BUNSEKI KAGAKU Abstracts

In order to describe the spatiotemporal dynamics of ocean biogeochemical cycles in detail, discrete chemical data based on shipboard observations cannot allow us to achieve our goal. By parameterizing biogeochemical parameters based on previous high-precision chemical data set, and applying the observation data derived from satellite and ocean profiling float, it is possible to reconstruct sophisticated pictures of the ocean biogeochemical cycle. With the introduction of some examples for parameterizing ocean carbonate system, the parameterization for the ocean nitrogen system was reported.

Iron is an important biogeochemical trace element in the ocean. However, the stable oxidation state of iron in oxic seawater is Fe(III) with an extremely low solubility in seawater. Recent studies of the Fe(III) hydroxide solubility in seawater suggest that Fe(III) solubility is controlled by organic complexation, which plays an important role in regulating dissolved Fe concentrations in seawater. In this study, we attempted to confirm that the vertical distributions of dissolved Fe in deep water are controlled primarily by the Fe(III) solubility, which is regulated by Fe(III) complexation with natural organic ligands, comparing the characteristic vertical distributions of iron, nutrients, apparent oxygen utilization, and humic-type fluorescence intensity in deep water of the North Pacific Ocean, Bering Sea and western Arctic Ocean. Dissolved Fe distributions in deep water column are mainly controlled by the production of dissolved Fe from particulate organic matter during carbon remineralization, the particle scavenging removal of dissolved Fe, and Fe(III) complexation with natural humic substances. Iron is generally supplied to surface water by upwelling, vertical water mixing, atmospheric and riverine inputs. In the western Arctic Ocean, the subsurface maxima of iron, nutrients, and humic substances were found in the halocline layer of slope and basin regions. The new finding results from the supply of chemical components from the continental-shelf sediments and lateral transport from the shelves to the Arctic basin.

A shipboard observation was conducted in Funka Bay of Hokkaido from October 2011 to August 2012. Volatile organic halogenated compounds (halocarbons) in seawater collected at coastal, basin and sea shore sampling sites were measured by purge and trap GC-MS method. The spatial and temporal distributions of bromoform (CHBr₃) were obtained, and we analyzed the origin of the compound. The minimum concentration of bromoform (15 pmol L⁻¹) was found in December. The bromoform concentration in the basin area increased from 20 pmol L⁻¹ to 25 pmol L⁻¹ at a rate of 5 pmol L⁻¹ month⁻¹ during the phytoplankton spring bloom period (March-April). This increase would have been derived from the phytoplankton production of bromoform. The concentration increased from April to August at a rate of 4 pmol L⁻¹ month⁻¹, and the maximum concentration of 42 pmol L⁻¹ in basin area was found in August. Much higher concentrations were found in the coastal area (125 pmol L⁻¹) and the sea shore (up to 1800 pmol L⁻¹). The late summer bromoform maximum found in the basin area would be derived from macro algal production near the sea shore.

The concentration of radioactive cesium in sediments of Tokyo-bay, released by the Fukushima Dai-ichi nuclear power station accident, was measured every half year from July ’10 to February ’13 in order to analyze the trend of concentration. The samples were collected at two artificial deeper sites in dredged trenches and one natural shallower site, which were located off Makuhari in Tokyo-bay, then they were brought into a Ge detector to measure the γ-rays. According to an analysis of the upper layer of the samples, both ¹³⁴Cs and ¹³⁷Cs had been detected since the samples of August ’11, and they must have been released by the accident. Furthermore, from February ’12 to February ’13, the concentrations of ¹³⁴Cs and ¹³⁷Cs in upper layer of sediments had been higher at deeper sites than shallower site. The deeper sites look like pitfall traps for fine particles clinging to ¹³⁴Cs and ¹³⁷Cs, so we can call these sites “the hotspot in the sea”. We also examined the depth profiles of ¹³⁴Cs and ¹³⁷Cs in samples taken on August ’12 and February ’13. As a result, ¹³⁴Cs and ¹³⁷Cs were found to have gone deeper in the sediment on February ’13 than on August ’12, and the inventory of them was also larger on February ’13. In addition, this phenomenon was observed more clearly at deeper sites than shallower site. Though ¹³⁴Cs and ¹³⁷Cs had not increased very much in upper layer from August ’12 to February ’13, we clarified that they had been flowing into the Tokyo-bay.

