Bioconcentration and biomagnification of polybrominated diphenyl ethers (PBDEs) through lower-trophic-level coastal marine food web

Bivalves, crabs, fishes, seawater, and sediment collected from the inner part of Tokyo Bay, Japan, were measured for 20 polybrominated diphenyl ether (PBDE) and 5 polychlorinated biphenyl (PCB) congeners. To determine the trophic levels of the organisms, carbon and nitrogen stable isotope ratios (δ¹³C and δ¹⁵N) were also measured. Bioconcentration factors of PBDE and PCB congeners increased as the octanol-water partition coefficient (K_ow) rose to log K_ow = 7, above which they decreased again. Biomagnification of PCBs and several PBDE congeners (BDE47, 99, 100, 153 and 154) up the trophic ladder was confirmed by a positive correlation between their concentrations and δ¹⁵N. Other PBDE congeners showed a negative or no correlation, suggesting their biotransformation through metabolism. The more hydrophobic congeners of both PBDEs (Br = 2-6) and PCBs (Cl = 6-9) were biomagnified more. It thus appears that PBDEs are less biomagnified than PCBs.     

DO-increasing effects of a microscopic bubble generating system in a fish farm

We have developed a "microscopic bubble generating system for the fish farm" and evaluated its ability to improve the quality of seawater and costs of it in marine cages of red sea bream (Pagrus major) in Kusuura Bay, Japan. Our results revealed that DO concentration of bubbling net pens increased and became significantly higher than the level outside the net pen (between 0.52 and 0.87 mg/L), and the whole water column was nearly saturated. Temperatures of the bubbling net pens decreased slightly between 0.08 and 0.12 degrees C in all the layers. Furthermore, micro-bubbles seemed to reach the deeper water due to the downward flow and diffusion. This study demonstrated that the microscopic bubble generating system developed in our research project could increase efficiently the dissolved oxygen concentration throughout all water layers of the fish farm. A capital and operation costs of the system is recoverable within a year.     

Numerical simulation of large wood deposition patterns and responses of bed morphology in a braided river using large wood dynamics model

This study discusses the reproducibility of a numerical model for simulating the morphodynamics involved in the transport of large pieces of wood in a braided river, considering the root wad effect and jam formation. The developed numerical model can simulate the behaviour of large pieces of wood using a two-dimensional depth-averaged Eulerian flow model that calculates the water flow and bed morphology. A Lagrange-type wood transport model is used herein, and the applicability of the combined model is discussed through a comparison with obtained experimental results. From the simulation results, we calculate the total braiding index and estimate the deposition patterns of wood pieces for comparison with the experimental results. We then analyse the bed morphology responses and wood deposition patterns in terms of the root wad effect and input supply. Moreover, we discuss the advantages and limitations of the proposed model to predict the large wood dynamics considering the bed morphology. © 2019 John Wiley & Sons, Ltd.     

Unstructured grid generation using LiDAR data for urban flood inundation modelling

Inundation disasters, caused by sudden water level rise or rapid flow, occur frequently in various parts of the world. Such catastrophes strike not only in thinly populated flood plains or farmland but also in highly populated villages or urban areas. Inundation of the populated areas causes severe damage to the economy, injury, and loss of life; therefore, a proper management scheme for the disaster has to be developed. To predict and manage such adversity, an understanding of the dynamic processes of inundation flow is necessary because risk estimation is performed based on inundation flow information. In this study, we developed a comprehensive method to conduct detailed inundation flow simulations for a populated area with quite complex topographical features using LiDAR (Light Detection and Ranging) data. Detailed geospatial information including the location and shape of each building was extracted from the LiDAR data and used for the grid generation. The developed approach can distinguish buildings from vegetation and treat them differently in the flow model. With this method, a fine unstructured grid can be generated representing the complicated urban land features precisely without exhausting labour for data preparation. The accuracy of the generated grid with different grid spacing and grid type is discussed and the optimal range of grid spacing for direct representation of urban topography is investigated. The developed method is applied to the estimation of inundation flows, which occurred in the basin of the Shin‐minato River. A detailed inundation flow structure is represented by the flow model, and the flow characteristics with respect to topographic features are discussed. Copyright © 2010 John Wiley & Sons, Ltd.     

