This paper summarizes the current status of measurement technology for the four measurable parameters of the ocean carbonate system: pH, pCO2, total inorganic carbon, and total alkalinity. They are keys to the future of global warming and its mitigation. The technology should be improved from batch measurement of water samples in the laboratory to in-situ measurement by sensors and automatic measurement deployed on buoys and floats: from point and line observations to three-dimensional and temporal observations. The best accuracy for practical measurements is 0.002 pH, 2-5 μatm, 2-4 μmol kg−1, and 2-3 μmol kg−1 for pH, pCO2, total inorganic carbon, and alkalinity, respectively. Automatic measurement of pH and pCO2 is now practical, but since both are extremely small components of the carbonate system and change synchronously, determining the carbonate system from these two parameters results in a large uncertainty. The combination of pH and total alkalinity provides the smallest error, and thus to develop an automatic measurement system for pH-total alkalinity is anticipated. All the parameters can be determined by equilibrating the sample and the solution or by measuring the pH after adding acid, so the key is to develop a stable pH measurement technique even in high-pressure deep seawater.
Based on increased knowledge about the surface environment of the planet and other bodies in the solar system, the possible presence of life in the solar system becomes the scientific research target. The existence of liquid water on the surface of Mars 4 billion years ago has been postulated. The surface environment of Mars used to be similar to the Earth then. These similarities between ancient Mars and Earth prompt us to consider the probable emergence of life on Mars. Methane, energetic substrates, and organic compounds have been found in the present Mars surface: Life may be present on Mars now. Phosphine at about 55 km above the surface of Venus has been reported recently. Because there is no known chemical process that can explain the presence of phosphine, the presence of life in the environment has been proposed. The life-search can be done either by in situ measurement with the equipment carried on the spacecraft or by the analysis of the samples returned to the Earth. The latter method can be done with state-of-art techniques using big and sensitive machines. However, because of the limitation of the sample amount that can be brought back to Earth, in situ measurements of the signature of life is also essential. In this chapter, we have reviewed the past life-signature exploration experiments, the possible life-signature search targets, possible life-signature search methods, and future life-signature search missions.
Catalytic combustion-type gas sensors which can detect CO gas concentration quantitatively even at as low as 70 °C were successfully fabricated by applying 10 wt% Pt/Ce0.68Zr0.17Sn0.15O2.0 catalyst. Since the Ce0.68Zr0.17Sn0.15O2.0 solid can provide active oxygen from the inside of its lattice to Pt, an extraordinal CO oxidation activity was achieved, resulting in high CO sensing performance of the sensor. The response time of the sensor was drastically improved by combining aluminum nitride as a heat transfer layer between Pt coil and catalyst. Moreover, the high oxygen release ability of the Ce0.68Zr0.17Sn0.15O2.0 solid also realized the sensor operation at 130 °C with the precious metal-free catalyst, 15.9 wt% La0.87Co1.13O3/Ce0.67Zr0.18Sn0.25O2.0.
Microorganisms, which are important in the origin of life, live in various environments on Earth. Some microorganisms can survive in extreme environments, including the very specific environment of an intracellular ultra-small confined space. We are developing several techniques for culturing and analyzing the microorganisms in an ultra-small confined space (10–40 μm), such as water-in-oil (w/o) droplets or giant unilamellar vesicles (GUV). In this review, w/o droplets and GUV are considered as a special/extreme environment regarding their size. We introduce the culturing, analysis, and detection technologies of microorganisms inside the w/o droplets and the GUV that have been developed. Our developed technology can be expected to contribute to the field of biotechnology as a new microbial culture/screening system. We hope that it will lead to the study of an endosymbiotic model that serves as a model for eukaryotic cells at the time of the origin of life.
Onsite analysis is an important technology to protect the environment and human health that are included in the 2030 Agenda of Sustainable Development. We focus on three topics: i) micro 3D fabrication by using poly(dimethylsiloxane) molds with high oxygen permeability and photocurable polymer based on thiol-ene reaction without expensive, large, and specific instruments that requires just portable UV light, the combination of electroosmotic pump and molecular imprinting for selective molecular sensing, and a device control technique with sound data.
We have developed an isotope analysis method to measure hydrogen isotope diffusion profiles in ice, hydroxides and related materials at high pressure. The calibration curves for quantitative analysis of deuterium in the materials were constructed using micro-Raman spectroscopy. Hydrogen-deuterium exchange diffusion experiments of ices VI, VII and Ca(OH)2 up to 20 GPa were carried out using micro-Raman spectroscopy and a diamond anvil cell. The pressure dependences of the diffusion coefficients of hydrogens in ice VII and Ca(OH)2 showed that hydrogen migration mechanisms changed drastically at high pressures. The changes in the mechanisms must be caused by strengthening of hydrogen bonds. This article describes the methodology and background for study of hydrogen diffusion in solids at high pressure.
