low atmospheric pressure due to the development of upflow by urban warming. (2) Due to oxidants formed by photochemical reactions, sulfate and nitrate that are produced secondarily from SO₂ and NO_x become cloud condensation tuberculosis (CCN). (3) These CCNs generate many small cloud particles using water vapor evaporated from the urban area. (4) When the updraft is further developed, moist sea breezes containing sea salt particles, which are giant cloud condensations, flow in to form large cloud particles, which rapidly grow into raindrops due to collection with small water droplets.

The preparation of a polyamine-type chelate resin based on Kenaf, the adsorption of L-ascorbic acid on the above chelate resin, and the reduction of Cr(VI) by the chelate resin adsorbing L-ascorbic acid was studied. Kenaf was pretreated with concentrated hydrochloric acid, and oxidized with potassium permanganate. Carboxylic group generated on Kenaf was reacted with triethylenetetramine to give polyamine-type chelate resin. The optimum pH range for the adsorption of L-ascorbic acid was about 1 to 5. The adsorption capacity by a batch method was 1.55 mmol g⁻¹, and by a column method was 1.98 mmol g⁻¹. Cr(VI) was reduced by using chelate resin with L-ascorbic acid. In the batch method, reducing Cr(VI) in a sulfuric acid solution at 95°C, 6.54 mmol g⁻¹ of Cr(VI) was reduced. This reducing ability is almost the same as the reducing ability of sodium sulfite, which is conventionally used industrially. In the column method, when 100 mg L⁻¹ Cr(VI) in sulfuric acid solution was passed through the above-mentioned resin filling column, the treatment reducing of Cr(VI) abilities were 138 BV (bed volumes) at room temperature and 233 BV at 60°C, respectively.

Thermal desorption/pyrolysis (TDP)/Direct Analysis in Real Time (DART)-MS has recently been developed to characterize polymers by observing the gaseous products evolved from polymer samples during programmed heating. Because less care has been paid for the differences between volatile intacting oligomers and oligomeric pyrolysis products generated from high-molecular weight components, evolution profiles of intact oligomers and oligomeric pyrolysis products generated from polystyrene (PS) with well-defined molecular structure were observed by TDP/DART-MS as a fundamental investigation. Volatilization of the intact oligomers up to about 1000 Da started at around 200 °C. At higher temperature above about 270 °C, oligomeric pyrolysis products having an original butyl end group started to volatilize, and then above about 300 °C, evolution of oligomeric pyrolysis products originating from internal main chain by multiple chain cleavages was observed. Chain cleavage mainly proceeded oxidatively, resulting in the formation of oligomeric products having a carbonyl or aldehyde end. The relative intensities of the oligomeric pyrolysis products with the original end group was inversely proportional to the number-average molecular weight (M_n) of the sample. This result suggested that if a calibration curve can be made, M_n of the PS would be rapidly determined by TDP/DART-MS. The combination of mass spectra and evolution profiles observed by TDP/DART-MS can provide useful information concerning the molecular characterization of polymers.