A Challenge of Water Purification in Dokai Bay, Japan

A history of water pollution and countermeasures for water purification in Dokai Bay, Japan are reviewed. Now, Dokai Bay suffers from the occurrences of red tides and oxygen-deficiency in summer. In order to prevent the occurrences of red tides and oxygen-deficiency, an ecological numerical model has been developed. The model experiments forecast that when the phosphorus or nitrogen load from land will be cut by 90% or 95%, respectively, red tides and oxygen-deficiency will not occur in Dokai Bay. If the industrial and sewage facilities are not sufficient to cut the nutrients load to the necessary degree, we have to consider other countermeasures such as cultivating bivalves and algae in order to decrease the nutrients concentration in the bay. International co-operation related to coastal zone management is also discussed.     

Colonization of Sulfurovum sp. on the gill surfaces of Alvinocaris longirostris, a deep-sea hydrothermal vent shrimp

Deep‐sea hydrothermal vents are unique light‐independent ecosystems that are sustained by chemosynthetic bacteria. For many of the invertebrates inhabiting in such environments, bacteria play essential roles in both energy acquisition and detoxification of potentially toxic gases such as H₂S. In this study, the bacterial flora present on the gills of Alvinocaris longirostris (Bresiliidae: Caridea), a shrimp inhabiting hydrothermal vents (1532 m depth) at the Hatoma Knoll of the Okinawa Trough, was investigated. Bacterial 16S rDNA fragments were successfully amplified from the gills and 70% of these fragments showed an identical pattern in the restriction fragment length polymorphism analysis. These fragments were assigned to the ribotype AL‐1. Phylogenetic analyses suggest that AL‐1 forms a monophyletic clade with Sulfurovum spp. (ε‐Proteobacteria). Fluorescence in situ hybridization for AL‐1 and electron microscopy showed the presence of short‐rod bacteria lining up on the cuticular layer of the surface of the gill filaments. These results suggest that bacterial association with gills also occurs in bresiliid shrimps.     

Isotope dilution sector-field inductively coupled plasma mass spectrometry combined with extraction chromatography for rapid determination of 241Am in marine sediment samples: A case study in Sagami Bay, Japan

²⁴¹Am is a useful tracer for understanding biogeochemical processes in the marine environment. ²⁴¹Am also poses a potential radiation threat to human health due to the continuous increase of its concentration in the global environment. We report a rapid analytical method for determining ²⁴¹Am in marine sediments using isotope dilution sector-field inductively coupled plasma mass spectrometry (SF-ICP-MS) combined with a high-efficiency sample introduction system (APEX-Q). A selective CaF₂ co-precipitation procedure followed by TRU extraction chromatography was employed to effectively remove the major sediment matrix and to pre-concentrate ²⁴¹Am. We achieved an extremely low detection limit of 0.32 fg/g or 0.041 mBq/g (for 1 gram sediment), which is better than that of alpha spectrometry, and it allowed the accurate determination of ²⁴¹Am in low-level marine sediment samples. The accuracy and precision of the developed analytical method was evaluated using a laboratory prepared Am isotope standard solution and Ocean Sediment reference material (IAEA-368). The results were satisfactory. For sediment samples, overall chemical recoveries varied from 60–90%. The developed method was applied to the study of ²⁴¹Am depth distribution in Sagami Bay, Japan, where we observed different depth profiles between ²⁴¹Am activity and ^239+240Pu activity.     

Improving the prospects for detecting extrasolar planets in gravitational microlensing events in 2002

Gravitational microlensing events of high magnification have been shown to be promising targets for detecting extrasolar planets. However, only a few events of high magnification have been found using conventional survey techniques. Here we demonstrate that high-magnification events can be readily found in microlensing surveys using a strategy that combines high-frequency sampling of target fields with on-line difference imaging analysis. We present 10 microlensing events with peak magnifications greater than 40 that were detected in real-time towards the Galactic bulge during 2001 by the Microlensing Observations in Astrophysics (MOA) project. We show that Earth-mass planets can be detected in future events such as these through intensive follow-up observations around the event peaks. We report this result with urgency as a similar number of such events are expected in 2002.     