In order to clarify long-range transported PM2.5, a PM2.5 sequential sampler was installed at the Fuji meteorological station (3776 m a.s.l.) in the free troposphere and carried out PM2.5 sampling in daytime and the night from July 21 to August 15, 2017. Eight components of water-soluble inorganic ions and 68 elements were measured. The PM2.5 average concentrations in the daytime and night were 1.7±1.5 μg m−3 and 1.6±1.1 μg m−3, respectively. The total of NH4+ and SO42− concentration was 67 % of total inorganic ion concentrations. SO42− concentrations in the daytime was 1.3-times higher than those in the night. The concentrations of 17 elements (Na, Mg, Al, K, Ca, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Sr, Pb) were over the detection limit in more than a half of all 44 samples. The correlation coefficients (r) were evaluated between 21 components, including 17 elements and 4 ions. Components related with soil, urban pollutants and long-range transportation in the daytime and only long-range transportation in the night showed a high positive relationship (r≥0.7). Four samples with a high As/V ratio (≥0.9) were collected in the night, and their backward trajectories showed that the air mass was directly transported from the Asian continent. Anthropogenic V* was calculated with a concentration ratio of V based on Al in topsoil particles of Mt.Fuji. Three samples with V*≥0.2 ng m−3 were collected in the daytime, and their backward trajectories showed that the air mass was transported through over the Kansai area, including the Osaka city and Chukyo area, including Nagoya city. The As/V* ratio were consistent with those of PM2.5 collected in these area. Long-range transported PM2.5 was clearly detected by sample collection in the night on the top of Mt.Fuji.
SmFeO3 semiconductor thin film was formed on a Au comb-type microelectrode by using the EPD method and examined on its sensing property to NO2 gas. The SmFeO3 particles were prepared with the thermal decomposition of Sm[Fe(CN)6] · 4H2O complex at 500 and 900 °C. The EPD was performed in a liquid-droplet of the organic suspension containing the SmFeO3 particles. The EPD films formed on the micro comb-electrode were sintered at 400, 500 and 600 °C. The sensing property to NO2 was fairly affected not only by the decomposition temperature of the complex but also the sintering temperature of the EPD films. The films with the powder decomposed at 500 °C exhibited higher performance than those prepared at 900 °C. Sintering the film at 600 °C exhibited highest sensitivity to 10 ppm NO2 with S = 96 and good response and recovery behaviors were observed even at low temperature at 250 °C. Significant sensitivity was also obtained in 1 and 0.2 ppm NO2.
We developed a sensitive determination of hexavalent chromium (Cr(VI)) using a microfluidic paper-based analytical device (μPAD) by solid-phase extraction with a highly selective resin cartridge. This resin (MetaSEP AnaLig Cr-02), which could selectively adsorb Cr(VI) was used as the preconcentration of Cr(VI) for the sensitive analysis. The diphenylcarbazide (DPC) colorimetry was utilized for a Cr(VI) assay. After solid-phase extraction was carried out, the eluent was dropped to the sample zone of the μPAD added with DPC solution. The intensity of detection zone image for the colored μPAD was analyzed with the image processing software to determine Cr(VI). The effect of the sample volume on the intensity was investigated, the intensity linearly increased with the sample volume. The concentration of Ba(II), Ca(II), Cu(II), Fe(III), Mg(II), Ni(II), and Pb(II) was 10 times higher than that of Cr(VI), but they had no effect on the determination of Cr(VI). In the range of Cr(VI) concentration from 0 to 20 μg L−1, a good linear calibration curve with a coefficient of determination of 0.9978 was obtained. The detection limit and the limit of quantification were 1.3 μg L−1 and 4.3 μg L−1, respectively. The proposed method was applied to the determination of Cr(VI) in the river water and the tap water, no influence of coexisting substances was observed, and good results were obtained.
Qualitative analysis of serpentine asbestos in samples such as construction materials using TG-DTA-MS was researched. Dehydration of crystal water of three types of serpentine mineral was observed by thermo MS iongram of m/z = 18 measured by TG-DTA-MS. The peak of dehydration in the thermo MS iongram of chrysotile, which is a type of asbestos, was between 600 and 650 °C. On the other hand, the peak of dehydration of lizardite and antigorite, which are not asbestos, was between 500 and 600 °C and 700 °C or higher, respectively. The same observation was executed on actual samples the respective asbestos content of which was quantified. The results showed the possibility of distinguishing serpentine minerals contained in actual samples by the temperature range of dehydration. JIS A 1481-2 and 3, which are Japanese standard methods for qualitative and quantitative analysis of asbestos in building material products, prescribe the use of XRD to detect and quantify asbestos. However, it is difficult to distinguish chrysotile from the other two non-asbestos serpentine minerals by XRD, which opens the door to misjudgement, such as erroneous determination of non-asbestos samples as asbestos-containing, and overestimation of asbestos content. Observation of dehydration by thermo MS iongram of m/z = 18 measured by TG-DTA-MS was shown to detect such misjudgments.
A method combined with sampling technology using a semi-active air sampler (SAAS) that uses PDMS as the collection material and analysis by TD-GC × GC-HRToFMS was developed for the purpose of implementing countermeasures against chemical substances remaining in the atmosphere, and the collection characteristics and applicability of persistent organic pollutants in the atmosphere by the developed method was evaluated. SAAS is small, light, easy to carry, and can be driven by dry batteries for 2 weeks, so there are few restrictions on the sampling location. It is also cheaper than the traditional high volume air sampler (HVAS) and has excellent versatility, such as observations at multiple points. Furthermore, unlike a passive sampler, the sampling flow rate can be calculated, so it is thought that the concentration can be estimated by validating applicable compounds. In this study, air sampling was performed at National Institute for Environmental Studies by SAAS using polydimethylsiloxane (PDMS) and by conventional HVAS. The concentrations of organohalogen compound obtained by two sampling techniques were compared. As a result, although it was difficult to collect compounds with high vapor pressure such as pentachlorobenzene with the SAAS using PDMS, it could be applied to compounds with the vapor pressure of PCBs from nonachlor. In the future, collecting agents other than PDMS will be considered, and we would like to build a system that can handle a wide range of physical properties by combining multiple collecting agents.