Influence of chemical characteristics of humic substances on the partition coefficient of a chlorinated dioxin

The partition coefficients (Koc) of 1,2,3,4,6,7,8-heptachlorodibenzo-p-dioxin (HpCDD) with respect to a variety of humic substances (HSs) were evaluated by a method involving solid-phase microextraction and gas chromatography-electron capture detection. The log Koc values for each of the HS samples were in the range of 6.4-7.7. The log Koc values for HAs from tropical peat, brown forest and ando soils were in the range of 7.3-7.6, similar to the calculated value for the octanol-water partition coefficient (log Koc=7.56). In contrast, the log Koc values for FAs and peat HAs were 0.5-1 unit lower than the calculated value. The parameters for the polarity of HSs, as calculated from (N+O)/C, O/C atomic ratios and the carboxyl group content, were numerically similar related to the log Koc for HpCDD. These results show that the Koc values for HpCDD are significantly influenced by the polarity of HSs.     

Polycyclic aromatic hydrocarbons (PAHs) in the aerosol in Beijing, China, measured by aminopropylsilane chemically-bonded stationary-phase column chromatography and HPLC/fluorescence detection

We developed a useful analytical method for the determination of polycyclic aromatic hydrocarbons (PAH) concentrations in the aerosol of China. We used an accelerated solvent extraction (ASE) method for the extraction of PAHs from the aerosol samples, in order to reduce the extraction time and the solvent volume used. The optimum purification method was developed, with aminopropylsilane chemically-bonded stationary-phase column chromatography, in order to remove many co-extractives which cannot be removed by conventional purification methods using silica-gel column chromatography. HPLC/fluorescence detection (FLD) was adopted as the analytical method, because it has very high sensitivity to PAH and it is easy to install, operate, and maintain as compared with GC/MS. With the analytical method developed in this study, the recovery and precision (RSD) for most of the PAHs ranged from 75% to 129% and from 2.8% to 22.7%, respectively. The concentrations of PAHs in the aerosol samples collected from October 2003 to April 2005 in Beijing, China were determined using the newly developed method. SigmaPAHs, which is the sum of the concentrations of all detected PAHs, was 177.8 +/- 239.9 ng m(-3) (n = 64). The SigmaPAHs concentration in the heating season (305.1 +/- 279.0 ng m(-3), n = 33) was 7.2 times higher than that in the non-heating season (42.3 +/- 32.0 ng m(-3), n = 31). These strong seasonal variations in atmospheric PAH concentration are possibly due to coal combustion for residential heating in winter.     

Metals leachability from medical waste incinerator fly ash: A case study on particle size comparison

This paper presents the results from a study of metals leachability of medical waste incinerator fly ash in Japan on the basis of particle size. Sequential extraction and Toxicity Characteristic Leaching Procedure (TCLP) analysis were carried out in order to quantify the leaching amount of metals in each categorized particle size. Sequential extraction was also subjected to identify the preference of binding matrix of metals. The results of sequential extraction showed an increase both exchangeable and carbonate associated chromium concentrations in the bigger particle size fractions. Likewise, concentrations of carbonate matrix of arsenic and tin tended to increase in the bigger particle size fractions. In contrast, exchangeable associated cadmium as well as both exchangeable and carbonate matrices of barium were found higher in the smaller particle size fractions. However, no correlation was found in Kendal-tau correlation analysis between particle size of the ash and metals leachability of the TCLP.     

Seasonal variations in 228Ra/226Ra ratio within coastal waters of the Sea of Japan: implications for water circulation patterns in coastal areas

