Seasonal variation in the Ra/Ra ratio of coastal water within the Sea of Japan: Implications for the origin and circulation patterns of the Tsushima Coastal Branch Current

In the current study, low-background γ-spectrometry was employed to determine the ²²⁸Ra/²²⁶Ra activity ratio and ¹³⁷Cs activity of 84 coastal water samples collected at six sites along the main island of Japan (Honshu Island) within the Sea of Japan, including the Tsushima Strait, and two other representative sites on Honshu Island (a Pacific shore and the Tsugaru Strait) at 1-month intervals in 2006.The ²²⁸Ra/²²⁶Ra ratio of coastal waters in the Sea of Japan exhibited similar patterns of seasonal variation, with minimum values during early summer (²²⁸Ra/²²⁶Ra = 0.6–0.8), maximum values during autumn (²²⁸Ra/²²⁶Ra = 1.5–3), and a time lag in their temporal changes ( 2.5 months and over  1300 km distance). However, the 2 other sites represented no clear periodic variation.In contrast to the positive correlation between ¹³⁷Cs activity (0.6–1.7 mBq/L) and salinity (15–35), the ²²⁸Ra/²²⁶Ra ratio of coastal water samples from the Sea of Japan was not observed to correlate with salinity, and the increase in the ²²⁸Ra/²²⁶Ra ratio was not as marked (0.5–1; May–June 2004 and 2005) during the migration along Honshu Island. The input of land-derived water and/or the diffusion of radium from coastal sediments is unlikely to have affected the wide seasonal variation in the ²²⁸Ra/²²⁶Ra ratio observed in these water samples.The seasonal variation in the ²²⁸Ra/²²⁶Ra ratio recorded for the coastal waters of the Sea of Japan is considered to be mainly controlled by the remarkable changes in the mixing ratio of the ²²⁸Ra-poor Kuroshio and the ²²⁸Ra-rich continental shelf waters within the East China Sea (ECS). After passing through the Tsushima Strait, this water mass moves northeast along the coastline of the Sea of Japan as the Tsushima Coastal Branch Current (TCBC).     

High-time resolution AMS C data sets for Lake Baikal and Lake Hovsgol sediment cores: Changes in radiocarbon age and sedimentation rates during the transition from the last glacial to the Holocene

High-time resolution ¹⁴C dating of Lake Baikal sediment cores indicates negative and positive anomalies of calculated linear sedimentation rate (LSR; 1.1 and 35.6 cm/ka, respectively) during the period of climate transition from the last glacial to Holocene. The timing of the Lake Baikal apparent LSR anomalies is consistent with that of the changes in the atmospheric radiocarbon concentration (Δ¹⁴C) during Younger Dryas rapid cooling event. ¹⁴C dating of lipids in the Lake Baikal surface sediments revealed that the sources of sedimentary lipids were different in each basin. In the Northern Basin of Lake Baikal, the ¹⁴C age of total lipids from the surface sediment (4.0 ¹⁴C ka) was found to be older than that of TOC (1.6 ¹⁴C ka). By contrast, the ¹⁴C age of total lipids in the Southern Basin was younger than that of the TOC by ca. 0.7–3.0 ka.In the Lake Hovsgol sediment cores, ages of the main lithologic boundaries during the last glacial–interglacial transition were estimated based on new ¹⁴C data sets. TOC concentration in the cores started to rapidly increase at 13.8 ± 0.3 ¹⁴C ka at the base of the basinwide finely laminated layer deposited during Bølling/Allerød. The base of the layer diatomaceous mud corresponds to the end of Younger Dryas event (10.6 ± 0.1 ¹⁴C ka).     