Water has several special properties, such as extremely high melting and boiling points. Although the existence of water clusters has been suggested, the cluster size distributions of water have not yet been known. Water clusters under atmospheric pressure at an ambient temperature were measured by liquid-ionization (LPI) tandem mass spectrometry. All ions observed as LPI mass spectra were expressed as (H₂O)_nH⁺. The number of molecules (n) in a cluster observed at the liquid surface ranged from 2 to around 30, and the average number (N) of water molecules was around 15 – 17. (N = Σn I_n/ΣI_n, I_n: peak intensity). Water clusters also existed in the gas phase, but their sizes were smaller than those at the liquid surface, and became smaller with the distance (d) apart from the liquid surface. The size distributions of water clusters should be related to the absolute abundance of water in the unit space, and such abundance of water was diluted with Ar gas flow. When the flow rate of water (liquid) was increased over 10 μL h⁻¹, mass spectra observed by the second mass spectrometer (Q3: 3rd quadrupole) showed much larger cluster ions than those observed by the first mass spectrometer (Q1: 1st quadrupole). The ion-molecule reactions between ions and sample vapor occurred mainly in the collision chamber (Q2) may cause the formation of large cluster ions. Because water clusters are formed by hydrogen bonding, the results and the fact that steam and fog are visible, indicate that large clusters (aggregate) of water may exist in gas and liquid phases. The existence of these clusters may cause special properties of water.

Microbial communities transported by Asian desert dust (KOSA) events have attracted much attention as bioaerosols, because the transported microorganisms are thought to influence biological ecosystems, and human life as well as atmospheric processes in downwind areas. However, the microbial dynamics in Japan during a KOSA dust event are unclear. In this study, sequential air sampling was performed on the top of a building (10 m altitude) within the KOSA arrival area (Kanazawa City, Japan: 36.6°N, 136.7°E) from May 1 to May 7, 2013, when a dust event occurred. A 16S rDNA clone library prepared from air samples mainly belonged to three phyla, such as Firmicutes, Cyanobacteria, and Alpha-proteobacteria. Some clones of Firmicutes appeared specifically during the midst of a dust event, and consisted primarily of Bacillus subtilis and B. pumilus, which are known to dominantly inhabit atmospheric area in the KOSA source area (Chinese desert). The clones belonging to Cyanobacteria and Alpha-proteobacteria were mainly detected at the initial and last periods of dust events; they are relatives to marine bacterial species. Our results suggest that airborne bacterial communities on the surface of ground during a dust event are composed of terrestrial and pelagic bacterial populations, and that the dust event influences the dynamics of airborne bacterial communities on the ground surface of a downwind area.

To detect explosives at train stations, shopping malls and sports stadiums, etc, we have developed a vapor sampler for checking residues adhering to an IC-card. The design of the vapor sampler is similar to the IC-card reader of an automated ticket gate used for a train station. When a passenger puts a hand and an IC-card close to the sampler, vaporized volatile explosives emitted from any explosives residues adhering to the hand and/or IC-card are collected by a push-pull type vapor sampler. Any vapor collected by the sampling port is sent to a mass spectrometer and analyzed in real time. We demonstrated that we can cloud detect volatile explosives, such as triacetone triperoxide (TATP) and 2,4,6-trinitrotoluene (TNT) within one second. Therefore, we concluded that the combination of our vapor sampler and the mass spectrometer would be a powerful tool for improving security in places where many people are coming and going.

Rapid and sample preparation using stir bar sorptive extraction (SBSE), followed by high-performance liquid chromatography with fluorescence detection to determine polycyclic aromatic hydrocarbons (PAHs) in atmospheric water was studied. Applying the SBSE method to authentic atmospheric water samples revealed that rainwater in Shinjuku contained a 226 pM concentration of total PAHs, which was 10-times as much as that at Mt. Fuji, especially in a higher concentration of soluble PAHs. There was no seasonal variation of the concentration and composition of PAHs in rainwater at Shinjuku. Comparing the concentration of PAHs in rain, cloud, and dew water collected at the foot of Mt. Fuji, 5- and 6-rings PAHs were enriched in cloud water. This result suggests that cloud droplets could condense PAHs, especially high molecular weight PAHs.

A pure oxygen certified reference material, NMIJ CRM 3404-c, was developed by National Metrology Institute of Japan, mainly for oxygen standard gases supplied by Japan Calibration Service System. The certified value for oxygen in the reference material was obtained by a paramagnetic oxygen analyzer, which was calibrated by standard gases prepared using a dynamic volumetric method with mass-flow controllers. The standard gases were prepared by mixing volumetrically pure nitrogen with NMIJ CRM 3404-a, whose certified value was obtained by a subtraction method. The uncertainty of the certified value of NMIJ CRM 3404-c originated from the repeatability of the oxygen analyzer. Standard deviation of the repeatability is 2.48 mV, which corresponds to 1.2 μmol mol⁻¹. An example of the certified value of NMIJ CRM 3404-c is (1.0000000 ± 3.1 × 10⁻⁶) mol mol⁻¹ (k = 2).