Vertical distributions of (99)Tc and the (99)Tc/(137)Cs activity ratio in the coastal water off Aomori, Japan

Using a sector-field ICP-MS the vertical distributions of the ⁹⁹Tc concentration and ⁹⁹Tc/¹³⁷Cs activity ratio were measured in the coastal waters off Aomori Prefecture, Japan, where a spent-nuclear-fuel reprocessing plant has begun test operation. The ⁹⁹Tc concentrations in surface water ranged from 1.8 to 2.4 mBq/m³, no greater than the estimated background level. Relatively high ⁹⁹Tc/¹³⁷Cs activity ratios (10-12 × 10⁻⁴) would be caused by the inflow of the high-⁹⁹Tc/¹³⁷Cs water mass from the Japan Sea. There is no observable contamination from the reprocessing plant in the investigated area. The ⁹⁹Tc concentration and the ⁹⁹Tc/¹³⁷Cs activity ratio in water column showed gradual decreases with depth. Our results implied that ⁹⁹Tc behaves in a more conservative manner than ¹³⁷Cs in marine environments.     

Subcellular distribution of trace elements in kidney of a mother-fetus pair of Dall's porpoises (Phocoenoides dalli)

Total and subcellular renal Zn, Cu, Se, Mn, V, Hg, Cd and Ag were determined by a mother-fetus pair of Dall's porpoises (Phocoenoides dalli). All element concentrations in the maternal individual were higher than those in the fetal individual. Most of total renal elements studied were present in the cytosol of both animals. In maternal cytosol, Mn, Hg and Ag were present in high molecular weight substances (HMW); Se was in low molecular weight substances (LMW); Zn, Cu, and Cd were in metallothionein (MT), mostly; and the distribution of V in percentage among the three renal cytosolic fractions was similar. In fetal cytosol, Zn, Mn, Hg, V, Cd, and Ag were present in HMW, Cu was present in MT, mostly. In contrast, Se was observed mostly in both LMW and HMW. MT isoforms were characterized. Three obvious peaks in retention time were found in either the maternal or fetal MT. The highest elemental ion intensities were in the 7.8min peak for the mother, and in the 4.3min peak for the fetus, respectively, implying that different MT isoforms may be closely associated with elemental accumulation between maternal and fetal renal cytosols.     

Episodic release of methane bubbles from peatland during spring thaw

Methane (CH(4)) flux into the atmosphere during spring thaw was investigated in a small ombrotrophic peatland (141 degrees 48'E, 43 degrees 19'N, Japan) using the conventional chamber method. More than 50 chamber deployments on top of the snow cover were carried out and continued for more than 165h until the surface snow and underlying ice cover on top of the peat layer had thawed completely. Methane emissions were almost absent in the presence of snow cover. At the very moment the surface ice cover thawed, a large CH(4) flush (>10mgCH(4)m(-2)h(-1)) was recorded, which was on the same order of magnitude as episodic ebullition previously observed in the high-summer. Gas bubbles trapped in the ice layer on top of the waterlogged peat were preliminarily analyzed for the volumetric percentage in the total ice volume and their gas species compositions. Results showed that the bubbles occupied about 3.2% volume and that the mixing ratio of CH(4) in the bubbles was about 20%. The abundance of the bubble-form CH(4) was sufficient to explain the observed episodic CH(4) release during the thaw. Results of this study show that CH(4) emissions during the thaw season have great temporal variability; emission occurs as an episodic release of bubble-form CH(4) stored in the frozen layer. The results also imply the possibility that gas-phase CH(4) plays an important role, not only during the growing season but also in cold-season CH(4) dynamics in northern peatlands.     

Transplacental transfer of phenyltins from a pregnant Dall's porpoise (Phocoenoides dalli) to her fetus

The maternal to fetal transfer of monophenyltin (MPT), diphenyltin (DPT), and triphenyltin (TPT) was investigated for the first time in a cetacean species, a mother-fetus pair of Dall's porpoises (Phocoenoides dalli) collected off the Sanriku coast, Japan. The mother individual was contaminated by phenyltin compounds, and the muscle, blubber, and liver accounted for 90% of the total phenyltin burden. A two-generation phenyltin contamination via transplacental transfer was demonstrated. This study revealed that the transfer rate was 0.29% for total phenyltins to a fetus of about 6-month-old. Unlike in the mother, the fetal liver could not be considered the target organ for all the phenyltins studied. In a ca. 100kg-weight mother Dall's porpoise and its fetus of 2.21kg-weight, approximately 153microg (TPT, 139microg; DPT, 9.4microg; MPT, 4.2microg) and 0.44microg of total phenyltins (TPT, 0.38microg; DPT, 0.03microg; MPT, 0.03microg) were found, respectively. The body burden of TPT consisted of 91% and 86% of the total phenyltin burdens in the maternal and fetal bodies, respectively.     