Phytoplankton assemblage in the Plio-Pleistocene record of Lake Baikal as indicated by sedimentary steryl chlorin esters

Past changes in phytoplankton assemblages in Lake Baikal over the last 4.5 Ma, both in population and composition, are inferred from the downcore profiles of the relatively stable chlorophyll derivatives steryl esters of pyropheophorbides a and b (steryl chlorine esters; SCEs) in the 0–200 m section of the BDP-98 drill core, supplemented by the data on biogenic silica (BSi) and total organic carbon (TOC) contents. SCEs-a and -b dominate among sedimentary chlorophyll derivatives in the BDP-98 sediments except for the upper few meters, indicating their high stability during diagenetic alteration of sediments. The depth (age) profiles of SCEs-a are consistent with BSi and TOC profiles and are interpreted as reflecting primary productivity of the lake in the past. Baikal proxies reveal close correlation with marine oxygen isotope records (MIS stratigraphy). These observations confirm that climate change in the northern hemisphere has been a primary factor controlling the total phytoplankton productivity in Lake Baikal during the last several million years.Among SCEs-a, C₃₀ (dinostanol)-SCE-a, a marker of dinoflagellates was identified by GC–MS analysis. SCE-b, a marker of green algae, was identified by its UV–vis spectrum. The ratio of C₃₀-SCE-a to total SCEs-a (TSCEs-a) was higher during 4.5–4.2 and 1.7–1.3 Ma, suggesting that dinoflagellates proliferated preferentially in those periods. The early Pleistocene maximum of this ratio corresponds to the broad minimum of diatom abundance previously suggested to have recorded a prolonged regional cooling. An abrupt increase in the SCE-b/TSCEs-a ratio was observed at 2.5–2.6 Ma, indicating that green algae containing chlorophyll b have proliferated in Lake Baikal during this period. This interval has also been suggested to contain evidence for a significant regional cooling based on minima of diatom abundance and BSi in sediments. The depth profile of C₂₇Δ⁵ (cholesterol)-SCE-a relative to TSCEs-a showed a trend similar to that of BSi, suggesting that C₂₇Δ⁵-SCE-a/TSCEs-a ratio is a potential marker of diatoms in Lake Baikal.Certain mismatches between the Lake Baikal profiles of biological indicators and the marine oxygen isotope records, as well as the slight temporal offsets between different Lake Baikal biological marker signals suggest that the regional component of climatic and/or lacustrine environmental changes also have played a role in determining the composition of the Lake Baikal Plio-Pleistocene phytoplankton assemblage.     

Seismological evidence for compositional variations at the base of the mantle transition zone under Japan Islands

Temperature and water content anomalies just above the 660-km discontinuity under the Japan Islands are estimated from seismological observations. Two sets of seismological observations of P-wave velocity perturbations and depth variations of the 660-km discontinuity are used, which are (1) long-wavelength (~ 500 km) variations from seismic tomography based on a grid parameterization and waveform analysis of ScS reverberations and (2) moderate-wavelength (~ 150 km) variations from seismic tomography with a block parameterization and receiver-function analysis. To estimate temperature and water content anomalies, partial derivatives of velocity and depth variations with respect to temperature and water content determined by mineral physics studies are used. Under Southwest Japan, low temperature and high water-content anomalies are obtained from both sets of seismological observations, which have already been found by a previous study. Under Northeast Japan, however, there are discrepancies between the results estimated from the two data sets, possibly due to the different resolution scales. This discrepancy is dismissed when examining distributions of the temperature and water content anomalies. These anomalies can be grouped into two geographical locations, one group under Southwest Japan, the other under Northeast Japan. The two groups are clearly separated and exhibit common features in both sets of the seismological observations. The grouping is interpreted by a compositional difference between the subducting Pacific slab under Southwest Japan and a normal mantle under Northeast Japan.     

Predicting community earthquake preparedness: a cross-cultural comparison of Japan and New Zealand

This paper reports on a study investigating cross-cultural equivalence in predictors of earthquake preparedness. Data were collected from Napier (New Zealand) and Kyoto (Japan). These locations were selected because they face comparable levels of seismic risk but differ with respect to their cultural characteristics. This mix of hazard similarity and cultural differences provided an opportunity to assess the degree of cross-cultural equivalence in predictors of earthquake preparedness. Cross-cultural equivalence was examined by assessing the degree to which individual hazard beliefs (outcome expectancies) and social characteristics (community participation, collective efficacy, empowerment, trust) could explain levels of hazard preparedness in each location. Structural equation modelling analyses revealed similarity in the pattern of relationships between predictor variables and intention prepare in the Napier and Kyoto data. It is argued that this provides support for the existence of some universal, cross-cultural equivalence in how hazard beliefs and social characteristics interact to predict the degree to which people adopt earthquake preparedness measures. Differences between the data sets are discussed in the context of the fundamental cultural differences between Japan and New Zealand. The theoretical and practical implications of the findings are discussed.     

