Quantifying the ecosystem service of non-native weed seed predation provided by invertebrates and vertebrates in upland wheat fields converted from paddy fields

The extent of post-dispersal weed seed predation in upland wheat fields converted from paddy fields was quantified in Shizuoka Prefecture, central Japan. We investigated the temporal variability in seed predation of Italian ryegrass (Lolium multiflorum Lam.), a non-native winter annual weed in Japan, during summer after the seed shed in both the field interior areas and boundary strips, and estimated the total seed loss due to predation during the summer. Furthermore, the contribution of invertebrates and vertebrates to seed predation was estimated by using exclosures. The total seed loss due to predation during four months (from late June to late October) in the field interior areas and boundary strips was estimated to be 35–43% (the maximum proportion of seed predation per two weeks = 27%) and 42% (25%), respectively. The seed predators in the field interior areas were vertebrates (rodents or birds) and invertebrates (crickets and ground beetles). In contrast, seed predators in the boundary strips were mainly invertebrates (crickets and ground beetles). The results of this study suggest that predators make a substantial contribution in the depletion of post-dispersal seeds of Italian ryegrass in converted paddy fields.     

Effects of biosurfactants on assays of PCB congeners in transgenic arabidopsis plants carrying a recombinant guinea pig AhR-mediated GUS reporter gene expression system

The transgenic Arabidopsis plants carrying a recombinant guinea pig (g) aryl hydrocarbon receptor (AhR)-mediated β-glucuronidase (GUS) reporter gene expression system were generated for assays of polychlorinated biphenyl (PCB) congeners. The selected transgenic Arabidopsis plant XgD2V11-6 exhibited a correlation between uptake of PCB126 and PCB126-induced GUS activity. Also, the plants showed induced GUS activity towards the supplemental indole 3-acetic acid (IAA). Thus, the GUS assay may reflect induction by both endogenous and exogenous AhR ligands. When biosurfactants, MEL-B, produced in the culture of yeast isolated from plants were used for assays of PCB congeners in the transgenic Arabidopsis plants, they showed marked PCB126 dose-dependent and toxic equivalency factor (TEF) dependent GUS activities. The effects of biosurfactants were clearer when the plants were cultivated on soils containing PCB congeners for 7 days as compared with on soils for 3 days as well as in the medium for 3 days. Threfore, it was estimated that biosurfactants form micellae with PCB congeners, which are easily uptaken by the plants in a mode of passive diffusion, transport into the aerial parts and then induce GUS activity.     

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.     

Mutagenicity of anaerobic fenitrothion metabolites after aerobic biodegradation

Previous studies have revealed that the mutagenicity of fenitrothion increases during anaerobic biodegradation, suggesting that this insecticide's mutagenicity could effectively increase after it pollutes anaerobic environments such as lake sediments. To investigate possible changes to the mutagenicity of fenitrothion under aerobic conditions after it had already been increased by anaerobic biodegradation, batch incubation cultures were maintained under aerobic conditions. The mutagenicity, which had increased during anaerobic biodegradation, decreased under aerobic conditions with aerobic or facultative bacteria, but did not disappear completely in 22 days. In contrast, it did not change under aerobic conditions without bacteria or under continued anaerobic conditions. These observations suggest that the mutagenicity of anaerobically metabolized fenitrothion would not necessarily decrease after it arrives in an aerobic environment: this would depend on the presence of suitable bacteria. Therefore, fenitrothion-derived mutagenic compounds may pollute the water environment, including our drinking water sources, after accidental pollution of aerobic waters. Although amino-fenitrothion generated during anaerobic biodegradation of fenitrothion was the principal mutagen, non-trivial contributions of other, unidentified metabolites to the mutagenicity were also observed.     

Photochemical generation rates of hydroxyl radical in aqueous solutions containing Fe(III)-hydroxy complex

The rates of photochemical generation of hydroxyl radical at 313 nm in aqueous solutions containing ferric ion at acidic pH were measured by the competitive kinetic method using 2-chlorophenol as a test compound and 1-octanol as a radical scavenger. The quantum yield of hydroxyl radical generation calculated from the rates was about 0.02. From the results, it was suggested that this system could be used as a method of wastewater treatment.     