He, Sr and Nd isotopes of mantle-derived xenoliths in volcanic rocks of NE China

Abundances and isotopic ratios of He and isotopic ratios of Sr and Nd have been measured for 18 mantle-derived xenoliths from three Cenozoic volcanic provinces in NE China. The xenoliths are characterized by low He concentrations (2.3×10⁻⁹–2.5×10⁻⁷ cm³ STP g⁻¹) and large variations of ³He/⁴He ratios (1.6×10⁻⁷–15.8×10⁻⁶ or R/Ra=0.1–11). ³He/⁴He, ⁸⁷Sr/⁸⁶Sr and ¹⁴³Nd/¹⁴⁴Nd ratios in xenoliths from Kuandian Holocene volcanic provinces are consistent with those observed in mid-oceanic ridge basalt (MORB), indicating that the source of He–Sr–Nd in the lithospheric mantle is chemically and isotopically identical to that of MORB reservoir. However, xenoliths in Huinan Pleisteocene–Holocene volcanic province are characterized by slightly low ³He/⁴He ratios (R/Ra=4.3–6.5) and more radiogenic Sr and Nd. The age-corrected ³He/⁴He ratios suggest that their time-integrated ratio of (U+Th)/³He is slightly elevated compared to the depleted upper mantle. The Hannuoba xenoliths in the Miocene volcanic province show much lower and wider variable ³He/⁴He ratios, which is most likely caused by in situ radiogenic ⁴He accumulation since it erupted on to the surface. The He–Sr–Nd results suggest chemical and isotopical heterogeneity in the subcontinental mantle beneath NE China.     

Satellite All-sky Infrared Radiance Assimilation: Recent Progress and Future Perspectives

Satellite infrared(IR)sounder and imager measurements have become one of the main sources of data used by data assimilation systems to generate initial conditions for numerical weather prediction(NWP)models and atmospheric analysis/reanalysis.This paper reviews the development of satellite IR data assimilation in NWP in recent years,especially the assimilation of all-sky satellite IR observations.The major challenges and future directions are outlined and discussed.     

Biogenic opal production changes during the Mid-Pleistocene Transition in the Bering Sea (IODP Expedition 323 Site U1343)

Biogenic opal content and mass accumulation rate (MAR) at IODP Expedition 323 Site U1343 were found to fluctuate consistently, generally being high under warm conditions and low under cold conditions during the last 2.4 Ma. Continuous wavelet transform analysis of the normalized biogenic opal content indicates that export production in the Bering Sea varied predominantly at 41-ka periodicity before 1.25 Ma, and shifted to 100-ka periodicity at the onset of the Mid-Pleistocene Transition (MPT; 1.25–0.7 Ma). The 100-ka cycles dominated until the Holocene. Export production in the Bering Sea decreased markedly in the Bering Sea two times during the MPT: the first occurred at the beginning of the MPT (1.25 Ma) and the second in the middle of the MPT (0.9 Ma). These decreases coincided with both increases in the relative abundance of sea-ice diatoms and decreases in the warm-water diatom species Neodenticula seminae, indicating that reductions in export production in the Bering Sea during the MPT were associated with climate cooling. Decreases in export production in the Bering Sea during the MPT were most likely associated with the increased influence of polar/Arctic domains on the high-latitude North Pacific.     

