Decomposition characteristics of particulate organic matter in hiroshima bay

The decomposition characteristics of particulate organic matter (POM) sampled with plankton nets in Hiroshima Bay were investigated under aerobic conditions in a laboratory experiment.The POM derived from plankton consisted of both a labile fraction (70–80 % of the whole) and a refractory fraction (20–30%). The labile fraction was completely decomposed within 40 days at 20°C. Although the concentrations of particulate organic carbon (POC) decreased gradually with time, an apparent lag phase was recognized in the decomposition of particulate phosphorus (PP) at an early stage, which might result from a specific uptake of dissolved inorganic phosphorus (DIP) by bacteria. A comparison of the metabolic activity between dissolved organic matter (DOM) and POM by measuring ATP contents showed that the former was one order of magnitude larger than the latter.On the other hand, there was no significant difference among the decomposition rates of POM collected at various depths. The change of the first-order rate constant (k) for the POM decomposition by temperature was expressed ask=0.0329 exp(0.0644T), and the Q₁₀ value was 1.94. There were fairly large variances ink values obtained from the various plankton species. Thek values averaged 0.144 day^–1 and ranged from 0.078 to 0.20 day^–1 at 20°C.     

Field-induced oscillation and rotation of diamagnetic oxide crystals

The harmonic oscillations of large diamagnetic mineral samples induced by a magnetic field is reported, for single crystals of quartz, corundum, and calcite. It was seen for the first time that the period of oscillation, , was proportional to the reciprocal of the magnetic field, H, where the restoring force of the string suspending the crystal became negligible in the high magnetic field. Accordingly, the value of diamagnetic anisotropy, , could be measured from the — H curve with a sensitivity of 5 × 10^–10 emu/cc. The values were 5.50 × 10^–9 emu/cc for quartz, 4.20 × 10^–9 emu/cc for corundum, 9.9 × 10^–8 emu/cc for calcite, and 8.8 × 10^–8 emu/cc for polycrystalline talc piled with the (001) planes aligned parallel. Significant field-induced rotations were observed for the suspended crystals. When the field was applied along the direction of the diamagnetic hard axis of the stationary crystal, the crystal gradually rotated with increasing field, so that the direction of the hard-axis was perpendicular to the applied field. The field-induced energy has a the maximum value when the field is applied along the diamagnetic hard axis. This reorientation of the crystal occurs because the torque due to the field-induced anisotropic energy exceeds that of the restoring force in high magnetic fields.     

Diamagnetic anisotropy of sheetsilicates

The diamagnetic properties of sheetsilicates are studied by measuring the magnetic orientation of micron-sized crystals. In the case of synthetic phlogopite with the average diameter of 0.65 μm and the thickness of 0.2 μm, the alignment of the grains is achieved in the magnetic field below 35 kOe. The planes of the platy single-crystal grains were alignned parallel to the field when the alignment was achieved. The alignment of the grains is realized because the field-induced anisotropic energy, caused by the diamagnetic anisotropy in the mineral's crystal structure, exceeds thermal agitation energy in the applied field. By analyzing the field dependence of grain alignment, the diamagnetic anisotropy per formula unit, Δ_χ, of sheetsilicate mineral is estimated even if a large single crystal is not provided. The field-induced anisotropic energy is proportional to NΔ_χ where N is the number of molecules in the grain. A linear correlation has been found between the Δ_χ value and the F/OH mole ratio among the measured sheetsilicates. This correlation supports the assumption that the hexagonally packed oxygen-layer in the crystal lattice induces the anisotropies of the sheetsilicates.     

Concentration of polychlorinated biphenyls (PCBs) in beached resin pellets: variability among individual particles and regional differences

Concentrations of polychlorinated biphenyls (PCBs) in beached resin pellets were examined to reveal variability between individual particles and differences among beaches. Fifty-five resin pellets from a beach in Tokyo were individually analyzed for PCBs, and showed concentrations ranging from <28 to 2,300 ng/g. This indicates that concentrations are highly variable between particles. Among several characters, discoloration (e.g., yellowing) had a positive relationship with PCB concentration: discolored pellets contained more PCBs than others on most of the beaches sampled. Given the color-selective ingestion of food by some organisms, this may be ecotoxicologically important. Measurements of samples from 47 beaches in Japan showed regional differences in PCB concentrations in resin pellets consistent with those in mussels. Sporadic high concentrations of PCBs were also found in pellets from remote islands, suggesting that resin pellets could be the dominant route of exposure to the contaminants at remote sites. The similarity of PCB concentrations between resin pellets and mussels suggests a potential use of resin pellets to monitor pollution in seawater.     

Long-period waves in the vicinity of Onagawa Bay (III)

Characteristics of seiches in Onagawa Bay are investigated on the basis of observations at the bay head, Konorihama, from May 1972 to May 1973 and at the outside of the bay, Enoshima during the same period. At Konorihama seiches with the double amplitude of 7 to 11 cm occurred most frequently (63 percent of the total samples) and the maximum reached 31 cm. Short-time spectral analyses indicate that the periods of the spectral peaks shift considerably with the lapse of time, and that the location of the nodal line near the bay mouth moves offshore and inshore of Enoshima. The cause of these phenomena seems to be attributed to the change of incident angle of waves coming from the open sea to excite seiches. Amplitudes of the fundamental and of the lateral modes of seiches increase or decrease alternately with time, suggesting the energy transfer between these modes. Bay oscillations induced by remarkable atmospheric pressure-waves were observed. However, the amplitudes of the oscillations were within a few centimeters and dissipated in a few hours.