Modification of carbon-coated TiO2 by iron to increase adsorptivity and photoactivity for phenol

Carbon-coated TiO(2) modified by iron, were prepared from TiO(2) of anatase structure and PET modified by FeC(2)O(4). Catalysts were prepared by mixing powders of TiO(2) and modified PET and heating at different temperatures, from 400 to 800 degrees C under flow of Ar gas. High adsorption of phenol was observed on the catalyst heated at 400 degrees C, confirmed by FT-IR analysis. On this catalyst, fast rate of phenol decomposition was achieved by addition of small amount of H(2)O(2) to the reaction mixture. Phenol decomposition proceeded mainly through the direct oxidation of phenol species adsorbed on the catalyst surface due to the photo-Fenton reaction. Iron-modified carbon-coated TiO(2) catalysts heated at 500-800 degrees C showed almost no phenol adsorption or oxidation.     

Estimation of mechanical dispersion and dispersivity in a soil-gas system by column experiments and the dusty gas model

In a previous study, column experiments were carried out with Toyoura sand (permeability 2.05×10(-11)m(2)) and Toyoura sand mixed with bentonite (permeability 9.96×10(-13)m(2)) to obtain the molecular diffusion coefficient, the Knudsen diffusion coefficient, the tortuosity for the molecular diffusion coefficient, and the mechanical dispersion coefficient of soil-gas systems. In this study, we conducted column experiments with field soil (permeability 2.0×10(-13)m(2)) and showed that the above parameters can be obtained for both less-permeable and more-permeable soils by using the proposed method for obtaining the parameters and performing column experiments. We then estimated dispersivity from the mechanical dispersion coefficients obtained by the column experiments. We found that the dispersivity depended on the mole fraction of the tracer gas and could be represented by a quadratic equation.     

Dependence of photocatalytic activity of anatase powders on their crystallinity

Structural changes in anatase phase in four TiO(2) photocatalysts with annealing at high temperatures were followed by evaluating crystallite size and lattice strain of anatase phase separately and measuring the content of anatase. The rate constant k for the decomposition of methylene blue in its aqueous solution under UV irradiation was determined as a measure of photocatalytic activity. Marked dependences in crystallinity improvement, i.e., the growth of crystallite and the decrease in lattice strain, and in phase transformation from anatase to rutile phases of TiO(2) on annealing temperature was observed above 500 degrees C, depending on starting photocatalysts used. The phase transformation to rutile started after reaching of crystallite size to about 32 nm and of lattice strain to about 0.5 x 10(-3). Rate constant k was found to depend on both crystallite size and lattice strain of anatase; it increased with increasing crystallite size up to about 32 nm and decreasing lattice strain down to about 0.5 x 10(-3). Further increase in crystallite size and decrease in lattice strain induced the decrease in rate constant k, mainly due to the partial transformation of anatase to rutile. The present results showed that the activity of the photocatalysts was possible to be improved by annealing at a high temperature, by selecting an optimal condition of annealing for getting a high crystallinity in anatase phase and no phase transformation to rutile phase.     

Converting waste polystyrene into a polymer flocculant for wastewater treatment

We have succeeded in converting waste polystyrene from electrical appliances into a polymer flocculant for treating some kinds of wastewater after chemical modification. Waste polystyrene, such as polystyrene foam and additive-containing TV cabinets, was converted into a water-soluble polymer, polystyrene sulfate (PSS), and PSS of various degrees of aqueous viscosity was obtained by introducing sulfone bridges during sulfonation. We examined the relationship between the degree of flocculation of wastewater and the aqueous viscosity of the PSS, and found that PSS with medium viscosity is most suitable for flocculating inorganic wastewater from a factory, and PSS with high viscosity is most suitable for dewatering organic domestic wastewater. We report how PSS containing sulfone bridges works as a polymer flocculant for treating wastewater. Received: July 19, 2000 / Accepted: September 21, 2000