Evaluation of environmental feasibility of steel pipe sheet pile cutoff wall at coastal landfill sites

An evaluation method that can express the local leakage of leachate from joint sections in steel pipe sheet pile (SPSP) cutoff walls is discussed in this study. In particular, the evaluation of environmental feasibility (containment of leachates containing toxic substances) considering a three-dimensional arrangement and hydraulic conductivity distribution of the joint sections in the SPSP cutoff wall is compared with an evaluation that uses the equivalent hydraulic conductivity. This equivalent hydraulic conductivity assumes that the joint section and the steel pipe are integrated; therefore, the hydraulic conductivity is substituted with a uniform permeable layer. However, in an evaluation that employs the equivalent hydraulic conductivity, it is difficult to consider the local leakage of leachate containing toxic substances from the joint sections in the SPSP cutoff wall. It was established that evaluations of the environmental feasibility of SPSP cutoff walls with joint sections must take into account the local leakage of leachates containing toxic substances from the joint sections. Also, it was clarified that technologies that lower the hydraulic conductivities of joint sections in SPSP cutoff walls and also facilitate the use of sparser joint arrangements contribute significantly to increasing the environmental feasibility of SPSP cutoff walls at landfill sites.     

Early life history of tropical Anguilla leptocephali in the western Pacific Ocean

In order to examine the early life-history characteristics of tropical eels, otolith microstructure and microchemistry were examined in leptocephali of Anguilla bicolor pacifica (27.6-54.1 mm TL, n=20) and A. marmorata (22.0-47.3 mm TL, n=8) collected during a cruise in the western Pacific. A. bicolor pacifica occurred between 10°N and 15°N in the west and between 5°S and 10°N farther to the east. A. marmorata also occurred in two different latitudinal ranges in the Northern (15-16°N) and Southern Hemispheres (3-15°S) of the western Pacific. The increment widths in the otoliths of these leptocephali increased between the hatch check (0 days) and about an age of 30 days in both species, and then gradually decreased toward the otolith edge. Otolith Sr:Ca ratios showed a gradual increase from the otolith center to the edge. The ages of A. bicolor pacifica and A. marmorata leptocephali ranged from 40 to 128 days and from 38 to 99 days, respectively. Growth rates of A. bicolor pacifica and A. marmorata leptocephali ranged from 0.33 to 0.71 mm day^-1 and from 0.45 to 0.63 mm day^-1, respectively. These leptocephali had estimated growth rates that were spread out throughout most of the reported range of growth rates of the leptocephali of the temperate species, the Japanese eel and the Atlantic eels. Differences in the spatial distribution in relation to current systems, and the age and size compositions of the leptocephali of A. bicolor pacifica and A. marmorata suggested different spawning locations for these two species.     

Early life history and recruitment of the tropical eel Anguilla bicolor pacifica, as revealed by otolith microstructure and microchemistry

Otolith microstructure and microchemistry of the tropical eel Anguilla bicolor pacifica Schmidt were examined in glass eels collected at the mouth of the Dumoga River, North Sulawesi Island, Indonesia. Ages of the glass eels examined (age at recruitment) ranged from 124 to 202 d (167 ± 19.3 d; mean ± SD), hatching being estimated as having occurred between November 1995 and March 1996. Otolith increment widths markedly increased from age 101 to 172 d (135 ± 18.2 d; mean ± SD), coincident with a drastic decrease in otolith Sr:Ca ratios, suggesting that metamorphosis began during that period. The duration of metamorphosis was estimated as 20 to 40 d, on the basis of otolith microstructural characteristics. The fluctuation patterns in otolith increment widths and Sr:Ca ratios were similar to those of the temperate Japanese eel A. japonica. Received: 20 May 1998 / Accepted: 7 October 1998     

A study on emission of phthalate esters from plastic materials using a passive flux sampler

Phthalate esters are used as plasticizer in many plastics, and several studies have shown their toxicity. Phthalate esters are gradually emitted over time, and so it is conceivable that they pose a significant health risk. This study aims to investigate the temperature dependence of the emissions of various phthalate esters and to estimate the health risks of these emissions at various temperatures. A passive-type sampler was developed to measure the flux of phthalate esters from the surface of plastic materials. With this sampler, we examined three widely used plastic materials: synthetic leather, wallpaper and vinyl flooring. The observed maximum emissions of diethyl phthalate, dibutyl phthalate, and diethylhexyl phthalate (DEHP) from these materials at 20°C were 0.89, 0.77, and 14 μg m⁻² h⁻¹, respectively. Emissions at 80°C were 2.8, 4.5×10², and 1.5×10³ μg m⁻² h⁻¹, respectively. The results showed this temperature dependence is determined primarily by the type of phthalate ester and less so by the type of material. The estimation from the results of temperature dependence indicated the concentration of DEHP in a vehicle left out in the sunshine during the day can exceed the recommended levels of Japan Ministry of Health, Labour and Welfare.     

