The first absolute gravity measurements in Indonesia

For the purposes of the calibration of the superconducting gravimeter (SG) in Bandung and the establishment of the absolute gravity (AG) points, we carried out AG measurements for the first time in Indonesia in November 2002. The measurements in Bandung were conducted between November 15th and 20th by means of a FG5 (#210), and 14,520 effective drops were obtained. The gravity value newly determined at the AG point in Bandung is 977976701.2 μgal (1 μgal = 10⁻⁸ ms⁻²) and the scale factor for the SG is −52.22 μgal/V. We also established another AG point in Yogyakarta near Merapi volcano and carried out AG measurements in Yogyakarta between November 22nd and 26th. The gravity value determined for this station is 978203093.5 μgal.     

Micro-X-ray fluorescence-based comparison of skeletal structure and P, Mg, Sr, O and Fe in a fossil of the cold-water coral Desmophyllum sp., NW Pacific

Micro-scale distributions of trace and minor elements in, for example, coral skeletons are crucial as geochemical tracers of past environmental conditions, because they have the inherent advantage of accounting for confounding diagenetic and physiological effects. To extract reproducible paleoceanographic records from coral skeletons, a selective measurement of specific ultrastructures at high spatial resolution is required. Compared to warm-water reef-building corals, such data are limited in cold-water corals and, to the best of the authors’ knowledge, the latter have to date not been examined by means of micro-X-ray fluorescence. This technique was used for micrometer-scale imaging of P, Mg, Sr, O, and Fe intensities (counts per unit time) in a fossil specimen (as yet unknown age) of the cold-water coral Desmophyllum sp. from surface sediments of the NW Pacific. Cross plots confirmed that the micro-XRF signals were associated with corresponding trends in elemental concentration (ppm). Two major structural components of the septum—centers of calcification (COCs) and the surrounding fibrous aragonite portion—differed in composition. The COCs were characterized by higher intensities of P and Mg (650 and 220 counts per 5 s, respectively), and lower intensities of Sr (2,800) and O (580; corresponding values for the fibrous aragonite are 370, 180, 3,300 and 620 counts per 5 s, respectively). Oxygen intensity values were mostly homogeneous, but slightly lower in COCs and substantially higher in a well-defined patch in the fibrous aragonite. The mostly homogeneous P signals in the fibrous aragonite confirm the utility of this structural component and of coral septa in general for tracer studies of oceanic P. Nevertheless, spot occurrences of elevated P (>950 counts per 5 s) spanning tens of micrometers in specific parts of the fibrous region of the septum would cause overestimates of oceanic P, and should evidently not be overlooked in future research. The distribution of Fe showed no correlation with P, indicating no significant contamination in the form of P-bearing diagenetic ferromanganese precipitates. Such hotspots plausibly reflect the presence of other mineral phases, such as crystalline hydroxylapatite inclusions or contamination with organic material. The P signal intensity was positively correlated with Mg (r=0.553, p<0.001), and negatively with Sr (r=–0.489, p<0.001) and O (r=–0.311, p<0.001). There was no discernible evidence of control by water temperature in the Sr distribution pattern. These findings establish micro-X-ray fluorescence as a highly suitable pre-screening tool in cold-water coral sclerochronology, which can serve to refine sampling strategies without sample damage, and complement other micrometer-scale spatial distribution analyses of elements (notably, Ca) based on well-known approaches involving micro-milling, electron microprobes, secondary ion mass spectrometry, and laser ablation.     

Adsorption of copper and zinc onto natural clay in single and binary systems

Calcareous and smectitic clay samples from the Coniacian–Lower Campanian system, Tunisia, were used as adsorbents for the removal of copper and zinc from aqueous solutions in single and binary systems. Calcareous clay sample was treated with acetic acid to obtain carbonate-free sample that was also used for metals removal. The adsorption of metal ions onto natural clay was tested in a batch method by mixing 1 g/L of each sample with a metal ion solution of zinc (300 μmol/L) and/or copper 600 μmol/L under the operating pH of 6, and agitation speed of 200 rpm within the equilibrium time of 60 min at 25 °C for single and binary systems. Our results showed that natural clay samples were mainly composed of silica, alumina, iron, and magnesium oxides. Adsorption data showed that the studied clay samples removed substantial amounts of heavy metals in single and mixed systems. Initial solution pH and carbonates contents enhanced the removal capacities of the studied clay samples, confirming their strong influencing effects. Thermodynamic parameters indicated an endothermic adsorption for metals removal by calcareous clay, but exothermic process for the smectitic sample. These results suggest that the Late Cretaceous clays, Tunisia, can be effectively used as natural adsorbents for the removal of toxic heavy metals in aqueous systems.     

Tectonics and sedimentation around Kashinosaki Knoll: A subducting basement high in the eastern Nankai Trough

Abstract   When seamounts and other topographic highs on an oceanic plate are subducted, they cause significant deformation of the overriding plate and may act as asperities deeper in the seismogenic zone. Kashinosaki Knoll (KK) is an isolated basement high of volcanic origin on the subducting Philippine Sea Plate that will soon be subducted at the eastern Nankai Trough. Seismic reflection imaging reveals a thick accumulation of sediments (∼1200 m) over and around the knoll. The lower portion of the sedimentary section has a package of high-amplitude, continuous reflections, interpreted as turbidites, that lap onto steep basement slopes but are parallel to the gentler basement slopes. Total sediment thickness on the western and northern slopes is approximately 40–50% more than on the summit and southeastern slopes of KK. These characteristics imply that the basal sedimentary section northwest of KK was deposited by infrequent high-energy turbidity currents, whereas the area southeast of KK was dominated by hemipelagic sedimentation over asymmetric basement relief. From the sediment structure and magnetic anomalies, we estimate that the knoll likely formed near the spreading center of the Shikoku Basin in the early Miocene. Its origin differs from that of nearby Zenisu Ridge, which is a piece of the Shikoku Basin crust uplifted along a thrust fault related to the collision of the Izu–Bonin arc and Honshu. KK has been carried into the margin of the Nankai Trough, and its high topography is deflecting Quaternary trench turbidites to the south. When KK collides with the accretionary prism in about 1 My, the associated variations in sediment type and thickness around the knoll will likely result in complex local variations in prism deformation.     