Tributyltin in blood of marine fish collected from a coastal area of northern Kyushu, Japan

We investigated levels of the pollutant tributyltin (TBT) in blood of pufferfishes (six species), Japanese sea perch, red sea bream, Japanese common goby, Japanese flounder, rockfish, conger eel, and sea mullet collected off the coast of northern Kyushu, Japan. We found considerable levels of TBT (1.4-190 ng/mL) accumulated in the blood of these fish. Blood TBT concentrations were 1.3-22.5 times liver concentrations and 4.9-78 times muscle concentrations, except in conger eel and mullet. We detected TBT (16-111 ng/mL-blood) in the plasma of the fine-patterned puffer (Takifugupoecilonotus) year-round, without any apparent seasonal trend. These results suggest that fish inhabiting coastal areas of Kyushu, Japan, continue to be contaminated with TBT.     

Hydration-dehydration interactions between glycine and anhydrous salts: Implications for a chemical evolution of life

Polymerizations of organic monomers including amino acids, nucleotides and monosaccharides are essential processes for chemical evolution of life. Since these reactions proceed with “dehydration” reactions, they are possibly promoted if combined with thermodynamically favorable “hydration” reactions of minerals and salts. To test the possibility, we conducted heating experiments of the simplest amino acid “glycine (Gly)” mixed with four simple anhydrous salts (MgSO₄, SrCl₂, BaCl₂ and Li₂SO₄) at 140 °C up to 20 days. Gly polymerization was strongly promoted by mixing with the salts in the order of MgSO₄ > SrCl₂ > BaCl₂ > Li₂SO₄. Up to 6-mer of Gly polymers were synthesized in the Gly-MgSO₄ mixture, and a total yield of Gly polymers attained about 7% of the initial amount of Gly by the 20 days heating. The total yield was about 200 times larger than that from the heating of Gly alone. XRD measurements of the Gly-MgSO₄ mixture revealed the generation of MgSO₄ monohydrate during Gly polymerization. These observations indicate that Gly polymerization was promoted by the salt hydrations through the hydration-dehydration interactions. Based on the observations, we tried to find a relationship between thermodynamic characteristics of the interactions and the promotion effects of each salt on Gly polymerization. It was found that the salts having lower hydration Δ_rG⁰ (easier to hydrate) promote Gly polymerization more strongly. The relationship was used to estimate promotion effects of simple oxide minerals on Gly polymerization. The estimations were consistent with previous observations about the effects of these minerals on Gly polymerization. The fact suggests that the hydration-dehydration interactions between amino acids and minerals are an important mechanism for amino acids’ polymerizations on minerals.     

Effects of the Chemical Compositions of Salars de Uyuni and Atacama Brines on Lithium Concentration during Evaporation

During Li recovery from salar brines, Li concentration is typically increased to about 60,000 mg L^?1 by evaporation. We investigated the concentration changes of Li, Na, K, Mg, Cl, SO₄, and B during evaporation of both natural Uyuni and artificial Atacama brines. The Uyuni brine exhibited a maximum Li concentration of 6810 mg L^?1 at 31 days of evaporation, at which point the majority of the Na and K in the brine was removed. The Li concentration decreased with further evaporation due to precipitation as Li₂SO₄, such that the level at the 56 day mark was approximately 4130 mg L^?1. In contrast, the artificial Atacama brine showed no pronounced Li precipitation, even after 54 days, at which point the Li concentration was 21,800 mg L^?1. The initial concentrations of Na and K in the Atacama brine were higher than those in the Uyuni brine, and the Atacama solution still retained K after 54 days of evaporation. The order of precipitation of cation species during the evaporation of both brines was: Na, followed by K, Mg, and Li. Thus, Li precipitation in the Atacama brine might be prevented due to the more favored precipitations of Na and K, such that significant Li removal did not occur in this brine.