Atmospheric and kinetic studies of OH and HO2 by the FAGE technique

A new FAGE setup has recently been built at the University of Lille, France. It permits the quantification of OH and HO₂ in the atmosphere with a detection limit of 3×10⁵ molecules/(cm³·min) for OH and 1×10⁶ molecules/(cm⁵·min) for HO₂. Its coupling to a photolysis cell enables the measurement of the total reactivity of the hydroxyl radical in ambient air and kinetic studies in laboratory. Two configurations have been considered: one with the photolysis cell at 90° to the FAGE nozzle, the other on line with the FAGE nozzle. The two configurations have been tested and validated by measuring the well known rate constants of OH with CH₄, C₃H₈ and CO. The advantages and drawbacks of each configuration have been evaluated. The “on line” configuration limits losses and permits measurements over a larger reactivity range but is affected by OH formation from the laser beam striking the FAGE nozzle, thus limiting the ability to carry out energy dependence studies which can, in contrast, be successfully performed in the 90° configuration.     

Reproductive biology and early life history of the hermaphroditic feather star Dorometra sesokonis (Echinodermata: Crinoidea)

Reproduction and larval/post-larval development of the one of the smallest known comatulid Dorometra sesokonis were studied on the coral reefs of Sesoko-jima Island, Okinawa, Japan. Breeding individuals were found every month from May 2003 to April 2004 indicating continuous reproduction. Individuals possessed both mature ovaries and testes, and were therefore characterized as simultaneous hermaphrodites. This species was observed to be an external brooder in which the embryos developed on the surface of parental genital pinnules until the doliolaria larval stage, and subsequently released doliolariae settled on substrata within 4 days after hatching. Larvae then metamorphosed into the post-larval cystidean stage, which lasted for more than a month. The reproductive features of this species are unique among crinoids, and, together with juvenile morphological features observed in adults, can be interpreted as adaptations to their cryptic habitat, which is subject to frequent natural disturbances.     

Population dynamics of Müllerian mimicry under interspecific competition

We ask what the effects of mutualism on population dynamics of two competitive species are. We model the population dynamics of mutualistic interactions with positive density- and frequency-dependences. We specifically assume the dynamics of Müllerian mimicry in butterflies, where the mortality of both species is reduced depending on the relative frequency of the other species. We assume that the two species are under Lotka–Volterra density-dependent competition. The equilibria are compared with the cases of competition alone. Unlike the traditional model of positive density-dependence, population explosion does not appear in the current dynamics, but the new equilibrium is simply achieved. It is because the effects of positive density- or frequency-dependence are restricted to parts of mortality. Both positive density- and frequency-dependences do promote coexistence of the mimetic species. However, the two models show a distinctive difference for coexistence. The effects of positive density-dependence are rather limited. In contrast, positive frequency-dependence always promotes coexistence, irrespective of environmental conditions. The results may imply that the evolutionary origin of Müllerian mimicry may depend on frequency-dependence (and density-dependence), but that its current population dynamics may depend solely on density-dependence. The role of frequency- and density-dependences on evolutionary dynamics is an open question.     

Application of High-Volume Fly Ash Concrete to Marine Structures

A new material with high content of fly ash named 'Ashcrete' has been developed. to examine the applicability of Ashcrete to marine structures, strength characteristics, resistance to sea water attack, and safety in the marine environment have been studied. the following results have been obtained:

1) the strength characteristics of high-volume fly ash concrete depend upon the type and proportions of chemical activators as well as curing conditions.

2) Ashcrete using sodium chloride (NaCI) as a chemical activator shows high initial strength and good strength development with age.

3) Ashcrete containing NaCI activator shows good resistance to sea water from the viewpoint of its strength characteristics, volume changes and microstructurcs.

4) Since 1980 many types of large-scale artificial reefs made of Ashcrete have been installed in the sea. As a result of long-term studies and underwater observations, the Japanese Government has demonstrated the durability of the material, safety in the marine environment and attractiveness to fish.

5) It is therefore proposed that Ashcrete might be used in constructing large-scale sea mounts in deep water for the purpose of generating upwelling.     

Concentrations of organotin compounds in sediment and clams collected from coastal areas in Vietnam

Levels of butyltin (BT) and phenyltin (PT) compounds were determined in sediments and clam Meretrix spp. collected from north and central coastal areas in Vietnam. Concentrations of TBT in sediments ranged from 0.89 to 34 ng g(-1) dry wt and those in clams ranged from 1.4 to 56 ng g(-1) wet wt. The levels of TBT in sediments and clams from Vietnam were within limits reported from other countries. Further, the TBT level in clams was lower than the tolerable average residue level (TARL) estimated based on tolerable daily intake (TDI). Trace amounts of PTs were also found in both sediment and clam samples. In sediments from north and central Vietnam, the concentrations of TBT were highest in the order of Hue (28 ng g(-1) dry wt), Cua Luc (15 ng g(-1) dry wt), Sam Son (6.3 ng g(-1) dry wt), and Tra Co (5.5 ng g(-1) dry wt). Among the clams from north and central Vietnam, the levels of TBT in clams from Cua Luc were dramatically high at 47 ng g(-1) wet wt. TBT formed the principal butyltin species in sediment at all sites studied. The ratios of TBT in sediment were higher among BT compounds at all study sites. Of total BTs, TBT was the dominant species in clams from almost all sites studied. In spatial distribution, TPT showed a pattern similar to TBT, suggesting the use of TPT as an antifouling paint. The partition coefficient between sediment and calms was calculated. The partition coefficients of TBT and TPT were 2.01 (0.56-5.5) and 9.23 (3.1-20), respectively. These results show that sediment-bound TBT is a source of contamination to clams in addition to dissolved TBT.