Investigation of excess argon in ultramafic rocks from the Kola Peninsula by the40Ar/39Ar method

In several xenolithic ultramafic rocks from the Kola Peninsula, including a magnetic separate, abnormally high⁴⁰Ar/³⁹Ar ratios persisted at low and high temperatures. The lowest⁴⁰Ar/³⁹Ar ratio was consistently observed at intermediate temperatures (900–1100°C), indicating an apparent age of 2.8–3.1 b.y.; however, this may not indicate the formation age.The quantity of excess⁴⁰Ar was estimated at each temperature fraction, adopting ages inferred from published Rb-Sr ages or the minimum⁴⁰Ar/³⁹Ar age. Excess⁴⁰Ar is abundantly trapped both in mineral lattices and nonretentive trapping sites, but the trapping sites are different from those of in-situ radiogenic⁴⁰Ar. The high temperature component of excess⁴⁰Ar is considered to represent Ar dissolved during mineral formation in the upper mantle or the lower crust.A correlation between the amount of high temperature excess⁴⁰Ar and³⁶Ar exists for some samples. The⁴⁰Ar_excess/³⁶Ar ratios of the rocks of probable upper mantle or lower crust origin vary from about 10 000 to 35 000, which may suggest large fluctuations of this ratio in the deep interior of the earth. The high value implies that most³⁶Ar was already degassed from the earth's interior at least 2 or 3 b.y. ago.     

Turbulent characteristics and bulk transfer coefficients over the desert in the HEIFE area

Observations of surface-layer turbulence and turbulent fluxes were made over a desert in northwestern China as a part of HEIFE (HEIhe river Field Experiment). These show that the normalized variations of the vertical wind component and of the air temperature obey Monin-Obukhov similarity well, especially in free convective conditions. However, the variations of specific humidity do not obey Monin-Obukhov similarity.Mean bulk transfer coefficients of sensible heat and momentum flux are obtained as functions of stability over a wide stability range from the observed data of turbulent fluxes and mast profiles. However, the bulk transfer coefficient for water vapor could not be obtained because of the large scatter of the data. In free convective conditions, the sensible heat flux was found to be approximately proportional to the 1.4 power of temperature difference between the surface and 20m. The bulk transfer coefficient of sensible heat is also obtained as a function of the bulk Richardson number for practical convenience.     

Interannual-decadal variability of wintertime mixed layer depths in the North Pacific detected by an ensemble of ocean syntheses

Climate Dynamics - The interannual-decadal variability of the wintertime mixed layer depths (MLDs) over the North Pacific is investigated from an empirical orthogonal function (EOF) analysis of an...     

X-ray topographic study of quartz crystals twinned according to japan twin law

Quartz crystals twinned according to Japan twin law were investigated by means of X-ray topography in order to understand the origin of characteristic morphology of twin crystals. It is demonstrated that the flattened and elongated morphology characteristic of quartz twins is due to preferential growth at twin junctions where dislocations with the Burgers vector direction 〈11 \(\overline {\text{2}} \) 1〉 concentrate, and that such preferential growth operates only when {10 \(\overline {\text{1}} \) 1} faces meet at the twin junction. Once {10 \(\overline {\text{1}} \) 0} faces appear at the twin junction due to the change of growth conditions, the effect diminishes sharply and the characteristic morphology becomes less pronounced. This leads to the conclusion that the characteristic morphology of quartz crystals twinned according to Japan twin law is formed at the earlier stage of growth and becomes less pronounced at the later stage of growth.     

Re-Estimation of Annual Anthropogenic Carbon Input from Oyashio into North Pacific Intermediate Water

The annual transport of anthropogenic carbon (C_anth) to the North Pacific Intermediate Water (NPIW) from the Western Subarctic Gyre (WSG) has been re-estimated by using newly estimated Oyashio transport and C_anth concentration, the latter calculated by the recently-established “ΔC*” method with some modifications. Estimated annual C_anth transport through the nearshore Oyashio west of 146°E was 0.020 ± 0.010 GtC y⁻¹, closely approximating the previous estimation based on a 1-D model calibrated with the CFC vertical distribution. The present study, however, found that an additional 0.025 ± 0.010 GtC y⁻¹ of C_anth was transported into NPIW in the region east of 146°E. Total C_anth transport, 0.045 GtC y⁻¹, contributes about 35% of annual C_anth accumulation of the whole temperate North Pacific. This revised version was published online in July 2006 with corrections to the Cover Date.