In this study, low-background gamma-spectrometry was used to determine the (228)Ra/(226)Ra ratio of 131 coastal water samples from various environments around Honshu Island, Japan (mainly around Noto Peninsula) at 1-3 month intervals from April 2003 until September 2005. Spatial variation in (228)Ra/(226)Ra ratios was also assessed by analyzing 34 coastal water samples from five areas within the Sea of Japan during May and June 2004. The (228)Ra/(226)Ra ratio of coastal water from all sites around Noto Peninsula shows seasonal variation, with minimum values during summer ((228)Ra/(226)Ra=0.7) and maximum values during autumn-winter ((228)Ra/(226)Ra=1.7-2). This seasonal variation is similar to that recorded for coastal water between Tsushima Strait and Noto Peninsula. The measured lateral variation in (228)Ra/(226)Ra ratios within coastal water between Tsushima Strait and Noto Peninsula is only minor (0.5-0.7; May-June 2004). Coastal waters from two other sites (Pacific shore and Tsugaru Strait, north Honshu) show no clear seasonal variation in (228)Ra/(226)Ra ratio. These measured variations in (228)Ra/(226)Ra ratio, especially the temporal variations, have important implications for seasonal changes in patterns of coastal water circulation within the Sea of Japan.     

Correlation between stomach temperatures and ambient water temperatures in free-ranging loggerhead turtles,Caretta caretta

Instruments were attached to loggerhead turtles, Caretta caretta, at Kamoda Point, Japan in 1989 and on the Senri-coast, Japan in 1991. We simultaneously obtained stomach temperatures, ambient water temperatures and diving depths from four free-ranging loggerhead turtles during the internesting periods, using small recorders. These data were analyzed to understand how body temperature was maintained. Ambient water temperatures changed coincidentally when turtles moved up or down, but a stable stomach temperatures was maintained despite water temperature fluctuations of ca. 20 to 90 min in duration. Loggerhead turtles also experienced water temperature fluctuations longer than 24 h. Stomach temperatures responded to those water temperature changes with a time lag of several hours (160, 170, 230 and 240 min). Stomach temperatures were higher than ambient water temperatures throughout the experimental periods. The median values of the thermal difference between stomach and water temperatures were 1.1, 1.3, 1.5 and 1.7°C. The higher stomach temperatures are thought to be caused by metabolic heat production.     

Growth dynamics and mortality of the intertidal encrusting sponge Halichondria okadai (Demospongiae, Halichondrida)

A periodical survey of the growth of an intertidal encrusting sponge Halichondria okadai was conducted on a rocky intertidal shore on the Izu Peninsula, southern Japan. The area covered by each of 16 marked sponges was monitored, and the fusion and fission of specimens were recorded from June 1995 to June 1998. During the investigation, 15 of the original specimens managed to survive accompanying fusions or fissions and only one colony completely disappeared. Ten fusions and 23 fissions were observed in total. The maximum death rate during a semilunar period was 16.7% and cumulative mortality throughout the study period was 46.1%, indicating that the mortality of H. okadai is lower than that of other species previously reported. There was no particular seasonal pattern in the occurrences of fusion, fission and death of sponges. However, fissions were frequently observed in the latter half of the study period and were sometimes followed by fusions or death of specimens. Positive growth rates were often observed during warmer months, and specimens showed little growth or regression in winter. Seasonal patterns in surface area were thought to be related to seasonality in reproductive activity.     

Hydrodynamic and towing characteristics of a modified model of the Clarke Jet Net

In a series of studies to develop an effective high speed plankton sampler, hydrodynamic research was carried out on a modified model of the Clarke Jet Net. A theoretical analysis of the motion of the sampler was made using an IBM 7040 computer, and test tows were made in an experimental ship tank and at sea. To maintain the roll angle of the sampler at approximately zero, a v-shape bridle was applied. A pair of towing holes should be selected for the particular range of towing velocity. The calculated longitudinal stability seemed good in all the cases examined. Towing tests in the ship tank at 2 to 3 m/sec revealed sufficient stability. The motion of the sampler at speeds higher than 3 m/sec can be assumed from hydrodynamic coefficients derived from the ship tank experiment. Towing-cable characteristics, assumed by computation, indicated that about 500 m at 6 kt and 1,000 m at 12 kt should be paid out to lower the sampler down to 100 m. The effect of the sampler on the cable is found only adjacent to it and is almost negligible beyond 50 m from it in depth. Results of sea tests at 6 and 9 kt confirmed the stability of the sampler. Examination of the catch suggested that the present model can be used, with some modifications, for the quantitative and qualitative sampling of large zooplankton.Contribution No. 231 from the Seikai Regional Fisheries Research Laboratory, Nagasaki.     