Disturbance of recruitment success of mantis shrimp in Tokyo Bay associated with effects of hypoxia on the early life history

We investigated effects of severe hypoxia (dissolved oxygen <1 ml l⁻¹) on recruitment of mantis shrimp Oratosquilla oratoria in Tokyo Bay. Ten-year field surveys were conducted to examine quantitative relationships in annual mean densities of larvae and juveniles, and spatial distribution of juveniles and severe hypoxia. There was no significant correlation between annual mean densities of larvae and juveniles, suggesting that mortality during larval or juvenile stages varies among years, which might have regulated abundance of young-of-the-year juveniles. Juvenile density was low in the severely hypoxic area, implying that hypoxia could affect survivals and spatial distribution of juveniles. Meanwhile, there are yearly fluctuations in juvenile density in normoxic areas of both northern and southern part of the bay. This evidence suggests that abundance of post-settled juveniles might have been determined by not only effects of hypoxia, but also other factors influencing mortality during the early life stages.     

Effect of NAPL Source Morphology on Mass Transfer in the Vadose Zone

The generation of vapor‐phase contaminant plumes within the vadose zone is of interest for contaminated site management. Therefore, it is important to understand vapor sources such as non‐aqueous‐phase liquids (NAPLs) and processes that govern their volatilization. The distribution of NAPL, gas, and water phases within a source zone is expected to influence the rate of volatilization. However, the effect of this distribution morphology on volatilization has not been thoroughly quantified. Because field quantification of NAPL volatilization is often infeasible, a controlled laboratory experiment was conducted in a two‐dimensional tank (28 cm × 15.5 cm × 2.5 cm) with water‐wet sandy media and an emplaced trichloroethylene (TCE) source. The source was emplaced in two configurations to represent morphologies encountered in field settings: (1) NAPL pools directly exposed to the air phase and (2) NAPLs trapped in water‐saturated zones that were occluded from the air phase. Airflow was passed through the tank and effluent concentrations of TCE were quantified. Models were used to analyze results, which indicated that mass transfer from directly exposed NAPL was fast and controlled by advective‐dispersive‐diffusive transport in the gas phase. However, sources occluded by pore water showed strong rate limitations and slower effective mass transfer. This difference is explained by diffusional resistance within the aqueous phase. Results demonstrate that vapor generation rates from a NAPL source will be influenced by the soil water content distribution within the source. The implications of the NAPL morphology on volatilization in the context of a dynamic water table or climate are discussed.     

Scale factor calibration of a superconducting gravimeter at Esashi Station, Japan, using absolute gravity measurements

The scale factor of a superconducting gravimeter (SG) at the Esashi Earth Tides Station, Japan, was revised by repeating co-located absolute gravity measurements with an FG5 gravimeter. Although the calibration results from the absolute gravimeter (AG) show an apparent secular change in the scale factor of the SG (0.4% for the period 1993–2002), the relative scale factors, which are determined by tidal analysis with the response method, indicate that it has changed by no more than 0.01% during the above period. If the mean scale factor over the 10 years is adopted, a value of –56.082±0.029 Gal/V (1 Gal =10^–8 m s^–2) is obtained, which is about 0.4% smaller than that used in the global geodynamics project (GGP) database. Based on this newly determined scale factor, the tidal gravity factors at Esashi have been re-estimated. The observed tidal factors, corrected for the ocean tide effects with recent models, indicate that the theoretical gravity factors for an inelastic Earth model are more consistent with the observations than are those for an elastic model.     

Three-dimensional distributions of sewage markers in Tokyo Bay water--fluorescent whitening agents (FWAs)

Three-dimensional distributions of fluorescent whitening agents (FWAs: more specifically, DSBP and DAS1), which are sewage-derived water-soluble markers, were observed in Tokyo Bay water through multi-layer sampling of water at 20 locations. In summer, FWAs predominated in the surface layers, with trace but significant concentration of FWAs in bottom water due to stratification of seawater. In winter, on the other hand, FWAs were extensively mixed into the bottom layers because of the vertical mixing of seawater. In the surface layer, FWA concentrations and the DSBP/DAS1 ratio (the concentration ratio of DSBP to DAS1) were lower in summer than in winter, suggesting more efficient photodegradation of FWAs in euphotic zones during the summer due to stronger solar radiation. Horizontally, FWAs were widely distributed over the surface layer of Tokyo Bay. Surface water with DSBP concentrations above 50ng/L, corresponding to <200 times dilution of sewage effluent, was found to have spread up to 10km from the coastline. In addition, an offshore decline in FWA concentrations was observed, showing a half-distance of 10-20km. The decrease was caused by dilution by seawater of fresh water containing FWAs. The eastern part of the bay was different with respect to surface layers, with higher concentrations seen in northeastern parts. Furthermore, dispersion of combined sewer overflow (CSO)-derived water mass was observed in Tokyo Bay after heavy rain.