P–V–T equation of state of Mn3Al2Si3O12 spessartine garnet

The thermoelastic parameters of synthetic Mn₃Al₂Si₃O₁₂ spessartine garnet were examined in situ at high pressure up to 13 GPa and high temperature up to 1,100 K, by synchrotron radiation energy dispersive X-ray diffraction within a DIA-type multi-anvil press apparatus. The analysis of room temperature data yielded K ₀ = 172 ± 4 GPa and K ₀ ^′  = 5.0 ± 0.9 when V _0,300 is fixed to 1,564.96 Å³. Fitting of P–V–T data by means of the high-temperature third-order Birch–Murnaghan EoS gives the thermoelastic parameters: K ₀ = 171 ± 4 GPa, K ₀ ^′  = 5.3 ± 0.8, (?K _0,T /?T) _P  = ?0.049 ± 0.007 GPa K^?1, a ₀ = 1.59 ± 0.33 × 10^?5 K^?1 and b ₀ = 2.91 ± 0.69 × 10^?8 K^?2 (e.g., α _0,300 = 2.46 ± 0.54 × 10^?5 K^?1). Comparison with thermoelastic properties of other garnet end-members indicated that the compression mechanism of spessartine might be the same as almandine and pyrope but differs from that of grossular. On the other hand, at high temperature, spessartine softens substantially faster than pyrope and grossular. Such softening, which is also reported for almandine, emphasize the importance of the cation in the dodecahedral site on the thermoelastic properties of aluminosilicate garnet.     

Movement of radiocaesium fallout released by the 2011 Fukushima nuclear accident

The moment magnitude (M _w) 9.0 Tohoku-Oki Earthquake occurred on March 11, 2011, generating an unusually large tsunami. The seismic shocks and tsunami inundation severely damaged the Fukushima Daiichi Nuclear Power Plant. Radionuclide emission due to reactor breakdown contaminated wide areas of Fukushima and its surroundings. Heavy rainfall causes runoff across surface soil, and fine soil particles are susceptible to uptake by the flowing water. The high radioactivity of grains suspended in floodwater indicates that radioactive fallout was streamed into rivers in particulate form and transported downstream under high-flow conditions. Here, we investigated the diachronic mode of ¹³⁴Cs and ¹³⁷Cs in central Fukushima, through which the contaminated air mass drifted and caused wet deposition of radionuclides. Stratigraphic measurements of radioactivity in sediment cores is the method employed in this study to determine the basin-wide movement of ¹³⁴Cs and ¹³⁷Cs, to evaluate the significance of the erosion–transportation–accumulation processes on natural decontamination in terrain characterized by steep slopes and high precipitation. Stratigraphic results illustrate the process of fluvial sediment discharge, and the massive deposition of radiocaesium suggests basin-wide movement of fallout during concentrated rainfall. Grain suspension in torrential currents is an important pathway for transportation of radionuclides from land to sea, and the appearance of hotspots on floodplains and the offshore sea floor is the consequence of erosion and transportation under seasonal heavy precipitation. Radioactive horizons occur in offshore sediment columns and thus radiocaesium discharged from the estuary will persist forever under the sea floor if no artificial disturbance occurs.     

Occurrence of hydroxylated polychlorinated biphenyls in the brain of cetaceans stranded along the Japanese coast

Levels of hydroxylated polychlorinated biphenyls (OH-PCBs) and PCBs were measured in the brain of melon-headed whales (MW: Peponocephala electra), striped dolphins (SD: Stenella coeruleoalba) and finless porpoises (FP: Neophocaena phocaenoides) stranded along the Japanese coast during 2002-2003. Levels of OH-PCBs (including identified and unknown OH-P(5)CB, -H(6)CB, -H(7)CB and O(8)CB congeners) in the brain of MW, SD and FP were in the range of 20-290, 21-330 and 170-240pg/g wet wt., respectively. Observed OH-PCB levels were 2-3 orders of magnitude lower than PCBs in the same individuals. OH-PCBs/PCBs ratios in MW, SD and FP brain were lower than those in blood of humans and wildlife and in the brain of polar bears reported previously. OH-PCBs were also detected in maternal and fetal brain of SD (1 pair), suggesting transfer of OH-PCBs into the fetal brain of odontocete cetaceans. When fetus/dam concentration ratios of OH-PCB congeners detected in maternal and fetal brain were estimated, the values were higher than those of PCB congeners, implying that OH-PCBs in maternal blood could be more easily transferred into fetal brain via placenta than PCBs.