Evolutionary relationships of deep-sea mussels inferred by mitochondrial DNA sequences

In order to elucidate the evolutionary process of deep-sea Bathymodiolus mussels, we investigated the phylogenetic relationships of 16 species worldwide by analyzing nucleotide sequences of the mitochondrial COI and ND4 genes. Deep-sea mussels were clustered into three groups by basal trichotomous divergence. The first was composed of four species found in Japanese waters and one species from the Gulf of Mexico, which contain methanotrophic endosymbiotic bacteria. The second included nine species distributed in the West and East Pacific, Indian, and Atlantic Oceans. Members of the second group were trichotomously divided into the Indo-West Pacific, Atlantic, and East Pacific subclusters. The Indo-West Pacific subcluster was composed of three very closely related species with mutual genetic distances at the intraspecific level (av. 0.019 in COI and 0.009 in ND4 relative to av. 0.156 in COI and 0.265 in ND4 among Bathymodiolus species other than Cluster A species), suggesting some gene flow among these species. The third consisted of two West Pacific species. Species in the second and third groups contain mainly thioautotrophic endosymbionts, including some species harboring both methanotrophs and thioautotrophs.     

Onsets of schooling behavior and social transmission in chub mackerel Scomber japonicus

Grouping behavior has various types of antipredator functions. Some of these functions require social transmission of information, such as the many-eyes effect, whereas others do not, such as the dilution and confusion effects. Functions of grouping behavior would enhance with social transmission among group members. We investigated and compared the onsets of schooling behavior and social transmission of information in chub mackerel Scomber japonicus. Onset of schooling behavior was observed in rearing tanks by calculating the degree of parallel swimming. Onset of social transmission was examined by using visual cues from conspecifics. A group of five individuals was put in each of three experimental chambers from which they could see a group of conspecifics in the neighboring chamber. A weak electric stimulus was given to one of these chambers, and information transfer among individuals was observed. We found that social transmission by visual cues started on 30 days posthatching (25.1 mm in standard length), which was 2 weeks after the onset of schooling behavior. The late onset of social transmission relative to schooling behavior might be attributed to different predation pressure with development, or by underdevelopment of optic tectum, as the volume of the optic tectum did not increase just after the onset of schooling behavior.     

Effect of low dissolved oxygen concentrations on behavior and predation rates on red sea bream Pagrus major larvae by the jellyfish Aurelia aurita and by juvenile Spanish mackerel Scomberomorus niphonius

A shift in outcomes of predator-prey interactions in plankton community may occur at sublethal dissolved oxygen concentrations that commonly occur in coastal waters. Laboratory experiments were conducted to investigate how a decline in dissolved oxygen concentration alters the predation rate on fish larvae by two estuarine predators. Behavior and consumption of larval fish by moon jellyfish Aurelia aurita (103.1±12.4 mm in bell diameter) and by a juvenile piscivore, Spanish mackerel Scomberomorus niphonius (30.1±2.1 mm in standard length: SL), were observed under four oxygen concentration treatments (1, 2 and 4 mg l^–1 and air-saturated: 5.8 mg l^–1). Larvae of a coastal marine fish species, red sea bream Pagrus major (7.21±0.52 mm SL), were used as prey for the experiment. Bell contraction rate of the jellyfish did not vary among the oxygen concentrations tested, indicating a tolerance to low oxygen concentration. Gill ventilation rate of the Spanish mackerel increased and swimming speed decreased as the oxygen concentration decreased, indicating that oxygen concentrations 4 mg l^–1 are physiologically stressful for this species. The number of larvae consumed in 15 min. by jellyfish increased whereas those consumed by Spanish mackerel decreased with the decrease in oxygen concentration. Low oxygen concentrations that are commonly observed in coastal waters of Japan during summer have the potential to increase the relative importance of jellyfish as predator of fish larvae and to change the importance of alternative trophic pathways in estuarine ecosystems.Communicated by T. Ikeda, Hakodate