Evaluation of the impact of matrix effects in LC/MS measurement on the accurate quantification of neonicotinoid pesticides in food by isotope-dilution mass spectrometry

The use of isotope-labeled internal standards is the most widely accepted approach to overcome the matrix effects on quantification of pesticides in food by LC/MS. We evaluated the impact of the matrix effects on quantification of six neonicotinoid pesticides, acetamiprid, clothianidin, dinotefuran, imidacloprid, thiacloprid, and thiamethoxam, in food by using deuterated internal standards. The calibration curves for each pesticide were obtained by using matrix-free and matrix-matched calibration solutions with blank brown rice, carrot, and green onion extracts. For brown rice and carrot, the matrix effects were not observed. In contrast, the slopes of calibration curves for each pesticide were influenced by presence of green onion extracts in calibration solutions (variability of the slopes was 4–9%), because the ratios of peak area for native pesticide to those for internal standards were influenced by matrix. The spike-and-recovery test with green onion was also performed. The analytical values obtained by using matrix-free calibration solution were biased from the spiked concentration, whereas those obtained by using matrix-matched calibration solution were comparable to the spiked concentration. These results indicate that matrix-matched calibration solution should be used for accurate quantification of neonicotinoid pesticides in food by LC/MS using deuterated internal standards.     

Multiresidue analysis and monitoring of pesticides in rice by pressurized liquid extraction

The aim of this study was to assess the performance of a method of analyzing pesticides in rice by using pressurized liquid extraction (PLE) and to perform a preliminary monitoring by using that method. The instrumental quantification limit, instrumental detection limit, method quantification limit, and method detection limit were determined. PLE temperature was also optimized for 6 target pesticides. Mean recoveries of spiked rice with target pesticides (4 ng/g and 40 ng/g) were 83%–109% with the repeatability of the analysis, represented as relative standard deviations, ranged from 1.3% to 11% (n = 5) for PLE at 130°C. These results were satisfactory according to the method of positive list in Japan. In a preliminary analysis of 10 target pesticides in 54 commercial rice samples, ferimzone was detected in only one unpolished rice sample.     

Study on anisotropy of effective diffusion coefficient and activation energy for deuterated water in compacted sodium bentonite

To quantify the effects of temperature on the diffusivity of deuterated water (HDO) in compacted sodium bentonite, through-diffusion experiments were conducted at elevated temperatures ranging from 298 to 333 K. Kunipia F (Na-montmorillonite content>98 wt.%; Kunimine Industries) was compacted to a dry density of 0.9 or 1.35 Mg/m(3). As montmorillonite particles were oriented perpendicular to the direction of compaction, the anisotropy of diffusivity was investigated both parallel and normal to the preferred orientation of the montmorillonite. The effective diffusion coefficient D(e) of HDO was larger when the diffusional direction was parallel as opposed to normal to the preferred orientation for both dry densities. The magnitude of D(e) and the anisotropy for HDO were in good accordance with previously reported results for tritiated water at room temperature. Activation energies of D(e) were isotropic and increased with increasing dry density over the range of 19-25 kJ/mol. This relationship was considered to be due to both pore structure development and the high activation energy of water near the montmorillonite surface.     

Evidence of a spawning area of <Emphasis Type="Italic">Anguilla</Emphasis><Emphasis Type="Italic">marmorata</Emphasis> in the western North Pacific

Leptocephali of the tropical eel Anguilla marmorata have been consistently collected in the same area of the North Equatorial Current (NEC) in the western North Pacific during three consecutive cruises in June and July of 1991 (N=28) and 1994 (N=20), and July and September of 1995 (N=27), indicating that this is a spawning area of this species. These leptocephali were collected from 130°E to 142°E and 12°N to 20°N, to the west of the Mariana Islands, in 20 tows in 1991, in 13 tows in 1994 and in 17 tows in 1995, indicating a widespread presence, but a relatively low abundance. Six of these specimens (16.3-36.0 mm total length) from the 1995 cruise, which were of the typical size range of these leptocephali, were genetically confirmed to be A. marmorata in a previous study. The consistent presence of recently spawned A. marmorata leptocephali (9-20 mm) in all 3 years, suggests that the western region of the NEC is the spawning area of the northern population of A. marmorata that was identified in a recent population genetics study. These leptocephali would thus be transported westward by the NEC and then transported north into the Kuroshio Current and toward Taiwan and Japan, or south toward the southern Philippines and into the Celebes Sea by the Mindanao Current. Available evidence indicates that A. marmorata may have potentially year-round spawning, and the presence of a spawning area of this species in the same region as that of Anguilla japonica suggests that the northern population of A. marmorata has evolved a spawning migration from East Asia, the Philippines and the Celebes Sea region to the NEC area, but differs from A. japonica by having some individuals that recruit to more southern areas.     

Changes in otolith strontium:calcium ratios in metamorphosing Conger myrisaster leptocephali

Content ratios of strontium (Sr) to calcium (Ca) in the otolith of Conger myriaster metamorphosing leptocephali and elvers increased with increasing increment number from the core to the 110th increment and subsequently decreased. The otolith region from the 110th increment to the edge corresponded to the metamorphic stage. The Sr:Ca ratios in otolith edges of metamorphosing leptocephali were inversely related to metamorphic stage, suggesting that the changes in otolith Sr:Ca ratios were influenced by some physiological factor(s) rather than by environmental factors. Sr concentration in leptocephalus somatic tissues was high and decreased as metamorphosis progressed until the late metamorphic stage when the preanal myomere to total myomere ratio was 0.4. Ca concentration was constant throughout ontogenesis. Body Sr:Ca ratios markedly decreased as metamorphosis progressed. Decrease in somatic Sr concentration and the consequent decrease in body Sr:Ca ratios seemed to be associated with the breakdown of glycosaminoglycan (GAG) in gelatinous matrix, which is the major constituent of soft tissue in leptocephali. Catabolism of GAG may also cause a decrease in otolith Sr:Ca ratios during metamorphosis. In leptocephalus otoliths, Sr:Ca ratios may change in association with the synthesis and breakdown of GAGs during ontogeny. Received: 29 November 1996 / Accepted: 6 January 1997